Fix insecure parsing of server command-line switches.

An oversight in commit e710b65c1c56ca7b91f662c63d37ff2e72862a94 allowed
database names beginning with "-" to be treated as though they were secure
command-line switches; and this switch processing occurs before client
authentication, so that even an unprivileged remote attacker could exploit
the bug, needing only connectivity to the postmaster's port.  Assorted
exploits for this are possible, some requiring a valid database login,
some not.  The worst known problem is that the "-r" switch can be invoked
to redirect the process's stderr output, so that subsequent error messages
will be appended to any file the server can write.  This can for example be
used to corrupt the server's configuration files, so that it will fail when
next restarted.  Complete destruction of database tables is also possible.

Fix by keeping the database name extracted from a startup packet fully
separate from command-line switches, as had already been done with the
user name field.

The Postgres project thanks Mitsumasa Kondo for discovering this bug,
Kyotaro Horiguchi for drafting the fix, and Noah Misch for recognizing
the full extent of the danger.

Security: CVE-2013-1899

diff --git a/src/backend/main/main.c b/src/backend/main/main.c
index c7d48e95ad6c3eeadf3e23aabdd162c64ea31334..e0183029e9f7de9557afbb3336a28a974a6e3c99 100644 (file)
--- a/src/backend/main/main.c
+++ b/src/backend/main/main.c
@@ -194,7 +194,7 @@ main(int argc, char *argv[])
                exit(GucInfoMain());
 
        if (argc > 1 && strcmp(argv[1], "--single") == 0)
-               exit(PostgresMain(argc, argv, get_current_username(progname)));
+               exit(PostgresMain(argc, argv, NULL, get_current_username(progname)));
 
        exit(PostmasterMain(argc, argv));
 }

diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index b81d7140992b9942f7d7a3a6ebb943d23d5ec000..437b7fae6deddaf98b6b973e6b66bd2d8a83b58f 100644 (file)
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -3573,7 +3573,7 @@ BackendRun(Port *port)
         * from ExtraOptions is (strlen(ExtraOptions) + 1) / 2; see
         * pg_split_opts().
         */
-       maxac = 5;                                      /* for fixed args supplied below */
+       maxac = 2;                                      /* for fixed args supplied below */
        maxac += (strlen(ExtraOptions) + 1) / 2;
 
        av = (char **) MemoryContextAlloc(TopMemoryContext,
@@ -3589,11 +3589,6 @@ BackendRun(Port *port)
         */
        pg_split_opts(av, &ac, ExtraOptions);
 
-       /*
-        * Tell the backend which database to use.
-        */
-       av[ac++] = port->database_name;
-
        av[ac] = NULL;
 
        Assert(ac < maxac);
@@ -3616,7 +3611,7 @@ BackendRun(Port *port)
         */
        MemoryContextSwitchTo(TopMemoryContext);
 
-       return (PostgresMain(ac, av, port->user_name));
+       return PostgresMain(ac, av, port->database_name, port->user_name);
 }
 
 

diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index f1633f9de396a49fdb50d88c636c6d928a361825..bb34fc751dd61e76c3e51be717a38d13fe6d2b17 100644 (file)
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -3230,13 +3230,14 @@ get_stats_option_name(const char *arg)
  * coming from the client, or PGC_SUSET for insecure options coming from
  * a superuser client.
  *
- * Returns the database name extracted from the command line, if any.
+ * If a database name is present in the command line arguments, it's
+ * returned into *dbname (this is allowed only if *dbname is initially NULL).
  * ----------------------------------------------------------------
  */
-const char *
-process_postgres_switches(int argc, char *argv[], GucContext ctx)
+void
+process_postgres_switches(int argc, char *argv[], GucContext ctx,
+                                                 const char **dbname)
 {
-       const char *dbname;
        bool            secure = (ctx == PGC_POSTMASTER);
        int                     errs = 0;
        GucSource       gucsource;
@@ -3287,7 +3288,8 @@ process_postgres_switches(int argc, char *argv[], GucContext ctx)
 
                        case 'b':
                                /* Undocumented flag used for binary upgrades */
-                               IsBinaryUpgrade = true;
+                               if (secure)
+                                       IsBinaryUpgrade = true;
                                break;
 
                        case 'C':
@@ -3304,7 +3306,8 @@ process_postgres_switches(int argc, char *argv[], GucContext ctx)
                                break;
 
                        case 'E':
-                               EchoQuery = true;
+                               if (secure)
+                                       EchoQuery = true;
                                break;
 
                        case 'e':
@@ -3329,7 +3332,8 @@ process_postgres_switches(int argc, char *argv[], GucContext ctx)
                                break;
 
                        case 'j':
-                               UseNewLine = 0;
+                               if (secure)
+                                       UseNewLine = 0;
                                break;
 
                        case 'k':
@@ -3447,13 +3451,10 @@ process_postgres_switches(int argc, char *argv[], GucContext ctx)
        }
 
        /*
-        * Should be no more arguments except an optional database name, and
-        * that's only in the secure case.
+        * Optional database name should be there only if *dbname is NULL.
         */
-       if (!errs && secure && argc - optind >= 1)
-               dbname = strdup(argv[optind++]);
-       else
-               dbname = NULL;
+       if (!errs && dbname && *dbname == NULL && argc - optind >= 1)
+               *dbname = strdup(argv[optind++]);
 
        if (errs || argc != optind)
        {
@@ -3482,8 +3483,6 @@ process_postgres_switches(int argc, char *argv[], GucContext ctx)
 #ifdef HAVE_INT_OPTRESET
        optreset = 1;                           /* some systems need this too */
 #endif
-
-       return dbname;
 }
 
 
@@ -3493,14 +3492,16 @@ process_postgres_switches(int argc, char *argv[], GucContext ctx)
  *
  * argc/argv are the command line arguments to be used.  (When being forked
  * by the postmaster, these are not the original argv array of the process.)
- * username is the (possibly authenticated) PostgreSQL user name to be used
- * for the session.
+ * dbname is the name of the database to connect to, or NULL if the database
+ * name should be extracted from the command line arguments or defaulted.
+ * username is the PostgreSQL user name to be used for the session.
  * ----------------------------------------------------------------
  */
 int
-PostgresMain(int argc, char *argv[], const char *username)
+PostgresMain(int argc, char *argv[],
+                        const char *dbname,
+                        const char *username)
 {
-       const char *dbname;
        int                     firstchar;
        StringInfoData input_message;
        sigjmp_buf      local_sigjmp_buf;
@@ -3547,7 +3548,7 @@ PostgresMain(int argc, char *argv[], const char *username)
        /*
         * Parse command-line options.
         */
-       dbname = process_postgres_switches(argc, argv, PGC_POSTMASTER);
+       process_postgres_switches(argc, argv, PGC_POSTMASTER, &dbname);
 
        /* Must have gotten a database name, or have a default (the username) */
        if (dbname == NULL)

diff --git a/src/backend/utils/init/postinit.c b/src/backend/utils/init/postinit.c
index 3dc5331772eeb09ed3dc3383048e2fc2de5b54c8..ff4df9010650b30a6589ee7bce441791e2b7d621 100644 (file)
--- a/src/backend/utils/init/postinit.c
+++ b/src/backend/utils/init/postinit.c
@@ -911,7 +911,7 @@ process_startup_options(Port *port, bool am_superuser)
 
                Assert(ac < maxac);
 
-               (void) process_postgres_switches(ac, av, gucctx);
+               (void) process_postgres_switches(ac, av, gucctx, NULL);
        }
 
        /*

diff --git a/src/include/tcop/tcopprot.h b/src/include/tcop/tcopprot.h
index 964dd19c2c363b5c116c90f9c8c6fbfd5200b7e7..c9bb12859088c4ee69fab6f797a4a1b496aadcdf 100644 (file)
--- a/src/include/tcop/tcopprot.h
+++ b/src/include/tcop/tcopprot.h
@@ -68,9 +68,10 @@ extern void RecoveryConflictInterrupt(ProcSignalReason reason); /* called from S
                                                                                                                                 * handler */
 extern void prepare_for_client_read(void);
 extern void client_read_ended(void);
-extern const char *process_postgres_switches(int argc, char *argv[],
-                                                 GucContext ctx);
-extern int     PostgresMain(int argc, char *argv[], const char *username);
+extern void process_postgres_switches(int argc, char *argv[],
+                                                 GucContext ctx, const char **dbname);
+extern int     PostgresMain(int argc, char *argv[],
+                                                const char *dbname, const char *username);
 extern long get_stack_depth_rlimit(void);
 extern void ResetUsage(void);
 extern void ShowUsage(const char *title);