| Initialisation | |||||
|---|---|---|---|---|---|
| Property | v3 | v4 | v5 | v6 | Notes |
| Extension data in SSH_FXP_INIT | yes (4) | no (4.1) | no (4.1) | no (4.1) | |
| Clients must support newline extension | no | yes (4.3) | yes (4.3) | yes (5.3) | |
| Server must send supported extension | no | no | yes (4.4) | no | |
| Server must send supported2 extension | no | no | no | yes (5.4) | |
| acl-supported extension | no (5) | no (5) | no (5) | yes (5.4) | |
| versions extension | no | no | no | yes (5.5) | Client uses version-select extension |
| Default filename encoding | unspecified | UTF-8 (6.2) | UTF-8 (6.2) | UTF-8 (6) | |
| filename-charset extension | no | no | no | yes (6) | |
| Attributes | |||||
| Property | v3 | v4 | v5 | v6 | Notes |
| Separate ACCESSTIME and MODIFYTIME | no (5) | yes (5.1) | yes (5.1) | yes (7.1) | ACMODTIME clashes with ACCESSTIME |
| type byte | no (5) | yes (5.2) | yes (5.2) | yes (7.2) | Always present (in v4 and beyond) |
| allocation-size | no (5) | no (5) | no (5) | yes (7.4) | ALLOCATION_SIZE flag |
| string owner/group | no (5) | yes (5.4) | yes (5.4) | yes (7.5) | UIDGID or OWNERGROUP flags |
| 64-bit timestamps | no (5) | yes (5) | yes (5) | yes (7.7) | |
| nanosecond precision timestamps | no (5) | yes (5) | yes (5) | yes (7.7) | SUBSECOND_TIMES flag |
| createtime field | no (5) | yes (5.6) | yes (5.6) | yes (7.7) | CREATETIME flag |
| ctime field | no (5) | no (5) | no (5) | yes (7.7) | CTIME flag |
| acl field | no (5) | yes (5.7) | yes (5.7) | yes (7.8) | ACL flag. Format varies between versions. |
| attrib-bits field | no (5) | no (5) | yes (5.8) | yes (7.9) | BITS flag |
| attrib-bits-valid field | no (5) | no (5) | no (5.8) | yes (7.9) | BITS flag |
| SSH_FILEXFER_ATTR_FLAGS_TRANSLATION_ERR | no (5) | no (5) | no (5.8) | yes (7.9) | Should imply UNTRANSLATED_NAME |
| text-hint field | no (5) | no (5) | no (5) | yes (7.10) | TEXT_HINT flag |
| mime-type field | no (5) | no (5) | no (5) | yes (7.11) | MIME_TYPE flag |
| link-count field | no (5) | no (5) | no (5) | yes (7.12) | LINK_COUNT flag |
| untranslated-name field | no (5) | no (5) | no (5) | yes (7.13) | UNTRANSLATED_NAME flag |
| Command Set | |||||
| Property | v3 | v4 | v5 | v6 | Notes |
| SSH_FXP_SYMLINK | yes (6.10) | yes (6.10) | yes (6.9) | no | v3-v5 can make symlinks only |
| SSH_FXP_LINK | no | no | no | yes (8.7) | v6 can make hard or symbolic links |
| SSH_FXP_BLOCK | no | no | no | yes (8.8.1) | |
| SSH_FXP_UNBLOCK | no | no | no | yes (8.8.2) | |
| Opening And Closing Files | |||||
| Property | v3 | v4 | v5 | v6 | Notes |
| SSH_FXP_OPEN pflags | yes (6.3) | yes (6.3) | no | no | |
| SSH_FXF_TEXT (or SSH_FXF_TEXT_MODE) | no | yes (6.3) | yes (6.3.1) | yes (8.1.1.3) | Also text-seek extension |
| SSH_FXP_OPEN flags | no | no | yes (6.3.1) | yes (8.1.1.3) | Similar role to pflags, different details |
| SSH_FXP_OPEN desired-access | no | no | yes (6.3.1) | yes (8.1.1.2) | |
| SSH_FXF_BLOCK_* | no | no | no | yes (8.1.1.3) | |
| SSH_FXF_NOFOLLOW | no | no | no | yes (8.1.1.3) | |
| SSH_FXF_DELETE_ON_CLOSE | no | no | no | yes (8.1.1.3) | |
| SSH_FXF_ACCESS_AUDIT_ALARM_INFO | no | no | no | yes (8.1.1.3) | |
| SSH_FXF_ACCESS_BACKUP | no | no | no | yes (8.1.1.3) | |
| SSH_FXF_BACKUP_STREAM | no | no | no | yes (8.1.1.3) | |
| SSH_FXF_OVERRIDE_OWNER | no | no | no | yes (8.1.1.3) | |
| Removing And Renaming Files | |||||
| Property | v3 | v4 | v5 | v6 | Notes |
| SSH_FXP_RENAME flags | no (6.5) | no (6.5) | yes (6.5) | yes (8.3) | No overwriting rename in v3/v4 |
| Retrieving File Attributes | |||||
| Property | v3 | v4 | v5 | v6 | Notes |
| SSH_FXP_*STAT flags | no (6.8) | yes (6.8) | yes (6.7) | yes (8.5) | |
| Canonicalizing the Server-Side Path Name | |||||
| Property | v3 | v4 | v5 | v6 | Notes |
| SSH_FXP_REALPATH control-byte | no | no | no | yes (8.9) | Optional. |
| SSH_FXP_REALPATH compose-path | no | no | no | yes (8.9) | Optional. |
| Responses from the Server to the Client | |||||
| Property | v3 | v4 | v5 | v6 | Notes |
| SSH_FXP_STATUS error-specific data | no | no | yes (7) | yes (9.1) | |
| SSH_FX_INVALID_HANDLE | no | yes (7) | yes (7) | yes (9.1) | |
| SSH_FX_NO_SUCH_PATH | no | yes (7) | yes (7) | yes (9.1) | |
| SSH_FX_FILE_ALREADY_EXISTS | no | yes (7) | yes (7) | yes (9.1) | |
| SSH_FX_WRITE_PROTECT | no | yes (7) | yes (7) | yes (9.1) | |
| SSH_FX_NO_MEDIA | no | yes (7) | yes (7) | yes (9.1) | |
| SSH_FX_NO_SPACE_ON_FILESYSTEM | no | no | yes (7) | yes (9.1) | |
| SSH_FX_QUOTA_EXCEEDED | no | no | yes (7) | yes (9.1) | |
| SSH_FX_UNKNOWN_PRINCIPAL | no | no | yes (7) | yes (9.1) | Has error-specific data |
| SSH_FX_LOCK_CONFLICT | no | no | yes (7) | yes (9.1) | |
| SSH_FX_DIR_NOT_EMPTY | no | no | no | yes (9.1) | |
| SSH_FX_NOT_A_DIRECTORY | no | no | no | yes (9.1) | |
| SSH_FX_INVALID_FILENAME | no | no | no | yes (9.1) | |
| SSH_FX_LINK_LOOP | no | no | no | yes (9.1) | |
| SSH_FX_CANNOT_DELETE | no | no | no | yes (9.1) | |
| SSH_FX_INVALID_PARAMETER | no | no | no | yes (9.1) | |
| SSH_FX_FILE_IS_A_DIRECTORY | no | no | no | yes (9.1) | |
| SSH_FX_BYTE_RANGE_LOCK_CONFLICT | no | no | no | yes (9.1) | |
| SSH_FX_BYTE_RANGE_LOCK_REFUSED | no | no | no | yes (9.1) | |
| SSH_FX_DELETE_PENDING | no | no | no | yes (9.1) | |
| SSH_FX_FILE_CORRUPT | no | no | no | yes (9.1) | |
| SSH_FX_OWNER_INVALID | no | no | no | yes (9.1) | |
| SSH_FX_GROUP_INVALID | no | no | no | yes (9.1) | |
| SSH_FX_NO_MATCHING_BYTE_RANGE_LOCK | no | no | no | yes (9.1) | |
| SSH_FXP_DATA end-of-file | no | no | no | yes (9.3) | Optional. |
| SSH_FXP_NAME longname | yes (7) | no | no | no | |
| SSH_FXP_NAME end-of-list | no | no | no | yes (9.4) | |
| Property | v3 | v4 | v5 | v6 | Notes |
| Command | v3 | v4 | v5 | v6 |
|---|---|---|---|---|
| SSH_FXP_INIT | Extension data | No extension data | ||
| SSH_FXP_OPEN | pflags field | flags field | ||
| SSH_FXP_CLOSE | Same everywhere | |||
| SSH_FXP_READ | max-read-size (8.2.1) | |||
| SSH_FXP_WRITE | Same everywhere | |||
| SSH_FXP_LSTAT | No flags | flags field | ||
| SSH_FXP_FSTAT | No flags | flags field | ||
| SSH_FXP_SETSTAT | Same everywhere | |||
| SSH_FXP_FSETSTAT | Same everywhere | |||
| SSH_FXP_OPENDIR | Same everywhere | |||
| SSH_FXP_READDIR | Same everywhere | |||
| SSH_FXP_REMOVE | Same everywhere | |||
| SSH_FXP_MKDIR | Same everywhere | |||
| SSH_FXP_RMDIR | Same everywhere | |||
| SSH_FXP_REALPATH | Just path | control-byte and compose-path | ||
| SSH_FXP_STAT | No flags | flags field | ||
| SSH_FXP_RENAME | No flags | flags | ||
| SSH_FXP_READLINK | Same everywhere | |||
| SSH_FXP_SYMLINK | Same | absent | ||
| SSH_FXP_LINK | absent | Hard and soft links | ||
This section just lists all the extensions I know anything about, with information about their specifications (such as they are) where available. Just because an extension is listed here doens't mean it's a good idea to implement it.
Defined in draft-ietf-secsh-filexfer-13 s5.4. Describes general server capabilities. v6 servers MUST send this extension.
Defined in draft-ietf-secsh-filexfer-05 s4.4. Describes general server capabilities. v5 servers MUST send this extension.
Defined in draft-ietf-secsh-filexfer-13 s5.4. Describes the server's support for ACLs.
Defined in draft-ietf-secsh-filexfer-13 s8.1.1.3. Supports seeking by line number within text files. Servers at v4 and higher SHOULD support it but clients MUST cope without.
Defined in draft-ietf-secsh-filexfer-13 s5.5. Used in v6 to allow more sophisticated version negotiation. If version-select is sent then it MUST be the first request (after SSH_FXP_INIT, presumably).
Defined in draft-ietf-secsh-filexfer-13 s6. filename-charset is optional and describes the likely encoding of untranslated names. filename-translation-control is mandatory if filename-charset was sent; it's used to suppress or re-enable filename translation.
Described in draft-ietf-secsh-filexfer-13. Document's the newline sequence expxected by the server for text files. v4 clients and higher MUST support it.
Defined in draft-ietf-secsh-filexfer-09 and draft-ietf-secsh-filexfer-extensions-00. Implemented by (for instance) WinSCP.
Described in draft-ietf-secsh-filexfer-09 s9.1.1 but not later versions (use check-file-handle and check-file-name instead). Computes the MD5 hash of a byte range of an open file.
Described in draft-ietf-secsh-filexfer-09 s9.1.2 and draft-ietf-secsh-filexfer-extensions-00. Computes various kinds of checksum of a byte range of a file.
Described in draft-ietf-secsh-filexfer-09 s9.2 and draft-ietf-secsh-filexfer-extensions-00. Implemented by (for instance) WinSCP.
Described in draft-ietf-secsh-filexfer-09 s9.3 and draft-ietf-secsh-filexfer-extensions-00.
Described in draft-ietf-secsh-filexfer-extensions-00.
Described in draft-ietf-secsh-filexfer-extensions-00.
Apparently reports a list of valid owner and group strings, which seems useful albeit potentially unbounded. Does not follow the rules for extension names (RFC4251 s6). Implemented by WinSCP. If you know where this is publicly documented, please let me know.
Mentioned in the revision history of WinSCP. Does not follow the rules for extension names. I know nothing about it. If you know where this is publicly documented, please let me know.
Apparently reports a list of available drives. Implemented WinSCP and I assume by the vandyke.com SFTP server. If you know where this is publicly documented, please let me know.
Exposes the UNIX statfs(2) system call via SFTP. Patch to OpenSSH (not applied at time of writing, link has bit-rotted).
Exposes the UNIX rename(2) system call via SFTP. Obsolete for protocol versions 5 and above but potentially useful for v3 and v4 which only have non-overwriting rename. Patch to OpenSSH (not applied at time of writing, link has bit-rotted).
Documents the order of the arguments to SSH_FXP_SYMLINK or SSH_FXP_LINK expected by the server (needed because some servers get it wrong). Specification.
Analogous to SSH_FXP_RENAME but uses the rename(2) syscall. PROTOCOL s3.3 describes. Implemented in OpenSSH since 2008.
Retrieve information about a filesystem. PROTOCOL s3.4 describes. Implemented in OpenSSH since 2008.
Retrieve information about a filesystem. PROTOCOL s3.4 describes. Implemented in OpenSSH since 2008.
Create a hard link. PROTOCOL s10 describes. Implemented in OpenSSH since 2010.
Please let me know if there are important version differences I have missed, or an errors. I would particularly appreciate points to specifications for proposed or implement SFTP extensions.
I know that ACLs are not really well-treated here.
Where more than one draft gives a specification for a particular protocol version, I've chosen the latest one (see the links below); it is to these drafts that the section numbers refer. I've ignored versions before 3 completely.
At the time of writing there is no SFTP RFC.