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common: New module to compute openpgp fingerprints
* common/openpgp-fpr.c: New. * common/Makefile.am (common_sources): Add it. -- This function is targeted to handle keys on smartcards. Signed-off-by: Werner Koch <wk@gnupg.org> (cherry picked from commit 2f2bdd9c0894eb43f719da8b529b4c7a46f742a0) Signed-off-by: Werner Koch <wk@gnupg.org>
This commit is contained in:
Werner Koch
parent
c825117c5f
commit
f3c98b8cb5
@ -98,6 +98,7 @@ common_sources = \
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name-value.c name-value.h \
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recsel.c recsel.h \
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ksba-io-support.c ksba-io-support.h \
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openpgp-fpr.c \
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compliance.c compliance.h
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283
common/openpgp-fpr.c
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283
common/openpgp-fpr.c
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@ -0,0 +1,283 @@
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/* openpgp-fpr.c - OpenPGP Fingerprint computation
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* Copyright (C) 2021 g10 Code GmbH
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*
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* This file is part of GnuPG.
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*
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* This file is free software; you can redistribute it and/or modify
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* it under the terms of either
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*
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* - the GNU Lesser General Public License as published by the Free
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* Software Foundation; either version 3 of the License, or (at
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* your option) any later version.
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*
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* or
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*
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* - the GNU General Public License as published by the Free
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* Software Foundation; either version 2 of the License, or (at
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* your option) any later version.
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*
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* or both in parallel, as here.
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*
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* This file is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <https://www.gnu.org/licenses/>.
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* SPDX-License-Identifier: (LGPL-3.0-or-later OR GPL-2.0-or-later)
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*/
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#include <config.h>
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#include <stdlib.h>
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#include <errno.h>
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#include <ctype.h>
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#include "util.h"
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#include "openpgpdefs.h"
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/* Count the number of bits, assuming the A represents an unsigned big
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* integer of length LEN bytes. */
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static unsigned int
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count_bits (const unsigned char *a, size_t len)
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{
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unsigned int n = len * 8;
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int i;
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for (; len && !*a; len--, a++, n -=8)
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;
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if (len)
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{
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for (i=7; i && !(*a & (1<<i)); i--)
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n--;
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}
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return n;
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}
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/* Variant of count_bits for simple octet strings. */
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static unsigned int
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count_sos_bits (const unsigned char *a, size_t len)
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{
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unsigned int n = len * 8;
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int i;
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if (len == 0 || *a == 0)
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return n;
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for (i=7; i && !(*a & (1<<i)); i--)
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n--;
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return n;
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}
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gpg_error_t
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compute_openpgp_fpr (int keyversion, int pgpalgo, unsigned long timestamp,
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gcry_buffer_t *iov, int iovcnt,
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unsigned char *result, unsigned int *r_resultlen)
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{
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gpg_error_t err;
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int hashalgo;
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unsigned char prefix[15];
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size_t n;
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int i;
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if (r_resultlen)
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*r_resultlen = 0;
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if (iovcnt < 2)
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return gpg_error (GPG_ERR_INV_ARG);
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/* Note that iov[0] is reserved. */
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for (n=0, i=1; i < iovcnt; i++)
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n += iov[i].len;
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i = 0;
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if (keyversion == 5)
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{
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hashalgo = GCRY_MD_SHA256;
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n += 10; /* Add the prefix length. */
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prefix[i++] = 0x9a;
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prefix[i++] = (n >> 24);
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prefix[i++] = (n >> 16);
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}
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else if (keyversion == 4)
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{
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hashalgo = GCRY_MD_SHA1;
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n += 6; /* Add the prefix length. */
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prefix[i++] = 0x99;
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}
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else
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return gpg_error (GPG_ERR_UNKNOWN_VERSION);
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prefix[i++] = (n >> 8);
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prefix[i++] = n;
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prefix[i++] = keyversion;
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prefix[i++] = (timestamp >> 24);
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prefix[i++] = (timestamp >> 16);
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prefix[i++] = (timestamp >> 8);
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prefix[i++] = (timestamp);
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prefix[i++] = pgpalgo;
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if (keyversion == 5)
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{
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prefix[i++] = ((n-10) >> 24);
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prefix[i++] = ((n-10) >> 16);
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prefix[i++] = ((n-10) >> 8);
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prefix[i++] = (n-10);
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}
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log_assert (i <= sizeof prefix);
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/* The first element is reserved for our use; set it. */
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iov[0].size = 0;
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iov[0].off = 0;
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iov[0].len = i;
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iov[0].data = prefix;
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/* for (i=0; i < iovcnt; i++) */
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/* log_printhex (iov[i].data, iov[i].len, "cmpfpr i=%d: ", i); */
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err = gcry_md_hash_buffers (hashalgo, 0, result, iov, iovcnt);
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/* log_printhex (result, 20, "fingerpint: "); */
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/* Better clear the first element because it was set by us. */
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iov[0].size = 0;
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iov[0].off = 0;
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iov[0].len = 0;
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iov[0].data = NULL;
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if (!err && r_resultlen)
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*r_resultlen = (hashalgo == GCRY_MD_SHA1)? 20 : 32;
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return err;
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}
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gpg_error_t
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compute_openpgp_fpr_rsa (int keyversion, unsigned long timestamp,
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const unsigned char *m, unsigned int mlen,
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const unsigned char *e, unsigned int elen,
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unsigned char *result, unsigned int *r_resultlen)
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{
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gcry_buffer_t iov[5] = { {0} };
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unsigned char nbits_m[2], nbits_e[2];
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unsigned int n;
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/* Strip leading zeroes. */
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for (; mlen && !*m; mlen--, m++)
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;
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for (; elen && !*e; elen--, e++)
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;
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/* Count bits. */
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n = count_bits (m, mlen);
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nbits_m[0] = n >> 8;
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nbits_m[1] = n;
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n = count_bits (e, elen);
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nbits_e[0] = n >> 8;
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nbits_e[1] = n;
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/* Put parms into the array. Note that iov[0] is reserved. */
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iov[1].len = 2;
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iov[1].data = nbits_m;
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iov[2].len = mlen;
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iov[2].data = (void*)m;
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iov[3].len = 2;
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iov[3].data = nbits_e;
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iov[4].len = elen;
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iov[4].data = (void*)e;
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return compute_openpgp_fpr (keyversion, PUBKEY_ALGO_RSA, timestamp,
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iov, 5, result, r_resultlen);
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}
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/* Determine KDF hash algorithm and KEK encryption algorithm by CURVE.
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* The returned buffer has a length of 4.
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* Note: This needs to be kept in sync with the table in g10/ecdh.c */
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static const unsigned char*
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default_ecdh_params (unsigned int nbits)
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{
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/* See RFC-6637 for those constants.
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0x03: Number of bytes
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0x01: Version for this parameter format
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KEK digest algorithm
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KEK cipher algorithm
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*/
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if (nbits <= 256)
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return (const unsigned char*)"\x03\x01\x08\x07";
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else if (nbits <= 384)
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return (const unsigned char*)"\x03\x01\x09\x09";
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else
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return (const unsigned char*)"\x03\x01\x0a\x09";
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}
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gpg_error_t
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compute_openpgp_fpr_ecc (int keyversion, unsigned long timestamp,
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const char *curvename, int for_encryption,
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const unsigned char *q, unsigned int qlen,
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const unsigned char *kdf, unsigned int kdflen,
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unsigned char *result, unsigned int *r_resultlen)
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{
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gpg_error_t err;
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const char *curveoidstr;
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gcry_mpi_t curveoid = NULL;
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unsigned int curvebits;
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int pgpalgo;
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const unsigned char *oidraw;
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size_t oidrawlen;
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gcry_buffer_t iov[5] = { {0} };
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unsigned int iovlen;
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unsigned char nbits_q[2];
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unsigned int n;
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curveoidstr = openpgp_curve_to_oid (curvename, &curvebits, &pgpalgo);
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err = openpgp_oid_from_str (curveoidstr, &curveoid);
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if (err)
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goto leave;
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oidraw = gcry_mpi_get_opaque (curveoid, &n);
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if (!oidraw)
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{
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err = gpg_error_from_syserror ();
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goto leave;
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}
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oidrawlen = (n+7)/8;
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/* If the curve does not enforce a certain algorithm, we use the
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* for_encryption flag to decide which algo to use. */
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if (!pgpalgo)
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pgpalgo = for_encryption? PUBKEY_ALGO_ECDH : PUBKEY_ALGO_ECDSA;
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/* Count bits. */
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n = count_sos_bits (q, qlen);
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nbits_q[0] = n >> 8;
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nbits_q[1] = n;
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/* Put parms into the array. Note that iov[0] is reserved. */
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iov[1].len = oidrawlen;
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iov[1].data = (void*)oidraw;
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iov[2].len = 2;
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iov[2].data = nbits_q;
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iov[3].len = qlen;
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iov[3].data = (void*)q;
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iovlen = 4;
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if (pgpalgo == PUBKEY_ALGO_ECDH)
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{
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if (!kdf || !kdflen || !kdf[0])
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{
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/* No KDF givem - use the default. */
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kdflen = 4;
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kdf = default_ecdh_params (curvebits);
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}
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iov[4].len = kdflen;
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iov[4].data = (void*)kdf;
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iovlen++;
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}
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err = compute_openpgp_fpr (keyversion, pgpalgo, timestamp,
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iov, iovlen, result, r_resultlen);
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leave:
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gcry_mpi_release (curveoid);
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return err;
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}
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@ -205,4 +205,26 @@ compress_algo_t;
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#define OPENPGP_MAX_NENC 2 /* Maximum number of encryption parameters. */
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/*-- openpgp-fpr.c --*/
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gpg_error_t compute_openpgp_fpr (int keyversion, int pgpalgo,
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unsigned long timestamp,
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gcry_buffer_t *iov, int iovcnt,
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unsigned char *result,
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unsigned int *r_resultlen);
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gpg_error_t compute_openpgp_fpr_rsa (int keyversion,
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unsigned long timestamp,
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const unsigned char *m, unsigned int mlen,
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const unsigned char *e, unsigned int elen,
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unsigned char *result,
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unsigned int *r_resultlen);
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gpg_error_t compute_openpgp_fpr_ecc (int keyversion,
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unsigned long timestamp,
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const char *curvename, int for_encryption,
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const unsigned char *q, unsigned int qlen,
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const unsigned char *kdf,
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unsigned int kdflen,
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unsigned char *result,
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unsigned int *r_resultlen);
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#endif /*GNUPG_COMMON_OPENPGPDEFS_H*/
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