sftp: Add new quote commands 'atime' and 'mtime'

[COFFEETALES]

In some situations, you may have to change the modified or last accessed date of a specific file.
This PR add new quote commands for sftp only.

[cvengler]

The two else if statements look very similar.
Why not try to put them into one and obfuscate the code a bit :-)

[bagder]

Thanks!

[PayBas]

@COFFEETALES @bagder I've been trying for 2 days now to get this working with curl version 7.85.0, but no luck so far.
But I'm not sure whether this is bug, a config error on my part, or some missing documentation on https://curl.se/docs/manpage.html#-Q

Server:

# cat sshd_config.d/sftp.conf 
Subsystem sftp internal-sftp

Match User sftp
     ChrootDirectory /opt/sftp/
     X11Forwarding no
     AllowTCPForwarding no
     ForceCommand internal-sftp

# ls -al /opt/sftp/
drwxr-xr-x. 3 root root 4096 Apr 27 01:16 .
drwxr-xr-x. 7 root root 4096 Apr 27 01:16 ..
drwxrwxrwx. 6 sftp sftp 4096 May  1 13:58 data

Client:

Working correctly:

$ curl -Q "mkdir data/foo" -u sftp:pass sftp://server.my.corp:22/data/
drwxrwxrwx    7 1010     1010         4096 May  1 12:16 .
drwxr-xr-x    3 root     root         4096 Apr 26 23:16 ..
drwxr-xr-x    4 1010     1010         4096 May  1 10:47 foo

$ curl -Q "rename data/foo data/bar" -u sftp:pass sftp://server.my.corp:22/data/
drwxrwxrwx    7 1010     1010         4096 May  1 12:16 .
drwxr-xr-x    3 root     root         4096 Apr 26 23:16 ..
drwxr-xr-x    4 1010     1010         4096 May  1 10:47 bar

$ curl -Q "ln data/foo data/bar" -u sftp:pass sftp://server.my.corp:22/data/
drwxrwxrwx    7 1010     1010         4096 May  1 12:16 .
drwxr-xr-x    3 root     root         4096 Apr 26 23:16 ..
drwxr-xr-x    4 1010     1010         4096 May  1 10:47 bar
lrwxrwxrwx    1 1010     1010         4096 May  1 10:58 foo -> data/bar

Problematic:

$ now=$(date '+%Y-%m-%d %H:%M:%S %z')
$ curl -Q "mtime $now data/bar" -u sftp:pass sftp://server.my.corp:22/data/
curl: (21) Attempt to get SFTP stats failed: 2

$ curl -Q "atime $now data/bar" -u sftp:pass sftp://server.my.corp:22/data/
curl: (21) Attempt to get SFTP stats failed: 2

Am I missing something? Are there server-side requirements? Verbose output doesn't provide any additional insights.

Looking through the server logs didn't show any clear causes. Or sshd is logging the error to some log unknown to me.

[dfandrich]

$ curl -Q "mtime $now data/bar" -u sftp:pass sftp://server.my.corp:22/data/

The parser expects a single argument for the date, so you need to either use a format without spaces (e.g. $(date +%s)) or quote it.

[PayBas]

@dfandrich thanks for the reply. Are you actually getting successful results with that?

$ curl -Q "mtime $(date +%s) data/bar" -u sftp:pass sftp://server.my.corp:22/data/
curl: (21) incorrect date format for mtime

$ now=$(date +%s)
$ curl -Q "mtime $now data/bar" -u sftp:pass sftp://server.my.corp:22/data/
curl: (21) incorrect date format for mtime

$ curl -Q "mtime 1682955360 data/bar" -u sftp:pass sftp://server.my.corp:22/data/
curl: (21) incorrect date format for mtime

$ curl -Q "mtime '2023-05-01 17:41:16 +0200' data/bar" -u sftp:pass sftp://server.my.corp:22/data/
curl: (21) incorrect date format for mtime

$ now=$(date '+%Y-%m-%d %H:%M:%S %z')
$ curl -Q "mtime '$now' data/bar" -u sftp:pass sftp://server.my.corp:22/data/
curl: (21) incorrect date format for mtime

$ now=$(date '+%Y-%m-%d %H:%M:%S %z')
$ curl -Q "mtime $now data/bar" -u sftp:pass sftp://server.my.corp:22/data/
curl: (21) Attempt to get SFTP stats failed: 2

I should clarify that both the client and server are both Fedora 37 machines.
curl version: 7.85.0
OpenSSL version: OpenSSL 3.0.8 7 Feb 2023 (Library: OpenSSL 3.0.8 7 Feb 2023)

[dfandrich]

It looks like the +%s format isn't actually supported, but this works fine: $ curl -Q "mtime \"$(date -R)\" /tmp/foo" sftp://server/tmp/foo

[PayBas]

Wow. That's a very specific syntax. I wouldn't have thought of explicitly using escaped double-quotes.
Seems to be working now. Thanks a bunch @dfandrich 👍