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upstream: UpdateHostkeys: better detect manual host entries

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Disable UpdateHostkeys if the known_hosts line has more than two
entries in the pattern-list. ssh(1) only writes "host" or "host,ip"
lines so anything else was added by a different tool or by a human.

ok markus@

OpenBSD-Commit-ID: e434828191fb5f3877d4887c218682825aa59820
This commit is contained in:
djm@openbsd.org 2020-10-11 22:12:44 +00:00 committed by Damien Miller
parent 6247812c76
commit af5941ae9b
1 changed files with 37 additions and 17 deletions
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54
clientloop.c
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@ -1,4 +1,4 @@
/* $OpenBSD: clientloop.c,v 1.349 2020/10/08 01:15:16 djm Exp $ */ /* $OpenBSD: clientloop.c,v 1.350 2020/10/11 22:12:44 djm Exp $ */
/* /*
* Author: Tatu Ylonen <ylo@cs.hut.fi> * Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@ -1830,7 +1830,7 @@ struct hostkeys_update_ctx {
size_t nold; size_t nold;
/* Various special cases. */ /* Various special cases. */
int wildcard_hostspec; /* saw wildcard or pattern-list host name */ int complex_hostspec; /* wildcard or manual pattern-list host name */
int ca_available; /* saw CA key for this host */ int ca_available; /* saw CA key for this host */
}; };
@ -1853,6 +1853,29 @@ hostkeys_update_ctx_free(struct hostkeys_update_ctx *ctx)
free(ctx); free(ctx);
} }
/*
* Returns non-zero if a known_hosts hostname list is not of a form that
* can be handled by UpdateHostkeys. These include wildcard hostnames and
* hostnames lists that do not follow the form host[,ip].
*/
static int
hostspec_is_complex(const char *hosts)
{
char *cp;
/* wildcard */
if (strchr(hosts, '*') != NULL || strchr(hosts, '?') != NULL)
return 1;
/* single host/ip = ok */
if ((cp = strchr(hosts, ',')) == NULL)
return 0;
/* more than two entries on the line */
if (strchr(cp + 1, ',') != NULL)
return 1;
/* XXX maybe parse cp+1 and ensure it is an IP? */
return 0;
}
static int static int
hostkeys_find(struct hostkey_foreach_line *l, void *_ctx) hostkeys_find(struct hostkey_foreach_line *l, void *_ctx)
{ {
@ -1860,22 +1883,19 @@ hostkeys_find(struct hostkey_foreach_line *l, void *_ctx)
size_t i; size_t i;
struct sshkey **tmp; struct sshkey **tmp;
if (l->status != HKF_STATUS_MATCHED || l->key == NULL) if (l->status != HKF_STATUS_MATCHED || l->key == NULL ||
l->marker != MRK_NONE)
return 0; return 0;
if (l->marker == MRK_REVOKE) /*
* UpdateHostkeys is skipped for wildcard host names and hostnames
* that contain more than two entries (ssh never writes these).
*/
if (hostspec_is_complex(l->hosts)) {
debug3("%s: hostkeys file %s:%ld complex host specification",
__func__, l->path, l->linenum);
ctx->complex_hostspec = 1;
return 0; return 0;
if (l->marker == MRK_CA) {
ctx->ca_available = 1;
return 0;
}
/* UpdateHostkeys is skipped for wildcard host names */
if (strchr(l->hosts, '*') != NULL ||
strchr(l->hosts, '?') != NULL) {
debug3("%s: hostkeys file %s:%ld contains wildcard", __func__,
l->path, l->linenum);
ctx->wildcard_hostspec = 1;
} }
/* Mark off keys we've already seen for this host */ /* Mark off keys we've already seen for this host */
@ -2223,8 +2243,8 @@ client_input_hostkeys(struct ssh *ssh)
debug3("%s: %zu keys from server: %zu new, %zu retained. %zu to remove", debug3("%s: %zu keys from server: %zu new, %zu retained. %zu to remove",
__func__, ctx->nkeys, ctx->nnew, ctx->nkeys - ctx->nnew, ctx->nold); __func__, ctx->nkeys, ctx->nnew, ctx->nkeys - ctx->nnew, ctx->nold);
if (ctx->wildcard_hostspec && (ctx->nnew != 0 || ctx->nold != 0)) { if (ctx->complex_hostspec && (ctx->nnew != 0 || ctx->nold != 0)) {
debug("%s: wildcard known hosts name found, " debug("%s: manual list or wildcard host pattern found, "
"skipping UserKnownHostsFile update", __func__); "skipping UserKnownHostsFile update", __func__);
goto out; goto out;
} else if (ctx->nnew == 0 && ctx->nold != 0) { } else if (ctx->nnew == 0 && ctx->nold != 0) {