2 rsa.c -- RSA key handling
3 Copyright (C) 2007 Guus Sliepen <guus@tinc-vpn.org>
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 2 of the License, or
8 (at your option) any later version.
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License along
16 with this program; if not, write to the Free Software Foundation, Inc.,
17 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
27 // Base64 decoding table
29 static const uint8_t b64d[128] = {
30 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
31 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
32 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
33 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
34 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
35 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
36 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
37 0xff, 0x3e, 0xff, 0xff, 0xff, 0x3f,
38 0x34, 0x35, 0x36, 0x37, 0x38, 0x39,
39 0x3a, 0x3b, 0x3c, 0x3d, 0xff, 0xff,
40 0xff, 0xff, 0xff, 0xff, 0xff, 0x00,
41 0x01, 0x02, 0x03, 0x04, 0x05, 0x06,
42 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c,
43 0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12,
44 0x13, 0x14, 0x15, 0x16, 0x17, 0x18,
45 0x19, 0xff, 0xff, 0xff, 0xff, 0xff,
46 0xff, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e,
47 0x1f, 0x20, 0x21, 0x22, 0x23, 0x24,
48 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a,
49 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30,
50 0x31, 0x32, 0x33, 0xff, 0xff, 0xff,
54 // PEM encoding/decoding functions
56 static bool pem_decode(FILE *fp, const char *header, uint8_t *buf, size_t size, size_t *outsize) {
64 if(!fgets(line, sizeof line, fp))
67 if(!decode && !strncmp(line, "-----BEGIN ", 11)) {
68 if(!strncmp(line + 11, header, strlen(header)))
73 if(decode && !strncmp(line, "-----END", 8)) {
80 for(i = 0; line[i] >= ' '; i++) {
81 if((signed char)line[i] < 0 || b64d[(int)line[i]] == 0xff)
83 word |= b64d[(int)line[i]] << shift;
104 // BER decoding functions
106 static int ber_read_id(unsigned char **p, size_t *buflen) {
110 if((**p & 0x1f) == 0x1f) {
116 more = *(*p)++ & 0x80;
124 return *(*p)++ & 0x1f;
128 static size_t ber_read_len(unsigned char **p, size_t *buflen) {
134 int len = *(*p)++ & 0x7f;
153 static bool ber_read_sequence(unsigned char **p, size_t *buflen, size_t *result) {
154 int tag = ber_read_id(p, buflen);
155 size_t len = ber_read_len(p, buflen);
166 static bool ber_read_mpi(unsigned char **p, size_t *buflen, gcry_mpi_t *mpi) {
167 int tag = ber_read_id(p, buflen);
168 size_t len = ber_read_len(p, buflen);
169 gcry_error_t err = 0;
171 if(tag != 0x02 || len > *buflen)
175 err = gcry_mpi_scan(mpi, GCRYMPI_FMT_USG, *p, len, NULL);
180 return mpi ? !err : true;
183 bool rsa_set_hex_public_key(rsa_t *rsa, char *n, char *e) {
184 gcry_error_t err = 0;
186 err = gcry_mpi_scan(&rsa->n, GCRYMPI_FMT_HEX, n, 0, NULL)
187 ?: gcry_mpi_scan(&rsa->e, GCRYMPI_FMT_HEX, e, 0, NULL);
190 logger(LOG_ERR, "Error while reading RSA public key: %s", gcry_strerror(errno));
197 bool rsa_set_hex_private_key(rsa_t *rsa, char *n, char *e, char *d) {
198 gcry_error_t err = 0;
200 err = gcry_mpi_scan(&rsa->n, GCRYMPI_FMT_HEX, n, 0, NULL)
201 ?: gcry_mpi_scan(&rsa->e, GCRYMPI_FMT_HEX, e, 0, NULL)
202 ?: gcry_mpi_scan(&rsa->d, GCRYMPI_FMT_HEX, d, 0, NULL);
205 logger(LOG_ERR, "Error while reading RSA public key: %s", gcry_strerror(errno));
214 bool rsa_read_pem_public_key(rsa_t *rsa, FILE *fp) {
215 uint8_t derbuf[8096], *derp = derbuf;
218 if(!pem_decode(fp, "RSA PUBLIC KEY", derbuf, sizeof derbuf, &derlen)) {
219 logger(LOG_ERR, "Unable to read RSA public key: %s", strerror(errno));
223 if(!ber_read_sequence(&derp, &derlen, NULL)
224 || !ber_read_mpi(&derp, &derlen, &rsa->n)
225 || !ber_read_mpi(&derp, &derlen, &rsa->e)
227 logger(LOG_ERR, "Error while decoding RSA public key");
234 bool rsa_read_pem_private_key(rsa_t *rsa, FILE *fp) {
235 uint8_t derbuf[8096], *derp = derbuf;
238 if(!pem_decode(fp, "RSA PRIVATE KEY", derbuf, sizeof derbuf, &derlen)) {
239 logger(LOG_ERR, "Unable to read RSA private key: %s", strerror(errno));
243 if(!ber_read_sequence(&derp, &derlen, NULL)
244 || !ber_read_mpi(&derp, &derlen, NULL)
245 || !ber_read_mpi(&derp, &derlen, &rsa->n)
246 || !ber_read_mpi(&derp, &derlen, &rsa->e)
247 || !ber_read_mpi(&derp, &derlen, &rsa->d)
248 || !ber_read_mpi(&derp, &derlen, NULL) // p
249 || !ber_read_mpi(&derp, &derlen, NULL) // q
250 || !ber_read_mpi(&derp, &derlen, NULL)
251 || !ber_read_mpi(&derp, &derlen, NULL)
252 || !ber_read_mpi(&derp, &derlen, NULL) // u
254 logger(LOG_ERR, "Error while decoding RSA private key");
261 size_t rsa_size(rsa_t *rsa) {
262 return (gcry_mpi_get_nbits(rsa->n) + 7) / 8;
265 /* Well, libgcrypt has functions to handle RSA keys, but they suck.
266 * So we just use libgcrypt's mpi functions, and do the math ourselves.
269 // TODO: get rid of this macro, properly clean up gcry_ structures after use
270 #define check(foo) { gcry_error_t err = (foo); if(err) {logger(LOG_ERR, "gcrypt error %s/%s at %s:%d\n", gcry_strsource(err), gcry_strerror(err), __FILE__, __LINE__); return false; }}
272 bool rsa_public_encrypt(rsa_t *rsa, void *in, size_t len, void *out) {
274 check(gcry_mpi_scan(&inmpi, GCRYMPI_FMT_USG, in, len, NULL));
276 gcry_mpi_t outmpi = gcry_mpi_new(len * 8);
277 gcry_mpi_powm(outmpi, inmpi, rsa->e, rsa->n);
279 int pad = len - (gcry_mpi_get_nbits(outmpi) + 7) / 8;
283 check(gcry_mpi_print(GCRYMPI_FMT_USG, out,len, NULL, outmpi));
288 bool rsa_private_decrypt(rsa_t *rsa, void *in, size_t len, void *out) {
290 check(gcry_mpi_scan(&inmpi, GCRYMPI_FMT_USG, in, len, NULL));
292 gcry_mpi_t outmpi = gcry_mpi_new(len * 8);
293 gcry_mpi_powm(outmpi, inmpi, rsa->d, rsa->n);
295 int pad = len - (gcry_mpi_get_nbits(outmpi) + 7) / 8;
299 check(gcry_mpi_print(GCRYMPI_FMT_USG, out,len, NULL, outmpi));