Introduce a psql "\connect -reuse-previous=on|off" option.

The decision to reuse values of parameters from a previous connection
has been based on whether the new target is a conninfo string.  Add this
means of overriding that default.  This feature arose as one component
of a fix for security vulnerabilities in pg_dump, pg_dumpall, and
pg_upgrade, so back-patch to 9.1 (all supported versions).  In 9.3 and
later, comment paragraphs that required update had already-incorrect
claims about behavior when no connection is open; fix those problems.

Security: CVE-2016-5424

diff --git a/doc/src/sgml/ref/psql-ref.sgml b/doc/src/sgml/ref/psql-ref.sgml
index 308e3900c092dd245dd5cc6fe9354c517918ec87..cf85de1ca78a230ff073cc834f7675be70c01337 100644 (file)
--- a/doc/src/sgml/ref/psql-ref.sgml
+++ b/doc/src/sgml/ref/psql-ref.sgml
@@ -799,7 +799,7 @@ testdb=>
       </varlistentry>
 
       <varlistentry>
-        <term><literal>\c</literal> or <literal>\connect</literal> <literal>[ <replaceable class="parameter">dbname</replaceable> [ <replaceable class="parameter">username</replaceable> ] [ <replaceable class="parameter">host</replaceable> ] [ <replaceable class="parameter">port</replaceable> ] ] | <replaceable class="parameter">conninfo</replaceable> </literal></term>
+        <term><literal>\c</literal> or <literal>\connect [ -reuse-previous=<replaceable class="parameter">on|off</replaceable> ] [ <replaceable class="parameter">dbname</replaceable> [ <replaceable class="parameter">username</replaceable> ] [ <replaceable class="parameter">host</replaceable> ] [ <replaceable class="parameter">port</replaceable> ] | <replaceable class="parameter">conninfo</replaceable> ]</literal></term>
         <listitem>
         <para>
         Establishes a new connection to a <productname>PostgreSQL</>
@@ -809,16 +809,19 @@ testdb=&gt;
         </para>
 
         <para>
-        When using positional parameters, if any of
-        <replaceable class="parameter">dbname</replaceable>,
+        Where the command omits database name, user, host, or port, the new
+        connection can reuse values from the previous connection.  By default,
+        values from the previous connection are reused except when processing
+        a <literal>conninfo</> string.  Passing a first argument
+        of <literal>-reuse-previous=on</>
+        or <literal>-reuse-previous=off</literal> overrides that default.
+        When the command neither specifies nor reuses a particular parameter,
+        the <application>libpq</application> default is used.  Specifying any
+        of <replaceable class="parameter">dbname</replaceable>,
         <replaceable class="parameter">username</replaceable>,
         <replaceable class="parameter">host</replaceable> or
-        <replaceable class="parameter">port</replaceable> are omitted or
-        specified as <literal>-</literal>, the value of that parameter from
-        the previous connection is used; if there is no previous connection,
-        the <application>libpq</application> default for the parameter's value
-        is used.  When using <literal>conninfo</> strings, no values from the
-        previous connection are used for the new connection.
+        <replaceable class="parameter">port</replaceable>
+        as <literal>-</literal> is equivalent to omitting that parameter.
         </para>
 
         <para>

diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
index 07d3e6998e5e8de2000dc46ef295d288ee7c8880..6a885674d0670f05736619ee8b9fd66e51abc93f 100644 (file)
--- a/src/bin/psql/command.c
+++ b/src/bin/psql/command.c
@@ -56,7 +56,8 @@ static backslashResult exec_command(const char *cmd,
             PQExpBuffer query_buf);
 static bool do_edit(const char *filename_arg, PQExpBuffer query_buf,
        int lineno, bool *edited);
-static bool do_connect(char *dbname, char *user, char *host, char *port);
+static bool do_connect(enum trivalue reuse_previous_specification,
+          char *dbname, char *user, char *host, char *port);
 static bool do_shell(const char *command);
 static bool do_watch(PQExpBuffer query_buf, long sleep);
 static bool lookup_function_oid(const char *desc, Oid *foid);
@@ -217,12 +218,9 @@ exec_command(const char *cmd,
    /*
     * \c or \connect -- connect to database using the specified parameters.
     *
-    * \c dbname user host port
+    * \c [-reuse-previous=BOOL] dbname user host port
     *
-    * If any of these parameters are omitted or specified as '-', the current
-    * value of the parameter will be used instead. If the parameter has no
-    * current value, the default value for that parameter will be used. Some
-    * examples:
+    * Specifying a parameter as '-' is equivalent to omitting it.  Examples:
     *
     * \c - - hst       Connect to current database on current port of host
     * "hst" as current user. \c - usr - prt   Connect to current database on
@@ -231,17 +229,31 @@ exec_command(const char *cmd,
     */
    else if (strcmp(cmd, "c") == 0 || strcmp(cmd, "connect") == 0)
    {
+       static const char prefix[] = "-reuse-previous=";
        char       *opt1,
                   *opt2,
                   *opt3,
                   *opt4;
+       enum trivalue reuse_previous;
 
        opt1 = read_connect_arg(scan_state);
+       if (opt1 != NULL && strncmp(opt1, prefix, sizeof(prefix) - 1) == 0)
+       {
+           reuse_previous =
+               ParseVariableBool(opt1 + sizeof(prefix) - 1, prefix) ?
+               TRI_YES : TRI_NO;
+
+           free(opt1);
+           opt1 = read_connect_arg(scan_state);
+       }
+       else
+           reuse_previous = TRI_DEFAULT;
+
        opt2 = read_connect_arg(scan_state);
        opt3 = read_connect_arg(scan_state);
        opt4 = read_connect_arg(scan_state);
 
-       success = do_connect(opt1, opt2, opt3, opt4);
+       success = do_connect(reuse_previous, opt1, opt2, opt3, opt4);
 
        free(opt1);
        free(opt2);
@@ -1599,22 +1611,25 @@ param_is_newly_set(const char *old_val, const char *new_val)
 /*
  * do_connect -- handler for \connect
  *
- * Connects to a database with given parameters. If there exists an
- * established connection, NULL values will be replaced with the ones
- * in the current connection. Otherwise NULL will be passed for that
- * parameter to PQconnectdbParams(), so the libpq defaults will be used.
+ * Connects to a database with given parameters. Absent an established
+ * connection, all parameters are required. Given -reuse-previous=off or a
+ * connection string without -reuse-previous=on, NULL values will pass through
+ * to PQconnectdbParams(), so the libpq defaults will be used. Otherwise, NULL
+ * values will be replaced with the ones in the current connection.
  *
  * In interactive mode, if connection fails with the given parameters,
  * the old connection will be kept.
  */
 static bool
-do_connect(char *dbname, char *user, char *host, char *port)
+do_connect(enum trivalue reuse_previous_specification,
+          char *dbname, char *user, char *host, char *port)
 {
    PGconn     *o_conn = pset.db,
               *n_conn;
    char       *password = NULL;
    bool        keep_password;
    bool        has_connection_string;
+   bool        reuse_previous;
 
    if (!o_conn && (!dbname || !user || !host || !port))
    {
@@ -1628,17 +1643,36 @@ do_connect(char *dbname, char *user, char *host, char *port)
        return false;
    }
 
-   /* grab values from the old connection, unless supplied by caller */
-   if (!user)
+   has_connection_string = dbname ?
+       recognized_connection_string(dbname) : false;
+   switch (reuse_previous_specification)
+   {
+       case TRI_YES:
+           reuse_previous = true;
+           break;
+       case TRI_NO:
+           reuse_previous = false;
+           break;
+       default:
+           reuse_previous = !has_connection_string;
+           break;
+   }
+   /* Silently ignore arguments subsequent to a connection string. */
+   if (has_connection_string)
+   {
+       user = NULL;
+       host = NULL;
+       port = NULL;
+   }
+
+   /* grab missing values from the old connection */
+   if (!user && reuse_previous)
        user = PQuser(o_conn);
-   if (!host)
+   if (!host && reuse_previous)
        host = PQhost(o_conn);
-   if (!port)
+   if (!port && reuse_previous)
        port = PQport(o_conn);
 
-   has_connection_string =
-       dbname ? recognized_connection_string(dbname) : false;
-
    /*
     * Any change in the parameters read above makes us discard the password.
     * We also discard it if we're to use a conninfo rather than the
@@ -1655,10 +1689,10 @@ do_connect(char *dbname, char *user, char *host, char *port)
            (port && PQport(o_conn) && strcmp(port, PQport(o_conn)) == 0);
 
    /*
-    * Grab dbname from old connection unless supplied by caller.  No password
-    * discard if this changes: passwords aren't (usually) database-specific.
+    * Grab missing dbname from old connection.  No password discard if this
+    * changes: passwords aren't (usually) database-specific.
     */
-   if (!dbname)
+   if (!dbname && reuse_previous)
        dbname = PQdb(o_conn);
 
    /*
@@ -1689,20 +1723,27 @@ do_connect(char *dbname, char *user, char *host, char *port)
 #define PARAMS_ARRAY_SIZE  8
        const char **keywords = pg_malloc(PARAMS_ARRAY_SIZE * sizeof(*keywords));
        const char **values = pg_malloc(PARAMS_ARRAY_SIZE * sizeof(*values));
-       int         paramnum = 0;
+       int         paramnum = -1;
 
-       keywords[0] = "dbname";
-       values[0] = dbname;
+       keywords[++paramnum] = "host";
+       values[paramnum] = host;
+       keywords[++paramnum] = "port";
+       values[paramnum] = port;
+       keywords[++paramnum] = "user";
+       values[paramnum] = user;
 
-       if (!has_connection_string)
-       {
-           keywords[++paramnum] = "host";
-           values[paramnum] = host;
-           keywords[++paramnum] = "port";
-           values[paramnum] = port;
-           keywords[++paramnum] = "user";
-           values[paramnum] = user;
-       }
+       /*
+        * Position in the array matters when the dbname is a connection
+        * string, because settings in a connection string override earlier
+        * array entries only.  Thus, user= in the connection string always
+        * takes effect, but client_encoding= often will not.
+        *
+        * If you change this code, also change the initial-connection code in
+        * main().  For no good reason, a connection string password= takes
+        * precedence in main() but not here.
+        */
+       keywords[++paramnum] = "dbname";
+       values[paramnum] = dbname;
        keywords[++paramnum] = "password";
        values[paramnum] = password;
        keywords[++paramnum] = "fallback_application_name";

diff --git a/src/bin/psql/startup.c b/src/bin/psql/startup.c
index 8b1777e24366eeaf1e6ccf5cee48db2784bdbd91..0c090d15c2e851dcabd9c15aee19a4b751aa58e8 100644 (file)
--- a/src/bin/psql/startup.c
+++ b/src/bin/psql/startup.c
@@ -215,7 +215,7 @@ main(int argc, char *argv[])
        values[2] = options.username;
        keywords[3] = "password";
        values[3] = password;
-       keywords[4] = "dbname";
+       keywords[4] = "dbname"; /* see do_connect() */
        values[4] = (options.action == ACT_LIST_DB &&
                     options.dbname == NULL) ?
            "postgres" : options.dbname;