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'JWT' ** Downref: Normative reference to an Historic RFC: RFC 1421 ** Obsolete normative reference: RFC 1738 (Obsoleted by RFC 4248, RFC 4266) ** Downref: Normative reference to an Informational RFC: RFC 2104 ** Obsolete normative reference: RFC 3447 (Obsoleted by RFC 8017) ** Obsolete normative reference: RFC 4627 (Obsoleted by RFC 7158, RFC 7159) ** Obsolete normative reference: RFC 5226 (Obsoleted by RFC 8126) ** Obsolete normative reference: RFC 5785 (Obsoleted by RFC 8615) -- Possible downref: Non-RFC (?) normative reference: ref. 'USA15' Summary: 8 errors (**), 0 flaws (~~), 2 warnings (==), 18 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group M. Jones 3 Internet-Draft Microsoft 4 Intended status: Standards Track D. Balfanz 5 Expires: September 26, 2011 Google 6 J. Bradley 7 independent 8 Y. Goland 9 Microsoft 10 J. Panzer 11 Google 12 N. Sakimura 13 Nomura Research Institute 14 P. Tarjan 15 Facebook 16 March 25, 2011 18 JSON Web Signature (JWS) 19 draft-jones-json-web-signature-01 21 Abstract 23 JSON Web Signature (JWS) is a means of representing signed content 24 using JSON data structures. Related encryption capabilities are 25 described in the separate JSON Web Encryption (JWE) specification. 27 Requirements Language 29 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 30 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 31 document are to be interpreted as described in RFC 2119 [RFC2119]. 33 Status of this Memo 35 This Internet-Draft is submitted in full conformance with the 36 provisions of BCP 78 and BCP 79. 38 Internet-Drafts are working documents of the Internet Engineering 39 Task Force (IETF). Note that other groups may also distribute 40 working documents as Internet-Drafts. The list of current Internet- 41 Drafts is at http://datatracker.ietf.org/drafts/current/. 43 Internet-Drafts are draft documents valid for a maximum of six months 44 and may be updated, replaced, or obsoleted by other documents at any 45 time. It is inappropriate to use Internet-Drafts as reference 46 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on September 26, 2011. 50 Copyright Notice 52 Copyright (c) 2011 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 This document is subject to BCP 78 and the IETF Trust's Legal 56 Provisions Relating to IETF Documents 57 (http://trustee.ietf.org/license-info) in effect on the date of 58 publication of this document. Please review these documents 59 carefully, as they describe your rights and restrictions with respect 60 to this document. Code Components extracted from this document must 61 include Simplified BSD License text as described in Section 4.e of 62 the Trust Legal Provisions and are provided without warranty as 63 described in the Simplified BSD License. 65 Table of Contents 67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 68 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 69 3. JSON Web Signature (JWS) Overview . . . . . . . . . . . . . . 5 70 3.1. Example JWS . . . . . . . . . . . . . . . . . . . . . . . 5 71 4. JWS Header . . . . . . . . . . . . . . . . . . . . . . . . . . 6 72 4.1. Reserved Header Parameter Names . . . . . . . . . . . . . 6 73 4.2. Public Header Parameter Names . . . . . . . . . . . . . . 9 74 4.3. Private Header Parameter Names . . . . . . . . . . . . . . 9 75 5. Rules for Creating and Validating a JWS . . . . . . . . . . . 9 76 6. Base64url encoding as used by JWSs . . . . . . . . . . . . . . 11 77 7. Signing JWSs with Cryptographic Algorithms . . . . . . . . . . 11 78 7.1. Creating a JWS with HMAC SHA-256, HMAC SHA-384, or 79 HMAC SHA-512 . . . . . . . . . . . . . . . . . . . . . . . 12 80 7.2. Creating a JWS with RSA SHA-256, RSA SHA-384, or RSA 81 SHA-512 . . . . . . . . . . . . . . . . . . . . . . . . . 13 82 7.3. Creating a JWS with ECDSA P-256 SHA-256, ECDSA P-384 83 SHA-384, or ECDSA P-521 SHA-512 . . . . . . . . . . . . . 14 84 7.4. Additional Algorithms . . . . . . . . . . . . . . . . . . 16 85 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 86 9. Security Considerations . . . . . . . . . . . . . . . . . . . 16 87 9.1. Unicode Comparison Security Issues . . . . . . . . . . . . 17 88 10. Open Issues and Things To Be Done (TBD) . . . . . . . . . . . 17 89 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19 90 11.1. Normative References . . . . . . . . . . . . . . . . . . . 19 91 11.2. Informative References . . . . . . . . . . . . . . . . . . 20 92 Appendix A. JWS Examples . . . . . . . . . . . . . . . . . . . . 20 93 A.1. JWS using HMAC SHA-256 . . . . . . . . . . . . . . . . . . 21 94 A.1.1. Encoding . . . . . . . . . . . . . . . . . . . . . . . 21 95 A.1.2. Decoding . . . . . . . . . . . . . . . . . . . . . . . 22 96 A.1.3. Validating . . . . . . . . . . . . . . . . . . . . . . 22 97 A.2. JWS using RSA SHA-256 . . . . . . . . . . . . . . . . . . 23 98 A.2.1. Encoding . . . . . . . . . . . . . . . . . . . . . . . 23 99 A.2.2. Decoding . . . . . . . . . . . . . . . . . . . . . . . 26 100 A.2.3. Validating . . . . . . . . . . . . . . . . . . . . . . 26 101 A.3. JWS using ECDSA P-256 SHA-256 . . . . . . . . . . . . . . 27 102 A.3.1. Encoding . . . . . . . . . . . . . . . . . . . . . . . 27 103 A.3.2. Decoding . . . . . . . . . . . . . . . . . . . . . . . 28 104 A.3.3. Validating . . . . . . . . . . . . . . . . . . . . . . 29 105 Appendix B. Algorithm Identifier Cross-Reference . . . . . . . . 29 106 Appendix C. Notes on implementing base64url encoding without 107 padding . . . . . . . . . . . . . . . . . . . . . . . 31 108 Appendix D. Acknowledgements . . . . . . . . . . . . . . . . . . 32 109 Appendix E. Document History . . . . . . . . . . . . . . . . . . 33 110 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 33 112 1. Introduction 114 JSON Web Signature (JWS) is a compact signature format intended for 115 space constrained environments such as HTTP Authorization headers and 116 URI query parameters. The JWS signature mechanisms are independent 117 of the type of content being signed, allowing arbitrary content to be 118 signed. A related encryption capability is described in a separate 119 JSON Web Encryption (JWE) [JWE] specification. 121 2. Terminology 123 JSON Web Signature (JWS) A data structure cryptographically securing 124 a JWS Header Input and a JWS Payload Input with a JWS Crypto 125 Output. 127 JWS Header Input A string containing a base64url encoded JSON object 128 that describes the cryptographic operations applied to the JWS 129 Header Input and the JWS Payload Input. 131 JWS Payload Input A string containing base64url encoded content. 133 JWS Crypto Output A string containing base64url encoded 134 cryptographic material that secures the contents of the JWS Header 135 Input and the JWS Payload Input. 137 Decoded JWS Header Input JWS Header Input that has been base64url 138 decoded back into a JSON object. 140 Decoded JWS Payload Input JWS Payload Input that has been base64url 141 decoded. 143 Decoded JWS Crypto Output JWS Crypto Output that has been base64url 144 decoded back into cryptographic material. 146 JWS Signing Input The concatenation of the JWS Header Input, a 147 period ('.') character, and the JWS Payload Input. 149 Header Parameter Names The names of the members within the JSON 150 object represented in a JWS Header Input. 152 Header Parameter Values The values of the members within the JSON 153 object represented in a JWS Header Input. 155 Digital Signature For the purposes of this specification, we use 156 this term to encompass both Hash-based Message Authentication 157 Codes (HMACs), which can provide authenticity but not non- 158 repudiation, and digital signatures using public key algorithms, 159 which can provide both. Readers should be aware of this 160 distinction, despite the decision to use a single term for both 161 concepts to improve readability of the specification. 163 Base64url Encoding For the purposes of this specification, this term 164 always refers to the he URL- and filename-safe Base64 encoding 165 described in RFC 4648 [RFC4648], Section 5, with the '=' padding 166 characters omitted, as permitted by Section 3.2. 168 3. JSON Web Signature (JWS) Overview 170 JWSs represent content that is base64url encoded and digitally 171 signed, and optionally encrypted, using JSON data structures. A 172 portion of the base64url encoded content that is signed is the JWS 173 Payload Input. An accompanying base64url encoded JSON object - the 174 JWS Header Input - describes the signature method used. 176 The member names within the Decoded JWS Header Input are referred to 177 as Header Parameter Names. These names MUST be unique. The 178 corresponding values are referred to as Header Parameter Values. 180 JWSs contain a signature that ensures the integrity of the contents 181 of the JWS Header Input and the JWS Payload Input. This signature 182 value is the JWS Crypto Output. The JSON Header object MUST contain 183 an "alg" parameter, the value of which is a string that unambiguously 184 identifies the algorithm used to sign the JWS Header Input and the 185 JWS Payload Input to produce the JWS Crypto Output. 187 3.1. Example JWS 189 The following example JSON header object declares that the encoded 190 object is a JSON Web Token (JWT) [JWT] and the JWS Header Input and 191 the JWS Payload Input are signed using the HMAC SHA-256 algorithm: 192 {"typ":"JWT", 193 "alg":"HS256"} 195 Base64url encoding the UTF-8 representation of the JSON header object 196 yields this JWS Header Input value: 197 eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9 199 The following is an example of a JSON object that can be encoded to 200 produce a JWS Payload Input. (Note that the payload can be any 201 base64url encoded content, and need not be a base64url encoded JSON 202 object.) 203 {"iss":"joe", 204 "exp":1300819380, 205 "http://example.com/is_root":true} 207 Base64url encoding the UTF-8 representation of the JSON object yields 208 the following JWS Payload Input. 209 eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ 211 Signing the UTF-8 representation of the JWS Signing Input (the 212 concatenation of the JWS Header Input, a period ('.') character, and 213 the JWS Payload Input) with the HMAC SHA-256 algorithm and base64url 214 encoding the result, as per Section 7.1, yields this JWS Crypto 215 Output value: 216 dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk 218 This computation is illustrated in more detail in Appendix A.1. 220 4. JWS Header 222 The members of the JSON object represented by the Decoded JWS Header 223 Input describe the signature applied to the JWS Header Input and the 224 JWS Payload Input and optionally additional properties of the JWS. 225 Implementations MUST understand the entire contents of the header; 226 otherwise, the JWS MUST be rejected for processing. 228 4.1. Reserved Header Parameter Names 230 The following header parameter names are reserved. All the names are 231 short because a core goal of JWSs is for the representations to be 232 compact. 234 +-----------+--------+--------------+-------------------------------+ 235 | Header | JSON | Header | Header Parameter Semantics | 236 | Parameter | Value | Parameter | | 237 | Name | Type | Syntax | | 238 +-----------+--------+--------------+-------------------------------+ 239 | alg | string | StringAndURI | The "alg" (algorithm) header | 240 | | | | parameter identifies the | 241 | | | | cryptographic algorithm used | 242 | | | | to secure the JWS. A list of | 243 | | | | reserved alg values is in | 244 | | | | Table 3. The processing of | 245 | | | | the "alg" (algorithm) header | 246 | | | | parameter, if present, | 247 | | | | requires that the value of | 248 | | | | the "alg" header parameter | 249 | | | | MUST be one that is both | 250 | | | | supported and for which there | 251 | | | | exists a key for use with | 252 | | | | that algorithm associated | 253 | | | | with the signer of the | 254 | | | | content. The "alg" parameter | 255 | | | | value is case sensitive. | 256 | | | | This header parameter is | 257 | | | | REQUIRED. | 258 | typ | string | String | The "typ" (type) header | 259 | | | | parameter is used to declare | 260 | | | | the type of the signed | 261 | | | | content. The "typ" value is | 262 | | | | case sensitive. This header | 263 | | | | parameter is OPTIONAL. | 264 | jku | string | URL | The "jku" (JSON Key URL) | 265 | | | | header parameter is a URL | 266 | | | | that points to JSON-encoded | 267 | | | | public key certificates that | 268 | | | | can be used to validate the | 269 | | | | signature. The specification | 270 | | | | for this encoding is TBD. | 271 | | | | This header parameter is | 272 | | | | OPTIONAL. | 273 | kid | string | String | The "kid" (key ID) header | 274 | | | | parameter is a hint | 275 | | | | indicating which specific key | 276 | | | | owned by the signer should be | 277 | | | | used to validate the | 278 | | | | signature. This allows | 279 | | | | signers to explicitly signal | 280 | | | | a change of key to | 281 | | | | recipients. Omitting this | 282 | | | | parameter is equivalent to | 283 | | | | setting it to an empty | 284 | | | | string. The interpretation | 285 | | | | of the contents of the "kid" | 286 | | | | parameter is unspecified. | 287 | | | | This header parameter is | 288 | | | | OPTIONAL. | 289 | x5u | string | URL | The "x5u" (X.509 URL) header | 290 | | | | parameter is a URL utilizing | 291 | | | | TLS RFC 5785 [RFC5785] that | 292 | | | | points to an X.509 public key | 293 | | | | certificate or certificate | 294 | | | | chain that can be used to | 295 | | | | validate the signature. This | 296 | | | | certificate or certificate | 297 | | | | chain MUST use the PEM | 298 | | | | encoding RFC 1421 [RFC1421] | 299 | | | | and MUST conform to RFC 5280 | 300 | | | | [RFC5280]. This header | 301 | | | | parameter is OPTIONAL. | 302 | x5t | string | String | The "x5t" (x.509 certificate | 303 | | | | thumbprint) header parameter | 304 | | | | provides a base64url encoded | 305 | | | | SHA-1 thumbprint (a.k.a. | 306 | | | | digest) of the DER encoding | 307 | | | | of an X.509 certificate that | 308 | | | | can be used to match the | 309 | | | | certificate. This header | 310 | | | | parameter is OPTIONAL. | 311 +-----------+--------+--------------+-------------------------------+ 313 Table 1: Reserved Header Parameter Definitions 315 Additional reserved header parameter names MAY be defined via the 316 IANA JSON Web Signature Header Parameters registry, as per Section 8. 317 The syntax values used above are defined as follows: 319 +--------------+----------------------------------------------------+ 320 | Syntax Name | Syntax Definition | 321 +--------------+----------------------------------------------------+ 322 | IntDate | The number of seconds from 1970-01-01T0:0:0Z as | 323 | | measured in UTC until the desired date/time. See | 324 | | RFC 3339 [RFC3339] for details regarding | 325 | | date/times in general and UTC in particular. | 326 | String | Any string value MAY be used. | 327 | StringAndURI | Any string value MAY be used but a value | 328 | | containing a ":" character MUST be a URI as | 329 | | defined in RFC 3986 [RFC3986]. | 330 | URL | A URL as defined in RFC 1738 [RFC1738]. | 331 +--------------+----------------------------------------------------+ 333 Table 2: Header Parameter Syntax Definitions 335 4.2. Public Header Parameter Names 337 Additional header parameter names can be defined by those using JWSs. 338 However, in order to prevent collisions, any new header parameter 339 name or algorithm value SHOULD either be defined in the IANA JSON Web 340 Signature Header Parameters registry or be defined as a URI that 341 contains a collision resistant namespace. In each case, the definer 342 of the name or value MUST take reasonable precautions to make sure 343 they are in control of the part of the namespace they use to define 344 the header parameter name. 346 New header parameters should be introduced sparingly, as they can 347 result in non-interoperable JWSs. 349 4.3. Private Header Parameter Names 351 A producer and consumer of a JWS may agree to any header parameter 352 name that is not a Reserved Name Section 4.1 or a Public Name 353 Section 4.2. Unlike Public Names, these private names are subject to 354 collision and should be used with caution. 356 New header parameters should be introduced sparingly, as they can 357 result in non-interoperable JWSs. 359 5. Rules for Creating and Validating a JWS 361 To create a JWS, one MUST follow these steps: 363 1. Create the payload content to be encoded as the Decoded JWS 364 Payload Input. 366 2. Base64url encode the Decoded JWS Payload Input. This encoding 367 becomes the JWS Payload Input. 369 3. Create a JSON object containing a set of desired header 370 parameters. Note that white space is explicitly allowed in the 371 representation and no canonicalization is performed before 372 encoding. 374 4. Translate this JSON object's Unicode code points into UTF-8, as 375 defined in RFC 3629 [RFC3629]. 377 5. Base64url encode the UTF-8 representation of this JSON object as 378 defined in this specification (without padding). This encoding 379 becomes the JWS Header Input. 381 6. Compute the JWS Crypto Output in the manner defined for the 382 particular algorithm being used. The JWS Signing Input is always 383 the concatenation of the JWS Header Input, a period ('.') 384 character, and the JWS Payload Input. The "alg" header parameter 385 MUST be present in the JSON Header Input, with the algorithm 386 value accurately representing the algorithm used to construct the 387 JWS Crypto Input. 389 When validating a JWS, the following steps MUST be taken. If any of 390 the listed steps fails, then the signed content MUST be rejected. 392 1. The JWS Payload Input MUST be successfully base64url decoded 393 following the restriction given in this specification that no 394 padding characters have been used. 396 2. The JWS Header Input MUST be successfully base64url decoded 397 following the restriction given in this specification that no 398 padding characters have been used. 400 3. The Decoded JWS Header Input MUST be completely valid JSON syntax 401 conforming to RFC 4627 [RFC4627]. 403 4. The JWS Crypto Output MUST be successfully base64url decoded 404 following the restriction given in this specification that no 405 padding characters have been used. 407 5. The JWS Header Input MUST be validated to only include parameters 408 and values whose syntax and semantics are both understood and 409 supported. 411 6. The JWS Crypto Output MUST be successfully validated against the 412 JWS Header Input and JWS Payload Input in the manner defined for 413 the algorithm being used, which MUST be accurately represented by 414 the value of the "alg" header parameter, which MUST be present. 416 Processing a JWS inevitably requires comparing known strings to 417 values in the header. For example, in checking what the algorithm 418 is, the Unicode string encoding "alg" will be checked against the 419 member names in the Decoded JWS Header Input to see if there is a 420 matching header parameter name. A similar process occurs when 421 determining if the value of the "alg" header parameter represents a 422 supported algorithm. Comparing Unicode strings, however, has 423 significant security implications, as per Section 9. 425 Comparisons between JSON strings and other Unicode strings MUST be 426 performed as specified below: 428 1. Remove any JSON applied escaping to produce an array of Unicode 429 code points. 431 2. Unicode Normalization [USA15] MUST NOT be applied at any point to 432 either the JSON string or to the string it is to be compared 433 against. 435 3. Comparisons between the two strings MUST be performed as a 436 Unicode code point to code point equality comparison. 438 6. Base64url encoding as used by JWSs 440 JWSs make use of the base64url encoding as defined in RFC 4648 441 [RFC4648]. As allowed by Section 3.2 of the RFC, this specification 442 mandates that base64url encoding when used with JWSs MUST NOT use 443 padding. The reason for this restriction is that the padding 444 character ('=') is not URL safe. 446 For notes on implementing base64url encoding without padding, see 447 Appendix C. 449 7. Signing JWSs with Cryptographic Algorithms 451 JWSs use specific cryptographic algorithms to sign the contents of 452 the JWS Header Input and the JWS Payload Input. The use of the 453 following algorithms for producing JWSs is defined in this section. 454 The table below is the list of "alg" header parameter values reserved 455 by this specification, each of which is explained in more detail in 456 the following sections: 458 +--------------------+----------------------------------------------+ 459 | Alg Parameter | Algorithm | 460 | Value | | 461 +--------------------+----------------------------------------------+ 462 | HS256 | HMAC using SHA-256 hash algorithm | 463 | HS384 | HMAC using SHA-384 hash algorithm | 464 | HS512 | HMAC using SHA-512 hash algorithm | 465 | RS256 | RSA using SHA-256 hash algorithm | 466 | RS384 | RSA using SHA-384 hash algorithm | 467 | RS512 | RSA using SHA-512 hash algorithm | 468 | ES256 | ECDSA using P-256 curve and SHA-256 hash | 469 | | algorithm | 470 | ES384 | ECDSA using P-384 curve and SHA-384 hash | 471 | | algorithm | 472 | ES512 | ECDSA using P-521 curve and SHA-512 hash | 473 | | algorithm | 474 +--------------------+----------------------------------------------+ 476 Table 3: JSON Web Signature Reserved Algorithm Values 478 See Appendix B for a table cross-referencing the "alg" values used in 479 this specification with the equivalent identifiers used by other 480 standards and software packages. 482 Of these algorithms, only HMAC SHA-256 MUST be implemented by 483 conforming implementations. It is RECOMMENDED that implementations 484 also support the RSA SHA-256 and ECDSA P-256 SHA-256 algorithms. 485 Support for other algorithms is OPTIONAL. 487 The signed content for a JWS is the same for all algorithms: the 488 concatenation of the JWS Header Input, a period ('.') character, and 489 the JWS Payload Input. This character sequence is referred to as the 490 JWS Signing Input. Note that if the JWS represents a JWT, this 491 corresponds to the portion of the JWT representation preceding the 492 second period character. The UTF-8 representation of the JWS Signing 493 Input is passed to the respective signing algorithms. 495 7.1. Creating a JWS with HMAC SHA-256, HMAC SHA-384, or HMAC SHA-512 497 Hash based Message Authentication Codes (HMACs) enable one to use a 498 secret plus a cryptographic hash function to generate a Message 499 Authentication Code (MAC). This can be used to demonstrate that the 500 MAC matches the hashed content, in this case the JWS Signing Input, 501 which therefore demonstrates that whoever generated the MAC was in 502 possession of the secret. The means of exchanging the shared key is 503 outside the scope of this specification. 505 The algorithm for implementing and validating HMACs is provided in 506 RFC 2104 [RFC2104]. This section defines the use of the HMAC SHA- 507 256, HMAC SHA-384, and HMAC SHA-512 cryptographic hash functions as 508 defined in FIPS 180-3 [FIPS.180-3]. The reserved "alg" header 509 parameter values "HS256", "HS384", and "HS512" are used in the JWS 510 Header Input to indicate that the JWS Crypto Output contains a 511 base64url encoded HMAC value using the respective hash function. 513 The HMAC SHA-256 MAC is generated as follows: 515 1. Apply the HMAC SHA-256 algorithm to the UTF-8 representation of 516 the JWS Signing Input using the shared key to produce an HMAC. 518 2. Base64url encode the HMAC, as defined in this specification. 520 The output is the JWS Crypto Output for that JWS. 522 The HMAC SHA-256 MAC for a JWS is validated as follows: 524 1. Apply the HMAC SHA-256 algorithm to the UTF-8 representation of 525 the JWS Signing Input of the JWS using the shared key. 527 2. Base64url encode the previously generated HMAC, as defined in 528 this specification. 530 3. If the JWS Crypto Output and the previously calculated value 531 exactly match, then one has confirmation that the key was used to 532 generate the HMAC on the JWS and that the contents of the JWS 533 have not be tampered with. 535 4. If the validation fails, the signed content MUST be rejected. 537 Signing with the HMAC SHA-384 and HMAC SHA-512 algorithms is 538 performed identically to the procedure for HMAC SHA-256 - just with 539 correspondingly longer key and result values. 541 7.2. Creating a JWS with RSA SHA-256, RSA SHA-384, or RSA SHA-512 543 This section defines the use of the RSASSA-PKCS1-v1_5 signature 544 algorithm as defined in RFC 3447 [RFC3447], Section 8.2 (commonly 545 known as PKCS#1), using SHA-256, SHA-384, or SHA-512 as the hash 546 function. The RSASSA-PKCS1-v1_5 algorithm is described in FIPS 186-3 547 [FIPS.186-3], Section 5.5, and the SHA-256, SHA-384, and SHA-512 548 cryptographic hash functions are defined in FIPS 180-3 [FIPS.180-3]. 549 The reserved "alg" header parameter values "RS256", "RS384", and 550 "RS512" are used in the JWS Header Input to indicate that the JWS 551 Crypto Output contains a base64url encoded RSA signature using the 552 respective hash function. 554 The public keys employed may be retrieved using Header Parameter 555 methods described in Section 4.1 or may be distributed using methods 556 that are outside the scope of this specification. 558 A 2048-bit or longer key length MUST be used with this algorithm. 560 The RSA SHA-256 signature is generated as follows: 562 1. Generate a digital signature of the UTF-8 representation of the 563 JWS Signing Input using RSASSA-PKCS1-V1_5-SIGN and the SHA-256 564 hash function with the desired private key. The output will be a 565 byte array. 567 2. Base64url encode the byte array, as defined in this 568 specification. 570 The output is the JWS Crypto Output for that JWS. 572 The RSA SHA-256 signature for a JWS is validated as follows: 574 1. Take the JWS Crypto Output and base64url decode it into a byte 575 array. If decoding fails, the signed content MUST be rejected. 577 2. Submit the UTF-8 representation of the JWS Signing Input and the 578 public key corresponding to the private key used by the signer to 579 the RSASSA-PKCS1-V1_5-VERIFY algorithm using SHA-256 as the hash 580 function. 582 3. If the validation fails, the signed content MUST be rejected. 584 Signing with the RSA SHA-384 and RSA SHA-512 algorithms is performed 585 identically to the procedure for RSA SHA-256 - just with 586 correspondingly longer key and result values. 588 7.3. Creating a JWS with ECDSA P-256 SHA-256, ECDSA P-384 SHA-384, or 589 ECDSA P-521 SHA-512 591 The Elliptic Curve Digital Signature Algorithm (ECDSA) is defined by 592 FIPS 186-3 [FIPS.186-3]. ECDSA provides for the use of Elliptic 593 Curve cryptography, which is able to provide equivalent security to 594 RSA cryptography but using shorter key lengths and with greater 595 processing speed. This means that ECDSA signatures will be 596 substantially smaller in terms of length than equivalently strong RSA 597 Digital Signatures. 599 This specification defines the use of ECDSA with the P-256 curve and 600 the SHA-256 cryptographic hash function, ECDSA with the P-384 curve 601 and the SHA-384 hash function, and ECDSA with the P-521 curve and the 602 SHA-512 hash function. The P-256, P-384, and P-521 curves are also 603 defined in FIPS 186-3. The reserved "alg" header parameter values 604 "ES256", "ES384", and "ES512" are used in the JWS Header Input to 605 indicate that the JWS Crypto Output contains a based64url encoded 606 ECDSA P-256 SHA-256, ECDSA P-384 SHA-384, or ECDSA P-521 SHA-512 607 signature, respectively. 609 The public keys employed may be retrieved using Header Parameter 610 methods described in Section 4.1 or may be distributed using methods 611 that are outside the scope of this specification. 613 A JWS is signed with an ECDSA P-256 SHA-256 signature as follows: 615 1. Generate a digital signature of the UTF-8 representation of the 616 JWS Signing Input using ECDSA P-256 SHA-256 with the desired 617 private key. The output will be the EC point (R, S), where R and 618 S are unsigned integers. 620 2. Turn R and S into byte arrays in big endian order. Each array 621 will be 32 bytes long. 623 3. Concatenate the two byte arrays in the order R and then S. 625 4. Base64url encode the 64 byte array, as defined in this 626 specification. 628 The output is the JWS Crypto Output for the JWS. 630 The ECDSA P-256 SHA-256 signature for a JWS is validated as follows: 632 1. Take the JWS Crypto Output and base64url decode it into a byte 633 array. If decoding fails, the signed content MUST be rejected. 635 2. The output of the base64url decoding MUST be a 64 byte array. 637 3. Split the 64 byte array into two 32 byte arrays. The first array 638 will be R and the second S. Remember that the byte arrays are in 639 big endian byte order; please check the ECDSA validator in use to 640 see what byte order it requires. 642 4. Submit the UTF-8 representation of the JWS Signing Input, R, S 643 and the public key (x, y) to the ECDSA P-256 SHA-256 validator. 645 5. If the validation fails, the signed content MUST be rejected. 647 The ECDSA validator will then determine if the digital signature is 648 valid, given the inputs. Note that ECDSA digital signature contains 649 a value referred to as K, which is a random number generated for each 650 digital signature instance. This means that two ECDSA digital 651 signatures using exactly the same input parameters will output 652 different signatures because their K values will be different. The 653 consequence of this is that one must validate an ECDSA signature by 654 submitting the previously specified inputs to an ECDSA validator. 656 Signing with the ECDSA P-384 SHA-384 and ECDSA P-521 SHA-512 657 algorithms is performed identically to the procedure for ECDSA P-256 658 SHA-256 - just with correspondingly longer key and result values. 660 7.4. Additional Algorithms 662 Additional algorithms MAY be used to protect JWSs with corresponding 663 "alg" header parameter values being defined to refer to them. New 664 "alg" header parameter values SHOULD either be defined in the IANA 665 JSON Web Signature Algorithms registry or be a URI that contains a 666 collision resistant namespace. In particular, the use of algorithm 667 identifiers defined in XML DSIG [RFC3275] and related specifications 668 is permitted. 670 8. IANA Considerations 672 This specification calls for: 674 o A new IANA registry entitled "JSON Web Signature Header 675 Parameters" for reserved header parameter names is defined in 676 Section 4.1. Inclusion in the registry is RFC Required in the RFC 677 5226 [RFC5226] sense for reserved JWS header parameter names that 678 are intended to be interoperable between implementations. The 679 registry will just record the reserved header parameter name and a 680 pointer to the RFC that defines it. This specification defines 681 inclusion of the header parameter names defined in Table 1. 683 o A new IANA registry entitled "JSON Web Signature Algorithms" for 684 reserved values used with the "alg" header parameter values is 685 defined in Section 7.4. Inclusion in the registry is RFC Required 686 in the RFC 5226 [RFC5226] sense. The registry will just record 687 the "alg" value and a pointer to the RFC that defines it. This 688 specification defines inclusion of the algorithm values defined in 689 Table 3. 691 9. Security Considerations 693 TBD: Lots of work to do here. We need to remember to look into any 694 issues relating to security and JSON parsing. One wonders just how 695 secure most JSON parsing libraries are. Were they ever hardened for 696 security scenarios? If not, what kind of holes does that open up? 697 Also, we need to walk through the JSON standard and see what kind of 698 issues we have especially around comparison of names. For instance, 699 comparisons of header parameter names and other parameters must occur 700 after they are unescaped. Need to also put in text about: Importance 701 of keeping secrets secret. Rotating keys. Strengths and weaknesses 702 of the different algorithms. 704 TBD: Need to put in text about why strict JSON validation is 705 necessary. Basically, that if malformed JSON is received then the 706 intent of the sender is impossible to reliably discern. 708 TBD: Write security considerations about the implications of using a 709 SHA-1 hash (for compatibility reasons) for the "x5t" (x.509 710 certificate thumbprint). 712 9.1. Unicode Comparison Security Issues 714 Header parameter names in JWSs are Unicode strings. For security 715 reasons, the representations of these names must be compared verbatim 716 after performing any escape processing (as per RFC 4627 [RFC4627], 717 Section 2.5). 719 This means, for instance, that these JSON strings must compare as 720 being equal ("sig", "\u0073ig"), whereas these must all compare as 721 being not equal to the first set or to each other ("SIG", "Sig", 722 "si\u0047"). 724 JSON strings MAY contain characters outside the Unicode Basic 725 Multilingual Plane. For instance, the G clef character (U+1D11E) may 726 be represented in a JSON string as "\uD834\uDD1E". Ideally, JWS 727 implementations SHOULD ensure that characters outside the Basic 728 Multilingual Plane are preserved and compared correctly; 729 alternatively, if this is not possible due to these characters 730 exercising limitations present in the underlying JSON implementation, 731 then input containing them MUST be rejected. 733 10. Open Issues and Things To Be Done (TBD) 735 The following items remain to be done in this draft (and related 736 drafts): 738 o Consider whether there is a better term than "Digital Signature" 739 for the concept that includes both HMACs and digital signatures 740 using public keys. 742 o Consider whether we really want to allow private header parameter 743 names that are not registered with IANA and are not in collision- 744 resistant namespaces. Eventually this could result in interop 745 nightmares where you need to have different code to talk to 746 different endpoints that "knows" about each endpoints' private 747 parameters. 749 o Clarify the optional ability to provide type information in the 750 JWS header. Specifically, clarify the intended use of the "typ" 751 Header Parameter, whether it conveys syntax or semantics, and 752 indeed, whether this is the right approach. Also clarify the 753 relationship between these type values and MIME [RFC2045] types. 755 o Clarify the semantics of the "kid" (key ID) header parameter. 756 Open issues include: What happens if a "kid" header is received 757 with an unrecognized value? Is that an error? Should it be 758 treated as if it's empty? What happens if the header has a 759 recognized value but the value doesn't match the key associated 760 with that value, but it does match another key that is associated 761 with the issuer? Is that an error? 763 o Consider whether a key type parameter should also be introduced. 765 o Since RFC 3447 Section 8 explicitly calls for people NOT to adopt 766 RSASSA-PKCS1 for new applications and instead requests that people 767 transition to RSASSA-PSS, we probably need some Security 768 Considerations text explaining why RSASSA-PKCS1 is being used 769 (it's what's commonly implemented) and what the potential 770 consequences are. 772 o Add Security Considerations text on timing attacks. 774 o Finish the Security Considerations section. 776 o Sort out what to do with the IANA registries if this is first 777 standardized as an OpenID specification. 779 o Write the related specification for encoding public keys using 780 JSON, as per the agreement documented at 781 http://self-issued.info/?p=390. This will be used by the "jku" 782 (JSON Key URL) header parameter. 784 o Finish the companion encryption specification, per the agreements 785 documented at http://self-issued.info/?p=378. 787 11. References 788 11.1. Normative References 790 [FIPS.180-3] 791 National Institute of Standards and Technology, "Secure 792 Hash Standard (SHS)", FIPS PUB 180-3, October 2008. 794 [FIPS.186-3] 795 National Institute of Standards and Technology, "Digital 796 Signature Standard (DSS)", FIPS PUB 186-3, June 2009. 798 [JWT] Jones, M., Balfanz, D., Bradley, J., Goland, Y., Panzer, 799 J., Sakimura, N., and P. Tarjan, "JSON Web Token (JWT)", 800 March 2011. 802 [RFC1421] Linn, J., "Privacy Enhancement for Internet Electronic 803 Mail: Part I: Message Encryption and Authentication 804 Procedures", RFC 1421, February 1993. 806 [RFC1738] Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform 807 Resource Locators (URL)", RFC 1738, December 1994. 809 [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail 810 Extensions (MIME) Part One: Format of Internet Message 811 Bodies", RFC 2045, November 1996. 813 [RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed- 814 Hashing for Message Authentication", RFC 2104, 815 February 1997. 817 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 818 Requirement Levels", BCP 14, RFC 2119, March 1997. 820 [RFC3339] Klyne, G., Ed. and C. Newman, "Date and Time on the 821 Internet: Timestamps", RFC 3339, July 2002. 823 [RFC3447] Jonsson, J. and B. Kaliski, "Public-Key Cryptography 824 Standards (PKCS) #1: RSA Cryptography Specifications 825 Version 2.1", RFC 3447, February 2003. 827 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 828 10646", STD 63, RFC 3629, November 2003. 830 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 831 Resource Identifier (URI): Generic Syntax", STD 66, 832 RFC 3986, January 2005. 834 [RFC4627] Crockford, D., "The application/json Media Type for 835 JavaScript Object Notation (JSON)", RFC 4627, July 2006. 837 [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data 838 Encodings", RFC 4648, October 2006. 840 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 841 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 842 May 2008. 844 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 845 Housley, R., and W. Polk, "Internet X.509 Public Key 846 Infrastructure Certificate and Certificate Revocation List 847 (CRL) Profile", RFC 5280, May 2008. 849 [RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known 850 Uniform Resource Identifiers (URIs)", RFC 5785, 851 April 2010. 853 [USA15] Davis, M., Whistler, K., and M. Duerst, "Unicode 854 Normalization Forms", Unicode Standard Annex 15, 09 2009. 856 11.2. Informative References 858 [CanvasApp] 859 Facebook, "Canvas Applications", 2010. 861 [JCA] Oracle, "Java Cryptography Architecture", 2011. 863 [JSS] Bradley, J. and N. Sakimura (editor), "JSON Simple Sign", 864 September 2010. 866 [JWE] Jones, M., Bradley, J., and N. Sakimura, "JSON Web 867 Encryption (JWE)", March 2011. 869 [MagicSignatures] 870 Panzer (editor), J., Laurie, B., and D. Balfanz, "Magic 871 Signatures", August 2010. 873 [RFC3275] Eastlake, D., Reagle, J., and D. Solo, "(Extensible Markup 874 Language) XML-Signature Syntax and Processing", RFC 3275, 875 March 2002. 877 Appendix A. JWS Examples 879 This section provides several examples of JWSs. While these examples 880 all represent JSON Web Tokens (JWTs) [JWT], the payload can be any 881 base64url encoded content. 883 A.1. JWS using HMAC SHA-256 885 A.1.1. Encoding 887 The following example JSON header object declares that the data 888 structure is a JSON Web Token (JWT) [JWT] and the JWS Signing Input 889 is signed using the HMAC SHA-256 algorithm. Note that white space is 890 explicitly allowed in Decoded JWS Header Input strings and no 891 canonicalization is performed before encoding. 892 {"typ":"JWT", 893 "alg":"HS256"} 895 The following byte array contains the UTF-8 characters for the 896 Decoded JWS Header Input: 898 [123, 34, 116, 121, 112, 34, 58, 34, 74, 87, 84, 34, 44, 13, 10, 32, 899 34, 97, 108, 103, 34, 58, 34, 72, 83, 50, 53, 54, 34, 125] 901 Base64url encoding this UTF-8 representation yields this JWS Header 902 Input value: 903 eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9 905 The Decoded JWS Payload Input used in this example follows. (Note 906 that the payload can be any base64url encoded content, and need not 907 be a base64url encoded JSON object.) 908 {"iss":"joe", 909 "exp":1300819380, 910 "http://example.com/is_root":true} 912 The following byte array contains the UTF-8 characters for the 913 Decoded JWS Payload Input: 915 [123, 34, 105, 115, 115, 34, 58, 34, 106, 111, 101, 34, 44, 13, 10, 916 32, 34, 101, 120, 112, 34, 58, 49, 51, 48, 48, 56, 49, 57, 51, 56, 917 48, 44, 13, 10, 32, 34, 104, 116, 116, 112, 58, 47, 47, 101, 120, 97, 918 109, 112, 108, 101, 46, 99, 111, 109, 47, 105, 115, 95, 114, 111, 919 111, 116, 34, 58, 116, 114, 117, 101, 125] 921 Base64url encoding the above yields the JWS Payload Input value: 922 eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ 924 Concatenating the JWS Header Input, a period character, and the JWS 925 Payload Input yields this JWS Signing Input value (with line breaks 926 for display purposes only): 927 eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9 928 . 929 eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ 930 The UTF-8 representation of the JWS Signing Input is the following 931 byte array: 933 [101, 121, 74, 48, 101, 88, 65, 105, 79, 105, 74, 75, 86, 49, 81, 934 105, 76, 65, 48, 75, 73, 67, 74, 104, 98, 71, 99, 105, 79, 105, 74, 935 73, 85, 122, 73, 49, 78, 105, 74, 57, 46, 101, 121, 74, 112, 99, 51, 936 77, 105, 79, 105, 74, 113, 98, 50, 85, 105, 76, 65, 48, 75, 73, 67, 937 74, 108, 101, 72, 65, 105, 79, 106, 69, 122, 77, 68, 65, 52, 77, 84, 938 107, 122, 79, 68, 65, 115, 68, 81, 111, 103, 73, 109, 104, 48, 100, 939 72, 65, 54, 76, 121, 57, 108, 101, 71, 70, 116, 99, 71, 120, 108, 76, 940 109, 78, 118, 98, 83, 57, 112, 99, 49, 57, 121, 98, 50, 57, 48, 73, 941 106, 112, 48, 99, 110, 86, 108, 102, 81] 943 HMACs are generated using keys. This example uses the key 944 represented by the following byte array: 946 [3, 35, 53, 75, 43, 15, 165, 188, 131, 126, 6, 101, 119, 123, 166, 947 143, 90, 179, 40, 230, 240, 84, 201, 40, 169, 15, 132, 178, 210, 80, 948 46, 191, 211, 251, 90, 146, 210, 6, 71, 239, 150, 138, 180, 195, 119, 949 98, 61, 34, 61, 46, 33, 114, 5, 46, 79, 8, 192, 205, 154, 245, 103, 950 208, 128, 163] 952 Running the HMAC SHA-256 algorithm on the UTF-8 representation of the 953 JWS Signing Input with this key yields the following byte array: 955 [116, 24, 223, 180, 151, 153, 224, 37, 79, 250, 96, 125, 216, 173, 956 187, 186, 22, 212, 37, 77, 105, 214, 191, 240, 91, 88, 5, 88, 83, 957 132, 141, 121] 959 Base64url encoding the above HMAC output yields the JWS Crypto Output 960 value: 961 dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk 963 A.1.2. Decoding 965 Decoding the JWS first requires removing the base64url encoding from 966 the JWS Header Input, the JWS Payload Input, and the JWS Crypto 967 Output. We base64url decode the inputs per Section 6 and turn them 968 into the corresponding byte arrays. We translate the header input 969 byte array containing UTF-8 encoded characters into the Decoded JWS 970 Header Input string. 972 A.1.3. Validating 974 Next we validate the decoded results. Since the "alg" parameter in 975 the header is "HS256", we validate the HMAC SHA-256 signature 976 contained in the JWS Crypto Output. If any of the validation steps 977 fail, the signed content MUST be rejected. 979 First, we validate that the decoded JWS Header Input string is legal 980 JSON. 982 To validate the signature, we repeat the previous process of using 983 the correct key and the UTF-8 representation of the JWS Signing Input 984 as input to a SHA-256 HMAC function and then taking the output and 985 determining if it matches the Decoded JWS Crypto Output. If it 986 matches exactly, the signature has been validated. 988 A.2. JWS using RSA SHA-256 990 A.2.1. Encoding 992 The Decoded JWS Header Input in this example is different from the 993 previous example in two ways: First, because a different algorithm is 994 being used, the "alg" value is different. Second, for illustration 995 purposes only, the optional "typ" parameter is not used. (This 996 difference is not related to the signature algorithm employed.) The 997 Decoded JWS Header Input used is: 998 {"alg":"RS256"} 1000 The following byte array contains the UTF-8 characters for the 1001 Decoded JWS Header Input: 1003 [123, 34, 97, 108, 103, 34, 58, 34, 82, 83, 50, 53, 54, 34, 125] 1005 Base64url encoding this UTF-8 representation yields this JWS Header 1006 Input value: 1007 eyJhbGciOiJSUzI1NiJ9 1009 The Decoded JWS Payload Input used in this example, which follows, is 1010 the same as in the previous example. Since the JWS Payload Input 1011 will therefore be the same, its computation is not repeated here. 1012 {"iss":"joe", 1013 "exp":1300819380, 1014 "http://example.com/is_root":true} 1016 Concatenating the JWS Header Input, a period character, and the JWS 1017 Payload Input yields this JWS Signing Input value (with line breaks 1018 for display purposes only): 1019 eyJhbGciOiJSUzI1NiJ9 1020 . 1021 eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ 1023 The UTF-8 representation of the JWS Signing Input is the following 1024 byte array: 1026 [101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 83, 85, 122, 73, 1027 49, 78, 105, 74, 57, 46, 101, 121, 74, 112, 99, 51, 77, 105, 79, 105, 1028 74, 113, 98, 50, 85, 105, 76, 65, 48, 75, 73, 67, 74, 108, 101, 72, 1029 65, 105, 79, 106, 69, 122, 77, 68, 65, 52, 77, 84, 107, 122, 79, 68, 1030 65, 115, 68, 81, 111, 103, 73, 109, 104, 48, 100, 72, 65, 54, 76, 1031 121, 57, 108, 101, 71, 70, 116, 99, 71, 120, 108, 76, 109, 78, 118, 1032 98, 83, 57, 112, 99, 49, 57, 121, 98, 50, 57, 48, 73, 106, 112, 48, 1033 99, 110, 86, 108, 102, 81] 1035 The RSA key consists of a public part (n, e), and a private exponent 1036 d. The values of the RSA key used in this example, presented as the 1037 byte arrays representing big endian integers are: 1039 +-----------+-------------------------------------------------------+ 1040 | Parameter | Value | 1041 | Name | | 1042 +-----------+-------------------------------------------------------+ 1043 | n | [161, 248, 22, 10, 226, 227, 201, 180, 101, 206, 141, | 1044 | | 45, 101, 98, 99, 54, 43, 146, 125, 190, 41, 225, 240, | 1045 | | 36, 119, 252, 22, 37, 204, 144, 161, 54, 227, 139, | 1046 | | 217, 52, 151, 197, 182, 234, 99, 221, 119, 17, 230, | 1047 | | 124, 116, 41, 249, 86, 176, 251, 138, 143, 8, 154, | 1048 | | 220, 75, 105, 137, 60, 193, 51, 63, 83, 237, 208, 25, | 1049 | | 184, 119, 132, 37, 47, 236, 145, 79, 228, 133, 119, | 1050 | | 105, 89, 75, 234, 66, 128, 211, 44, 15, 85, 191, 98, | 1051 | | 148, 79, 19, 3, 150, 188, 110, 155, 223, 110, 189, | 1052 | | 210, 189, 163, 103, 142, 236, 160, 198, 104, 247, 1, | 1053 | | 179, 141, 191, 251, 56, 200, 52, 44, 226, 254, 109, | 1054 | | 39, 250, 222, 74, 90, 72, 116, 151, 157, 212, 185, | 1055 | | 207, 154, 222, 196, 199, 91, 5, 133, 44, 44, 15, 94, | 1056 | | 248, 165, 193, 117, 3, 146, 249, 68, 232, 237, 100, | 1057 | | 193, 16, 198, 182, 71, 96, 154, 164, 120, 58, 235, | 1058 | | 156, 108, 154, 215, 85, 49, 48, 80, 99, 139, 131, | 1059 | | 102, 92, 111, 111, 122, 130, 163, 150, 112, 42, 31, | 1060 | | 100, 27, 130, 211, 235, 242, 57, 34, 25, 73, 31, 182, | 1061 | | 134, 135, 44, 87, 22, 245, 10, 248, 53, 141, 154, | 1062 | | 139, 157, 23, 195, 64, 114, 143, 127, 135, 216, 154, | 1063 | | 24, 216, 252, 171, 103, 173, 132, 89, 12, 46, 207, | 1064 | | 117, 147, 57, 54, 60, 7, 3, 77, 111, 96, 111, 158, | 1065 | | 33, 224, 84, 86, 202, 229, 233, 161] | 1066 | e | [1, 0, 1] | 1067 | d | [18, 174, 113, 164, 105, 205, 10, 43, 195, 126, 82, | 1068 | | 108, 69, 0, 87, 31, 29, 97, 117, 29, 100, 233, 73, | 1069 | | 112, 123, 98, 89, 15, 157, 11, 165, 124, 150, 60, 64, | 1070 | | 30, 63, 207, 47, 44, 211, 189, 236, 136, 229, 3, 191, | 1071 | | 198, 67, 155, 11, 40, 200, 47, 125, 55, 151, 103, 31, | 1072 | | 82, 19, 238, 216, 193, 90, 37, 216, 213, 206, 160, 2, | 1073 | | 94, 227, 171, 46, 139, 127, 121, 33, 111, 198, 59, | 1074 | | 234, 86, 39, 83, 180, 6, 68, 198, 161, 81, 39, 217, | 1075 | | 178, 149, 69, 64, 160, 187, 225, 163, 5, 86, 152, 45, | 1076 | | 78, 159, 222, 95, 100, 37, 241, 77, 75, 113, 52, 65, | 1077 | | 181, 93, 199, 59, 155, 74, 237, 204, 146, 172, 227, | 1078 | | 146, 126, 55, 245, 125, 12, 253, 94, 117, 129, 250, | 1079 | | 81, 44, 143, 73, 97, 169, 235, 11, 128, 248, 168, 7, | 1080 | | 70, 114, 138, 85, 255, 70, 71, 31, 52, 37, 6, 59, | 1081 | | 157, 83, 100, 47, 94, 222, 30, 132, 214, 19, 8, 26, | 1082 | | 250, 92, 34, 208, 81, 40, 91, 214, 59, 148, 59, 86, | 1083 | | 93, 137, 138, 5, 104, 84, 19, 229, 60, 60, 108, 101, | 1084 | | 37, 255, 31, 227, 78, 61, 220, 112, 240, 213, 100, | 1085 | | 80, 253, 164, 139, 161, 46, 16, 78, 157, 235, 159, | 1086 | | 184, 24, 129, 225, 196, 189, 242, 93, 146, 71, 244, | 1087 | | 80, 200, 101, 146, 121, 104, 231, 115, 52, 244, 65, | 1088 | | 79, 117, 167, 80, 225, 57, 84, 110, 58, 138, 115, | 1089 | | 157] | 1090 +-----------+-------------------------------------------------------+ 1092 The RSA private key (n, d) is then passed to the RSA signing 1093 function, which also takes the hash type, SHA-256, and the UTF-8 1094 representation of the JWS Signing Input as inputs. The result of the 1095 signature is a byte array S, which represents a big endian integer. 1096 In this example, S is: 1098 +--------+----------------------------------------------------------+ 1099 | Result | Value | 1100 | Name | | 1101 +--------+----------------------------------------------------------+ 1102 | S | [112, 46, 33, 137, 67, 232, 143, 209, 30, 181, 216, 45, | 1103 | | 191, 120, 69, 243, 65, 6, 174, 27, 129, 255, 247, 115, | 1104 | | 17, 22, 173, 209, 113, 125, 131, 101, 109, 66, 10, 253, | 1105 | | 60, 150, 238, 221, 115, 162, 102, 62, 81, 102, 104, 123, | 1106 | | 0, 11, 135, 34, 110, 1, 135, 237, 16, 115, 249, 69, 229, | 1107 | | 130, 173, 252, 239, 22, 216, 90, 121, 142, 232, 198, | 1108 | | 109, 219, 61, 184, 151, 91, 23, 208, 148, 2, 190, 237, | 1109 | | 213, 217, 217, 112, 7, 16, 141, 178, 129, 96, 213, 248, | 1110 | | 4, 12, 167, 68, 87, 98, 184, 31, 190, 127, 249, 217, 46, | 1111 | | 10, 231, 111, 36, 242, 91, 51, 187, 230, 244, 74, 230, | 1112 | | 30, 177, 4, 10, 203, 32, 4, 77, 62, 249, 18, 142, 212, | 1113 | | 1, 48, 121, 91, 212, 189, 59, 65, 238, 202, 208, 102, | 1114 | | 171, 101, 25, 129, 253, 228, 141, 247, 127, 55, 45, 195, | 1115 | | 139, 159, 175, 221, 59, 239, 177, 139, 93, 163, 204, 60, | 1116 | | 46, 176, 47, 158, 58, 65, 214, 18, 202, 173, 21, 145, | 1117 | | 18, 115, 160, 95, 35, 185, 232, 56, 250, 175, 132, 157, | 1118 | | 105, 132, 41, 239, 90, 30, 136, 121, 130, 54, 195, 212, | 1119 | | 14, 96, 69, 34, 165, 68, 200, 242, 122, 122, 45, 184, 6, | 1120 | | 99, 209, 108, 247, 202, 234, 86, 222, 64, 92, 178, 33, | 1121 | | 90, 69, 178, 194, 85, 102, 181, 90, 193, 167, 72, 160, | 1122 | | 112, 223, 200, 163, 42, 70, 149, 67, 208, 25, 238, 251, | 1123 | | 71] | 1124 +--------+----------------------------------------------------------+ 1126 Base64url encoding the signature produces this value for the JWS 1127 Crypto Output: 1128 cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZmh7AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjbKBYNX4BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHlb1L07Qe7K0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZESc6BfI7noOPqvhJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AXLIhWkWywlVmtVrBp0igcN_IoypGlUPQGe77Rw 1130 A.2.2. Decoding 1132 Decoding the JWS from this example requires processing the JWS Header 1133 Input and JWS Payload Input exactly as done in the first example. 1135 A.2.3. Validating 1137 Since the "alg" parameter in the header is "RS256", we validate the 1138 RSA SHA-256 signature contained in the JWS Crypto Output. If any of 1139 the validation steps fail, the signed content MUST be rejected. 1141 First, we validate that the decoded JWS Header Input string is legal 1142 JSON. 1144 Validating the JWS Crypto Output is a little different from the 1145 previous example. First, we base64url decode the JWS Crypto Output 1146 to produce a signature S to check. We then pass (n, e), S and the 1147 UTF-8 representation of the JWS Signing Input to an RSA signature 1148 verifier that has been configured to use the SHA-256 hash function. 1150 A.3. JWS using ECDSA P-256 SHA-256 1152 A.3.1. Encoding 1154 The Decoded JWS Header Input for this example differs from the 1155 previous example because a different algorithm is being used. The 1156 Decoded JWS Header Input used is: 1157 {"alg":"ES256"} 1159 The following byte array contains the UTF-8 characters for the 1160 Decoded JWS Header Input: 1162 [123, 34, 97, 108, 103, 34, 58, 34, 69, 83, 50, 53, 54, 34, 125] 1164 Base64url encoding this UTF-8 representation yields this JWS Header 1165 Input value: 1166 eyJhbGciOiJFUzI1NiJ9 1168 The Decoded JWS Payload Input used in this example, which follows, is 1169 the same as in the previous examples. Since the JWS Payload Input 1170 will therefore be the same, its computation is not repeated here. 1171 {"iss":"joe", 1172 "exp":1300819380, 1173 "http://example.com/is_root":true} 1175 Concatenating the JWS Header Input, a period character, and the JWS 1176 Payload Input yields this JWS Signing Input value (with line breaks 1177 for display purposes only): 1178 eyJhbGciOiJFUzI1NiJ9 1179 . 1180 eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ 1182 The UTF-8 representation of the JWS Signing Input is the following 1183 byte array: 1185 [101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 70, 85, 122, 73, 1186 49, 78, 105, 74, 57, 46, 101, 121, 74, 112, 99, 51, 77, 105, 79, 105, 1187 74, 113, 98, 50, 85, 105, 76, 65, 48, 75, 73, 67, 74, 108, 101, 72, 1188 65, 105, 79, 106, 69, 122, 77, 68, 65, 52, 77, 84, 107, 122, 79, 68, 1189 65, 115, 68, 81, 111, 103, 73, 109, 104, 48, 100, 72, 65, 54, 76, 1190 121, 57, 108, 101, 71, 70, 116, 99, 71, 120, 108, 76, 109, 78, 118, 1191 98, 83, 57, 112, 99, 49, 57, 121, 98, 50, 57, 48, 73, 106, 112, 48, 1192 99, 110, 86, 108, 102, 81] 1193 The ECDSA key consists of a public part, the EC point (x, y), and a 1194 private part d. The values of the ECDSA key used in this example, 1195 presented as the byte arrays representing big endian integers are: 1197 +-----------+-------------------------------------------------------+ 1198 | Parameter | Value | 1199 | Name | | 1200 +-----------+-------------------------------------------------------+ 1201 | x | [127, 205, 206, 39, 112, 246, 196, 93, 65, 131, 203, | 1202 | | 238, 111, 219, 75, 123, 88, 7, 51, 53, 123, 233, 239, | 1203 | | 19, 186, 207, 110, 60, 123, 209, 84, 69] | 1204 | y | [199, 241, 68, 205, 27, 189, 155, 126, 135, 44, 223, | 1205 | | 237, 185, 238, 185, 244, 179, 105, 93, 110, 169, 11, | 1206 | | 36, 173, 138, 70, 35, 40, 133, 136, 229, 173] | 1207 | d | [142, 155, 16, 158, 113, 144, 152, 191, 152, 4, 135, | 1208 | | 223, 31, 93, 119, 233, 203, 41, 96, 110, 190, 210, | 1209 | | 38, 59, 95, 87, 194, 19, 223, 132, 244, 178] | 1210 +-----------+-------------------------------------------------------+ 1212 The ECDSA private part d is then passed to an ECDSA signing function, 1213 which also takes the curve type, P-256, the hash type, SHA-256, and 1214 the UTF-8 representation of the JWS Signing Input as inputs. The 1215 result of the signature is the EC point (R, S), where R and S are 1216 unsigned integers. In this example, the R and S values, given as 1217 byte arrays representing big endian integers are: 1219 +--------+----------------------------------------------------------+ 1220 | Result | Value | 1221 | Name | | 1222 +--------+----------------------------------------------------------+ 1223 | R | [14, 209, 33, 83, 121, 99, 108, 72, 60, 47, 127, 21, 88, | 1224 | | 7, 212, 2, 163, 178, 40, 3, 58, 249, 124, 126, 23, 129, | 1225 | | 154, 195, 22, 158, 166, 101] | 1226 | S | [197, 10, 7, 211, 140, 60, 112, 229, 216, 241, 45, 175, | 1227 | | 8, 74, 84, 128, 166, 101, 144, 197, 242, 147, 80, 154, | 1228 | | 143, 63, 127, 138, 131, 163, 84, 213] | 1229 +--------+----------------------------------------------------------+ 1231 Concatenating the S array to the end of the R array and base64url 1232 encoding the result produces this value for the JWS Crypto Output: 1233 DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSApmWQxfKTUJqPP3-Kg6NU1Q 1235 A.3.2. Decoding 1237 Decoding the JWS from this example requires processing the JWS Header 1238 Input and JWS Payload Input exactly as done in the first example. 1240 A.3.3. Validating 1242 Since the "alg" parameter in the header is "ES256", we validate the 1243 ECDSA P-256 SHA-256 signature contained in the JWS Crypto Output. If 1244 any of the validation steps fail, the signed content MUST be 1245 rejected. 1247 First, we validate that the decoded JWS Header Input string is legal 1248 JSON. 1250 Validating the JWS Crypto Output is a little different from the first 1251 example. First, we base64url decode the JWS Crypto Output as in the 1252 previous examples but we then need to split the 64 member byte array 1253 that must result into two 32 byte arrays, the first R and the second 1254 S. We then pass (x, y), (R, S) and the UTF-8 representation of the 1255 JWS Signing Input to an ECDSA signature verifier that has been 1256 configured to use the P-256 curve with the SHA-256 hash function. 1258 As explained in Section 7.3, the use of the k value in ECDSA means 1259 that we cannot validate the correctness of the signature in the same 1260 way we validated the correctness of the HMAC. Instead, 1261 implementations MUST use an ECDSA validator to validate the 1262 signature. 1264 Appendix B. Algorithm Identifier Cross-Reference 1266 This appendix contains a table cross-referencing the "alg" values 1267 used in this specification with the equivalent identifiers used by 1268 other standards and software packages. See XML DSIG [RFC3275] and 1269 Java Cryptography Architecture [JCA] for more information about the 1270 names defined by those documents. 1272 +-------+-----+----------------------------+----------+-------------+ 1273 | Algor | JWS | XML DSIG | JCA | OID | 1274 | ithm | | | | | 1275 +-------+-----+----------------------------+----------+-------------+ 1276 | HMAC | HS2 | http://www.w3.org/2001/04/ | HmacSHA2 | 1.2.840.113 | 1277 | using | 56 | xmldsig-more#hmac-sha256 | 56 | 549.2.9 | 1278 | SHA-2 | | | | | 1279 | 56 | | | | | 1280 | hash | | | | | 1281 | algo | | | | | 1282 | rithm | | | | | 1283 | HMAC | HS3 | http://www.w3.org/2001/04/ | HmacSHA3 | 1.2.840.113 | 1284 | using | 84 | xmldsig-more#hmac-sha384 | 84 | 549.2.10 | 1285 | SHA-3 | | | | | 1286 | 84 | | | | | 1287 | hash | | | | | 1288 | algo | | | | | 1289 | rithm | | | | | 1290 | HMAC | HS5 | http://www.w3.org/2001/04/ | HmacSHA5 | 1.2.840.113 | 1291 | using | 12 | xmldsig-more#hmac-sha512 | 12 | 549.2.11 | 1292 | SHA-5 | | | | | 1293 | 12 | | | | | 1294 | hash | | | | | 1295 | algo | | | | | 1296 | rithm | | | | | 1297 | RSA | RS2 | http://www.w3.org/2001/04/ | SHA256wi | 1.2.840.113 | 1298 | using | 56 | xmldsig-more#rsa-sha256 | thRSA | 549.1.1.11 | 1299 | SHA-2 | | | | | 1300 | 56 | | | | | 1301 | hash | | | | | 1302 | algo | | | | | 1303 | rithm | | | | | 1304 | RSA | RS3 | http://www.w3.org/2001/04/ | SHA384wi | 1.2.840.113 | 1305 | using | 84 | xmldsig-more#rsa-sha384 | thRSA | 549.1.1.12 | 1306 | SHA-3 | | | | | 1307 | 84 | | | | | 1308 | hash | | | | | 1309 | algo | | | | | 1310 | rithm | | | | | 1311 | RSA | RS5 | http://www.w3.org/2001/04/ | SHA512wi | 1.2.840.113 | 1312 | using | 12 | xmldsig-more#rsa-sha512 | thRSA | 549.1.1.13 | 1313 | SHA-5 | | | | | 1314 | 12 | | | | | 1315 | hash | | | | | 1316 | algo | | | | | 1317 | rithm | | | | | 1318 | ECDSA | ES2 | http://www.w3.org/2001/04/ | SHA256wi | 1.2.840.100 | 1319 | using | 56 | xmldsig-more#ecdsa-sha256 | thECDSA | 45.3.1.7 | 1320 | P-256 | | | | | 1321 | curve | | | | | 1322 | and | | | | | 1323 | SHA-2 | | | | | 1324 | 56 | | | | | 1325 | hash | | | | | 1326 | algo | | | | | 1327 | rithm | | | | | 1328 | ECDSA | ES3 | http://www.w3.org/2001/04/ | SHA384wi | 1.3.132.0.3 | 1329 | using | 84 | xmldsig-more#ecdsa-sha384 | thECDSA | 4 | 1330 | P-384 | | | | | 1331 | curve | | | | | 1332 | and | | | | | 1333 | SHA-3 | | | | | 1334 | 84 | | | | | 1335 | hash | | | | | 1336 | algo | | | | | 1337 | rithm | | | | | 1338 | ECDSA | ES5 | http://www.w3.org/2001/04/ | SHA512wi | 1.3.132.0.3 | 1339 | using | 12 | xmldsig-more#ecdsa-sha512 | thECDSA | 5 | 1340 | P-521 | | | | | 1341 | curve | | | | | 1342 | and | | | | | 1343 | SHA-5 | | | | | 1344 | 12 | | | | | 1345 | hash | | | | | 1346 | algo | | | | | 1347 | rithm | | | | | 1348 +-------+-----+----------------------------+----------+-------------+ 1350 Table 4: Algorithm Identifier Cross-Reference 1352 Appendix C. Notes on implementing base64url encoding without padding 1354 This appendix describes how to implement base64url encoding and 1355 decoding functions without padding based upon standard base64 1356 encoding and decoding functions that do use padding. 1358 To be concrete, example C# code implementing these functions is shown 1359 below. Similar code could be used in other languages. 1361 static string base64urlencode(byte [] arg) 1362 { 1363 string s = Convert.ToBase64String(arg); // Standard base64 encoder 1364 s = s.Split('=')[0]; // Remove any trailing '='s 1365 s = s.Replace('+', '-'); // 62nd char of encoding 1366 s = s.Replace('/', '_'); // 63rd char of encoding 1367 return s; 1368 } 1370 static byte [] base64urldecode(string arg) 1371 { 1372 string s = arg; 1373 s = s.Replace('-', '+'); // 62nd char of encoding 1374 s = s.Replace('_', '/'); // 63rd char of encoding 1375 switch (s.Length % 4) // Pad with trailing '='s 1376 { 1377 case 0: break; // No pad chars in this case 1378 case 2: s += "=="; break; // Two pad chars 1379 case 3: s += "="; break; // One pad char 1380 default: throw new System.Exception( 1381 "Illegal base64url string!"); 1382 } 1383 return Convert.FromBase64String(s); // Standard base64 decoder 1384 } 1386 As per the example code above, the number of '=' padding characters 1387 that needs to be added to the end of a base64url encoded string 1388 without padding to turn it into one with padding is a deterministic 1389 function of the length of the encoded string. Specifically, if the 1390 length mod 4 is 0, no padding is added; if the length mod 4 is 2, two 1391 '=' padding characters are added; if the length mod 4 is 3, one '=' 1392 padding character is added; if the length mod 4 is 1, the input is 1393 malformed. 1395 An example correspondence between unencoded and encoded values 1396 follows. The byte sequence below encodes into the string below, 1397 which when decoded, reproduces the byte sequence. 1398 3 236 255 224 193 1399 A-z_4ME 1401 Appendix D. Acknowledgements 1403 Solutions for signing JSON content were previously explored by Magic 1404 Signatures [MagicSignatures], JSON Simple Sign [JSS], and Canvas 1405 Applications [CanvasApp], all of which influenced this draft. 1407 Appendix E. Document History 1409 -01 1411 o Changed RSA SHA-256 from MUST be supported to RECOMMENDED that it 1412 be supported. Rationale: Several people have objected to the 1413 requirement for implementing RSA SHA-256, some because they will 1414 only be using HMACs and symmetric keys, and others because they 1415 only want to use ECDSA when using asymmetric keys, either for 1416 security or key length reasons, or both. 1418 o Clarified that "x5u" is an HTTPS URL referencing a PEM-encoded 1419 certificate or certificate chain. 1421 o Clarified that the "alg" parameter value is case sensitive. 1423 o Changed "x5t" (x.509 certificate thumbprint) to use a SHA-1 hash, 1424 rather than a SHA-256 hash, for compatibility reasons. 1426 -00 1428 o Created first signature draft using content split from 1429 draft-jones-json-web-token-01. This split introduced no semantic 1430 changes. 1432 Authors' Addresses 1434 Michael B. Jones 1435 Microsoft 1437 Email: mbj@microsoft.com 1438 URI: http://self-issued.info/ 1440 Dirk Balfanz 1441 Google 1443 Email: balfanz@google.com 1445 John Bradley 1446 independent 1448 Email: ve7jtb@ve7jtb.com 1449 Yaron Y. Goland 1450 Microsoft 1452 Email: yarong@microsoft.com 1454 John Panzer 1455 Google 1457 Email: jpanzer@google.com 1459 Nat Sakimura 1460 Nomura Research Institute 1462 Email: n-sakimura@nri.co.jp 1464 Paul Tarjan 1465 Facebook 1467 Email: pt@fb.com