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agent: PKSIGN should return signature in same format for card. 

* agent/pksign.c (agent_pksign_do):

--

It's best to keep same data format by libgcrypt.

For card (due to historical reasons), gpg-agent or scdaemon used to
prefix 0x00 when it starts 0x80, so that it can be parsed signed MPI
as well as unsigned MPI.  It used to do nothing for preceding zeros.

Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>
This commit is contained in:
NIIBE Yutaka 2019-02-27 10:37:26 +09:00
parent c2235d994d
commit 0173b249cf
1 changed files with 37 additions and 47 deletions
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84
agent/pksign.c
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@ -367,20 +367,29 @@ agent_pksign_do (ctrl_t ctrl, const char *cache_nonce,
if (is_RSA)
{
check_signature = 1;
if (*buf & 0x80)
{
len++;
buf = xtryrealloc (buf, len);
if (!buf)
goto leave;
unsigned char *p = buf;
memmove (buf + 1, buf, len - 1);
*buf = 0;
check_signature = 1;
/*
* Smartcard returns fixed-size data, which is good for
* PKCS1. If variable-size unsigned MPI is needed, remove
* zeros.
*/
if (ctrl->digest.algo == MD_USER_TLS_MD5SHA1
|| ctrl->digest.raw_value)
{
int i;
for (i = 0; i < len - 1; i++)
if (p[i])
break;
p += i;
len -= i;
}
err = gcry_sexp_build (&s_sig, NULL, "(sig-val(rsa(s%b)))",
(int)len, buf);
(int)len, p);
}
else if (is_EdDSA)
{
@ -389,53 +398,34 @@ agent_pksign_do (ctrl_t ctrl, const char *cache_nonce,
}
else if (is_ECDSA)
{
unsigned char *r_buf_allocated = NULL;
unsigned char *s_buf_allocated = NULL;
unsigned char *r_buf, *s_buf;
int r_buflen, s_buflen;
int i;
r_buflen = s_buflen = len/2;
if (*buf & 0x80)
{
r_buflen++;
r_buf_allocated = xtrymalloc (r_buflen);
if (!r_buf_allocated)
{
err = gpg_error_from_syserror ();
goto leave;
}
/*
* Smartcard returns fixed-size data. For ECDSA signature,
* variable-size unsigned MPI is assumed, thus, remove
* zeros.
*/
r_buf = buf;
for (i = 0; i < r_buflen - 1; i++)
if (r_buf[i])
break;
r_buf += i;
r_buflen -= i;
r_buf = r_buf_allocated;
memcpy (r_buf + 1, buf, len/2);
*r_buf = 0;
}
else
r_buf = buf;
if (*(buf + len/2) & 0x80)
{
s_buflen++;
s_buf_allocated = xtrymalloc (s_buflen);
if (!s_buf_allocated)
{
err = gpg_error_from_syserror ();
xfree (r_buf_allocated);
goto leave;
}
s_buf = s_buf_allocated;
memcpy (s_buf + 1, buf + len/2, len/2);
*s_buf = 0;
}
else
s_buf = buf + len/2;
s_buf = buf + len/2;
for (i = 0; i < s_buflen - 1; i++)
if (s_buf[i])
break;
s_buf += i;
s_buflen -= i;
err = gcry_sexp_build (&s_sig, NULL, "(sig-val(ecdsa(r%b)(s%b)))",
r_buflen, r_buf,
s_buflen, s_buf);
xfree (r_buf_allocated);
xfree (s_buf_allocated);
}
else
err = gpg_error (GPG_ERR_NOT_IMPLEMENTED);