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sm: Do not expect X.509 keyids to be unique

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* sm/certlist.c (gpgsm_find_cert): Add arg allow_ambiguous and use it.
* sm/call-dirmngr.c (inq_certificate): Pass true to ALLOW_AMBIGUOUS
(run_command_inq_cb): Ditto.
* sm/gpgsm.c (main): Pass false.
* sm/server.c (cmd_passwd): Pass false.

--

As described in my report T1644, it is possible that multiple
certificates exist with the same Distinguished Name and the same key.
In this case, verifying S/MIME signatures and other actions fail with
"certificate not found: Ambiguous name". For details see the bug
report.

To circumvent the problem, I am patching GnuPG since 2014 so that in
this case the newest of the ambiguous certificates is used.

This is not an ultimate solution of the problem: You should try every
certificate with the same DN until verification succeeds or until all
certificates fail, and if multiple certificates of a chain are
ambiguous you even have to check every combination. You may even
consider checking the keyUsage attributes of the ambiguous certificates
to reduce the number of combinations.

But in the existing case of the certificates in the German Research
Network (DFN) PKI where the newest one is the valid one and all
ambiguous certificates have the same keyUsage attributes, this patch
has proven to be sufficient over the last three years.

With every GnuPG update, I have adapted the patch, luckily I never
needed to change anything except line numbers.

GnuPG-bug-id: 1644

ChangeLog log written by wk, comment taken from mail.  Signed-off line
was missing in the plain diff.  However the mail with the patch and
the DCO posted as reply to that mail were both signed.

Signed-off-by: Werner Koch <wk@gnupg.org>
This commit is contained in:
Rainer Perske 2017-10-24 17:29:04 +02:00 committed by Werner Koch
parent 6e808ae470
commit 1067403c8a
No known key found for this signature in database
GPG Key ID: E3FDFF218E45B72B
5 changed files with 44 additions and 6 deletions
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4
sm/call-dirmngr.c
View File

@ -415,7 +415,7 @@ inq_certificate (void *opaque, const char *line)
ksba_cert_t cert;
err = gpgsm_find_cert (parm->ctrl, line, ski, &cert);
err = gpgsm_find_cert (parm->ctrl, line, ski, &cert, 1);
if (err)
{
log_error ("certificate not found: %s\n", gpg_strerror (err));
@ -936,7 +936,7 @@ run_command_inq_cb (void *opaque, const char *line)
if (!*line)
return gpg_error (GPG_ERR_ASS_PARAMETER);
err = gpgsm_find_cert (parm->ctrl, line, NULL, &cert);
err = gpgsm_find_cert (parm->ctrl, line, NULL, &cert, 1);
if (err)
{
log_error ("certificate not found: %s\n", gpg_strerror (err));

40
sm/certlist.c
View File

@ -489,7 +489,8 @@ gpgsm_release_certlist (certlist_t list)
subjectKeyIdentifier. */
int
gpgsm_find_cert (ctrl_t ctrl,
const char *name, ksba_sexp_t keyid, ksba_cert_t *r_cert)
const char *name, ksba_sexp_t keyid, ksba_cert_t *r_cert,
int allow_ambiguous)
{
int rc;
KEYDB_SEARCH_DESC desc;
@ -537,6 +538,16 @@ gpgsm_find_cert (ctrl_t ctrl,
won't lead to ambiguous names. */
if (!rc && !keyid)
{
ksba_isotime_t notbefore = "";
const unsigned char *image = NULL;
size_t length = 0;
if (allow_ambiguous)
{
/* We want to return the newest certificate */
if (ksba_cert_get_validity (*r_cert, 0, notbefore))
*notbefore = '\0';
image = ksba_cert_get_image (*r_cert, &length);
}
next_ambiguous:
rc = keydb_search (ctrl, kh, &desc, 1);
if (rc == -1)
@ -546,6 +557,10 @@ gpgsm_find_cert (ctrl_t ctrl,
if (!rc)
{
ksba_cert_t cert2 = NULL;
ksba_isotime_t notbefore2 = "";
const unsigned char *image2 = NULL;
size_t length2 = 0;
int cmp = 0;
if (!keydb_get_cert (kh, &cert2))
{
@ -554,6 +569,29 @@ gpgsm_find_cert (ctrl_t ctrl,
ksba_cert_release (cert2);
goto next_ambiguous;
}
if (allow_ambiguous)
{
if (ksba_cert_get_validity (cert2, 0, notbefore2))
*notbefore2 = '\0';
image2 = ksba_cert_get_image (cert2, &length2);
cmp = strcmp (notbefore, notbefore2);
/* use certificate image bits as last resort for stable ordering */
if (!cmp)
cmp = memcmp (image, image2, length < length2 ? length : length2);
if (!cmp)
cmp = length < length2 ? -1 : length > length2 ? 1 : 0;
if (cmp < 0)
{
ksba_cert_release (*r_cert);
*r_cert = cert2;
strcpy (notbefore, notbefore2);
image = image2;
length = length2;
}
else
ksba_cert_release (cert2);
goto next_ambiguous;
}
ksba_cert_release (cert2);
}
rc = gpg_error (GPG_ERR_AMBIGUOUS_NAME);

2
sm/gpgsm.c
View File

@ -2052,7 +2052,7 @@ main ( int argc, char **argv)
ksba_cert_t cert = NULL;
char *grip = NULL;
rc = gpgsm_find_cert (&ctrl, *argv, NULL, &cert);
rc = gpgsm_find_cert (&ctrl, *argv, NULL, &cert, 0);
if (rc)
;
else if (!(grip = gpgsm_get_keygrip_hexstring (cert)))

2
sm/gpgsm.h
View File

@ -328,7 +328,7 @@ int gpgsm_add_to_certlist (ctrl_t ctrl, const char *name, int secret,
certlist_t *listaddr, int is_encrypt_to);
void gpgsm_release_certlist (certlist_t list);
int gpgsm_find_cert (ctrl_t ctrl, const char *name, ksba_sexp_t keyid,
ksba_cert_t *r_cert);
ksba_cert_t *r_cert, int allow_ambiguous);
/*-- keylist.c --*/
gpg_error_t gpgsm_list_keys (ctrl_t ctrl, strlist_t names,

2
sm/server.c
View File

@ -1179,7 +1179,7 @@ cmd_passwd (assuan_context_t ctx, char *line)
line = skip_options (line);
err = gpgsm_find_cert (ctrl, line, NULL, &cert);
err = gpgsm_find_cert (ctrl, line, NULL, &cert, 0);
if (err)
;
else if (!(grip = gpgsm_get_keygrip_hexstring (cert)))