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sm: Add special case for expired intermediate certificates.

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* sm/gpgsm.h (struct server_control_s): Add field 'current_time'.
* sm/certchain.c (find_up_search_by_keyid): Detect a corner case.
Also simplify by using ref-ed cert objects in place of an anyfound
var.
--

See the code for a description of the problem. Tested using the certs
from the bug report and various command lines

  gpgsm --faked-system-time=XXXX --disable-crl-checks \
         -ea -v --debug x509  -r 0x95599828

with XXXX being 20190230T000000 -> target cert too young
with XXXX being 20190330T000000 -> okay
with XXXX being 20190830T000000 -> okay, using the long term cert
with XXXX being 20220330T000000 -> target cert expired

The --disabled-crl-checks option is required because in our a simple
test setting dirmngr does not know about the faked time.

GnuPG-bug-id: 4696
Signed-off-by: Werner Koch <wk@gnupg.org>
This commit is contained in:
Werner Koch 2019-12-06 20:12:22 +01:00
parent 8a6ecc6ff5
commit d246f317c0
No known key found for this signature in database
GPG Key ID: E3FDFF218E45B72B
2 changed files with 91 additions and 17 deletions
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105
sm/certchain.c
View File

@ -445,8 +445,9 @@ find_up_search_by_keyid (ctrl_t ctrl, KEYDB_HANDLE kh,
int rc;
ksba_cert_t cert = NULL;
ksba_sexp_t subj = NULL;
int anyfound = 0;
ksba_isotime_t not_before, last_not_before;
ksba_isotime_t not_before, not_after, last_not_before, ne_last_not_before;
ksba_cert_t found_cert = NULL;
ksba_cert_t ne_found_cert = NULL;
keydb_search_reset (kh);
while (!(rc = keydb_search_subject (ctrl, kh, issuer)))
@ -457,7 +458,7 @@ find_up_search_by_keyid (ctrl_t ctrl, KEYDB_HANDLE kh,
{
log_error ("keydb_get_cert() failed: rc=%d\n", rc);
rc = -1;
break;
goto leave;
}
xfree (subj);
if (!ksba_cert_get_subj_key_id (cert, NULL, &subj))
@ -466,34 +467,103 @@ find_up_search_by_keyid (ctrl_t ctrl, KEYDB_HANDLE kh,
{
/* Found matching cert. */
rc = ksba_cert_get_validity (cert, 0, not_before);
if (!rc)
rc = ksba_cert_get_validity (cert, 1, not_after);
if (rc)
{
log_error ("keydb_get_validity() failed: rc=%d\n", rc);
rc = -1;
break;
goto leave;
}
if (!anyfound || strcmp (last_not_before, not_before) < 0)
if (!found_cert
|| strcmp (last_not_before, not_before) < 0)
{
/* This certificate is the first one found or newer
than the previous one. This copes with
re-issuing CA certificates while keeping the same
key information. */
anyfound = 1;
* than the previous one. This copes with
* re-issuing CA certificates while keeping the same
* key information. */
gnupg_copy_time (last_not_before, not_before);
ksba_cert_release (found_cert);
ksba_cert_ref ((found_cert = cert));
keydb_push_found_state (kh);
}
if (*not_after && strcmp (ctrl->current_time, not_after) > 0 )
; /* CERT has expired - don't consider it. */
else if (!ne_found_cert
|| strcmp (ne_last_not_before, not_before) < 0)
{
/* This certificate is the first non-expired one
* found or newer than the previous non-expired one. */
gnupg_copy_time (ne_last_not_before, not_before);
ksba_cert_release (ne_found_cert);
ksba_cert_ref ((ne_found_cert = cert));
}
}
}
}
if (anyfound)
if (!found_cert)
goto leave;
/* Take the last saved one. Note that push/pop_found_state are
* misnomers because there is no stack of states. Renaming them to
* save/restore_found_state would be better. */
keydb_pop_found_state (kh);
rc = 0; /* Ignore EOF or other error after the first cert. */
/* We need to consider some corner cases. It is possible that we
* have a long term certificate (e.g. valid from 2008 to 2033) as
* well as a re-issued (i.e. using the same key material) short term
* certificate (say from 2016 to 2019). Using the short term
* certificate is the proper solution. But we need to take care if
* there is no re-issued new short term certificate (e.g. from 2020
* to 2023) available. In that case it is better to use the long
* term certificate which is still valid. The code may run into
* minor problems in the case of the chain validation mode. Given
* that this corner case is due to non-diligent PKI management we
* ignore this problem. */
/* The most common case is that the found certificate is not expired
* and thus identical to the one found from the list of non-expired
* certs. We can stop here. */
if (found_cert == ne_found_cert)
goto leave;
/* If we do not have a non expired certificate the actual cert is
* expired and we can also stop here. */
if (!ne_found_cert)
goto leave;
/* Now we need to see whether the found certificate is expired and
* only in this case we return the certificate found in the list of
* non-expired certs. */
rc = ksba_cert_get_validity (found_cert, 1, not_after);
if (rc)
{
/* Take the last saved one. */
keydb_pop_found_state (kh);
rc = 0; /* Ignore EOF or other error after the first cert. */
log_error ("keydb_get_validity() failed: rc=%d\n", rc);
rc = -1;
goto leave;
}
if (*not_after && strcmp (ctrl->current_time, not_after) > 0 )
{ /* CERT has expired. Use the NE_FOUND_CERT. Because we have no
* found state for this we need to search for it again. */
unsigned char fpr[20];
gpgsm_get_fingerprint (ne_found_cert, GCRY_MD_SHA1, fpr, NULL);
keydb_search_reset (kh);
rc = keydb_search_fpr (ctrl, kh, fpr);
if (rc)
{
log_error ("keydb_search_fpr() failed: rc=%d\n", rc);
rc = -1;
goto leave;
}
/* Ready. The NE_FOUND_CERT is availabale via keydb_get_cert. */
}
leave:
ksba_cert_release (found_cert);
ksba_cert_release (ne_found_cert);
ksba_cert_release (cert);
xfree (subj);
return rc? -1:0;
@ -643,7 +713,7 @@ find_up_dirmngr (ctrl_t ctrl, KEYDB_HANDLE kh,
issuer used as a fallback if the other methods don't work. If
FIND_NEXT is true, the function shall return the next possible
issuer. The certificate itself is not directly returned but a
keydb_get_cert on the keyDb context KH will return it. Returns 0
keydb_get_cert on the keydb context KH will return it. Returns 0
on success, -1 if not found or an error code. */
static int
find_up (ctrl_t ctrl, KEYDB_HANDLE kh,
@ -699,7 +769,7 @@ find_up (ctrl_t ctrl, KEYDB_HANDLE kh,
if (rc == -1 && keyid && !find_next)
{
/* Not found by AIK.issuer_sn. Lets try the AIK.ki
/* Not found by AKI.issuer_sn. Lets try the AKI.ki
instead. Loop over all certificates with that issuer as
subject and stop for the one with a matching
subjectKeyIdentifier. */
@ -1037,7 +1107,7 @@ is_cert_still_valid (ctrl_t ctrl, int force_ocsp, int lm, estream_t fp,
/* Helper for gpgsm_validate_chain to check the validity period of
SUBJECT_CERT. The caller needs to pass EXPTIME which will be
updated to the nearest expiration time seen. A DEPTH of 0 indicates
the target certifciate, -1 the final root certificate and other
the target certificate, -1 the final root certificate and other
values intermediate certificates. */
static gpg_error_t
check_validity_period (ksba_isotime_t current_time,
@ -1296,6 +1366,7 @@ do_validate_chain (ctrl_t ctrl, ksba_cert_t cert, ksba_isotime_t checktime_arg,
gnupg_get_isotime (current_time);
gnupg_copy_time (ctrl->current_time, current_time);
if ( (flags & VALIDATE_FLAG_CHAIN_MODEL) )
{
@ -1516,7 +1587,7 @@ do_validate_chain (ctrl_t ctrl, ksba_cert_t cert, ksba_isotime_t checktime_arg,
_("root certificate is not marked trusted"));
/* If we already figured out that the certificate is
expired it does not make much sense to ask the user
whether we wants to trust the root certificate. We
whether they want to trust the root certificate. We
should do this only if the certificate under question
will then be usable. If the certificate has a well
known private key asking the user does not make any

3
sm/gpgsm.h
View File

@ -228,6 +228,9 @@ struct server_control_s
1 := chain model,
2 := STEED model. */
int offline; /* If true gpgsm won't do any network access. */
/* The current time. Used as a helper in certchain.c. */
ksba_isotime_t current_time;
};