Obstruct shell, SQL, and conninfo injection via database and role names.

Due to simplistic quoting and confusion of database names with conninfo
strings, roles with the CREATEDB or CREATEROLE option could escalate to
superuser privileges when a superuser next ran certain maintenance
commands.  The new coding rule for PQconnectdbParams() calls, documented
at conninfo_array_parse(), is to pass expand_dbname=true and wrap
literal database names in a trivial connection string.  Escape
zero-length values in appendConnStrVal().  Back-patch to 9.1 (all
supported versions).

Nathan Bossart, Michael Paquier, and Noah Misch.  Reviewed by Peter
Eisentraut.  Reported by Nathan Bossart.

Security: CVE-2016-5424

Author: nmisch

src/bin/pg_basebackup/streamutil.c

@@ -64,9 +64,15 @@ GetConnection(void)
 	PQconninfoOption *conn_opt;
 	char	   *err_msg = NULL;
 
+	/* pg_recvlogical uses dbname only; others use connection_string only. */
+	Assert(dbname == NULL || connection_string == NULL);
+
 	/*
 	 * Merge the connection info inputs given in form of connection string,
 	 * options and default values (dbname=replication, replication=true, etc.)
+	 * Explicitly discard any dbname value in the connection string;
+	 * otherwise, PQconnectdbParams() would interpret that value as being
+	 * itself a connection string.
 	 */
 	i = 0;
 	if (connection_string)
@@ -80,7 +86,8 @@ GetConnection(void)
 
 		for (conn_opt = conn_opts; conn_opt->keyword != NULL; conn_opt++)
 		{
-			if (conn_opt->val != NULL && conn_opt->val[0] != '\0')
+			if (conn_opt->val != NULL && conn_opt->val[0] != '\0' &&
+				strcmp(conn_opt->keyword, "dbname") != 0)
 				argcount++;
 		}
 
@@ -89,7 +96,8 @@ GetConnection(void)
 
 		for (conn_opt = conn_opts; conn_opt->keyword != NULL; conn_opt++)
 		{
-			if (conn_opt->val != NULL && conn_opt->val[0] != '\0')
+			if (conn_opt->val != NULL && conn_opt->val[0] != '\0' &&
+				strcmp(conn_opt->keyword, "dbname") != 0)
 			{
 				keywords[i] = conn_opt->keyword;
 				values[i] = conn_opt->val;

src/bin/pg_dump/dumputils.c

@@ -339,6 +339,210 @@ appendStringLiteralDQ(PQExpBuffer buf, const char *str, const char *dqprefix)
 }
 
 
+/*
+ * Append the given string to the shell command being built in the buffer,
+ * with suitable shell-style quoting to create exactly one argument.
+ *
+ * Forbid LF or CR characters, which have scant practical use beyond designing
+ * security breaches.  The Windows command shell is unusable as a conduit for
+ * arguments containing LF or CR characters.  A future major release should
+ * reject those characters in CREATE ROLE and CREATE DATABASE, because use
+ * there eventually leads to errors here.
+ */
+void
+appendShellString(PQExpBuffer buf, const char *str)
+{
+	const char *p;
+
+#ifndef WIN32
+	appendPQExpBufferChar(buf, '\'');
+	for (p = str; *p; p++)
+	{
+		if (*p == '\n' || *p == '\r')
+		{
+			fprintf(stderr,
+					_("shell command argument contains a newline or carriage return: \"%s\"\n"),
+					str);
+			exit(EXIT_FAILURE);
+		}
+
+		if (*p == '\'')
+			appendPQExpBufferStr(buf, "'\"'\"'");
+		else
+			appendPQExpBufferChar(buf, *p);
+	}
+	appendPQExpBufferChar(buf, '\'');
+#else							/* WIN32 */
+	int			backslash_run_length = 0;
+
+	/*
+	 * A Windows system() argument experiences two layers of interpretation.
+	 * First, cmd.exe interprets the string.  Its behavior is undocumented,
+	 * but a caret escapes any byte except LF or CR that would otherwise have
+	 * special meaning.  Handling of a caret before LF or CR differs between
+	 * "cmd.exe /c" and other modes, and it is unusable here.
+	 *
+	 * Second, the new process parses its command line to construct argv (see
+	 * https://msdn.microsoft.com/en-us/library/17w5ykft.aspx).  This treats
+	 * backslash-double quote sequences specially.
+	 */
+	appendPQExpBufferStr(buf, "^\"");
+	for (p = str; *p; p++)
+	{
+		if (*p == '\n' || *p == '\r')
+		{
+			fprintf(stderr,
+					_("shell command argument contains a newline or carriage return: \"%s\"\n"),
+					str);
+			exit(EXIT_FAILURE);
+		}
+
+		/* Change N backslashes before a double quote to 2N+1 backslashes. */
+		if (*p == '"')
+		{
+			while (backslash_run_length)
+			{
+				appendPQExpBufferStr(buf, "^\\");
+				backslash_run_length--;
+			}
+			appendPQExpBufferStr(buf, "^\\");
+		}
+		else if (*p == '\\')
+			backslash_run_length++;
+		else
+			backslash_run_length = 0;
+
+		/*
+		 * Decline to caret-escape the most mundane characters, to ease
+		 * debugging and lest we approach the command length limit.
+		 */
+		if (!((*p >= 'a' && *p <= 'z') ||
+			  (*p >= 'A' && *p <= 'Z') ||
+			  (*p >= '0' && *p <= '9')))
+			appendPQExpBufferChar(buf, '^');
+		appendPQExpBufferChar(buf, *p);
+	}
+
+	/*
+	 * Change N backslashes at end of argument to 2N backslashes, because they
+	 * precede the double quote that terminates the argument.
+	 */
+	while (backslash_run_length)
+	{
+		appendPQExpBufferStr(buf, "^\\");
+		backslash_run_length--;
+	}
+	appendPQExpBufferStr(buf, "^\"");
+#endif   /* WIN32 */
+}
+
+
+/*
+ * Append the given string to the buffer, with suitable quoting for passing
+ * the string as a value, in a keyword/pair value in a libpq connection
+ * string
+ */
+void
+appendConnStrVal(PQExpBuffer buf, const char *str)
+{
+	const char *s;
+	bool		needquotes;
+
+	/*
+	 * If the string is one or more plain ASCII characters, no need to quote
+	 * it. This is quite conservative, but better safe than sorry.
+	 */
+	needquotes = true;
+	for (s = str; *s; s++)
+	{
+		if (!((*s >= 'a' && *s <= 'z') || (*s >= 'A' && *s <= 'Z') ||
+			  (*s >= '0' && *s <= '9') || *s == '_' || *s == '.'))
+		{
+			needquotes = true;
+			break;
+		}
+		needquotes = false;
+	}
+
+	if (needquotes)
+	{
+		appendPQExpBufferChar(buf, '\'');
+		while (*str)
+		{
+			/* ' and \ must be escaped by to \' and \\ */
+			if (*str == '\'' || *str == '\\')
+				appendPQExpBufferChar(buf, '\\');
+
+			appendPQExpBufferChar(buf, *str);
+			str++;
+		}
+		appendPQExpBufferChar(buf, '\'');
+	}
+	else
+		appendPQExpBufferStr(buf, str);
+}
+
+
+/*
+ * Append a psql meta-command that connects to the given database with the
+ * then-current connection's user, host and port.
+ */
+void
+appendPsqlMetaConnect(PQExpBuffer buf, const char *dbname)
+{
+	const char *s;
+	bool		complex;
+
+	/*
+	 * If the name is plain ASCII characters, emit a trivial "\connect "foo"".
+	 * For other names, even many not technically requiring it, skip to the
+	 * general case.  No database has a zero-length name.
+	 */
+	complex = false;
+	for (s = dbname; *s; s++)
+	{
+		if (*s == '\n' || *s == '\r')
+		{
+			fprintf(stderr,
+					_("database name contains a newline or carriage return: \"%s\"\n"),
+					dbname);
+			exit(EXIT_FAILURE);
+		}
+
+		if (!((*s >= 'a' && *s <= 'z') || (*s >= 'A' && *s <= 'Z') ||
+			  (*s >= '0' && *s <= '9') || *s == '_' || *s == '.'))
+		{
+			complex = true;
+		}
+	}
+
+	appendPQExpBufferStr(buf, "\\connect ");
+	if (complex)
+	{
+		PQExpBufferData connstr;
+
+		initPQExpBuffer(&connstr);
+		appendPQExpBuffer(&connstr, "dbname=");
+		appendConnStrVal(&connstr, dbname);
+
+		appendPQExpBuffer(buf, "-reuse-previous=on ");
+
+		/*
+		 * As long as the name does not contain a newline, SQL identifier
+		 * quoting satisfies the psql meta-command parser.  Prefer not to
+		 * involve psql-interpreted single quotes, which behaved differently
+		 * before PostgreSQL 9.2.
+		 */
+		appendPQExpBufferStr(buf, fmtId(connstr.data));
+
+		termPQExpBuffer(&connstr);
+	}
+	else
+		appendPQExpBufferStr(buf, fmtId(dbname));
+	appendPQExpBufferChar(buf, '\n');
+}
+
+
 /*
  * Convert a bytea value (presented as raw bytes) to an SQL string literal
  * and append it to the given buffer.  We assume the specified

src/bin/pg_dump/dumputils.h

@@ -81,6 +81,9 @@ extern void appendStringLiteralDQ(PQExpBuffer buf, const char *str,
 extern void appendByteaLiteral(PQExpBuffer buf,
 				   const unsigned char *str, size_t length,
 				   bool std_strings);
+extern void appendShellString(PQExpBuffer buf, const char *str);
+extern void appendConnStrVal(PQExpBuffer buf, const char *str);
+extern void appendPsqlMetaConnect(PQExpBuffer buf, const char *dbname);
 extern bool parsePGArray(const char *atext, char ***itemarray, int *nitems);
 extern bool buildACLCommands(const char *name, const char *subname,
 				 const char *type, const char *acls, const char *owner,

src/bin/pg_dump/pg_backup.h

@@ -102,7 +102,7 @@ typedef struct _restoreOptions
 	SimpleStringList tableNames;
 
 	int			useDB;
-	char	   *dbname;
+	char	   *dbname;			/* subject to expand_dbname */
 	char	   *pgport;
 	char	   *pghost;
 	char	   *username;
@@ -120,7 +120,7 @@ typedef struct _restoreOptions
 
 typedef struct _dumpOptions
 {
-	const char *dbname;
+	const char *dbname;			/* subject to expand_dbname */
 	const char *pghost;
 	const char *pgport;
 	const char *username;

src/bin/pg_dump/pg_backup_archiver.c

@@ -762,9 +762,16 @@ restore_toc_entry(ArchiveHandle *AH, TocEntry *te, bool is_parallel)
 		/* If we created a DB, connect to it... */
 		if (strcmp(te->desc, "DATABASE") == 0)
 		{
+			PQExpBufferData connstr;
+
+			initPQExpBuffer(&connstr);
+			appendPQExpBufferStr(&connstr, "dbname=");
+			appendConnStrVal(&connstr, te->tag);
+			/* Abandon struct, but keep its buffer until process exit. */
+
 			ahlog(AH, 1, "connecting to new database \"%s\"\n", te->tag);
 			_reconnectToDB(AH, te->tag);
-			ropt->dbname = pg_strdup(te->tag);
+			ropt->dbname = connstr.data;
 		}
 	}
 
@@ -2921,12 +2928,17 @@ _reconnectToDB(ArchiveHandle *AH, const char *dbname)
 		ReconnectToServer(AH, dbname, NULL);
 	else
 	{
-		PQExpBuffer qry = createPQExpBuffer();
+		if (dbname)
+		{
+			PQExpBufferData connectbuf;
 
-		appendPQExpBuffer(qry, "\\connect %s\n\n",
-						  dbname ? fmtId(dbname) : "-");
-		ahprintf(AH, "%s", qry->data);
-		destroyPQExpBuffer(qry);
+			initPQExpBuffer(&connectbuf);
+			appendPsqlMetaConnect(&connectbuf, dbname);
+			ahprintf(AH, "%s\n", connectbuf.data);
+			termPQExpBuffer(&connectbuf);
+		}
+		else
+			ahprintf(AH, "%s\n", "\\connect -\n");
 	}
 
 	/*
@@ -4400,7 +4412,7 @@ CloneArchive(ArchiveHandle *AH)
 	}
 	else
 	{
-		char	   *dbname;
+		PQExpBufferData connstr;
 		char	   *pghost;
 		char	   *pgport;
 		char	   *username;
@@ -4413,14 +4425,18 @@ CloneArchive(ArchiveHandle *AH)
 		 * because all just return a pointer and do not actually send/receive
 		 * any data to/from the database.
 		 */
-		dbname = PQdb(AH->connection);
+		initPQExpBuffer(&connstr);
+		appendPQExpBuffer(&connstr, "dbname=");
+		appendConnStrVal(&connstr, PQdb(AH->connection));
 		pghost = PQhost(AH->connection);
 		pgport = PQport(AH->connection);
 		username = PQuser(AH->connection);
 
 		/* this also sets clone->connection */
-		ConnectDatabase((Archive *) clone, dbname, pghost, pgport, username, TRI_NO);
+		ConnectDatabase((Archive *) clone, connstr.data,
+						pghost, pgport, username, TRI_NO);
 
+		termPQExpBuffer(&connstr);
 		/* setupDumpWorker will fix up connection state */
 	}
 

src/bin/pg_dump/pg_backup_db.c

@@ -128,6 +128,7 @@ ReconnectToServer(ArchiveHandle *AH, const char *dbname, const char *username)
 static PGconn *
 _connectDB(ArchiveHandle *AH, const char *reqdb, const char *requser)
 {
+	PQExpBufferData connstr;
 	PGconn	   *newConn;
 	const char *newdb;
 	const char *newuser;
@@ -156,6 +157,10 @@ _connectDB(ArchiveHandle *AH, const char *reqdb, const char *requser)
 			exit_horribly(modulename, "out of memory\n");
 	}
 
+	initPQExpBuffer(&connstr);
+	appendPQExpBuffer(&connstr, "dbname=");
+	appendConnStrVal(&connstr, newdb);
+
 	do
 	{
 		const char *keywords[7];
@@ -170,7 +175,7 @@ _connectDB(ArchiveHandle *AH, const char *reqdb, const char *requser)
 		keywords[3] = "password";
 		values[3] = password;
 		keywords[4] = "dbname";
-		values[4] = newdb;
+		values[4] = connstr.data;
 		keywords[5] = "fallback_application_name";
 		values[5] = progname;
 		keywords[6] = NULL;
@@ -222,6 +227,8 @@ _connectDB(ArchiveHandle *AH, const char *reqdb, const char *requser)
 	if (password)
 		free(password);
 
+	termPQExpBuffer(&connstr);
+
 	/* check for version mismatch */
 	_check_database_version(AH);