NB: big update - may break stuff. Please test!

 - (djm) OpenBSD CVS sync:
   - markus@cvs.openbsd.org  2001/02/03 03:08:38
     [auth-options.c auth-rh-rsa.c auth-rhosts.c auth.c canohost.c]
     [canohost.h servconf.c servconf.h session.c sshconnect1.c sshd.8]
     [sshd_config]
     make ReverseMappingCheck optional in sshd_config; ok djm@,dugsong@
   - markus@cvs.openbsd.org  2001/02/03 03:19:51
     [ssh.1 sshd.8 sshd_config]
     Skey is now called ChallengeResponse
   - markus@cvs.openbsd.org  2001/02/03 03:43:09
     [sshd.8]
     use no-pty option in .ssh/authorized_keys* if you need a 8-bit clean
     channel. note from Erik.Anggard@cygate.se (pr/1659)
   - stevesk@cvs.openbsd.org 2001/02/03 10:03:06
     [ssh.1]
     typos; ok markus@
   - djm@cvs.openbsd.org     2001/02/04 04:11:56
     [scp.1 sftp-server.c ssh.1 sshd.8 sftp-client.c sftp-client.h]
     [sftp-common.c sftp-common.h sftp-int.c sftp-int.h sftp.1 sftp.c]
     Basic interactive sftp client; ok theo@
 - (djm) Update RPM specs for new sftp binary
 - (djm) Update several bits for new optional reverse lookup stuff. I
   think I got them all.

1 files changed, 104 insertions, 95 deletions

diff --git a/canohost.c b/canohost.c
index f3a659328..8253e9b6e 100644
--- a/canohost.c
+++ b/canohost.c
@@ -12,35 +12,35 @@
  */
 
 #include "includes.h"
-RCSID("$OpenBSD: canohost.c,v 1.19 2001/01/29 19:42:33 markus Exp $");
+RCSID("$OpenBSD: canohost.c,v 1.20 2001/02/03 10:08:37 markus Exp $");
 
 #include "packet.h"
 #include "xmalloc.h"
 #include "log.h"
 
+void    check_ip_options(int socket, char *ipaddr);
+
 /*
  * Return the canonical name of the host at the other end of the socket. The
  * caller should free the returned string with xfree.
  */
 
 char *
-get_remote_hostname(int socket)
+get_remote_hostname(int socket, int reverse_mapping_check)
 {
         struct sockaddr_storage from;
         int i;
         socklen_t fromlen;
         struct addrinfo hints, *ai, *aitop;
-        char name[MAXHOSTNAMELEN];
-        char ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
+        char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
 
         /* Get IP address of client. */
         fromlen = sizeof(from);
         memset(&from, 0, sizeof(from));
-        if (getpeername(socket, (struct sockaddr *) & from, &fromlen) < 0) {
+        if (getpeername(socket, (struct sockaddr *) &from, &fromlen) < 0) {
                 debug("getpeername failed: %.100s", strerror(errno));
                 fatal_cleanup();
         }
-
 #ifdef IPV4_IN_IPV6
         if (from.ss_family == AF_INET6) {
                 struct sockaddr_in6 *from6 = (struct sockaddr_in6 *)&from;
@@ -63,6 +63,8 @@ get_remote_hostname(int socket)
                 }
         }
 #endif
+        if (from.ss_family == AF_INET)
+                check_ip_options(socket, ntop);
 
         if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
              NULL, 0, NI_NUMERICHOST) != 0)
@@ -70,120 +72,127 @@ get_remote_hostname(int socket)
 
         /* Map the IP address to a host name. */
         if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
-             NULL, 0, NI_NAMEREQD) == 0) {
-                /* Got host name. */
-                name[sizeof(name) - 1] = '\0';
-                /*
-                 * Convert it to all lowercase (which is expected by the rest
-                 * of this software).
-                 */
-                for (i = 0; name[i]; i++)
-                        if (isupper(name[i]))
-                                name[i] = tolower(name[i]);
-
-                /*
-                 * Map it back to an IP address and check that the given
-                 * address actually is an address of this host.  This is
-                 * necessary because anyone with access to a name server can
-                 * define arbitrary names for an IP address. Mapping from
-                 * name to IP address can be trusted better (but can still be
-                 * fooled if the intruder has access to the name server of
-                 * the domain).
-                 */
-                memset(&hints, 0, sizeof(hints));
-                hints.ai_family = from.ss_family;
-                hints.ai_socktype = SOCK_STREAM;
-                if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
-                        log("reverse mapping checking getaddrinfo for %.700s failed - POSSIBLE BREAKIN ATTEMPT!", name);
-                        strlcpy(name, ntop, sizeof name);
-                        goto check_ip_options;
-                }
-                /* Look for the address from the list of addresses. */
-                for (ai = aitop; ai; ai = ai->ai_next) {
-                        if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
-                            sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
-                            (strcmp(ntop, ntop2) == 0))
-                                        break;
-                }
-                freeaddrinfo(aitop);
-                /* If we reached the end of the list, the address was not there. */
-                if (!ai) {
-                        /* Address not found for the host name. */
-                        log("Address %.100s maps to %.600s, but this does not map back to the address - POSSIBLE BREAKIN ATTEMPT!",
-                            ntop, name);
-                        strlcpy(name, ntop, sizeof name);
-                        goto check_ip_options;
-                }
-                /* Address was found for the host name.  We accept the host name. */
-        } else {
-                /* Host name not found.  Use ascii representation of the address. */
-                strlcpy(name, ntop, sizeof name);
-                log("Could not reverse map address %.100s.", name);
+             NULL, 0, NI_NAMEREQD) != 0) {
+                /* Host name not found.  Use ip address. */
+                log("Could not reverse map address %.100s.", ntop);
+                return xstrdup(ntop);
         }
 
-check_ip_options:
+        /* Got host name. */
+        name[sizeof(name) - 1] = '\0';
+        /*
+         * Convert it to all lowercase (which is expected by the rest
+         * of this software).
+         */
+        for (i = 0; name[i]; i++)
+                if (isupper(name[i]))
+                        name[i] = tolower(name[i]);
 
+        if (!reverse_mapping_check)
+                return xstrdup(name);
         /*
-         * If IP options are supported, make sure there are none (log and
-         * disconnect them if any are found).  Basically we are worried about
-         * source routing; it can be used to pretend you are somebody
-         * (ip-address) you are not. That itself may be "almost acceptable"
-         * under certain circumstances, but rhosts autentication is useless
-         * if source routing is accepted. Notice also that if we just dropped
-         * source routing here, the other side could use IP spoofing to do
-         * rest of the interaction and could still bypass security.  So we
-         * exit here if we detect any IP options.
+         * Map it back to an IP address and check that the given
+         * address actually is an address of this host.  This is
+         * necessary because anyone with access to a name server can
+         * define arbitrary names for an IP address. Mapping from
+         * name to IP address can be trusted better (but can still be
+         * fooled if the intruder has access to the name server of
+         * the domain).
          */
-        /* IP options -- IPv4 only */
-        if (from.ss_family == AF_INET) {
-                u_char options[200], *ucp;
-                char text[1024], *cp;
-                socklen_t option_size;
-                int ipproto;
-                struct protoent *ip;
-
-                if ((ip = getprotobyname("ip")) != NULL)
-                        ipproto = ip->p_proto;
-                else
-                        ipproto = IPPROTO_IP;
-                option_size = sizeof(options);
-                if (getsockopt(socket, ipproto, IP_OPTIONS, (char *) options,
-                    &option_size) >= 0 && option_size != 0) {
-                        cp = text;
-                        /* Note: "text" buffer must be at least 3x as big as options. */
-                        for (ucp = options; option_size > 0; ucp++, option_size--, cp += 3)
-                                sprintf(cp, " %2.2x", *ucp);
-                        log("Connection from %.100s with IP options:%.800s",
-                            ntop, text);
-                        packet_disconnect("Connection from %.100s with IP options:%.800s",
-                                          ntop, text);
-                }
+        memset(&hints, 0, sizeof(hints));
+        hints.ai_family = from.ss_family;
+        hints.ai_socktype = SOCK_STREAM;
+        if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
+                log("reverse mapping checking getaddrinfo for %.700s "
+                    "failed - POSSIBLE BREAKIN ATTEMPT!", name);
+                return xstrdup(ntop);
+        }
+        /* Look for the address from the list of addresses. */
+        for (ai = aitop; ai; ai = ai->ai_next) {
+                if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
+                    sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
+                    (strcmp(ntop, ntop2) == 0))
+                                break;
+        }
+        freeaddrinfo(aitop);
+        /* If we reached the end of the list, the address was not there. */
+        if (!ai) {
+                /* Address not found for the host name. */
+                log("Address %.100s maps to %.600s, but this does not "
+                    "map back to the address - POSSIBLE BREAKIN ATTEMPT!",
+                    ntop, name);
+                return xstrdup(ntop);
         }
-
         return xstrdup(name);
 }
 
 /*
+ * If IP options are supported, make sure there are none (log and
+ * disconnect them if any are found).  Basically we are worried about
+ * source routing; it can be used to pretend you are somebody
+ * (ip-address) you are not. That itself may be "almost acceptable"
+ * under certain circumstances, but rhosts autentication is useless
+ * if source routing is accepted. Notice also that if we just dropped
+ * source routing here, the other side could use IP spoofing to do
+ * rest of the interaction and could still bypass security.  So we
+ * exit here if we detect any IP options.
+ */
+/* IPv4 only */
+void
+check_ip_options(int socket, char *ipaddr)
+{
+        u_char options[200], *ucp;
+        char text[1024], *cp;
+        socklen_t option_size;
+        int ipproto;
+        struct protoent *ip;
+
+        if ((ip = getprotobyname("ip")) != NULL)
+                ipproto = ip->p_proto;
+        else
+                ipproto = IPPROTO_IP;
+        option_size = sizeof(options);
+        if (getsockopt(socket, ipproto, IP_OPTIONS, (void *)options,
+            &option_size) >= 0 && option_size != 0) {
+                cp = text;
+                /* Note: "text" buffer must be at least 3x as big as options. */
+                for (ucp = options; option_size > 0; ucp++, option_size--, cp += 3)
+                        sprintf(cp, " %2.2x", *ucp);
+                log("Connection from %.100s with IP options:%.800s",
+                    ipaddr, text);
+                packet_disconnect("Connection from %.100s with IP options:%.800s",
+                    ipaddr, text);
+        }
+}
+
+/*
  * Return the canonical name of the host in the other side of the current
  * connection.  The host name is cached, so it is efficient to call this
  * several times.
  */
 
 const char *
-get_canonical_hostname()
+get_canonical_hostname(int reverse_mapping_check)
 {
         static char *canonical_host_name = NULL;
+        static int reverse_mapping_checked = 0;
 
-        /* Check if we have previously retrieved this same name. */
-        if (canonical_host_name != NULL)
-                return canonical_host_name;
+        /* Check if we have previously retrieved name with same option. */
+        if (canonical_host_name != NULL) {
+                if (reverse_mapping_checked != reverse_mapping_check)
+                        xfree(canonical_host_name);
+                else
+                        return canonical_host_name;
+        }
 
         /* Get the real hostname if socket; otherwise return UNKNOWN. */
         if (packet_connection_is_on_socket())
-                canonical_host_name = get_remote_hostname(packet_get_connection_in());
+                canonical_host_name = get_remote_hostname(
+                    packet_get_connection_in(), reverse_mapping_check);
         else
                 canonical_host_name = xstrdup("UNKNOWN");
 
+        reverse_mapping_checked = reverse_mapping_check;
         return canonical_host_name;
 }