From c554155b58f5c0dda132048bb0a68a2d1a463d98 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Bodo=20M=C3=B6ller?= Date: Thu, 20 Mar 2003 17:31:30 +0000 Subject: [PATCH] make sure RSA blinding works when the PRNG is not properly seeded; enable it automatically for the built-in engine --- CHANGES | 13 ++++++++++++- crypto/rsa/rsa.h | 7 +++++++ crypto/rsa/rsa_eay.c | 35 +++++++++++++++++++++++++++-------- crypto/rsa/rsa_lib.c | 21 +++++++++++++++++---- 4 files changed, 63 insertions(+), 13 deletions(-) diff --git a/CHANGES b/CHANGES index 0a5913ce15..a03875767c 100644 --- a/CHANGES +++ b/CHANGES @@ -469,8 +469,19 @@ in ssl3_get_client_key_exchange (ssl/s3_srvr.c). [Bodo Moeller] + *) Turn on RSA blinding by default in the default implementation + to avoid a timing attack. Applications that don't want it can call + RSA_blinding_off() or use the new flag RSA_FLAG_NO_BLINDING. + They would be ill-advised to do so in most cases. + [Ben Laurie, Steve Henson, Geoff Thorpe] + + *) Change RSA blinding code so that it works when the PRNG is not + seeded (in this case, the secret RSA exponent is abused as + an unpredictable seed -- if it is not unpredictable, there + is no point in blinding anyway). + [Bodo Moeller] + yet to be integrated into this CVS branch: -- RSA blinding changes - Geoff's ENGINE_set_default() fix *) Target "mingw" now allows native Windows code to be generated in diff --git a/crypto/rsa/rsa.h b/crypto/rsa/rsa.h index b005b4b0b3..604fc26442 100644 --- a/crypto/rsa/rsa.h +++ b/crypto/rsa/rsa.h @@ -162,6 +162,11 @@ struct rsa_st #define RSA_FLAG_CACHE_PUBLIC 0x02 #define RSA_FLAG_CACHE_PRIVATE 0x04 #define RSA_FLAG_BLINDING 0x08 +#define RSA_FLAG_NO_BLINDING 0x80 /* new with 0.9.6j and 0.9.7b; the built-in + * RSA implementation now uses blinding by + * default (ignoring RSA_FLAG_BLINDING), + * but other engines might not need it + */ #define RSA_FLAG_THREAD_SAFE 0x10 /* This flag means the private key operations will be handled by rsa_mod_exp * and that they do not depend on the private key components being present: @@ -174,6 +179,8 @@ struct rsa_st */ #define RSA_FLAG_SIGN_VER 0x40 +#define RSA_FLAG_NO_BLINDING 0x80 + #define RSA_PKCS1_PADDING 1 #define RSA_SSLV23_PADDING 2 #define RSA_NO_PADDING 3 diff --git a/crypto/rsa/rsa_eay.c b/crypto/rsa/rsa_eay.c index 24c77699fe..6bc6ef3913 100644 --- a/crypto/rsa/rsa_eay.c +++ b/crypto/rsa/rsa_eay.c @@ -211,6 +211,25 @@ err: return(r); } +static int rsa_eay_blinding(RSA *rsa, BN_CTX *ctx) + { + int ret = 1; + CRYPTO_w_lock(CRYPTO_LOCK_RSA); + /* Check again inside the lock - the macro's check is racey */ + if(rsa->blinding == NULL) + ret = RSA_blinding_on(rsa, ctx); + CRYPTO_w_unlock(CRYPTO_LOCK_RSA); + return ret; + } + +#define BLINDING_HELPER(rsa, ctx, err_instr) \ + do { \ + if((!((rsa)->flags & RSA_FLAG_NO_BLINDING)) && \ + ((rsa)->blinding == NULL) && \ + !rsa_eay_blinding(rsa, ctx)) \ + err_instr \ + } while(0) + /* signing */ static int RSA_eay_private_encrypt(int flen, const unsigned char *from, unsigned char *to, RSA *rsa, int padding) @@ -255,9 +274,9 @@ static int RSA_eay_private_encrypt(int flen, const unsigned char *from, goto err; } - if ((rsa->flags & RSA_FLAG_BLINDING) && (rsa->blinding == NULL)) - RSA_blinding_on(rsa,ctx); - if (rsa->flags & RSA_FLAG_BLINDING) + BLINDING_HELPER(rsa, ctx, goto err;); + + if (!(rsa->flags & RSA_FLAG_NO_BLINDING)) if (!BN_BLINDING_convert(&f,rsa->blinding,ctx)) goto err; if ( (rsa->flags & RSA_FLAG_EXT_PKEY) || @@ -274,7 +293,7 @@ static int RSA_eay_private_encrypt(int flen, const unsigned char *from, rsa->_method_mod_n)) goto err; } - if (rsa->flags & RSA_FLAG_BLINDING) + if (!(rsa->flags & RSA_FLAG_NO_BLINDING)) if (!BN_BLINDING_invert(&ret,rsa->blinding,ctx)) goto err; /* put in leading 0 bytes if the number is less than the @@ -336,9 +355,9 @@ static int RSA_eay_private_decrypt(int flen, const unsigned char *from, goto err; } - if ((rsa->flags & RSA_FLAG_BLINDING) && (rsa->blinding == NULL)) - RSA_blinding_on(rsa,ctx); - if (rsa->flags & RSA_FLAG_BLINDING) + BLINDING_HELPER(rsa, ctx, goto err;); + + if (!(rsa->flags & RSA_FLAG_NO_BLINDING)) if (!BN_BLINDING_convert(&f,rsa->blinding,ctx)) goto err; /* do the decrypt */ @@ -357,7 +376,7 @@ static int RSA_eay_private_decrypt(int flen, const unsigned char *from, goto err; } - if (rsa->flags & RSA_FLAG_BLINDING) + if (!(rsa->flags & RSA_FLAG_NO_BLINDING)) if (!BN_BLINDING_invert(&ret,rsa->blinding,ctx)) goto err; p=buf; diff --git a/crypto/rsa/rsa_lib.c b/crypto/rsa/rsa_lib.c index 889c36d3a6..33ca8330c9 100644 --- a/crypto/rsa/rsa_lib.c +++ b/crypto/rsa/rsa_lib.c @@ -72,7 +72,9 @@ static const RSA_METHOD *default_RSA_meth=NULL; RSA *RSA_new(void) { - return(RSA_new_method(NULL)); + RSA *r=RSA_new_method(NULL); + + return r; } void RSA_set_default_method(const RSA_METHOD *meth) @@ -307,7 +309,8 @@ void RSA_blinding_off(RSA *rsa) BN_BLINDING_free(rsa->blinding); rsa->blinding=NULL; } - rsa->flags&= ~RSA_FLAG_BLINDING; + rsa->flags &= ~RSA_FLAG_BLINDING; + rsa->flags |= RSA_FLAG_NO_BLINDING; } int RSA_blinding_on(RSA *rsa, BN_CTX *p_ctx) @@ -328,13 +331,23 @@ int RSA_blinding_on(RSA *rsa, BN_CTX *p_ctx) BN_CTX_start(ctx); A = BN_CTX_get(ctx); - if (!BN_rand_range(A,rsa->n)) goto err; + if ((RAND_status() == 0) && rsa->d != NULL && rsa->d->d != NULL) + { + /* if PRNG is not properly seeded, resort to secret exponent as unpredictable seed */ + RAND_add(rsa->d->d, rsa->d->dmax * sizeof rsa->d->d[0], 0); + if (!BN_pseudo_rand_range(A,rsa->n)) goto err; + } + else + { + if (!BN_rand_range(A,rsa->n)) goto err; + } if ((Ai=BN_mod_inverse(NULL,A,rsa->n,ctx)) == NULL) goto err; if (!rsa->meth->bn_mod_exp(A,A,rsa->e,rsa->n,ctx,rsa->_method_mod_n)) goto err; rsa->blinding=BN_BLINDING_new(A,Ai,rsa->n); - rsa->flags|=RSA_FLAG_BLINDING; + rsa->flags |= RSA_FLAG_BLINDING; + rsa->flags &= ~RSA_FLAG_NO_BLINDING; BN_free(Ai); ret=1; err: -- 2.25.1