main: guess_shell: use $SHELL variable if set

fixes #983

1 files changed, 10 insertions, 1 deletions

diff --git a/src/firejail/main.c b/src/firejail/main.c
index 15820f7dd..c74fb02d2 100644
--- a/src/firejail/main.c
+++ b/src/firejail/main.c
@@ -754,12 +754,21 @@ static void delete_x11_file(pid_t pid) {
 
 char *guess_shell(void) {
         char *shell = NULL;
+        struct stat s;
+
+        shell = getenv("SHELL");
+        if (shell) {
+                // TODO: handle rogue shell variables?
+                if (stat(shell, &s) == 0 && access(shell, R_OK) == 0) {
+                        return shell;
+                }
+        }
+
         // shells in order of preference
         char *shells[] = {"/bin/bash", "/bin/csh", "/usr/bin/zsh", "/bin/sh", "/bin/ash", NULL };
 
         int i = 0;
         while (shells[i] != NULL) {
-                struct stat s;
                 // access call checks as real UID/GID, not as effective UID/GID
                 if (stat(shells[i], &s) == 0 && access(shells[i], R_OK) == 0) {
                         shell = shells[i];