Detect and execute shell scripts based on presence of '#!'

1 files changed, 24 insertions, 6 deletions

diff --git a/libbb/execable.c b/libbb/execable.c
index e35dad208..afb957e43 100644
--- a/libbb/execable.c
+++ b/libbb/execable.c
@@ -16,15 +16,31 @@
 int FAST_FUNC execable_file(const char *name)
 {
         struct stat s;
-        if (ENABLE_PLATFORM_MINGW32) {
-                int len = strlen(name);
-                return len > 4 &&
+#if ENABLE_PLATFORM_MINGW32
+        if (!stat(name, &s) && S_ISREG(s.st_mode)) {
+                int len, fd, n;
+                char buf[100];
+
+                if ((len=strlen(name)) > 4 &&
                         (!strcasecmp(name+len-4, ".exe") ||
-                         !strcasecmp(name+len-4, ".com")) &&
-                        !stat(name, &s) &&
-                        S_ISREG(s.st_mode);
+                         !strcasecmp(name+len-4, ".com"))) {
+                        return 1;
+                }
+
+                fd = open(name, O_RDONLY);
+                if (fd < 0)
+                        return 0;
+                n = read(fd, buf, sizeof(buf)-1);
+                close(fd);
+                if (n < 4)      /* at least '#!/x' and not error */
+                        return 0;
+
+                return (buf[0] == '#' && buf[1] == '!');
         }
+        return 0;
+#else
         return (!access(name, X_OK) && !stat(name, &s) && S_ISREG(s.st_mode));
+#endif
 }
 
 /* search (*PATHp) for an executable file;
@@ -67,11 +83,13 @@ char* FAST_FUNC find_execable(const char *filename, char **PATHp)
                                         memcpy(np+len, ".exe", 5);
                                         if (execable_file(np)) {
                                                 *PATHp = n;
+                                                free(p);
                                                 return np;
                                         }
                                         memcpy(np+len, ".com", 5);
                                         if (execable_file(np)) {
                                                 *PATHp = n;
+                                                free(p);
                                                 return np;
                                         }
                                 }