mingw32: make access(2) check file format for executables

3 files changed, 74 insertions, 26 deletions

diff --git a/include/mingw.h b/include/mingw.h
index 08d776c84..1ef13c638 100644
--- a/include/mingw.h
+++ b/include/mingw.h
@@ -337,6 +337,7 @@ static inline void sync(void) {}
 NOIMPL(ttyname_r,int fd UNUSED_PARAM, char *buf UNUSED_PARAM, int sz UNUSED_PARAM);
 int mingw_unlink(const char *pathname);
 NOIMPL(vfork,void);
+int mingw_access(const char *name, int mode);
 
 #define dup2 mingw_dup2
 #define getcwd mingw_getcwd
@@ -344,6 +345,9 @@ NOIMPL(vfork,void);
 #define open mingw_open
 #define unlink mingw_unlink
 
+#undef access
+#define access mingw_access
+
 /*
  * utime.h
  */
diff --git a/libbb/execable.c b/libbb/execable.c
index afb957e43..c2a7bf0ca 100644
--- a/libbb/execable.c
+++ b/libbb/execable.c
@@ -16,31 +16,7 @@
 int FAST_FUNC execable_file(const char *name)
 {
         struct stat s;
-#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"))) {
-                        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;
@@ -76,7 +52,7 @@ char* FAST_FUNC find_execable(const char *filename, char **PATHp)
                                 if (len > 4 &&
                                     (!strcasecmp(p+len-4, ".exe") ||
                                      !strcasecmp(p+len-4, ".com")))
-                                        ; /* nothing, already tested by find_execable() */
+                                        ; /* nothing, already tested by execable_file() */
                                 else {
                                         char *np = xmalloc(len+4+1);
                                         memcpy(np, p, len);
diff --git a/win32/mingw.c b/win32/mingw.c
index be08c5bd5..a6c969596 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -225,7 +225,8 @@ static int do_lstat(int follow, const char *file_name, struct stat *buf)
                 buf->st_uid = 0;
                 buf->st_nlink = 1;
                 buf->st_mode = file_attr_to_st_mode(fdata.dwFileAttributes);
-                if (len > 4 && !strcmp(file_name+len-4, ".exe"))
+                if (len > 4 && (!strcasecmp(file_name+len-4, ".exe") ||
+                                                !strcasecmp(file_name+len-4, ".com")))
                         buf->st_mode |= S_IEXEC;
                 buf->st_size = fdata.nFileSizeLow |
                         (((off64_t)fdata.nFileSizeHigh)<<32);
@@ -762,3 +763,70 @@ char *strptime(const char *s UNUSED_PARAM, const char *format UNUSED_PARAM, stru
 {
         return NULL;
 }
+
+#undef access
+int mingw_access(const char *name, int mode)
+{
+        int ret;
+        struct stat s;
+        int fd, n, offset, sig;
+        unsigned char buf[1024];
+
+        /* Windows can only handle test for existence, read or write */
+        if (mode == F_OK || (mode & ~X_OK)) {
+                ret = _access(name, mode & ~X_OK);
+                if (ret < 0 || !(mode & X_OK)) {
+                        return ret;
+                }
+        }
+
+        if (!mingw_stat(name, &s) && S_ISREG(s.st_mode)) {
+
+                /* stat marks .exe and .com files as executable */
+                if ((s.st_mode&S_IEXEC)) {
+                        return 0;
+                }
+
+                fd = open(name, O_RDONLY);
+                if (fd < 0)
+                        return -1;
+                n = read(fd, buf, sizeof(buf)-1);
+                close(fd);
+                if (n < 4)      /* at least '#!/x' and not error */
+                        return -1;
+
+                /* shell script */
+                if (buf[0] == '#' && buf[1] == '!') {
+                        return 0;
+                }
+
+                /*
+                 * Poke about in file to see if it's a PE binary.  I've just copied
+                 * the magic from the file command.
+                 */
+                if (buf[0] == 'M' && buf[1] == 'Z') {
+                        offset = (buf[0x19] << 8) + buf[0x18];
+                        if (offset > 0x3f) {
+                                offset = (buf[0x3f] << 24) + (buf[0x3e] << 16) +
+                                                        (buf[0x3d] << 8) + buf[0x3c];
+                                if (offset < sizeof(buf)-100) {
+                                        if (memcmp(buf+offset, "PE\0\0", 4) == 0) {
+                                                sig = (buf[offset+25] << 8) + buf[offset+24];
+                                                if (sig == 0x10b || sig == 0x20b) {
+                                                        sig = (buf[offset+23] << 8) + buf[offset+22];
+                                                        if ((sig & 0x2000) != 0) {
+                                                                /* DLL */
+                                                                return -1;
+                                                        }
+                                                        sig = buf[offset+92];
+                                                        return !(sig == 1 || sig == 2 ||
+                                                                                sig == 3 || sig == 7);
+                                                }
+                                        }
+                                }
+                        }
+                }
+        }
+
+        return -1;
+}