Follow up on bug #71270

Using the max allowed command line length for an underlying OS.

1 files changed, 51 insertions, 5 deletions

diff --git a/ext/standard/exec.c b/ext/standard/exec.c
index c4afce3337..747f765dd4 100644
--- a/ext/standard/exec.c
+++ b/ext/standard/exec.c
@@ -46,10 +46,32 @@
 #include <fcntl.h>
 #endif
 
-#if HAVE_NICE && HAVE_UNISTD_H
+#if (HAVE_NICE || defined(__linux__)) && HAVE_UNISTD_H
 #include <unistd.h>
 #endif
 
+static int cmd_max_len;
+
+/* {{{ PHP_MINIT_FUNCTION(exec) */
+PHP_MINIT_FUNCTION(exec)
+{
+#ifdef __linux__
+	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)
@@ -245,13 +267,19 @@ PHP_FUNCTION(passthru)
 */
 PHPAPI zend_string *php_escape_shell_cmd(char *str)
 {
-	register int x, y, l = (int)strlen(str);
-	size_t estimate = (2 * l) + 1;
+	register int x, y;
+	size_t l = strlen(str);
+	uint64_t estimate = (2 * (uint64_t)l) + 1;
 	zend_string *cmd;
 #ifndef PHP_WIN32
 	char *p = NULL;
 #endif
 
+	/* max command line length - two single quotes - \0 byte length */
+	if (l > cmd_max_len - 2 - 1) {
+		php_error_docref(NULL, E_ERROR, "Command exceeds the allowed length of %d bytes", cmd_max_len);
+		return ZSTR_EMPTY_ALLOC();
+	}
 
 	cmd = zend_string_safe_alloc(2, l, 0, 0);
 
@@ -324,6 +352,12 @@ PHPAPI zend_string *php_escape_shell_cmd(char *str)
 	}
 	ZSTR_VAL(cmd)[y] = '\0';
 
+	if (y - 1 > cmd_max_len) {
+		php_error_docref(NULL, E_ERROR, "Escaped command exceeds the allowed length of %d bytes", cmd_max_len);
+		zend_string_release(cmd);
+		return ZSTR_EMPTY_ALLOC();
+	}
+
 	if ((estimate - y) > 4096) {
 		/* realloc if the estimate was way overill
 		 * Arbitrary cutoff point of 4096 */
@@ -340,10 +374,16 @@ PHPAPI zend_string *php_escape_shell_cmd(char *str)
  */
 PHPAPI zend_string *php_escape_shell_arg(char *str)
 {
-	int x, y = 0, l = (int)strlen(str);
+	int x, y = 0;
+	size_t l = strlen(str);
 	zend_string *cmd;
-	size_t estimate = (4 * l) + 3;
+	uint64_t estimate = (4 * (uint64_t)l) + 3;
 
+	/* max command line length - two single quotes - \0 byte length */
+	if (l > cmd_max_len - 2 - 1) {
+		php_error_docref(NULL, E_ERROR, "Argument exceeds the allowed length of %d bytes", cmd_max_len);
+		return ZSTR_EMPTY_ALLOC();
+	}
 
 	cmd = zend_string_safe_alloc(4, l, 2, 0); /* worst case */
 
@@ -399,6 +439,12 @@ PHPAPI zend_string *php_escape_shell_arg(char *str)
 #endif
 	ZSTR_VAL(cmd)[y] = '\0';
 
+	if (y - 1 > cmd_max_len) {
+		php_error_docref(NULL, E_ERROR, "Escaped argument exceeds the allowed length of %d bytes", cmd_max_len);
+		zend_string_release(cmd);
+		return ZSTR_EMPTY_ALLOC();
+	}
+
 	if ((estimate - y) > 4096) {
 		/* realloc if the estimate was way overill
 		 * Arbitrary cutoff point of 4096 */