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 5e86987f221fee01c5049f925492e0f9c441d372..15a01a8324b8a6ff9727a1b02e7ba8fe385d3a39 100644 (file)
--- a/src/backend/libpq/pqcomm.c
+++ b/src/backend/libpq/pqcomm.c
@@ -308,6 +308,14 @@ StreamServerPort(int family, char *hostName, unsigned short portNumber,
                 * that file path
                 */
                UNIXSOCK_PATH(unixSocketPath, portNumber, unixSocketDir);
+               if (strlen(unixSocketPath) >= UNIXSOCK_PATH_BUFLEN)
+               {
+                       ereport(LOG,
+                                       (errmsg("Unix-domain socket path \"%s\" is too long (maximum %d bytes)",
+                                                       unixSocketPath,
+                                                       (int) (UNIXSOCK_PATH_BUFLEN - 1))));
+                       return STATUS_ERROR;
+               }
                if (Lock_AF_UNIX(unixSocketDir, unixSocketPath) != STATUS_OK)
                        return STATUS_ERROR;
                service = unixSocketPath;

diff --git a/src/include/libpq/pqcomm.h b/src/include/libpq/pqcomm.h
index 604b5535df6b24885b782688fee9ff7fd284746b..635132dec9317b4045108c75cd8c67a70c360968 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 9eaf41025beb652c6c242035490d93319a6bc5d0..1386bb791a96fab087af1ba33546ab89772327fd 100644 (file)
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -1322,7 +1322,7 @@ static int
 connectDBStart(PGconn *conn)
 {
        int                     portnum;
-       char            portstr[128];
+       char            portstr[MAXPGPATH];
        struct addrinfo *addrs = NULL;
        struct addrinfo hint;
        const char *node;
@@ -1384,6 +1384,15 @@ 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;