1 files changed, 138 insertions, 13 deletions

diff --git a/auth.c b/auth.c
index 214c2c708..24527dd7c 100644
--- a/auth.c
+++ b/auth.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: auth.c,v 1.113 2015/08/21 03:42:19 djm Exp $ */
+/* $OpenBSD: auth.c,v 1.115 2016/06/15 00:40:40 dtucker Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  *
@@ -27,6 +27,7 @@
 
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <sys/socket.h>
 
 #include <netinet/in.h>
 
@@ -50,6 +51,7 @@
 #include <string.h>
 #include <unistd.h>
 #include <limits.h>
+#include <netdb.h>
 
 #include "xmalloc.h"
 #include "match.h"
@@ -97,6 +99,7 @@ int auth_debug_init;
 int
 allowed_user(struct passwd * pw)
 {
+        struct ssh *ssh = active_state; /* XXX */
         struct stat st;
         const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL;
         u_int i;
@@ -182,8 +185,8 @@ allowed_user(struct passwd * pw)
 
         if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
             options.num_deny_groups > 0 || options.num_allow_groups > 0) {
-                hostname = get_canonical_hostname(options.use_dns);
-                ipaddr = get_remote_ipaddr();
+                hostname = auth_get_canonical_hostname(ssh, options.use_dns);
+                ipaddr = ssh_remote_ipaddr(ssh);
         }
 
         /* Return false if user is listed in DenyUsers */
@@ -274,6 +277,7 @@ void
 auth_log(Authctxt *authctxt, int authenticated, int partial,
     const char *method, const char *submethod)
 {
+        struct ssh *ssh = active_state; /* XXX */
         void (*authlog) (const char *fmt,...) = verbose;
         char *authmsg;
 
@@ -300,8 +304,8 @@ auth_log(Authctxt *authctxt, int authenticated, int partial,
             submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod,
             authctxt->valid ? "" : "invalid user ",
             authctxt->user,
-            get_remote_ipaddr(),
-            get_remote_port(),
+            ssh_remote_ipaddr(ssh),
+            ssh_remote_port(ssh),
             compat20 ? "ssh2" : "ssh1",
             authctxt->info != NULL ? ": " : "",
             authctxt->info != NULL ? authctxt->info : "");
@@ -314,11 +318,12 @@ auth_log(Authctxt *authctxt, int authenticated, int partial,
             strncmp(method, "keyboard-interactive", 20) == 0 ||
             strcmp(method, "challenge-response") == 0))
                 record_failed_login(authctxt->user,
-                    get_canonical_hostname(options.use_dns), "ssh");
+                    auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
 # ifdef WITH_AIXAUTHENTICATE
         if (authenticated)
                 sys_auth_record_login(authctxt->user,
-                    get_canonical_hostname(options.use_dns), "ssh", &loginmsg);
+                    auth_get_canonical_hostname(ssh, options.use_dns), "ssh",
+                    &loginmsg);
 # endif
 #endif
 #ifdef SSH_AUDIT_EVENTS
@@ -331,12 +336,14 @@ auth_log(Authctxt *authctxt, int authenticated, int partial,
 void
 auth_maxtries_exceeded(Authctxt *authctxt)
 {
+        struct ssh *ssh = active_state; /* XXX */
+
         error("maximum authentication attempts exceeded for "
             "%s%.100s from %.200s port %d %s",
             authctxt->valid ? "" : "invalid user ",
             authctxt->user,
-            get_remote_ipaddr(),
-            get_remote_port(),
+            ssh_remote_ipaddr(ssh),
+            ssh_remote_port(ssh),
             compat20 ? "ssh2" : "ssh1");
         packet_disconnect("Too many authentication failures");
         /* NOTREACHED */
@@ -348,6 +355,8 @@ auth_maxtries_exceeded(Authctxt *authctxt)
 int
 auth_root_allowed(const char *method)
 {
+        struct ssh *ssh = active_state; /* XXX */
+
         switch (options.permit_root_login) {
         case PERMIT_YES:
                 return 1;
@@ -364,7 +373,8 @@ auth_root_allowed(const char *method)
                 }
                 break;
         }
-        logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr());
+        logit("ROOT LOGIN REFUSED FROM %.200s port %d",
+            ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
         return 0;
 }
 
@@ -604,6 +614,7 @@ auth_openprincipals(const char *file, struct passwd *pw, int strict_modes)
 struct passwd *
 getpwnamallow(const char *user)
 {
+        struct ssh *ssh = active_state; /* XXX */
 #ifdef HAVE_LOGIN_CAP
         extern login_cap_t *lc;
 #ifdef BSD_AUTH
@@ -639,11 +650,11 @@ getpwnamallow(const char *user)
         }
 #endif
         if (pw == NULL) {
-                logit("Invalid user %.100s from %.100s",
-                    user, get_remote_ipaddr());
+                logit("Invalid user %.100s from %.100s port %d",
+                    user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
 #ifdef CUSTOM_FAILED_LOGIN
                 record_failed_login(user,
-                    get_canonical_hostname(options.use_dns), "ssh");
+                    auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
 #endif
 #ifdef SSH_AUDIT_EVENTS
                 audit_event(SSH_INVALID_USER);
@@ -773,3 +784,117 @@ fakepw(void)
 
         return (&fake);
 }
+
+/*
+ * Returns the remote DNS hostname as a string. The returned string must not
+ * be freed. NB. this will usually trigger a DNS query the first time it is
+ * called.
+ * This function does additional checks on the hostname to mitigate some
+ * attacks on legacy rhosts-style authentication.
+ * XXX is RhostsRSAAuthentication vulnerable to these?
+ * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?)
+ */
+
+static char *
+remote_hostname(struct ssh *ssh)
+{
+        struct sockaddr_storage from;
+        socklen_t fromlen;
+        struct addrinfo hints, *ai, *aitop;
+        char name[NI_MAXHOST], ntop2[NI_MAXHOST];
+        const char *ntop = ssh_remote_ipaddr(ssh);
+
+        /* Get IP address of client. */
+        fromlen = sizeof(from);
+        memset(&from, 0, sizeof(from));
+        if (getpeername(ssh_packet_get_connection_in(ssh),
+            (struct sockaddr *)&from, &fromlen) < 0) {
+                debug("getpeername failed: %.100s", strerror(errno));
+                return strdup(ntop);
+        }
+
+        ipv64_normalise_mapped(&from, &fromlen);
+        if (from.ss_family == AF_INET6)
+                fromlen = sizeof(struct sockaddr_in6);
+
+        debug3("Trying to reverse map address %.100s.", ntop);
+        /* Map the IP address to a host name. */
+        if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
+            NULL, 0, NI_NAMEREQD) != 0) {
+                /* Host name not found.  Use ip address. */
+                return strdup(ntop);
+        }
+
+        /*
+         * if reverse lookup result looks like a numeric hostname,
+         * someone is trying to trick us by PTR record like following:
+         *      1.1.1.10.in-addr.arpa.  IN PTR  2.3.4.5
+         */
+        memset(&hints, 0, sizeof(hints));
+        hints.ai_socktype = SOCK_DGRAM; /*dummy*/
+        hints.ai_flags = AI_NUMERICHOST;
+        if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
+                logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
+                    name, ntop);
+                freeaddrinfo(ai);
+                return strdup(ntop);
+        }
+
+        /* Names are stored in lowercase. */
+        lowercase(name);
+
+        /*
+         * 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) {
+                logit("reverse mapping checking getaddrinfo for %.700s "
+                    "[%s] failed.", name, ntop);
+                return strdup(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 == NULL) {
+                /* Address not found for the host name. */
+                logit("Address %.100s maps to %.600s, but this does not "
+                    "map back to the address.", ntop, name);
+                return strdup(ntop);
+        }
+        return strdup(name);
+}
+
+/*
+ * 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 *
+auth_get_canonical_hostname(struct ssh *ssh, int use_dns)
+{
+        static char *dnsname;
+
+        if (!use_dns)
+                return ssh_remote_ipaddr(ssh);
+        else if (dnsname != NULL)
+                return dnsname;
+        else {
+                dnsname = remote_hostname(ssh);
+                return dnsname;
+        }
+}