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257 lines
8.1 KiB
257 lines
8.1 KiB
/* crypto/rsa/rsa_oaep.c */ |
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/* |
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* Written by Ulf Moeller. This software is distributed on an "AS IS" basis, |
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. |
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*/ |
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|
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/* EME-OAEP as defined in RFC 2437 (PKCS #1 v2.0) */ |
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|
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/* |
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* See Victor Shoup, "OAEP reconsidered," Nov. 2000, <URL: |
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* http://www.shoup.net/papers/oaep.ps.Z> for problems with the security |
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* proof for the original OAEP scheme, which EME-OAEP is based on. A new |
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* proof can be found in E. Fujisaki, T. Okamoto, D. Pointcheval, J. Stern, |
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* "RSA-OEAP is Still Alive!", Dec. 2000, <URL: |
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* http://eprint.iacr.org/2000/061/>. The new proof has stronger requirements |
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* for the underlying permutation: "partial-one-wayness" instead of |
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* one-wayness. For the RSA function, this is an equivalent notion. |
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*/ |
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#include "constant_time_locl.h" |
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|
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#if !defined(OPENSSL_NO_SHA) && !defined(OPENSSL_NO_SHA1) |
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# include <stdio.h> |
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# include "cryptlib.h" |
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# include <openssl/bn.h> |
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# include <openssl/rsa.h> |
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# include <openssl/evp.h> |
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# include <openssl/rand.h> |
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# include <openssl/sha.h> |
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static int MGF1(unsigned char *mask, long len, |
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const unsigned char *seed, long seedlen); |
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|
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int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen, |
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const unsigned char *from, int flen, |
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const unsigned char *param, int plen) |
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{ |
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int i, emlen = tlen - 1; |
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unsigned char *db, *seed; |
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unsigned char *dbmask, seedmask[SHA_DIGEST_LENGTH]; |
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if (flen > emlen - 2 * SHA_DIGEST_LENGTH - 1) { |
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RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, |
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RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE); |
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return 0; |
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} |
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if (emlen < 2 * SHA_DIGEST_LENGTH + 1) { |
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RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, RSA_R_KEY_SIZE_TOO_SMALL); |
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return 0; |
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} |
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to[0] = 0; |
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seed = to + 1; |
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db = to + SHA_DIGEST_LENGTH + 1; |
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if (!EVP_Digest((void *)param, plen, db, NULL, EVP_sha1(), NULL)) |
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return 0; |
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memset(db + SHA_DIGEST_LENGTH, 0, |
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emlen - flen - 2 * SHA_DIGEST_LENGTH - 1); |
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db[emlen - flen - SHA_DIGEST_LENGTH - 1] = 0x01; |
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memcpy(db + emlen - flen - SHA_DIGEST_LENGTH, from, (unsigned int)flen); |
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if (RAND_bytes(seed, SHA_DIGEST_LENGTH) <= 0) |
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return 0; |
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# ifdef PKCS_TESTVECT |
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memcpy(seed, |
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"\xaa\xfd\x12\xf6\x59\xca\xe6\x34\x89\xb4\x79\xe5\x07\x6d\xde\xc2\xf0\x6c\xb5\x8f", |
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20); |
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# endif |
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dbmask = OPENSSL_malloc(emlen - SHA_DIGEST_LENGTH); |
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if (dbmask == NULL) { |
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RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, ERR_R_MALLOC_FAILURE); |
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return 0; |
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} |
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if (MGF1(dbmask, emlen - SHA_DIGEST_LENGTH, seed, SHA_DIGEST_LENGTH) < 0) |
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return 0; |
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for (i = 0; i < emlen - SHA_DIGEST_LENGTH; i++) |
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db[i] ^= dbmask[i]; |
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if (MGF1(seedmask, SHA_DIGEST_LENGTH, db, emlen - SHA_DIGEST_LENGTH) < 0) |
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return 0; |
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for (i = 0; i < SHA_DIGEST_LENGTH; i++) |
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seed[i] ^= seedmask[i]; |
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OPENSSL_free(dbmask); |
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return 1; |
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} |
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int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen, |
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const unsigned char *from, int flen, int num, |
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const unsigned char *param, int plen) |
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{ |
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int i, dblen, mlen = -1, one_index = 0, msg_index; |
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unsigned int good, found_one_byte; |
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const unsigned char *maskedseed, *maskeddb; |
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/* |
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* |em| is the encoded message, zero-padded to exactly |num| bytes: em = |
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* Y || maskedSeed || maskedDB |
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*/ |
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unsigned char *db = NULL, *em = NULL, seed[EVP_MAX_MD_SIZE], |
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phash[EVP_MAX_MD_SIZE]; |
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if (tlen <= 0 || flen <= 0) |
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return -1; |
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/* |
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* |num| is the length of the modulus; |flen| is the length of the |
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* encoded message. Therefore, for any |from| that was obtained by |
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* decrypting a ciphertext, we must have |flen| <= |num|. Similarly, |
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* num < 2 * SHA_DIGEST_LENGTH + 2 must hold for the modulus |
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* irrespective of the ciphertext, see PKCS #1 v2.2, section 7.1.2. |
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* This does not leak any side-channel information. |
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*/ |
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if (num < flen || num < 2 * SHA_DIGEST_LENGTH + 2) |
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goto decoding_err; |
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dblen = num - SHA_DIGEST_LENGTH - 1; |
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db = OPENSSL_malloc(dblen); |
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em = OPENSSL_malloc(num); |
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if (db == NULL || em == NULL) { |
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RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, ERR_R_MALLOC_FAILURE); |
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goto cleanup; |
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} |
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/* |
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* Always do this zero-padding copy (even when num == flen) to avoid |
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* leaking that information. The copy still leaks some side-channel |
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* information, but it's impossible to have a fixed memory access |
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* pattern since we can't read out of the bounds of |from|. |
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* |
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* TODO(emilia): Consider porting BN_bn2bin_padded from BoringSSL. |
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*/ |
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memset(em, 0, num); |
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memcpy(em + num - flen, from, flen); |
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/* |
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* The first byte must be zero, however we must not leak if this is |
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* true. See James H. Manger, "A Chosen Ciphertext Attack on RSA |
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* Optimal Asymmetric Encryption Padding (OAEP) [...]", CRYPTO 2001). |
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*/ |
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good = constant_time_is_zero(em[0]); |
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maskedseed = em + 1; |
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maskeddb = em + 1 + SHA_DIGEST_LENGTH; |
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if (MGF1(seed, SHA_DIGEST_LENGTH, maskeddb, dblen)) |
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goto cleanup; |
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for (i = 0; i < SHA_DIGEST_LENGTH; i++) |
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seed[i] ^= maskedseed[i]; |
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if (MGF1(db, dblen, seed, SHA_DIGEST_LENGTH)) |
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goto cleanup; |
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for (i = 0; i < dblen; i++) |
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db[i] ^= maskeddb[i]; |
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if (!EVP_Digest((void *)param, plen, phash, NULL, EVP_sha1(), NULL)) |
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goto cleanup; |
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good &= |
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constant_time_is_zero(CRYPTO_memcmp(db, phash, SHA_DIGEST_LENGTH)); |
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found_one_byte = 0; |
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for (i = SHA_DIGEST_LENGTH; i < dblen; i++) { |
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/* |
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* Padding consists of a number of 0-bytes, followed by a 1. |
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*/ |
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unsigned int equals1 = constant_time_eq(db[i], 1); |
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unsigned int equals0 = constant_time_is_zero(db[i]); |
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one_index = constant_time_select_int(~found_one_byte & equals1, |
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i, one_index); |
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found_one_byte |= equals1; |
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good &= (found_one_byte | equals0); |
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} |
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good &= found_one_byte; |
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/* |
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* At this point |good| is zero unless the plaintext was valid, |
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* so plaintext-awareness ensures timing side-channels are no longer a |
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* concern. |
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*/ |
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if (!good) |
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goto decoding_err; |
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msg_index = one_index + 1; |
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mlen = dblen - msg_index; |
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if (tlen < mlen) { |
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RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_DATA_TOO_LARGE); |
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mlen = -1; |
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} else { |
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memcpy(to, db + msg_index, mlen); |
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goto cleanup; |
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} |
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decoding_err: |
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/* |
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* To avoid chosen ciphertext attacks, the error message should not |
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* reveal which kind of decoding error happened. |
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*/ |
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RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_OAEP_DECODING_ERROR); |
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cleanup: |
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if (db != NULL) |
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OPENSSL_free(db); |
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if (em != NULL) |
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OPENSSL_free(em); |
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return mlen; |
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} |
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int PKCS1_MGF1(unsigned char *mask, long len, |
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const unsigned char *seed, long seedlen, const EVP_MD *dgst) |
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{ |
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long i, outlen = 0; |
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unsigned char cnt[4]; |
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EVP_MD_CTX c; |
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unsigned char md[EVP_MAX_MD_SIZE]; |
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int mdlen; |
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int rv = -1; |
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EVP_MD_CTX_init(&c); |
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mdlen = EVP_MD_size(dgst); |
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if (mdlen < 0) |
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goto err; |
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for (i = 0; outlen < len; i++) { |
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cnt[0] = (unsigned char)((i >> 24) & 255); |
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cnt[1] = (unsigned char)((i >> 16) & 255); |
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cnt[2] = (unsigned char)((i >> 8)) & 255; |
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cnt[3] = (unsigned char)(i & 255); |
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if (!EVP_DigestInit_ex(&c, dgst, NULL) |
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|| !EVP_DigestUpdate(&c, seed, seedlen) |
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|| !EVP_DigestUpdate(&c, cnt, 4)) |
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goto err; |
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if (outlen + mdlen <= len) { |
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if (!EVP_DigestFinal_ex(&c, mask + outlen, NULL)) |
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goto err; |
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outlen += mdlen; |
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} else { |
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if (!EVP_DigestFinal_ex(&c, md, NULL)) |
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goto err; |
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memcpy(mask + outlen, md, len - outlen); |
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outlen = len; |
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} |
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} |
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rv = 0; |
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err: |
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EVP_MD_CTX_cleanup(&c); |
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return rv; |
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} |
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static int MGF1(unsigned char *mask, long len, const unsigned char *seed, |
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long seedlen) |
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{ |
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return PKCS1_MGF1(mask, len, seed, seedlen, EVP_sha1()); |
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} |
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#endif
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