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dirmngr: Allow for other hash algorithms than SHA-1 in OCSP. 

* dirmngr/ocsp.c (do_ocsp_request): Remove arg md.  Add args r_sigval,
r_produced_at, and r_md.  Get the hash algo from the signature and
create the context here.
(check_signature): Allow any hash algo.  Print a diagnostic if the
signature does not verify.
--

GnuPG-bug-id: 3966
Signed-off-by: Werner Koch <wk@gnupg.org>
This commit is contained in:
Werner Koch 2019-05-28 12:27:00 +02:00
parent 582dee2418
commit 5281ecbe3a
No known key found for this signature in database
GPG Key ID: E3FDFF218E45B72B
1 changed files with 80 additions and 25 deletions
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105
dirmngr/ocsp.c
View File

@ -116,10 +116,15 @@ read_response (estream_t fp, unsigned char **r_buffer, size_t *r_buflen)
/* Construct an OCSP request, send it to the configured OCSP responder
and parse the response. On success the OCSP context may be used to
further process the response. */
further process the response. The signature value and the
production date are returned at R_SIGVAL and R_PRODUCED_AT; they
may be NULL or an empty string if not available. A new hash
context is returned at R_MD. */
static gpg_error_t
do_ocsp_request (ctrl_t ctrl, ksba_ocsp_t ocsp, gcry_md_hd_t md,
const char *url, ksba_cert_t cert, ksba_cert_t issuer_cert)
do_ocsp_request (ctrl_t ctrl, ksba_ocsp_t ocsp,
const char *url, ksba_cert_t cert, ksba_cert_t issuer_cert,
ksba_sexp_t *r_sigval, ksba_isotime_t r_produced_at,
gcry_md_hd_t *r_md)
{
gpg_error_t err;
unsigned char *request, *response;
@ -132,6 +137,10 @@ do_ocsp_request (ctrl_t ctrl, ksba_ocsp_t ocsp, gcry_md_hd_t md,
(void)ctrl;
*r_sigval = NULL;
*r_produced_at = 0;
*r_md = NULL;
if (dirmngr_use_tor ())
{
/* For now we do not allow OCSP via Tor due to possible privacy
@ -263,6 +272,7 @@ do_ocsp_request (ctrl_t ctrl, ksba_ocsp_t ocsp, gcry_md_hd_t md,
xfree (free_this);
return err;
}
/* log_printhex (response, responselen, "ocsp response"); */
err = ksba_ocsp_parse_response (ocsp, response, responselen,
&response_status);
@ -290,11 +300,34 @@ do_ocsp_request (ctrl_t ctrl, ksba_ocsp_t ocsp, gcry_md_hd_t md,
}
if (response_status == KSBA_OCSP_RSPSTATUS_SUCCESS)
{
int hash_algo;
if (opt.verbose)
log_info (_("OCSP responder at '%s' status: %s\n"), url, t);
/* Get the signature value now because we can all this fucntion
* only once. */
*r_sigval = ksba_ocsp_get_sig_val (ocsp, r_produced_at);
hash_algo = hash_algo_from_sigval (*r_sigval);
if (!hash_algo)
{
if (opt.verbose)
log_info ("ocsp: using SHA-256 as fallback hash algo.\n");
hash_algo = GCRY_MD_SHA256;
}
err = gcry_md_open (r_md, hash_algo, 0);
if (err)
{
log_error (_("failed to establish a hashing context for OCSP: %s\n"),
gpg_strerror (err));
goto leave;
}
if (DBG_HASHING)
gcry_md_debug (*r_md, "ocsp");
err = ksba_ocsp_hash_response (ocsp, response, responselen,
HASH_FNC, md);
HASH_FNC, *r_md);
if (err)
log_error (_("hashing the OCSP response for '%s' failed: %s\n"),
url, gpg_strerror (err));
@ -305,8 +338,17 @@ do_ocsp_request (ctrl_t ctrl, ksba_ocsp_t ocsp, gcry_md_hd_t md,
err = gpg_error (GPG_ERR_GENERAL);
}
leave:
xfree (response);
xfree (free_this);
if (err)
{
xfree (*r_sigval);
*r_sigval = NULL;
*r_produced_at = 0;
gcry_md_close (*r_md);
*r_md = NULL;
}
return err;
}
@ -391,7 +433,7 @@ check_signature_core (ctrl_t ctrl, ksba_cert_t cert, gcry_sexp_t s_sig,
/* We simply ignore all errors. */
gcry_sexp_release (s_pkey);
return -1;
return err;
}
@ -410,18 +452,27 @@ check_signature (ctrl_t ctrl,
int algo, cert_idx;
gcry_sexp_t s_hash;
ksba_cert_t cert;
const char *s;
/* Create a suitable S-expression with the hash value of our response. */
gcry_md_final (md);
algo = gcry_md_get_algo (md);
if (algo != GCRY_MD_SHA1 )
s = gcry_md_algo_name (algo);
if (algo && s && strlen (s) < 16)
{
log_error (_("only SHA-1 is supported for OCSP responses\n"));
return gpg_error (GPG_ERR_DIGEST_ALGO);
char hashalgostr[16+1];
int i;
for (i=0; s[i]; i++)
hashalgostr[i] = ascii_tolower (s[i]);
hashalgostr[i] = 0;
err = gcry_sexp_build (&s_hash, NULL, "(data(flags pkcs1)(hash %s %b))",
hashalgostr,
(int)gcry_md_get_algo_dlen (algo),
gcry_md_read (md, algo));
}
err = gcry_sexp_build (&s_hash, NULL, "(data(flags pkcs1)(hash sha1 %b))",
gcry_md_get_algo_dlen (algo),
gcry_md_read (md, algo));
else
err = gpg_error (GPG_ERR_DIGEST_ALGO);
if (err)
{
log_error (_("creating S-expression failed: %s\n"), gcry_strerror (err));
@ -465,6 +516,7 @@ check_signature (ctrl_t ctrl,
{
cert_ref_t cref;
/* dump_cert ("from ocsp response", cert); */
cref = xtrymalloc (sizeof *cref);
if (!cref)
log_error (_("allocating list item failed: %s\n"),
@ -500,8 +552,6 @@ check_signature (ctrl_t ctrl,
}
log_printf ("not found\n");
}
ksba_free (name);
ksba_free (keyid);
if (cert)
{
@ -510,10 +560,24 @@ check_signature (ctrl_t ctrl,
ksba_cert_release (cert);
if (!err)
{
ksba_free (name);
ksba_free (keyid);
gcry_sexp_release (s_hash);
return 0; /* Successfully verified the signature. */
}
log_error ("responder certificate ");
if (name)
log_printf ("'/%s' ", name);
if (keyid)
{
log_printf ("{");
dump_serial (keyid);
log_printf ("} ");
}
log_printf ("did not verify: %s\n", gpg_strerror (err));
}
ksba_free (name);
ksba_free (keyid);
}
gcry_sexp_release (s_hash);
@ -588,8 +652,6 @@ ocsp_isvalid (ctrl_t ctrl, ksba_cert_t cert, const char *cert_fpr,
goto leave;
}
/* Figure out the OCSP responder to use.
1. Try to get the reponder from the certificate.
We do only take http and https style URIs into account.
@ -646,14 +708,8 @@ ocsp_isvalid (ctrl_t ctrl, ksba_cert_t cert, const char *cert_fpr,
}
/* Ask the OCSP responder. */
err = gcry_md_open (&md, GCRY_MD_SHA1, 0);
if (err)
{
log_error (_("failed to establish a hashing context for OCSP: %s\n"),
gpg_strerror (err));
goto leave;
}
err = do_ocsp_request (ctrl, ocsp, md, url, cert, issuer_cert);
err = do_ocsp_request (ctrl, ocsp, url, cert, issuer_cert,
&sigval, produced_at, &md);
if (err)
goto leave;
@ -685,8 +741,7 @@ ocsp_isvalid (ctrl_t ctrl, ksba_cert_t cert, const char *cert_fpr,
}
/* We got a useful answer, check that the answer has a valid signature. */
sigval = ksba_ocsp_get_sig_val (ocsp, produced_at);
if (!sigval || !*produced_at)
if (!sigval || !*produced_at || !md)
{
err = gpg_error (GPG_ERR_INV_OBJ);
goto leave;