Bug#1131161: proftpd-mod-crypto: SFTPExtensions +checkFile does not enable check-file

[Jörg Eichhorn]

Package: proftpd-mod-crypto
Version: 1.3.8.c+dfsg-4+deb13u1
Severity: important
X-Debbugs-Cc: joerg.eichhorn at sys-mail.net



Ahoi,
I have installed proftpd to make use of check-file sftp extension. proftpd accepts config line:
``` 
SFTPExtensions +vendorID +checkFile +xattr
```

I see xattr extension as well as vendorID beeing enabled, but checkFile missing. When connecting, it is not reported:

```
2026-03-18 11:30:34,824 [40967] <sftp:7>: received request: INIT 3
2026-03-18 11:30:34,824 [40967] <sftp:8>: sending response: VERSION 3
2026-03-18 11:30:34,824 [40967] <sftp:11>: + SFTP extension: vendor-id = { vendorName = 'ProFTPD Project', productName = 'mod_sftp', productVersion = 'mod_sftp/1.1.1', buildNumber = 16975
880 }
2026-03-18 11:30:34,824 [40967] <sftp:11>: + SFTP extension: versions = '2,3,4,5,6'
2026-03-18 11:30:34,824 [40967] <sftp:11>: + SFTP extension: fsync at openssh.com = '1'
2026-03-18 11:30:34,824 [40967] <sftp:11>: + SFTP extension: posix-rename at openssh.com = '1'
2026-03-18 11:30:34,824 [40967] <sftp:11>: + SFTP extension: statvfs at openssh.com = '2'
2026-03-18 11:30:34,824 [40967] <sftp:11>: + SFTP extension: fstatvfs at openssh.com = '2'
2026-03-18 11:30:34,824 [40967] <sftp:11>: + SFTP extension: hardlink at openssh.com = '1'
2026-03-18 11:30:34,824 [40967] <sftp:11>: + SFTP extension: home-directory = '1'
2026-03-18 11:30:34,824 [40967] <sftp:11>: + SFTP extension: xattr at proftpd.org = '1'
2026-03-18 11:30:34,824 [40967] <encode:5>: decoded 'INIT' into 'INIT'
2026-03-18 11:30:34,824 [40967] <encode:5>: decoded '3' into '3'
```


When using paramiko.sftp_file.SFTPFile.check anyways - the request won't be accepted:
```
2026-03-18 11:59:13,373 [42043] <sftp:7>: received request: EXTENDED check-file
2026-03-18 11:59:13,373 [42043] <encode:5>: decoded 'EXTENDED' into 'EXTENDED'
2026-03-18 11:59:13,373 [42043] <encode:5>: decoded 'check-file' into 'check-file'
2026-03-18 11:59:13,373 [42043] <command:7>: dispatching POST_CMD_ERR command 'EXTENDED check-file' to mod_exec.c
2026-03-18 11:59:13,373 [42043] <command:7>: dispatching LOG_CMD_ERR command 'EXTENDED check-file' to mod_log.c
2026-03-18 11:59:13,373 [42043] <sftp:8>: sending response: STATUS 8 'Unsupported operation'
2026-03-18 11:59:13,373 [42043] <response:7>: response added to pending list: 8 Unsupported operation
2026-03-18 11:59:13,373 [42043] <ssh2:9>: sending CHANNEL_DATA (remote channel ID 0, 47 data bytes)
``` 


Do you have any hints about this?

Thanks a lot, Joerg



-- System Information:
Debian Release: 13.3
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable-security'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 6.12.73+deb13-amd64 (SMP w/7 CPU threads; PREEMPT)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US:en
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages proftpd-mod-crypto depends on:
ii  libc6         2.41-12+deb13u2
ii  libpam0g      1.7.0-5
ii  libsodium23   1.0.18-1+deb13u1
ii  libssl3t64    3.5.5-1~deb13u1
ii  proftpd-core  1.3.8.c+dfsg-4+deb13u1
ii  zlib1g        1:1.3.dfsg+really1.3.1-1+b1

proftpd-mod-crypto recommends no packages.

proftpd-mod-crypto suggests no packages.

-- no debconf information