zlib plugin: Uncompress if the message begins with zlib header instead of

looking at the 'Z' flag. This fixes copying with hard links. Based on a
patch by Richard Platel.

--HG--
branch : HEAD

diff --git a/src/plugins/zlib/zlib-plugin.c b/src/plugins/zlib/zlib-plugin.c
index 41e0d0c54fa82b1be5827059f767ddd892e83154..acf1a4be1bebcdbbb1da04bfce250f6e26677ac7 100644 (file)
--- a/src/plugins/zlib/zlib-plugin.c
+++ b/src/plugins/zlib/zlib-plugin.c
@@ -26,18 +26,32 @@ static MODULE_CONTEXT_DEFINE_INIT(zlib_storage_module,
                                  &mail_storage_module_register);
 static MODULE_CONTEXT_DEFINE_INIT(zlib_mail_module, &mail_module_register);
 
+static int zlib_mail_is_compressed(struct istream *mail)
+{
+       const unsigned char *zheader;
+       size_t header_size;
+
+       /* Peek in to the mail and see if it looks like it's compressed
+          (it has the correct 2 byte zlib header). This also means that users
+          can try to exploit security holes in zlib by APPENDing a specially
+          crafted mail. So let's hope zlib is free of holes. */
+       if (i_stream_read_data(mail, &zheader, &header_size, 2) <= 0)
+               return 0;
+       i_stream_seek(mail, 0);
+
+       return header_size >= 2 && zheader &&
+               zheader[0] == 31 && zheader[1] == 139;
+}
+
 static int zlib_maildir_get_stream(struct mail *_mail,
                                   struct message_size *hdr_size,
                                   struct message_size *body_size,
                                   struct istream **stream_r)
 {
-       struct maildir_mailbox *mbox = (struct maildir_mailbox *)_mail->box;
        struct mail_private *mail = (struct mail_private *)_mail;
        struct index_mail *imail = (struct index_mail *)mail;
        union mail_module_context *zmail = ZLIB_MAIL_CONTEXT(mail);
        struct istream *input;
-       const char *fname, *p;
-        enum maildir_uidlist_rec_flag flags;
        int fd;
 
        if (imail->data.stream != NULL) {
@@ -49,10 +63,7 @@ static int zlib_maildir_get_stream(struct mail *_mail,
                return -1;
        i_assert(input == imail->data.stream);
 
-       fname = maildir_uidlist_lookup(mbox->uidlist, _mail->uid, &flags);
-       p = fname == NULL ? NULL : strstr(fname, ":2,");
-       if (p != NULL && strchr(p + 3, 'Z') != NULL) {
-               /* has a Z flag - it's compressed */
+       if (zlib_mail_is_compressed(imail->data.stream)) {
                fd = dup(i_stream_get_fd(imail->data.stream));
                if (fd == -1)
                        i_error("zlib plugin: dup() failed: %m");