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Code Activity

gpg: Make the use of "--verify FILE" for detached sigs harder.

Browse source 
* g10/openfile.c (open_sigfile): Factor some code out to ...
(get_matching_datafile): new function.
* g10/plaintext.c (hash_datafiles): Do not try to find matching file
in batch mode.
* g10/mainproc.c (check_sig_and_print): Print a warning if a possibly
matching data file is not used by a standard signatures.
--

Allowing to use the abbreviated form for detached signatures is a long
standing bug which has only been noticed by the public with the
release of 2.1.0.  :-(

What we do is to remove the ability to check detached signature in
--batch using the one file abbreviated mode.  This should exhibit
problems in scripts which use this insecure practice.  We also print a
warning if a matching data file exists but was not considered because
the detached signature was actually a standard signature:

  gpgv: Good signature from "Werner Koch (dist sig)"
  gpgv: WARNING: not a detached signature; \
  file 'gnupg-2.1.0.tar.bz2' was NOT verified!

We can only print a warning because it is possible that a standard
signature is indeed to be verified but by coincidence a file with a
matching name is stored alongside the standard signature.

Reported-by: Simon Nicolussi (to gnupg-users on Nov 7)
Signed-off-by: Werner Koch <wk@gnupg.org>
This commit is contained in:
Werner Koch 2014-11-13 17:39:31 +01:00
parent 22748338da
commit 69384568f6
5 changed files with 125 additions and 51 deletions
Download patch file Download diff file Expand all files Collapse all files

31
g10/plaintext.c
View file

@ -607,10 +607,8 @@ leave:
/****************
* Hash the given files and append the hash to hash context md.
* If FILES is NULL, hash stdin.
*/
/* Hash the given files and append the hash to hash contexts MD and
* MD2. If FILES is NULL, stdin is hashed. */
int
hash_datafiles (gcry_md_hd_t md, gcry_md_hd_t md2, strlist_t files,
const char *sigfilename, int textmode)
@ -623,15 +621,22 @@ hash_datafiles (gcry_md_hd_t md, gcry_md_hd_t md2, strlist_t files,
if (!files)
{
/* check whether we can open the signed material */
fp = open_sigfile (sigfilename, pfx);
if (fp)
{
do_hash (md, md2, fp, textmode);
iobuf_close (fp);
release_progress_context (pfx);
return 0;
}
/* Check whether we can open the signed material. We avoid
trying to open a file if run in batch mode. This assumed
data file for a sig file feature is just a convenience thing
for the command line and the user needs to read possible
warning messages. */
if (!opt.batch)
{
fp = open_sigfile (sigfilename, pfx);
if (fp)
{
do_hash (md, md2, fp, textmode);
iobuf_close (fp);
release_progress_context (pfx);
return 0;
}
}
log_error (_("no signed data\n"));
release_progress_context (pfx);
return gpg_error (GPG_ERR_NO_DATA);