Look for FamilyLocal if inet or inet6 address is loopback

libxcb uses FamilyLocal authorization if the host name or IP in the
display string is from the loopback device. This patch adds the same
behavior to xauth.
This fixes a long standing problem that for ssh tunneled connections
a display variable of the form: localhost:<N>.<M> leads to correct
authorization when an X client is started but "xauth list $DISPLAY"
returns nothing.

Signed-off-by: Egbert Eich <eich@freedesktop.org>

1 files changed, 35 insertions, 5 deletions

diff --git a/gethost.c b/gethost.c
index 8f77c80..8f282c7 100644
--- a/gethost.c
+++ b/gethost.c
@@ -227,16 +227,36 @@ struct addrlist *get_address_info (
 	for (ai = firstai; ai != NULL; ai = ai->ai_next) {
 	    struct addrlist *duplicate;
 
+            len = 0;
 	    if (ai->ai_family == AF_INET) {
 		struct sockaddr_in *sin = (struct sockaddr_in *)ai->ai_addr;
 		src = &(sin->sin_addr);
-		len = sizeof(sin->sin_addr);
-		family = FamilyInternet;
+                if (*(in_addr_t *) src == htonl(INADDR_LOOPBACK)) {
+                    family = FamilyLocal;
+                    if (get_local_hostname (buf, sizeof buf)) {
+                        src = buf;
+                        len = strlen (buf);
+                    } else
+                        src = NULL;
+                } else {
+                    len = sizeof(sin->sin_addr);
+                    family = FamilyInternet;
+                }
 	    } else if (ai->ai_family == AF_INET6) {
 		struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)ai->ai_addr;
 		src = &(sin6->sin6_addr);
-		len = sizeof(sin6->sin6_addr);
-		family = FamilyInternet6;
+                if (IN6_IS_ADDR_V4MAPPED((struct sockaddr_in6 *)src)
+                    || IN6_IS_ADDR_LOOPBACK((struct sockaddr_in6 *)src)) {
+                    family = FamilyLocal;
+                    if (get_local_hostname (buf, sizeof buf)) {
+                        src = buf;
+                        len = strlen (buf);
+                    } else
+                        src = NULL;
+                } else {
+                    len = sizeof(sin6->sin6_addr);
+                    family = FamilyInternet6;
+                }
 	    }
 
 	    for(duplicate = retval; duplicate != NULL; duplicate = duplicate->next) {
@@ -275,7 +295,17 @@ struct addrlist *get_address_info (
 #else
 	if (!get_inet_address (host, &hostinetaddr)) return NULL;
 	src = (char *) &hostinetaddr;
-	len = 4; /* sizeof inaddr.sin_addr, would fail on Cray */
+        if (*(in_addr_t *) src == htonl(INADDR_LOOPBACK)) {
+            family = FamilyLocal;
+            if (get_local_hostname (buf, sizeof buf)) {
+                src = buf;
+                len = strlen (buf);
+            } else {
+                len = 0;
+                src = NULL;
+            }
+        } else
+            len = 4; /* sizeof inaddr.sin_addr, would fail on Cray */
 	break;
 #endif /* IPv6 */
 #else