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author | Niels Möller <nisse@lysator.liu.se> | 2012-04-09 21:46:13 +0200 |
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committer | Niels Möller <nisse@lysator.liu.se> | 2012-04-09 21:46:13 +0200 |
commit | 479aafcc16f505a5e3127fedabb624a2cf6e70c9 (patch) | |
tree | 447c2d2e114689193972ca5af06d35fbe1ebf375 /pkcs1-decrypt.c | |
parent | e9045bd365003feb8ca68d3da29e39a1f64c1e23 (diff) | |
download | nettle-479aafcc16f505a5e3127fedabb624a2cf6e70c9.tar.gz |
New function pkcs1_decrypt, use in rsa_decrypt.
Diffstat (limited to 'pkcs1-decrypt.c')
-rw-r--r-- | pkcs1-decrypt.c | 72 |
1 files changed, 72 insertions, 0 deletions
diff --git a/pkcs1-decrypt.c b/pkcs1-decrypt.c new file mode 100644 index 00000000..bd21f88b --- /dev/null +++ b/pkcs1-decrypt.c @@ -0,0 +1,72 @@ +/* pkcs1-decrypt.c + * + */ + +/* nettle, low-level cryptographics library + * + * Copyright (C) 2001, 2012 Niels Möller + * + * The nettle library is free software; you can redistribute it and/or modify + * it under the terms of the GNU Lesser General Public License as published by + * the Free Software Foundation; either version 2.1 of the License, or (at your + * option) any later version. + * + * The nettle library is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY + * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public + * License for more details. + * + * You should have received a copy of the GNU Lesser General Public License + * along with the nettle library; see the file COPYING.LIB. If not, write to + * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, + * MA 02111-1307, USA. + */ + +#if HAVE_CONFIG_H +# include "config.h" +#endif + +#include <string.h> + +#include "pkcs1.h" + +#include "bignum.h" +#include "nettle-internal.h" + +int +pkcs1_decrypt (unsigned key_size, + const mpz_t m, + unsigned *length, uint8_t *message) +{ + TMP_DECL(em, uint8_t, NETTLE_MAX_BIGNUM_BITS / 8); + uint8_t *terminator; + unsigned padding; + unsigned message_length; + + TMP_ALLOC(em, key_size); + nettle_mpz_get_str_256(key_size, em, m); + + /* Check format */ + if (em[0] || em[1] != 2) + return 0; + + terminator = memchr(em + 2, 0, key_size - 2); + + if (!terminator) + return 0; + + padding = terminator - (em + 2); + if (padding < 8) + return 0; + + message_length = key_size - 3 - padding; + + if (*length < message_length) + return 0; + + memcpy(message, terminator + 1, message_length); + *length = message_length; + + return 1; +} + |