Win32: Fix, comment capture reparse-point fixups
authorEric Biggers <ebiggers3@gmail.com>
Fri, 26 Apr 2013 04:52:58 +0000 (23:52 -0500)
committerEric Biggers <ebiggers3@gmail.com>
Fri, 26 Apr 2013 04:52:58 +0000 (23:52 -0500)
src/symlink.c
src/win32.c

index 21a564f..f005cd7 100644 (file)
@@ -392,12 +392,6 @@ fixup_symlink(tchar *dest, u64 capture_root_ino, u64 capture_root_dev)
 {
        tchar *p = dest;
 
-#ifdef __WIN32__
-       /* Skip over drive letter */
-       if (!is_rp_path_separator(*p))
-               p += 2;
-#endif
-
        DEBUG("Fixing symlink or junction \"%"TS"\"", dest);
        for (;;) {
                tchar save;
@@ -424,14 +418,6 @@ fixup_symlink(tchar *dest, u64 capture_root_ino, u64 capture_root_dev)
                                *(p - 1) = RP_PATH_SEPARATOR;
                        while (p - 1 >= dest && is_rp_path_separator(*(p - 1)))
                                p--;
-               #ifdef __WIN32__
-                       /* Add back drive letter */
-                       if (!is_rp_path_separator(*dest)) {
-                               *--p = *(dest + 1);
-                               *--p = *dest;
-                       }
-               #endif
-                       wimlib_assert(p >= dest);
                        return p;
                }
 
index 0db8c3b..643832f 100644 (file)
@@ -618,14 +618,47 @@ win32_get_file_and_vol_ids(const wchar_t *path, u64 *ino_ret, u64 *dev_ret)
        return ret;
 }
 
+/* Reparse point fixup status code */
 enum rp_status {
+       /* Reparse point corresponded to an absolute symbolic link or junction
+        * point that pointed outside the directory tree being captured, and
+        * therefore was excluded. */
        RP_EXCLUDED       = 0x0,
+
+       /* Reparse point was not fixed as it was either a relative symbolic
+        * link, a mount point, or something else we could not understand. */
        RP_NOT_FIXED      = 0x1,
+
+       /* Reparse point corresponded to an absolute symbolic link or junction
+        * point that pointed inside the directory tree being captured, where
+        * the target was specified by a "full" \??\ prefixed path, and
+        * therefore was fixed to be relative to the root of the directory tree
+        * being captured. */
        RP_FIXED_FULLPATH = 0x2,
+
+       /* Same as RP_FIXED_FULLPATH, except the absolute link target did not
+        * have the \??\ prefix.  It may have begun with a drive letter though.
+        * */
        RP_FIXED_ABSPATH  = 0x4,
+
+       /* Either RP_FIXED_FULLPATH or RP_FIXED_ABSPATH. */
        RP_FIXED          = RP_FIXED_FULLPATH | RP_FIXED_ABSPATH,
 };
 
+/* Given the "substitute name" target of a Windows reparse point, try doing a
+ * fixup where we change it to be absolute relative to the root of the directory
+ * tree being captured.
+ *
+ * Note that this is only executed when WIMLIB_ADD_IMAGE_FLAG_RPFIX has been
+ * set.
+ *
+ * @capture_root_ino and @capture_root_dev indicate the inode number and device
+ * of the root of the directory tree being captured.  They are meant to identify
+ * this directory (as an alternative to its actual path, which could potentially
+ * be reached via multiple destinations due to other symbolic links).  This may
+ * not work properly on FAT, which doesn't seem to supply proper inode numbers
+ * or file IDs.  However, FAT doesn't support reparse points so this function
+ * wouldn't even be called anyway.  */
 static enum rp_status
 win32_maybe_rpfix_target(wchar_t *target, size_t *target_nchars_p,
                         u64 capture_root_ino, u64 capture_root_dev)
@@ -635,11 +668,12 @@ win32_maybe_rpfix_target(wchar_t *target, size_t *target_nchars_p,
        wchar_t *orig_target;
 
        if (target_nchars == 0)
+               /* Invalid reparse point (empty target) */
                return RP_NOT_FIXED;
 
        if (target[0] == L'\\') {
                if (target_nchars >= 2 && target[1] == L'\\') {
-                       /* Probaby a volume.  Can't do anything with it. */
+                       /* Probably a volume.  Can't do anything with it. */
                        DEBUG("Not fixing target (probably a volume)");
                        return RP_NOT_FIXED;
                } else if (target_nchars >= 7 &&
@@ -653,7 +687,7 @@ win32_maybe_rpfix_target(wchar_t *target, size_t *target_nchars_p,
                        DEBUG("Full style path");
                        /* Full \??\x:\ style path (may be junction or symlink)
                         * */
-                       stripped_chars = 4;
+                       stripped_chars = 6;
                } else {
                        DEBUG("Absolute target without drive letter");
                        /* Absolute target, without drive letter */
@@ -666,7 +700,7 @@ win32_maybe_rpfix_target(wchar_t *target, size_t *target_nchars_p,
        {
                DEBUG("Absolute target with drive letter");
                /* Absolute target, with drive letter */
-               stripped_chars = 0;
+               stripped_chars = 2;
        } else {
                DEBUG("Relative symlink or other link");
                /* Relative symlink or other unexpected format */
@@ -675,15 +709,17 @@ win32_maybe_rpfix_target(wchar_t *target, size_t *target_nchars_p,
        target[target_nchars] = L'\0';
        orig_target = target;
        target = fixup_symlink(target + stripped_chars, capture_root_ino, capture_root_dev);
-       if (target) {
-               target_nchars = wcslen(target);
-               wmemmove(orig_target + stripped_chars, target, target_nchars + 1);
-               *target_nchars_p = target_nchars + stripped_chars;
-               DEBUG("Fixed reparse point (new target: \"%ls\")", orig_target);
-               return stripped_chars ? RP_FIXED_FULLPATH : RP_FIXED_ABSPATH;
-       } else {
+       if (!target)
                return RP_EXCLUDED;
-       }
+
+       target_nchars = wcslen(target);
+       wmemmove(orig_target + stripped_chars, target, target_nchars + 1);
+       *target_nchars_p = target_nchars + stripped_chars;
+       DEBUG("Fixed reparse point (new target: \"%ls\")", orig_target);
+       if (stripped_chars == 6)
+               return RP_FIXED_FULLPATH;
+       else
+               return RP_FIXED_ABSPATH;
 }
 
 static enum rp_status
@@ -700,21 +736,22 @@ win32_do_capture_rpfix(char *rpbuf, DWORD *rpbuflen_p,
        u32 rptag;
        DWORD rpbuflen = *rpbuflen_p;
 
-       if (rpbuflen < 16)
-               return RP_EXCLUDED;
+       if (rpbuflen < 16) /* Invalid reparse point (length too small) */
+               return RP_NOT_FIXED;
        p_get = get_u32(rpbuf, &rptag);
        p_get += 4;
        p_get = get_u16(p_get, &substitute_name_offset);
        p_get = get_u16(p_get, &substitute_name_len);
        p_get += 4;
-       if ((size_t)substitute_name_offset + substitute_name_len > rpbuflen)
-               return RP_EXCLUDED;
        if (rptag == WIM_IO_REPARSE_TAG_SYMLINK) {
-               if (rpbuflen < 20)
-                       return RP_EXCLUDED;
+               if (rpbuflen < 20) /* Invalid reparse point (length too small) */
+                       return RP_NOT_FIXED;
                p_get += 4;
        }
-
+       if ((DWORD)substitute_name_offset +
+           substitute_name_len + (p_get - rpbuf) > rpbuflen)
+               /* Invalid reparse point (length too small) */
+               return RP_NOT_FIXED;
 
        target = (wchar_t*)&p_get[substitute_name_offset];
        target_nchars = substitute_name_len / 2;
@@ -729,6 +766,9 @@ win32_do_capture_rpfix(char *rpbuf, DWORD *rpbuflen_p,
                wchar_t *print_name = target_copy;
 
                if (status == RP_FIXED_FULLPATH) {
+                       /* "full path", meaning \??\ prefixed.  We should not
+                        * include this prefix in the print name, as it is
+                        * apparently meant for the filesystem driver only. */
                        print_nbytes -= 8;
                        print_name += 4;
                }
@@ -744,6 +784,9 @@ win32_do_capture_rpfix(char *rpbuf, DWORD *rpbuflen_p,
                p_put = put_u16(p_put, 0);
                p_put = put_bytes(p_put, print_nbytes, print_name);
                p_put = put_u16(p_put, 0);
+
+               /* Wrote the end of the reparse data.  Recalculate the length,
+                * set the length field correctly, and return it. */
                rpbuflen = p_put - rpbuf;
                put_u16(rpbuf + 4, rpbuflen - 8);
                *rpbuflen_p = rpbuflen;
@@ -799,16 +842,20 @@ win32_capture_reparse_point(struct wim_dentry **root_p,
            (inode->i_reparse_tag == WIM_IO_REPARSE_TAG_SYMLINK ||
             inode->i_reparse_tag == WIM_IO_REPARSE_TAG_MOUNT_POINT))
        {
+               /* Try doing reparse point fixup */
                enum rp_status status;
                status = win32_do_capture_rpfix(reparse_point_buf,
                                                &bytesReturned,
                                                params->capture_root_ino,
                                                params->capture_root_dev);
                if (status == RP_EXCLUDED) {
+                       /* Absolute path points out of capture tree.  Free the
+                        * dentry; we're not including it at all. */
                        free_dentry(*root_p);
                        *root_p = NULL;
                        return 0;
                } else if (status & RP_FIXED) {
+                       /* Absolute path fixup was done. */
                        inode->i_not_rpfixed = 0;
                }
        }