upstream commit

when hostname canonicalisation is enabled, try to parse
 hostnames as addresses before looking them up for canonicalisation. fixes
 bz#2074 and avoids needless DNS lookups in some cases; ok markus

1 files changed, 72 insertions, 5 deletions

diff --git a/ssh.c b/ssh.c
index df7274f4c..5190f1f9b 100644
--- a/ssh.c
+++ b/ssh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh.c,v 1.412 2015/01/14 20:05:27 djm Exp $ */
+/* $OpenBSD: ssh.c,v 1.413 2015/01/16 07:19:48 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -277,6 +277,60 @@ resolve_host(const char *name, int port, int logerr, char *cname, size_t clen)
 }
 
 /*
+ * Attempt to resolve a numeric host address / port to a single address.
+ * Returns a canonical address string.
+ * Returns NULL on failure.
+ * NB. this function must operate with a options having undefined members.
+ */
+static struct addrinfo *
+resolve_addr(const char *name, int port, char *caddr, size_t clen)
+{
+        char addr[NI_MAXHOST], strport[NI_MAXSERV];
+        struct addrinfo hints, *res;
+        int gaierr;
+
+        if (port <= 0)
+                port = default_ssh_port();
+        snprintf(strport, sizeof strport, "%u", port);
+        memset(&hints, 0, sizeof(hints));
+        hints.ai_family = options.address_family == -1 ?
+            AF_UNSPEC : options.address_family;
+        hints.ai_socktype = SOCK_STREAM;
+        hints.ai_flags = AI_NUMERICHOST|AI_NUMERICSERV;
+        if ((gaierr = getaddrinfo(name, strport, &hints, &res)) != 0) {
+                debug2("%s: could not resolve name %.100s as address: %s",
+                    __func__, name, ssh_gai_strerror(gaierr));
+                return NULL;
+        }
+        if (res == NULL) {
+                debug("%s: getaddrinfo %.100s returned no addresses",
+                 __func__, name);
+                return NULL;
+        }
+        if (res->ai_next != NULL) {
+                debug("%s: getaddrinfo %.100s returned multiple addresses",
+                    __func__, name);
+                goto fail;
+        }
+        if ((gaierr = getnameinfo(res->ai_addr, res->ai_addrlen,
+            addr, sizeof(addr), NULL, 0, NI_NUMERICHOST)) != 0) {
+                debug("%s: Could not format address for name %.100s: %s",
+                    __func__, name, ssh_gai_strerror(gaierr));
+                goto fail;
+        }
+        if (strlcpy(caddr, addr, clen) >= clen) {
+                error("%s: host \"%s\" addr \"%s\" too long (max %lu)",
+                    __func__, name,  addr, (u_long)clen);
+                if (clen > 0)
+                        *caddr = '\0';
+ fail:
+                freeaddrinfo(res);
+                return NULL;
+        }
+        return res;
+}
+
+/*
  * Check whether the cname is a permitted replacement for the hostname
  * and perform the replacement if it is.
  * NB. this function must operate with a options having undefined members.
@@ -326,7 +380,7 @@ static struct addrinfo *
 resolve_canonicalize(char **hostp, int port)
 {
         int i, ndots;
-        char *cp, *fullhost, cname_target[NI_MAXHOST];
+        char *cp, *fullhost, newname[NI_MAXHOST];
         struct addrinfo *addrs;
 
         if (options.canonicalize_hostname == SSH_CANONICALISE_NO)
@@ -340,6 +394,19 @@ resolve_canonicalize(char **hostp, int port)
             options.canonicalize_hostname != SSH_CANONICALISE_ALWAYS)
                 return NULL;
 
+        /* Try numeric hostnames first */
+        if ((addrs = resolve_addr(*hostp, port,
+            newname, sizeof(newname))) != NULL) {
+                debug2("%s: hostname %.100s is address", __func__, *hostp);
+                if (strcasecmp(*hostp, newname) != 0) {
+                        debug2("%s: canonicalised address \"%s\" => \"%s\"",
+                            __func__, *hostp, newname);
+                        free(*hostp);
+                        *hostp = xstrdup(newname);
+                }
+                return addrs;
+        }
+
         /* Don't apply canonicalization to sufficiently-qualified hostnames */
         ndots = 0;
         for (cp = *hostp; *cp != '\0'; cp++) {
@@ -353,20 +420,20 @@ resolve_canonicalize(char **hostp, int port)
         }
         /* Attempt each supplied suffix */
         for (i = 0; i < options.num_canonical_domains; i++) {
-                *cname_target = '\0';
+                *newname = '\0';
                 xasprintf(&fullhost, "%s.%s.", *hostp,
                     options.canonical_domains[i]);
                 debug3("%s: attempting \"%s\" => \"%s\"", __func__,
                     *hostp, fullhost);
                 if ((addrs = resolve_host(fullhost, port, 0,
-                    cname_target, sizeof(cname_target))) == NULL) {
+                    newname, sizeof(newname))) == NULL) {
                         free(fullhost);
                         continue;
                 }
                 /* Remove trailing '.' */
                 fullhost[strlen(fullhost) - 1] = '\0';
                 /* Follow CNAME if requested */
-                if (!check_follow_cname(&fullhost, cname_target)) {
+                if (!check_follow_cname(&fullhost, newname)) {
                         debug("Canonicalized hostname \"%s\" => \"%s\"",
                             *hostp, fullhost);
                 }