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

Package:
proftpd-mod-crypto
Source:
proftpd-mod-crypto
Description:
Versatile, virtual-hosting FTP daemon - TLS/SSL/SFTP modules
Submitter:
Jörg Eichhorn
Date:
2026-03-18 22:57:02 UTC
Severity:
normal
#1131161#5
Date:
2026-03-18 11:25:31 UTC
From:
To:

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@openssh.com = '1'
2026-03-18 11:30:34,824 [40967] <sftp:11>: + SFTP extension: posix-rename@openssh.com = '1'
2026-03-18 11:30:34,824 [40967] <sftp:11>: + SFTP extension: statvfs@openssh.com = '2'
2026-03-18 11:30:34,824 [40967] <sftp:11>: + SFTP extension: fstatvfs@openssh.com = '2'
2026-03-18 11:30:34,824 [40967] <sftp:11>: + SFTP extension: hardlink@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@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
#1131161#10
Date:
2026-03-18 22:56:18 UTC
From:
To:
Am 18.03.2026 um 12:25 schrieb Jörg Eichhorn:

Hello,

At [1] I can read "All extensions except vendorID and xattr are enabled
by default." The page reports more extensions, than these from your log
file, e.g. limits. I'm not sure if the log is complete.

I guess this your proof that, that the extension is really not
activated, right?

Before opening a bug at upstream: do you have an unstable installation
running 1.3.9 and could test if the issue is solved there? If needed I
can provide backports for Debian stable.

Hilmar

[1] http://www.proftpd.org/docs/contrib/mod_sftp.html#SFTPExtensions