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sshd: do not resolve refused client hostname

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This is a compromise between POLA and practical reasoning.  We don't
want to block the main server loop in an attempt to resolve.  But we
need to keep the format of the logged message as is, for sake of
sshguard and other scripts.  So let's print just the IP address twice,
this is what libwrap's refuse() would do if it failed to resolve.

Reviewed by:		philip
PR:			269456
Differential revision:	https://reviews.freebsd.org/D40069
This commit is contained in:
Gleb Smirnoff 2023-07-20 14:56:20 -07:00
parent 90f10db8a9
commit 9ff45b8ed8
1 changed files with 15 additions and 4 deletions
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19
crypto/openssh/sshd.c
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@ -1297,13 +1297,24 @@ server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s)
SO_LINGER, &l, sizeof(l));
(void )close(*newsock);
/*
* Mimic message from libwrap's refuse()
* exactly. sshguard, and supposedly lots
* of custom made scripts rely on it.
* Mimic message from libwrap's refuse() as
* precisely as we can afford. The authentic
* message prints the IP address and the
* hostname it resolves to in parentheses. If
* the IP address cannot be resolved to a
* hostname, the IP address will be repeated
* in parentheses. As name resolution in the
* main server loop could stall, and logging
* resolved names adds little or no value to
* incident investigation, this implementation
* only repeats the IP address in parentheses.
* This should resemble librwap's refuse()
* closely enough not to break auditing
* software like sshguard or custom scripts.
*/
syslog(LOG_WARNING,
"refused connect from %s (%s)",
eval_client(&req),
eval_hostaddr(req.client),
eval_hostaddr(req.client));
debug("Connection refused by tcp wrapper");
continue;