fix: prevent crash when result of SendMessage is 0 #63
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openssh 8.9 introduces feature "SSH agent restriction", which means protocol extension (SSH_AGENTC_EXTENSION) will be used (https://www.openssh.com/agent-restrict.html#limitations). When connecting to older pageant with openssh 8.9 client, the message with type SSH_AGENTC_EXTENSION can't be processed by pageant, thus SendMessage returns 0, in which case `psd` and `usersid` is likely to be freed twice in the code, causing crash. This commit fixes this.
cuviper
reviewed
Apr 27, 2022
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Thanks, that was a clear oversight. 😬
While we're here (or perhaps another PR), do you want to increase AGENT_MAX_MSGLEN? Putty has been using 256kB for a while now:
https://git.tartarus.org/?p=simon/putty.git;a=commitdiff;h=98528db25a9df211141b8711a3756ee2b6ea26e9
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openssh 8.9 introduces feature "SSH agent restriction", which
means protocol extension (SSH_AGENTC_EXTENSION) will be used
(https://www.openssh.com/agent-restrict.html#limitations).
When connecting to older pageant with openssh 8.9 client,
the message with type SSH_AGENTC_EXTENSION can't be processed
by pageant, thus SendMessage returns 0, in which case
psdandusersidis likely to be freed twice in the code,causing crash.
This commit fixes this.