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 ff8e87b6681b1eb08f0eeab20c5e0f47185b6e40..1b04596fc6f1f7d7f5313219b6064ca146eb7d51 100644 (file)
--- a/src/backend/main/main.c
+++ b/src/backend/main/main.c
@@ -183,7 +183,7 @@ 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 b6ebbb8d16555264070745458a501ad10ce2a426..c10ce1a7fe841bc4b2de8e1e31e90c266fdf0395 100644 (file)
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -3525,7 +3525,7 @@ 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,
@@ -3541,11 +3541,6 @@ 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);
@@ -3568,7 +3563,7 @@ 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 b79ffbfef272363b2ea9815bcb5e4827619484ac..363b60891e06a0e9be0855b0b83232d6148e2a9a 100644 (file)
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -3271,13 +3271,14 @@ 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;
@@ -3326,7 +3327,8 @@ process_postgres_switches(int argc, char *argv[], GucContext ctx)
                break;
 
            case 'E':
-               EchoQuery = true;
+               if (secure)
+                   EchoQuery = true;
                break;
 
            case 'e':
@@ -3351,7 +3353,8 @@ process_postgres_switches(int argc, char *argv[], GucContext ctx)
                break;
 
            case 'j':
-               UseNewLine = 0;
+               if (secure)
+                   UseNewLine = 0;
                break;
 
            case 'k':
@@ -3466,10 +3469,12 @@ 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 || argc - optind > 1 || (argc != optind && !secure))
+   if (!errs && dbname && *dbname == NULL && argc - optind >= 1)
+       *dbname = strdup(argv[optind++]);
+
+   if (errs || argc != optind)
    {
        /* spell the error message a bit differently depending on context */
        if (IsUnderPostmaster)
@@ -3485,11 +3490,6 @@ process_postgres_switches(int argc, char *argv[], GucContext ctx)
              errhint("Try \"%s --help\" for more information.", progname)));
    }
 
-   if (argc - optind == 1)
-       dbname = strdup(argv[optind]);
-   else
-       dbname = NULL;
-
    /*
     * Reset getopt(3) library so that it will work correctly in subprocesses
     * or when this function is called a second time with another array.
@@ -3498,8 +3498,6 @@ process_postgres_switches(int argc, char *argv[], GucContext ctx)
 #ifdef HAVE_INT_OPTRESET
    optreset = 1;               /* some systems need this too */
 #endif
-
-   return dbname;
 }
 
 
@@ -3509,14 +3507,16 @@ 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;
@@ -3563,7 +3563,7 @@ 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 045410519fccd10850a9301367dc14f42054b680..c413127daab6a68a2ee0924d1e1f2abc6da9078e 100644 (file)
--- a/src/backend/utils/init/postinit.c
+++ b/src/backend/utils/init/postinit.c
@@ -904,7 +904,7 @@ 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 216980ab9e7120af3820ef9c0a161a5d95db591f..923175c08d0574f12c13b06b4e918b8b67b65544 100644 (file)
--- a/src/include/tcop/tcopprot.h
+++ b/src/include/tcop/tcopprot.h
@@ -69,9 +69,10 @@ 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);