diff options
Diffstat (limited to 'crypto/rsa')
| -rw-r--r-- | crypto/rsa/Makefile | 5 | ||||
| -rw-r--r-- | crypto/rsa/rsa.h | 3 | ||||
| -rw-r--r-- | crypto/rsa/rsa_err.c | 1 | ||||
| -rw-r--r-- | crypto/rsa/rsa_oaep.c | 149 | ||||
| -rw-r--r-- | crypto/rsa/rsa_pk1.c | 103 |
5 files changed, 167 insertions, 94 deletions
diff --git a/crypto/rsa/Makefile b/crypto/rsa/Makefile index 5d1bdf9975..ba0bb7a2da 100644 --- a/crypto/rsa/Makefile +++ b/crypto/rsa/Makefile @@ -206,7 +206,7 @@ rsa_oaep.o: ../../include/openssl/opensslv.h ../../include/openssl/ossl_typ.h rsa_oaep.o: ../../include/openssl/rand.h ../../include/openssl/rsa.h rsa_oaep.o: ../../include/openssl/safestack.h ../../include/openssl/sha.h rsa_oaep.o: ../../include/openssl/stack.h ../../include/openssl/symhacks.h -rsa_oaep.o: ../cryptlib.h rsa_oaep.c +rsa_oaep.o: ../constant_time_locl.h ../cryptlib.h rsa_oaep.c rsa_pk1.o: ../../e_os.h ../../include/openssl/asn1.h rsa_pk1.o: ../../include/openssl/bio.h ../../include/openssl/bn.h rsa_pk1.o: ../../include/openssl/buffer.h ../../include/openssl/crypto.h @@ -215,7 +215,8 @@ rsa_pk1.o: ../../include/openssl/lhash.h ../../include/openssl/opensslconf.h rsa_pk1.o: ../../include/openssl/opensslv.h ../../include/openssl/ossl_typ.h rsa_pk1.o: ../../include/openssl/rand.h ../../include/openssl/rsa.h rsa_pk1.o: ../../include/openssl/safestack.h ../../include/openssl/stack.h -rsa_pk1.o: ../../include/openssl/symhacks.h ../cryptlib.h rsa_pk1.c +rsa_pk1.o: ../../include/openssl/symhacks.h ../constant_time_locl.h +rsa_pk1.o: ../cryptlib.h rsa_pk1.c rsa_pmeth.o: ../../e_os.h ../../include/openssl/asn1.h rsa_pmeth.o: ../../include/openssl/asn1t.h ../../include/openssl/bio.h rsa_pmeth.o: ../../include/openssl/bn.h ../../include/openssl/buffer.h diff --git a/crypto/rsa/rsa.h b/crypto/rsa/rsa.h index 79905fec7f..f164d74e30 100644 --- a/crypto/rsa/rsa.h +++ b/crypto/rsa/rsa.h @@ -616,6 +616,7 @@ void ERR_load_RSA_strings(void); #define RSA_R_OAEP_DECODING_ERROR 121 #define RSA_R_OPERATION_NOT_SUPPORTED_FOR_THIS_KEYTYPE 148 #define RSA_R_PADDING_CHECK_FAILED 114 +#define RSA_R_PKCS_DECODING_ERROR 159 #define RSA_R_P_NOT_PRIME 128 #define RSA_R_Q_NOT_PRIME 129 #define RSA_R_RSA_OPERATIONS_NOT_SUPPORTED 130 @@ -624,7 +625,7 @@ void ERR_load_RSA_strings(void); #define RSA_R_SSLV3_ROLLBACK_ATTACK 115 #define RSA_R_THE_ASN1_OBJECT_IDENTIFIER_IS_NOT_KNOWN_FOR_THIS_MD 116 #define RSA_R_UNKNOWN_ALGORITHM_TYPE 117 -#define RSA_R_UNKNOWN_DIGEST 159 +#define RSA_R_UNKNOWN_DIGEST 166 #define RSA_R_UNKNOWN_MASK_DIGEST 151 #define RSA_R_UNKNOWN_PADDING_TYPE 118 #define RSA_R_UNKNOWN_PSS_DIGEST 152 diff --git a/crypto/rsa/rsa_err.c b/crypto/rsa/rsa_err.c index 6a5685ba52..60cf77cdb8 100644 --- a/crypto/rsa/rsa_err.c +++ b/crypto/rsa/rsa_err.c @@ -181,6 +181,7 @@ static ERR_STRING_DATA RSA_str_reasons[]= {ERR_REASON(RSA_R_OAEP_DECODING_ERROR) ,"oaep decoding error"}, {ERR_REASON(RSA_R_OPERATION_NOT_SUPPORTED_FOR_THIS_KEYTYPE),"operation not supported for this keytype"}, {ERR_REASON(RSA_R_PADDING_CHECK_FAILED) ,"padding check failed"}, +{ERR_REASON(RSA_R_PKCS_DECODING_ERROR) ,"pkcs decoding error"}, {ERR_REASON(RSA_R_P_NOT_PRIME) ,"p not prime"}, {ERR_REASON(RSA_R_Q_NOT_PRIME) ,"q not prime"}, {ERR_REASON(RSA_R_RSA_OPERATIONS_NOT_SUPPORTED),"rsa operations not supported"}, diff --git a/crypto/rsa/rsa_oaep.c b/crypto/rsa/rsa_oaep.c index 882c7c582e..18ee6f4b88 100644 --- a/crypto/rsa/rsa_oaep.c +++ b/crypto/rsa/rsa_oaep.c @@ -20,6 +20,7 @@ #define OPENSSL_FIPSAPI +#include "../constant_time_locl.h" #if !defined(OPENSSL_NO_SHA) && !defined(OPENSSL_NO_SHA1) #include <stdio.h> @@ -121,12 +122,13 @@ int RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen, const unsigned char *param, int plen, const EVP_MD *md, const EVP_MD *mgf1md) { - int i, dblen, mlen = -1; - const unsigned char *maskeddb; - int lzero; - unsigned char *db = NULL, seed[EVP_MAX_MD_SIZE], phash[EVP_MAX_MD_SIZE]; - unsigned char *padded_from; - int bad = 0; + int i, dblen, mlen = -1, one_index = 0, msg_index; + unsigned int good, found_one_byte; + const unsigned char *maskedseed, *maskeddb; + /* |em| is the encoded message, zero-padded to exactly |num| bytes: + * em = Y || maskedSeed || maskedDB */ + unsigned char *db = NULL, *em = NULL, seed[EVP_MAX_MD_SIZE], + phash[EVP_MAX_MD_SIZE]; int mdlen; if (md == NULL) @@ -136,85 +138,108 @@ int RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen, mdlen = EVP_MD_size(md); - if (--num < 2 * mdlen + 1) - /* 'num' is the length of the modulus, i.e. does not depend on the - * particular ciphertext. */ + if (tlen <= 0 || flen <= 0) + return -1; + /* + * |num| is the length of the modulus; |flen| is the length of the + * encoded message. Therefore, for any |from| that was obtained by + * decrypting a ciphertext, we must have |flen| <= |num|. Similarly, + * num < 2 * mdlen + 2 must hold for the modulus irrespective of + * the ciphertext, see PKCS #1 v2.2, section 7.1.2. + * This does not leak any side-channel information. + */ + if (num < flen || num < 2 * mdlen + 2) goto decoding_err; - lzero = num - flen; - if (lzero < 0) - { - /* signalling this error immediately after detection might allow - * for side-channel attacks (e.g. timing if 'plen' is huge - * -- cf. James H. Manger, "A Chosen Ciphertext Attack on RSA Optimal - * Asymmetric Encryption Padding (OAEP) [...]", CRYPTO 2001), - * so we use a 'bad' flag */ - bad = 1; - lzero = 0; - flen = num; /* don't overflow the memcpy to padded_from */ - } - - dblen = num - mdlen; - db = OPENSSL_malloc(dblen + num); - if (db == NULL) + dblen = num - mdlen - 1; + db = OPENSSL_malloc(dblen); + em = OPENSSL_malloc(num); + if (db == NULL || em == NULL) { RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, ERR_R_MALLOC_FAILURE); - return -1; + goto cleanup; } - /* Always do this zero-padding copy (even when lzero == 0) - * to avoid leaking timing info about the value of lzero. */ - padded_from = db + dblen; - memset(padded_from, 0, lzero); - memcpy(padded_from + lzero, from, flen); - - maskeddb = padded_from + mdlen; + /* + * Always do this zero-padding copy (even when num == flen) to avoid + * leaking that information. The copy still leaks some side-channel + * information, but it's impossible to have a fixed memory access + * pattern since we can't read out of the bounds of |from|. + * + * TODO(emilia): Consider porting BN_bn2bin_padded from BoringSSL. + */ + memset(em, 0, num); + memcpy(em + num - flen, from, flen); + + /* + * The first byte must be zero, however we must not leak if this is + * true. See James H. Manger, "A Chosen Ciphertext Attack on RSA + * Optimal Asymmetric Encryption Padding (OAEP) [...]", CRYPTO 2001). + */ + good = constant_time_is_zero(em[0]); + + maskedseed = em + 1; + maskeddb = em + 1 + mdlen; if (PKCS1_MGF1(seed, mdlen, maskeddb, dblen, mgf1md)) - return -1; + goto cleanup; for (i = 0; i < mdlen; i++) - seed[i] ^= padded_from[i]; - + seed[i] ^= maskedseed[i]; + if (PKCS1_MGF1(db, dblen, seed, mdlen, mgf1md)) - return -1; + goto cleanup; for (i = 0; i < dblen; i++) db[i] ^= maskeddb[i]; if (!EVP_Digest((void *)param, plen, phash, NULL, md, NULL)) - return -1; + goto cleanup; + + good &= constant_time_is_zero(CRYPTO_memcmp(db, phash, mdlen)); + + found_one_byte = 0; + for (i = mdlen; i < dblen; i++) + { + /* Padding consists of a number of 0-bytes, followed by a 1. */ + unsigned int equals1 = constant_time_eq(db[i], 1); + unsigned int equals0 = constant_time_is_zero(db[i]); + one_index = constant_time_select_int(~found_one_byte & equals1, + i, one_index); + found_one_byte |= equals1; + good &= (found_one_byte | equals0); + } + + good &= found_one_byte; - if (CRYPTO_memcmp(db, phash, mdlen) != 0 || bad) + /* + * At this point |good| is zero unless the plaintext was valid, + * so plaintext-awareness ensures timing side-channels are no longer a + * concern. + */ + if (!good) goto decoding_err; + + msg_index = one_index + 1; + mlen = dblen - msg_index; + + if (tlen < mlen) + { + RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, RSA_R_DATA_TOO_LARGE); + mlen = -1; + } else { - for (i = mdlen; i < dblen; i++) - if (db[i] != 0x00) - break; - if (i == dblen || db[i] != 0x01) - goto decoding_err; - else - { - /* everything looks OK */ - - mlen = dblen - ++i; - if (tlen < mlen) - { - RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, RSA_R_DATA_TOO_LARGE); - mlen = -1; - } - else - memcpy(to, db + i, mlen); - } + memcpy(to, db + msg_index, mlen); + goto cleanup; } - OPENSSL_free(db); - return mlen; decoding_err: - /* to avoid chosen ciphertext attacks, the error message should not reveal - * which kind of decoding error happened */ + /* To avoid chosen ciphertext attacks, the error message should not reveal + * which kind of decoding error happened. */ RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, RSA_R_OAEP_DECODING_ERROR); +cleanup: if (db != NULL) OPENSSL_free(db); - return -1; + if (em != NULL) OPENSSL_free(em); + return mlen; } int PKCS1_MGF1(unsigned char *mask, long len, diff --git a/crypto/rsa/rsa_pk1.c b/crypto/rsa/rsa_pk1.c index 0cce4bf657..e01fe62add 100644 --- a/crypto/rsa/rsa_pk1.c +++ b/crypto/rsa/rsa_pk1.c @@ -58,6 +58,8 @@ #define OPENSSL_FIPSAPI +#include "../constant_time_locl.h" + #include <stdio.h> #include "cryptlib.h" #include <openssl/bn.h> @@ -183,44 +185,87 @@ int RSA_padding_add_PKCS1_type_2(unsigned char *to, int tlen, int RSA_padding_check_PKCS1_type_2(unsigned char *to, int tlen, const unsigned char *from, int flen, int num) { - int i,j; - const unsigned char *p; + int i; + /* |em| is the encoded message, zero-padded to exactly |num| bytes */ + unsigned char *em = NULL; + unsigned int good, found_zero_byte; + int zero_index = 0, msg_index, mlen = -1; - p=from; - if ((num != (flen+1)) || (*(p++) != 02)) - { - RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2,RSA_R_BLOCK_TYPE_IS_NOT_02); - return(-1); - } -#ifdef PKCS1_CHECK - return(num-11); -#endif + if (tlen < 0 || flen < 0) + return -1; - /* scan over padding data */ - j=flen-1; /* one for type. */ - for (i=0; i<j; i++) - if (*(p++) == 0) break; + /* PKCS#1 v1.5 decryption. See "PKCS #1 v2.2: RSA Cryptography + * Standard", section 7.2.2. */ - if (i == j) + if (flen > num) + goto err; + + if (num < 11) + goto err; + + em = OPENSSL_malloc(num); + if (em == NULL) { - RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2,RSA_R_NULL_BEFORE_BLOCK_MISSING); - return(-1); + RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2, ERR_R_MALLOC_FAILURE); + return -1; } + memset(em, 0, num); + /* + * Always do this zero-padding copy (even when num == flen) to avoid + * leaking that information. The copy still leaks some side-channel + * information, but it's impossible to have a fixed memory access + * pattern since we can't read out of the bounds of |from|. + * + * TODO(emilia): Consider porting BN_bn2bin_padded from BoringSSL. + */ + memcpy(em + num - flen, from, flen); - if (i < 8) + good = constant_time_is_zero(em[0]); + good &= constant_time_eq(em[1], 2); + + found_zero_byte = 0; + for (i = 2; i < num; i++) { - RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2,RSA_R_BAD_PAD_BYTE_COUNT); - return(-1); + unsigned int equals0 = constant_time_is_zero(em[i]); + zero_index = constant_time_select_int(~found_zero_byte & equals0, i, zero_index); + found_zero_byte |= equals0; } - i++; /* Skip over the '\0' */ - j-=i; - if (j > tlen) + + /* + * PS must be at least 8 bytes long, and it starts two bytes into |em|. + * If we never found a 0-byte, then |zero_index| is 0 and the check + * also fails. + */ + good &= constant_time_ge((unsigned int)(zero_index), 2 + 8); + + /* Skip the zero byte. This is incorrect if we never found a zero-byte + * but in this case we also do not copy the message out. */ + msg_index = zero_index + 1; + mlen = num - msg_index; + + /* For good measure, do this check in constant time as well; it could + * leak something if |tlen| was assuming valid padding. */ + good &= constant_time_ge((unsigned int)(tlen), (unsigned int)(mlen)); + + /* + * We can't continue in constant-time because we need to copy the result + * and we cannot fake its length. This unavoidably leaks timing + * information at the API boundary. + * TODO(emilia): this could be addressed at the call site, + * see BoringSSL commit 0aa0767340baf925bda4804882aab0cb974b2d26. + */ + if (!good) { - RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2,RSA_R_DATA_TOO_LARGE); - return(-1); + mlen = -1; + goto err; } - memcpy(to,p,(unsigned int)j); - return(j); - } + memcpy(to, em + msg_index, mlen); +err: + if (em != NULL) + OPENSSL_free(em); + if (mlen == -1) + RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2, RSA_R_PKCS_DECODING_ERROR); + return mlen; + } |