backport the escapeshell* functions hardening branch

Author: weltling

ext/standard/basic_functions.c

@@ -3674,6 +3674,7 @@ PHP_MINIT_FUNCTION(basic) /* {{{ */
 #ifdef PHP_CAN_SUPPORT_PROC_OPEN
 	BASIC_MINIT_SUBMODULE(proc_open)
 #endif
+	BASIC_MINIT_SUBMODULE(exec)
 
 	BASIC_MINIT_SUBMODULE(user_streams)
 	BASIC_MINIT_SUBMODULE(imagetypes)

ext/standard/exec.c

@@ -46,10 +46,42 @@
 #include <fcntl.h>
 #endif
 
-#if HAVE_NICE && HAVE_UNISTD_H
+#if HAVE_UNISTD_H
 #include <unistd.h>
 #endif
 
+#ifdef PHP_WIN32
+# include "win32/php_stdint.h"
+#else
+# if HAVE_INTTYPES_H
+#  include <inttypes.h>
+# elif HAVE_STDINT_H
+#  include <stdint.h>
+# endif
+#endif
+
+static int cmd_max_len;
+
+/* {{{ PHP_MINIT_FUNCTION(exec) */
+PHP_MINIT_FUNCTION(exec)
+{
+#ifdef _SC_ARG_MAX
+	cmd_max_len = sysconf(_SC_ARG_MAX);
+#elif defined(ARG_MAX)
+	cmd_max_len = ARG_MAX;
+#elif defined(PHP_WIN32)
+	/* Executed commands will run through cmd.exe. As long as it's the case,
+		it's just the constant limit.*/
+	cmd_max_len = 8192;
+#else
+	/* This is just an arbitrary value for the fallback case. */
+	cmd_max_len = 4096;
+#endif
+
+	return SUCCESS;
+}
+/* }}} */
+
 /* {{{ php_exec
  * If type==0, only last line of output is returned (exec)
  * If type==1, all lines will be printed and last lined returned (system)
@@ -244,13 +276,20 @@ PHP_FUNCTION(passthru)
 */
 PHPAPI char *php_escape_shell_cmd(char *str)
 {
-	register int x, y, l = strlen(str);
+	register int x, y;
+	size_t l = strlen(str);
+	uint64_t estimate = (2 * (uint64_t)l) + 1;
 	char *cmd;
 	char *p = NULL;
-	size_t estimate = (2 * l) + 1;
 
 	TSRMLS_FETCH();
 
+	/* max command line length - two single quotes - \0 byte length */
+	if (l > cmd_max_len - 2 - 1) {
+		php_error_docref(NULL TSRMLS_CC, E_ERROR, "Command exceeds the allowed length of %d bytes", cmd_max_len);
+		return NULL;
+	}
+
 	cmd = safe_emalloc(2, l, 1);
 
 	for (x = 0, y = 0; x < l; x++) {
@@ -322,6 +361,12 @@ PHPAPI char *php_escape_shell_cmd(char *str)
 	}
 	cmd[y] = '\0';
 
+	if (y - 1 > cmd_max_len) {
+		php_error_docref(NULL TSRMLS_CC, E_ERROR, "Escaped command exceeds the allowed length of %d bytes", cmd_max_len);
+		efree(cmd);
+		return NULL;
+	}
+
 	if ((estimate - y) > 4096) {
 		/* realloc if the estimate was way overill
 		 * Arbitrary cutoff point of 4096 */
@@ -336,12 +381,19 @@ PHPAPI char *php_escape_shell_cmd(char *str)
  */
 PHPAPI char *php_escape_shell_arg(char *str)
 {
-	int x, y = 0, l = strlen(str);
+	int x, y = 0;
+	size_t l = strlen(str);
 	char *cmd;
-	size_t estimate = (4 * l) + 3;
+	uint64_t estimate = (4 * (uint64_t)l) + 3;
 
 	TSRMLS_FETCH();
 
+	/* max command line length - two single quotes - \0 byte length */
+	if (l > cmd_max_len - 2 - 1) {
+		php_error_docref(NULL TSRMLS_CC, E_ERROR, "Argument exceeds the allowed length of %d bytes", cmd_max_len);
+		return NULL;
+	}
+
 	cmd = safe_emalloc(4, l, 3); /* worst case */
 
 #ifdef PHP_WIN32
@@ -396,6 +448,12 @@ PHPAPI char *php_escape_shell_arg(char *str)
 #endif
 	cmd[y] = '\0';
 
+	if (y - 1 > cmd_max_len) {
+		php_error_docref(NULL TSRMLS_CC, E_ERROR, "Escaped argument exceeds the allowed length of %d bytes", cmd_max_len);
+		efree(cmd);
+		return NULL;
+	}
+
 	if ((estimate - y) > 4096) {
 		/* realloc if the estimate was way overill
 		 * Arbitrary cutoff point of 4096 */
@@ -418,6 +476,10 @@ PHP_FUNCTION(escapeshellcmd)
 	}
 
 	if (command_len) {
+		if (command_len != strlen(command)) {
+			php_error_docref(NULL TSRMLS_CC, E_ERROR, "Input string contains NULL bytes");
+			return;
+		}
 		cmd = php_escape_shell_cmd(command);
 		RETVAL_STRING(cmd, 0);
 	} else {
@@ -439,6 +501,10 @@ PHP_FUNCTION(escapeshellarg)
 	}
 
 	if (argument) {
+		if (argument_len != strlen(argument)) {
+			php_error_docref(NULL TSRMLS_CC, E_ERROR, "Input string contains NULL bytes");
+			return;
+		}
 		cmd = php_escape_shell_arg(argument);
 		RETVAL_STRING(cmd, 0);
 	}

ext/standard/exec.h

@@ -33,6 +33,7 @@ PHP_FUNCTION(proc_close);
 PHP_FUNCTION(proc_terminate);
 PHP_FUNCTION(proc_nice);
 PHP_MINIT_FUNCTION(proc_open);
+PHP_MINIT_FUNCTION(exec);
 
 PHPAPI char *php_escape_shell_cmd(char *);
 PHPAPI char *php_escape_shell_arg(char *);