Produce a more useful error message for over-length Unix socket paths.

The length of a socket path name is constrained by the size of struct
sockaddr_un, and there's not a lot we can do about it since that is a
kernel API.  However, it would be a good thing if we produced an
intelligible error message when the user specifies a socket path that's too
long --- and getaddrinfo's standard API is too impoverished to do this in
the natural way.  So insert explicit tests at the places where we construct
a socket path name.  Now you'll get an error that makes sense and even
tells you what the limit is, rather than something generic like
"Non-recoverable failure in name resolution".

Per trouble report from Jeremy Drake and a fix idea from Andrew Dunstan.

diff --git a/src/backend/libpq/pqcomm.c b/src/backend/libpq/pqcomm.c
index b83a2efb6989383552166bd6ddfa95ae046f809d..c79c846a66006103337d93bd0785dc08ec5a4885 100644 (file)
--- a/src/backend/libpq/pqcomm.c
+++ b/src/backend/libpq/pqcomm.c
@@ -493,6 +493,14 @@ static int
 Lock_AF_UNIX(unsigned short portNumber, char *unixSocketName)
 {
        UNIXSOCK_PATH(sock_path, portNumber, unixSocketName);
+       if (strlen(sock_path) >= UNIXSOCK_PATH_BUFLEN)
+       {
+               ereport(LOG,
+                               (errmsg("Unix-domain socket path \"%s\" is too long (maximum %d bytes)",
+                                               sock_path,
+                                               (int) (UNIXSOCK_PATH_BUFLEN - 1))));
+               return STATUS_ERROR;
+       }
 
        /*
         * Grab an interlock file associated with the socket file.

diff --git a/src/include/libpq/pqcomm.h b/src/include/libpq/pqcomm.h
index bd0fa2507780fae20b926287ca20ecbd9608ef88..c28ada8b187e10cb9524967f29b68d9f35643329 100644 (file)
--- a/src/include/libpq/pqcomm.h
+++ b/src/include/libpq/pqcomm.h
@@ -73,6 +73,19 @@ typedef struct
                                DEFAULT_PGSOCKET_DIR, \
                                (port))
 
+/*
+ * The maximum workable length of a socket path is what will fit into
+ * struct sockaddr_un.  This is usually only 100 or so bytes :-(.
+ *
+ * For consistency, always pass a MAXPGPATH-sized buffer to UNIXSOCK_PATH(),
+ * then complain if the resulting string is >= UNIXSOCK_PATH_BUFLEN bytes.
+ * (Because the standard API for getaddrinfo doesn't allow it to complain in
+ * a useful way when the socket pathname is too long, we have to test for
+ * this explicitly, instead of just letting the subroutine return an error.)
+ */
+#define UNIXSOCK_PATH_BUFLEN sizeof(((struct sockaddr_un *) NULL)->sun_path)
+
+
 /*
  * These manipulate the frontend/backend protocol version number.
  *

diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 704885bbbed20e0baa273110a44a6541c682d68d..3ff9ee307e85914d931226024b45aaf2eca99e70 100644 (file)
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -1259,7 +1259,7 @@ static int
 connectDBStart(PGconn *conn)
 {
        int                     portnum;
-       char            portstr[128];
+       char            portstr[MAXPGPATH];
        struct addrinfo *addrs = NULL;
        struct addrinfo hint;
        const char *node;
@@ -1321,6 +1321,15 @@ connectDBStart(PGconn *conn)
                node = NULL;
                hint.ai_family = AF_UNIX;
                UNIXSOCK_PATH(portstr, portnum, conn->pgunixsocket);
+               if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
+               {
+                       appendPQExpBuffer(&conn->errorMessage,
+                                                         libpq_gettext("Unix-domain socket path \"%s\" is too long (maximum %d bytes)\n"),
+                                                                                       portstr,
+                                                                                       (int) (UNIXSOCK_PATH_BUFLEN - 1));
+                       conn->options_valid = false;
+                       goto connect_errReturn;
+               }
 #else
                /* Without Unix sockets, default to localhost instead */
                node = DefaultHost;