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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group J. Salowey 3 Internet-Draft Cisco Systems 4 Expires: August 5, 2006 S. Suehring 5 February 1, 2006 7 Uniform Resource Identifier (URI) Scheme for Secure File Transfer 8 Protocol (SFTP) and Secure Shell (SSH) 9 draft-ietf-secsh-scp-sftp-ssh-uri-04.txt 11 Status of this Memo 13 By submitting this Internet-Draft, each author represents that any 14 applicable patent or other IPR claims of which he or she is aware 15 have been or will be disclosed, and any of which he or she becomes 16 aware will be disclosed, in accordance with Section 6 of BCP 79. 18 Internet-Drafts are working documents of the Internet Engineering 19 Task Force (IETF), its areas, and its working groups. Note that 20 other groups may also distribute working documents as Internet- 21 Drafts. 23 Internet-Drafts are draft documents valid for a maximum of six months 24 and may be updated, replaced, or obsoleted by other documents at any 25 time. It is inappropriate to use Internet-Drafts as reference 26 material or to cite them other than as "work in progress." 28 The list of current Internet-Drafts can be accessed at 29 http://www.ietf.org/ietf/1id-abstracts.txt. 31 The list of Internet-Draft Shadow Directories can be accessed at 32 http://www.ietf.org/shadow.html. 34 This Internet-Draft will expire on August 5, 2006. 36 Copyright Notice 38 Copyright (C) The Internet Society (2006). 40 Abstract 42 This document describes the Uniform Resource Identifiers used to 43 locate resources for the Secure File Transfer Protocol (SFTP) and the 44 Secure Shell (SSH) protocols. The document describes the generic 45 syntax involved in URI definitions as well as specific definitions 46 for each protocol. These specific definitions may include user 47 credentials such as username and also may include other parameters 48 such as host key fingerprint. In addition, security considerations 49 and examples are also provided within this document. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 54 2. General Syntax . . . . . . . . . . . . . . . . . . . . . . . 3 55 3. Secure Shell (SSH) URI . . . . . . . . . . . . . . . . . . . 3 56 3.1 Scheme Name . . . . . . . . . . . . . . . . . . . . . . . 3 57 3.2 Status . . . . . . . . . . . . . . . . . . . . . . . . . . 3 58 3.3 URI Scheme Syntax . . . . . . . . . . . . . . . . . . . . 3 59 3.4 URI Semantics . . . . . . . . . . . . . . . . . . . . . . 4 60 3.5 Encoding Considerations . . . . . . . . . . . . . . . . . 4 61 3.6 Protocols using this URI scheme . . . . . . . . . . . . . 4 62 3.7 Security Considerations . . . . . . . . . . . . . . . . . 5 63 3.8 Contact . . . . . . . . . . . . . . . . . . . . . . . . . 5 64 4. Secure File Transfer Protocol (SFTP) URI . . . . . . . . . . 5 65 4.1 Scheme Name . . . . . . . . . . . . . . . . . . . . . . . 5 66 4.2 Status . . . . . . . . . . . . . . . . . . . . . . . . . . 5 67 4.3 URI Scheme Syntax . . . . . . . . . . . . . . . . . . . . 5 68 4.4 URI Semantics . . . . . . . . . . . . . . . . . . . . . . 6 69 4.5 Encoding Considerations . . . . . . . . . . . . . . . . . 6 70 4.6 Protocols using this URI scheme . . . . . . . . . . . . . 6 71 4.7 Security Considerations . . . . . . . . . . . . . . . . . 6 72 4.8 Contact . . . . . . . . . . . . . . . . . . . . . . . . . 7 73 5. Parameters . . . . . . . . . . . . . . . . . . . . . . . . . 7 74 5.1 SSH connection parameters . . . . . . . . . . . . . . . . 7 75 5.2 SFTP Parameters . . . . . . . . . . . . . . . . . . . . . 7 76 6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 8 77 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . 8 78 8. Security Considerations . . . . . . . . . . . . . . . . . . 9 79 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 80 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 81 10.1 Normative References . . . . . . . . . . . . . . . . . . 9 82 10.2 Informative References . . . . . . . . . . . . . . . . . 10 83 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 10 84 Intellectual Property and Copyright Statements . . . . . . . 11 86 1. Introduction 88 This document describes the Uniform Resource Identifiers (URIs) to be 89 used with the Secure File Transfer Protocol (SFTP) [I-D.ietf-secsh- 90 filexfer] and Secure Shell (SSH) [RFC4251] protocols. 92 2. General Syntax 94 A hierarchical URI shall consist of the scheme and the scheme 95 specific portion separated by a colon ":" followed by the 96 hierarchical part, as discussed in [RFC3986]. This specification 97 uses the definitions "port", "host", "scheme", "userinfo", "path- 98 empty", "path-abempty" and "authority" from [RFC3986]. This document 99 follows the ABNF notation defined in [RFC4234]. 101 3. Secure Shell (SSH) URI 103 This section describes the SSH URI and contains the information 104 necessary to register the URI according to the template in 105 [I-D.hansen-2717bis-2718bis-uri-guidelines]. 107 3.1 Scheme Name 109 The Secure Shell scheme name is "ssh". 111 3.2 Status 113 The requested status of the SSH URI is "permanent". 115 3.3 URI Scheme Syntax 117 The Secure Shell (SSH) scheme shall consist of the scheme name "ssh" 118 followed by a colon ":" followed by hier-part defined in [RFC3986]. 119 The SSH URI ABNF definition follows. 121 sshURI = "ssh:" hier-part 122 hier-part = "//" authority path-abempty 123 authority = [ [ ssh-info ] "@" ] host [ ":" port ] 124 host = 125 port = 126 path-abempty = 127 ssh-info = [ userinfo ] [";" c-param *("," c-param)] 128 userinfo = 129 c-param = paramname "=" paramvalue 130 paramname = *( ALPHA / DIGIT / "-" ) 131 paramvalue = *( ALPHA / DIGIT / "-" ) 132 The following reserved characters from [RFC3986] are used as 133 delimiters within the SSH URI: ";", ",", ":", and "=" . They must 134 not be escaped when used as delimiters and must be escaped when the 135 appear in other uses. 137 3.4 URI Semantics 139 The intended usage of the SSH URI is to establish an interactive SSH 140 terminal session with the host defined in the authority portion of 141 the URI. The only operation defined for the URI is to establish an 142 SSH terminal session with a remote host. 144 If the userinfo or connection parameters are present the at-sign "@" 145 shall precede the authority section of the URI. Optionally, the 146 authority section MAY also include the port preceded by a colon ":". 147 The host SHOULD be a non-empty string. If the port is not included, 148 the default port is assumed. 150 The ssh-info portion of the URI MAY include credentials consisting of 151 a username followed by optional parameters. The convention of 152 including the password separated from the username by a ":" in the 153 URI is NOT RECOMMENDED and is deprecated in accordance with 154 [RFC3986]. 156 One or more optional connection parameters (c-param) may be specified 157 within the userinfo section of the URI. These conn-parameters are 158 separated from the userinfo by a semi-colon ";". The only connection 159 parameter defined in this document is for the host-key fingerprint 160 described in Section 5.1. It is possible that additional parameters 161 be defined in the future. If a connection parameter is not 162 understood it SHOULD be ignored. 164 The SSH URI does not define a usage for a non-empty path element. If 165 a non-empty path element is included in an SSH URI then it SHOULD be 166 ignored. 168 3.5 Encoding Considerations 170 The encoding of the "host" portion of the URI is as defined in 171 [RFC3986]. The encoding of the connection parameters is described in 172 Section 5.1 174 3.6 Protocols using this URI scheme 176 This URI scheme is used by the SSH protocol version 2 defined in 177 [RFC4251]. 179 3.7 Security Considerations 181 See Section 8. 183 3.8 Contact 185 This document is a product of the SSH working group. 187 4. Secure File Transfer Protocol (SFTP) URI 189 This section describes the Secure File Transfer protocol URI and 190 contains the information necessary to register the URI according to 191 the template in [I-D.hansen-2717bis-2718bis-uri-guidelines]. 193 4.1 Scheme Name 195 The Secure File Transfer Protocol (SFTP) scheme name is "sftp". 197 4.2 Status 199 The requested status of the SFTP URI is "permanent". 201 4.3 URI Scheme Syntax 203 The SFTP URI scheme shall consist of the scheme name "sftp" followed 204 by a colon ":" followed by hier-part defined in [RFC3986]. The SFTP 205 URI ABNF definition follows. 207 sftpURI = "sftp:" hier-part 208 hier-part = "//" authority path [";" s-param *("," s-param)] 209 path = path-abempty 210 path-abempty = 211 authority = [ ssh-info "@" ] host [ ":" port ] 212 host = 213 port = 214 ssh-info = [ userinfo ] [";" c-param *("," c-param)] 215 userinfo = 216 c-param = paramname "=" paramvalue 217 paramname = *( ALPHA / DIGIT / "-" ) 218 paramvalue = *( ALPHA / DIGIT / "-" ) 219 s-param = paramname "=" paramvalue 221 The authority part is the same as that defined in the SSH scheme. 222 The following reserved characters from [RFC3986] are used as 223 delimiters within the SFTP URI: ";", ",", ":", "=" and "/". They 224 must not be escaped when used as delimiters and must be escaped when 225 the appear in other uses. 227 4.4 URI Semantics 229 The intended usage of the SFTP URI is to retrieve the contents of a 230 file or directory listing. The only operation defined for the URI is 231 this "GET" operation. 233 The authority portion of the SFTP URL is the same as for the SSH URL 234 defined in Section 3.4. The URIs for SFTP are hierarchical URIs 235 where each component of the path consists of path elements separated 236 by a '/'. This formatting is meant to represent the path information 237 as in Section 5 of [I-D.ietf-secsh-filexfer]. The SFTP 238 implementation determines where the root of the path in the URI is. 239 It is RECOMMENDED that path be interpreted as an absolute path from 240 the root of the file system. An implementation MAY use the tilde 241 ("~") character as the first path element in the path to denote a 242 path relative to the user's home directory. Note that dot segments 243 "." and ".." are only interpreted within the URI path hierarchy and 244 are removed as part of the URL resolution process defined in 245 [RFC3986]. 247 Following the path additional sftp specific parameters may be 248 specified. These are described in Section 5.2. It is possible that 249 additional parameters be defined in the future. If a sftp parameter 250 is not understood it SHOULD be ignored. 252 4.5 Encoding Considerations 254 Path segments SHOULD be represented in the UTF-8 [RFC3629] character 255 set and clients SHOULD NOT disable UTF-8 translation on the server 256 with the filename-translation-control extension. The shortest valid 257 UTF-8 encoding of the UNICODE data MUST be used. The encoding of the 258 "host" portion of the URI is as defined in [RFC3986]. The encoding 259 of the connection parameters is described in Section 5.1 and the 260 encoding of SFTP parameters is described in Section 5.2. 262 4.6 Protocols using this URI scheme 264 This URI scheme is used by the SFTP protocol defined in [I-D.ietf- 265 secsh-filexfer]. 267 4.7 Security Considerations 269 The SFTP URI retrieves data from a remote host. Even though the 270 connection is secured by SFTP care should be taken in handling and 271 processing data retrieved from potentially unknown sources to avoid 272 malicious content from an attacker that may have been placed on the 273 host. For additional security considerations see Section 8. 275 4.8 Contact 277 This document is a product of the SSH working group. 279 5. Parameters 281 5.1 SSH connection parameters 283 The following parameters are associated with an SSH connection and 284 are applicable to SSH and SFTP. All parameters are optional and MUST 285 NOT overwrite configured defaults. Individual parameters are 286 separated by a comma (","). 288 fingerprint 290 The fingerprint parameter contains the fingerprint of the host key 291 for the host specified in the URL. The fingerprint is encoded as 292 host-key-alg-fingerprint. Host-key-alg is host public key 293 algorithm defined in [RFC4253] and the fingerprint format is 294 [I-D.ietf-secsh-publickeyfile]. For use in a URI, the fingerprint 295 shall use a single dash "-" as a separator instead of the colon 296 ":" as described in [I-D.ietf-secsh-publickeyfile]. This 297 parameter MUST NOT overwrite a key that is already configured for 298 the host. The fingerprint MAY be used to validate the 299 authenticity of the host key if the URL was obtained from an 300 authenticated source with its integrity protected. If this 301 parameter is not included then the host key is validated using 302 another method. See Security Considerations section for 303 additional considerations. There MUST be only one fingerprint 304 parameter present in a given URL. 306 5.2 SFTP Parameters 308 The SFTP parameters determine how to handle the file transfer 309 character translation. Additional parameters MAY be used. 311 typecode 313 The typecode identifies the type of file which determines how it 314 will be treated. The name for the typecode attribute is "type". 315 The value "i" indicates that a file should be transmitted without 316 character conversion performed. The value "a" indicates that the 317 file should be opened with the SSH_FXF_ACCESS_TEXT_MODE flag set 318 so it is converted to the canonical newline convention in use. 319 The value "d" indicates that the path is a directory and should be 320 opened using SSH_FXP_OPENDIR. 322 6. Examples 324 The following section shows basic examples of URLs for each protocol. 325 This section should not be considered to include all possible 326 combinations of URLs for each protocol. 328 An SSH connection to the host host.example.com on the standard port 329 using username user. 331 ssh://user@host.example.com 333 An SSH connection to the host host.example.com on port 2222 using 334 username user. 336 ssh://user@host.example.com:2222 338 An SSH connection to the host having the specified host-key 339 fingerprint at host.example.com on the standard port using username 340 user. 342 ssh://user;fingerprint=ssh-dss-c1-b1-30-29-d7-b8-de-6c-97- 343 77-10-d7-46-41-63-87@host.example.com 345 Retrieve file.txt from the user's home directory on the host at 346 host.example.com using SFTP using username user. This example 347 assumes that the implementation supports the indication of a path 348 relative to the home directory using a leading tilde. 350 sftp://user@host.example.com/~/file.txt 352 Retrieve file.txt from the absolute path /dir/path on the host at 353 host.example.com using SFTP using username user. 355 sftp://user@host.example.com/dir/path/file.txt 357 Retrieve the directory listing of user's home directory on the host 358 having the specified host-key fingerprint at host.example.com using 359 SFTP. 361 sftp://user;fingerprint=ssh-dss-c1-b1-30-29-d7-b8-de-6c-97- 362 77-10-d7-46-41-63-87@host.example.com:2222/;type=d 364 7. IANA Considerations 366 Section 3 and Section 4 provide the information required in the URL 367 registration template in accordance with [I-D.hansen-2717bis-2718bis- 368 uri-guidelines]. 370 8. Security Considerations 372 Passwords SHOULD NOT be included within the URI as doing so poses a 373 security risk. URIs are usually sent in the clear with no encryption 374 or other security, any password or other credentials included in the 375 userinfo could be seen by a potential attacker. 377 Although the host-key fingerprint is not confidential information, 378 care must be taken in handling fingerprints associated with URIs 379 because URIs transmitted or stored without protection may be modified 380 by an attacker. In general an implementation cannot determine the 381 source of a URI so a fingerprint received in a URI should have no 382 more trust associated with it than a raw public key received in the 383 SSH protocol itself. If a locally configured key exists for the 384 server already it MUST NOT be automatically overwritten with 385 information from the URI. If the host is unknown then the 386 implementation should treat the fingerprint received with the same 387 caution that it does with any unknown public key. The client MAY 388 offer the fingerprint and URI for external validation before allowing 389 a connection based on this information. If the client chooses to 390 make a connection based on the URI information and it finds that the 391 fingerprint in the URI and the public key offered by the server do 392 not match then it SHOULD provide a warning and provide a means to 393 abort the connection. Sections 4.1 and 9.2.4 of [RFC4251] provide a 394 good discussion of handling public keys received in the SSH protocol. 396 9. Acknowledgements 398 Ben Harris, Tom Petch and the members of the SSH working group have 399 provided much useful feedback in the preparation of this document. 401 10. References 403 10.1 Normative References 405 [I-D.ietf-secsh-filexfer] 406 Galbraith, J. and O. Saarenmaa, "SSH File Transfer 407 Protocol", draft-ietf-secsh-filexfer-12 (work in 408 progress), January 2006. 410 [I-D.ietf-secsh-publickeyfile] 411 Galbraith, J. and R. Thayer, "SSH Public Key File Format", 412 draft-ietf-secsh-publickeyfile-11 (work in progress), 413 January 2006. 415 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 416 10646", STD 63, RFC 3629, November 2003. 418 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 419 Resource Identifier (URI): Generic Syntax", STD 66, 420 RFC 3986, January 2005. 422 [RFC4234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 423 Specifications: ABNF", RFC 4234, October 2005. 425 [RFC4251] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH) 426 Protocol Architecture", RFC 4251, January 2006. 428 [RFC4253] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH) 429 Transport Layer Protocol", RFC 4253, January 2006. 431 10.2 Informative References 433 [I-D.hansen-2717bis-2718bis-uri-guidelines] 434 Hansen, T., "Guidelines and Registration Procedures for 435 new URI Schemes", 436 draft-hansen-2717bis-2718bis-uri-guidelines-06 (work in 437 progress), October 2005. 439 Authors' Addresses 441 Joseph Salowey 442 Cisco Systems 443 2901 3rd Ave 444 Seattle, WA 98121 445 US 447 Email: jsalowey@cisco.com 449 Steve Suehring 450 PO BOX 1033 451 Stevens Point, WI 54481 452 US 454 Email: suehring@braingia.com 456 Intellectual Property Statement 458 The IETF takes no position regarding the validity or scope of any 459 Intellectual Property Rights or other rights that might be claimed to 460 pertain to the implementation or use of the technology described in 461 this document or the extent to which any license under such rights 462 might or might not be available; nor does it represent that it has 463 made any independent effort to identify any such rights. 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