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dirmngr: Support rsaPSS also in the general validate module. 

* dirmngr/validate.c (hash_algo_from_buffer): New.
(uint_from_buffer): New.
(check_cert_sig): Support rsaPSS.
* sm/certcheck.c (gpgsm_check_cert_sig): Fix small memory leak on
error.
--

Yes, I know that there is a lot of code duplication.  In fact some of
the code is ugly and it would be better if we enhance Libgcrypt to
guarantee that returned memory buffers via gcry_sexp_extract_param are
allways Nul terminated and we should also enhance that function to
directly extract into an unsigned int or char *.

GnuPG-bug-id: 4538
Signed-off-by: Werner Koch <wk@gnupg.org>
This commit is contained in:
Werner Koch 2020-04-09 13:05:55 +02:00
parent b45ab0ca08
commit ba34f14153
No known key found for this signature in database
GPG Key ID: E3FDFF218E45B72B
2 changed files with 133 additions and 46 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

173
dirmngr/validate.c
View File

@ -888,6 +888,53 @@ pk_algo_from_sexp (gcry_sexp_t pkey)
}
/* Return the hash algorithm's algo id from its name given in the
* non-null termnated string in (buffer,buflen). Returns 0 on failure
* or if the algo is not known. */
static int
hash_algo_from_buffer (const void *buffer, size_t buflen)
{
char *string;
int algo;
string = xtrymalloc (buflen + 1);
if (!string)
{
log_error (_("out of core\n"));
return 0;
}
memcpy (string, buffer, buflen);
string[buflen] = 0;
algo = gcry_md_map_name (string);
if (!algo)
log_error ("unknown digest algorithm '%s' used in certificate\n", string);
xfree (string);
return algo;
}
/* Return an unsigned integer from the non-null termnated string
* (buffer,buflen). Returns 0 on failure. */
static unsigned int
uint_from_buffer (const void *buffer, size_t buflen)
{
char *string;
unsigned int val;
string = xtrymalloc (buflen + 1);
if (!string)
{
log_error (_("out of core\n"));
return 0;
}
memcpy (string, buffer, buflen);
string[buflen] = 0;
val = strtoul (string, NULL, 10);
xfree (string);
return val;
}
/* Check the signature on CERT using the ISSUER_CERT. This function
* does only test the cryptographic signature and nothing else. It is
* assumed that the ISSUER_CERT is valid. */
@ -897,32 +944,85 @@ check_cert_sig (ksba_cert_t issuer_cert, ksba_cert_t cert)
gpg_error_t err;
const char *algoid;
gcry_md_hd_t md;
int i, algo;
int algo;
ksba_sexp_t p;
size_t n;
gcry_sexp_t s_sig, s_hash, s_pkey;
const char *s;
char algo_name[16+1]; /* hash algorithm name converted to lower case. */
const char *algo_name; /* hash algorithm name converted to lower case. */
int digestlen;
unsigned char *digest;
int use_pss = 0;
unsigned int saltlen;
/* Hash the target certificate using the algorithm from that certificate. */
algoid = ksba_cert_get_digest_algo (cert);
algo = gcry_md_map_name (algoid);
if (!algo)
if (!algo && algoid && !strcmp (algoid, "1.2.840.113549.1.1.10"))
use_pss = 1;
else if (!algo)
{
log_error (_("unknown hash algorithm '%s'\n"), algoid? algoid:"?");
return gpg_error (GPG_ERR_GENERAL);
}
s = gcry_md_algo_name (algo);
for (i=0; *s && i < sizeof algo_name - 1; s++, i++)
algo_name[i] = tolower (*s);
algo_name[i] = 0;
/* Get the signature value out of the target certificate. */
p = ksba_cert_get_sig_val (cert);
n = gcry_sexp_canon_len (p, 0, NULL, NULL);
if (!n)
{
log_error ("libksba did not return a proper S-Exp\n");
ksba_free (p);
return gpg_error (GPG_ERR_BUG);
}
err = gcry_sexp_sscan ( &s_sig, NULL, p, n);
ksba_free (p);
if (err)
{
log_error ("gcry_sexp_scan failed: %s\n", gpg_strerror (err));
return err;
}
if (DBG_CRYPTO)
gcry_log_debugsxp ("sigval", s_sig);
if (use_pss)
{
/* Extract the hash algorithm and the salt length from the sigval. */
gcry_buffer_t ioarray[2] = { {0}, {0} };
err = gcry_sexp_extract_param (s_sig, "sig-val",
"&'hash-algo''salt-length'",
ioarray+0, ioarray+1, NULL);
if (err)
{
gcry_sexp_release (s_sig);
log_error ("extracting params from PSS failed: %s\n",
gpg_strerror (err));
return err;
}
algo = hash_algo_from_buffer (ioarray[0].data, ioarray[0].len);
saltlen = uint_from_buffer (ioarray[1].data, ioarray[1].len);
xfree (ioarray[0].data);
xfree (ioarray[1].data);
if (saltlen < 20)
{
log_error ("length of PSS salt too short\n");
gcry_sexp_release (s_sig);
return gpg_error (GPG_ERR_DIGEST_ALGO);
}
if (!algo)
{
gcry_sexp_release (s_sig);
return gpg_error (GPG_ERR_DIGEST_ALGO);
}
/* log_debug ("PSS hash=%d saltlen=%u\n", algo, saltlen); */
}
algo_name = hash_algo_to_string (algo);
err = gcry_md_open (&md, algo, 0);
if (err)
{
log_error ("md_open failed: %s\n", gpg_strerror (err));
gcry_sexp_release (s_sig);
return err;
}
if (DBG_HASHING)
@ -933,38 +1033,11 @@ check_cert_sig (ksba_cert_t issuer_cert, ksba_cert_t cert)
{
log_error ("ksba_cert_hash failed: %s\n", gpg_strerror (err));
gcry_md_close (md);
gcry_sexp_release (s_sig);
return err;
}
gcry_md_final (md);
/* Get the signature value out of the target certificate. */
p = ksba_cert_get_sig_val (cert);
n = gcry_sexp_canon_len (p, 0, NULL, NULL);
if (!n)
{
log_error ("libksba did not return a proper S-Exp\n");
gcry_md_close (md);
ksba_free (p);
return gpg_error (GPG_ERR_BUG);
}
if (DBG_CRYPTO)
{
int j;
log_debug ("signature value:");
for (j=0; j < n; j++)
log_printf (" %02X", p[j]);
log_printf ("\n");
}
err = gcry_sexp_sscan ( &s_sig, NULL, p, n);
ksba_free (p);
if (err)
{
log_error ("gcry_sexp_scan failed: %s\n", gpg_strerror (err));
gcry_md_close (md);
return err;
}
/* Get the public key from the issuer certificate. */
p = ksba_cert_get_public_key (issuer_cert);
n = gcry_sexp_canon_len (p, 0, NULL, NULL);
@ -994,10 +1067,22 @@ check_cert_sig (ksba_cert_t issuer_cert, ksba_cert_t cert)
* S_SIG - Signature value as given in the certificate.
* MD - Finalized hash context with hash of the certificate.
* ALGO_NAME - Lowercase hash algorithm name
* SALTLEN - Salt length for rsaPSS.
*/
digestlen = gcry_md_get_algo_dlen (algo);
digest = gcry_md_read (md, algo);
if (pk_algo_from_sexp (s_pkey) == GCRY_PK_DSA)
if (use_pss)
{
err = gcry_sexp_build (&s_hash, NULL,
"(data (flags pss)"
"(hash %s %b)"
"(salt-length %u))",
algo_name,
(int)digestlen,
digest,
saltlen);
}
else if (pk_algo_from_sexp (s_pkey) == GCRY_PK_DSA)
{
/* NB.: We support only SHA-1 here because we had problems back
* then to get test data for DSA-2. Meanwhile DSA has been
@ -1010,19 +1095,17 @@ check_cert_sig (ksba_cert_t issuer_cert, ksba_cert_t cert)
gcry_sexp_release (s_pkey);
return gpg_error (GPG_ERR_INTERNAL);
}
if ( gcry_sexp_build (&s_hash, NULL, "(data(flags raw)(value %b))",
(int)digestlen, digest) )
BUG ();
err = gcry_sexp_build (&s_hash, NULL, "(data(flags raw)(value %b))",
(int)digestlen, digest);
}
else /* Not DSA - we assume RSA */
{
if ( gcry_sexp_build (&s_hash, NULL, "(data(flags pkcs1)(hash %s %b))",
algo_name, (int)digestlen, digest) )
BUG ();
err = gcry_sexp_build (&s_hash, NULL, "(data(flags pkcs1)(hash %s %b))",
algo_name, (int)digestlen, digest);
}
err = gcry_pk_verify (s_sig, s_hash, s_pkey);
if (!err)
err = gcry_pk_verify (s_sig, s_hash, s_pkey);
if (DBG_X509)
log_debug ("gcry_pk_verify: %s\n", gpg_strerror (err));
gcry_md_close (md);

6
sm/certcheck.c
View File

@ -340,10 +340,14 @@ gpgsm_check_cert_sig (ksba_cert_t issuer_cert, ksba_cert_t cert)
if (saltlen < 20)
{
log_error ("length of PSS salt too short\n");
gcry_sexp_release (s_sig);
return gpg_error (GPG_ERR_DIGEST_ALGO);
}
if (!algo)
return gpg_error (GPG_ERR_DIGEST_ALGO);
{
gcry_sexp_release (s_sig);
return gpg_error (GPG_ERR_DIGEST_ALGO);
}
/* log_debug ("PSS hash=%d saltlen=%u\n", algo, saltlen); */
}