Bug: scanf class of functions doesn't support conversion specifier [

[kedorlaomer]

Contact Details

adler@openhardware.de

What happened?

Thumbs up for the lovely cosmopolitan libc, I'm using it almost daily!

I was trying to compile openssh-client (9.9, but I tried an older one, too). With a few minor tweaks of the source code, the compilation succeeds. The resulting binary, however, claims to be unable to parse the remote's version string and yields errors such as:

Bad remote protocol version identification: 'SSH-2.0-OpenSSH_9.9'
banner exchange: Connection to 1.2.3.4 port 22: invalid format

The reasons is that in the function kex_exchange_identification in kex.c of openssh, the function sscanf is used with a conversion specifier [ to parse the version string:

 if (sscanf(peer_version_string, "SSH-%d.%d-%[^\n]",
            &remote_major, &remote_minor, remote_version) != 3) {
                error("Bad remote protocol version identification: '%.100s'",
                    peer_version_string);
 invalid:
                send_error(ssh, "Invalid SSH identification string.");

This use of sscanf is mandated in POSIX, so we should also have it.

Before I start warming up my C compiler and preparing a merge request: Do we want this functionality in cosmopolitan libc? Is it somewhere on the roadmap already? Should I indeed try to implement it myself? I estimate it's two or three dozens lines, but I'm not quite sure which infrastructure exists in libc/stdio/vcscanf.c since I haven't studied it properly yet.

Version

cosmocc (GCC) 14.1.0

What operating system are you seeing the problem on?

Linux

Relevant log output

No response