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make RSA blinding thread-safe

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This commit is contained in:
Bodo Möller 2003-04-02 09:50:22 +00:00
parent 24692fc5d7
commit 5679bcce07
4 changed files with 124 additions and 12 deletions
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9
CHANGES
View File

@ -483,12 +483,17 @@
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]
[Ben Laurie, Steve Henson, Geoff Thorpe, Bodo Moeller]
*) 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).
is no point in blinding anyway). Make RSA blinding thread-safe
by remembering the creator's thread ID in rsa->blinding and
having all other threads use local one-time blinding factors
(this requires more computation than sharing rsa->blinding, but
avoids excessive locking; and if an RSA object is not shared
between threads, blinding will still be very fast).
[Bodo Moeller]
yet to be integrated into this CVS branch:

2
crypto/bn/bn.h
View File

@ -261,6 +261,8 @@ typedef struct bn_blinding_st
BIGNUM *A;
BIGNUM *Ai;
BIGNUM *mod; /* just a reference */
unsigned long thread_id; /* added in OpenSSL 0.9.6j and 0.9.7b;
* used only by crypto/rsa/rsa_eay.c, rsa_lib.c */
} BN_BLINDING;
/* Used for montgomery multiplication */

114
crypto/rsa/rsa_eay.c
View File

@ -230,6 +230,40 @@ static int rsa_eay_blinding(RSA *rsa, BN_CTX *ctx)
err_instr \
} while(0)
static BN_BLINDING *setup_blinding(RSA *rsa, BN_CTX *ctx)
{
BIGNUM *A, *Ai;
BN_BLINDING *ret = NULL;
/* added in OpenSSL 0.9.6j and 0.9.7b */
/* NB: similar code appears in RSA_blinding_on (rsa_lib.c);
* this should be placed in a new function of its own, but for reasons
* of binary compatibility can't */
BN_CTX_start(ctx);
A = BN_CTX_get(ctx);
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;
ret = BN_BLINDING_new(A,Ai,rsa->n);
BN_free(Ai);
err:
BN_CTX_end(ctx);
return ret;
}
/* signing */
static int RSA_eay_private_encrypt(int flen, const unsigned char *from,
unsigned char *to, RSA *rsa, int padding)
@ -238,6 +272,8 @@ static int RSA_eay_private_encrypt(int flen, const unsigned char *from,
int i,j,k,num=0,r= -1;
unsigned char *buf=NULL;
BN_CTX *ctx=NULL;
int local_blinding = 0;
BN_BLINDING *blinding = NULL;
BN_init(&f);
BN_init(&ret);
@ -275,9 +311,38 @@ static int RSA_eay_private_encrypt(int flen, const unsigned char *from,
}
BLINDING_HELPER(rsa, ctx, goto err;);
blinding = rsa->blinding;
/* Now unless blinding is disabled, 'blinding' is non-NULL.
* But the BN_BLINDING object may be owned by some other thread
* (we don't want to keep it constant and we don't want to use
* lots of locking to avoid race conditions, so only a single
* thread can use it; other threads have to use local blinding
* factors) */
if (!(rsa->flags & RSA_FLAG_NO_BLINDING))
if (!BN_BLINDING_convert(&f,rsa->blinding,ctx)) goto err;
{
if (blinding == NULL)
{
RSAerr(RSA_F_RSA_EAY_PRIVATE_ENCRYPT, ERR_R_INTERNAL_ERROR);
goto err;
}
}
if (blinding != NULL)
{
if (blinding->thread_id != CRYPTO_thread_id())
{
/* we need a local one-time blinding factor */
blinding = setup_blinding(rsa, ctx);
if (blinding == NULL)
goto err;
local_blinding = 1;
}
}
if (blinding)
if (!BN_BLINDING_convert(&f, blinding, ctx)) goto err;
if ( (rsa->flags & RSA_FLAG_EXT_PKEY) ||
((rsa->p != NULL) &&
@ -293,8 +358,8 @@ static int RSA_eay_private_encrypt(int flen, const unsigned char *from,
rsa->_method_mod_n)) goto err;
}
if (!(rsa->flags & RSA_FLAG_NO_BLINDING))
if (!BN_BLINDING_invert(&ret,rsa->blinding,ctx)) goto err;
if (blinding)
if (!BN_BLINDING_invert(&ret, blinding, ctx)) goto err;
/* put in leading 0 bytes if the number is less than the
* length of the modulus */
@ -308,6 +373,8 @@ err:
if (ctx != NULL) BN_CTX_free(ctx);
BN_clear_free(&ret);
BN_clear_free(&f);
if (local_blinding)
BN_BLINDING_free(blinding);
if (buf != NULL)
{
OPENSSL_cleanse(buf,num);
@ -324,6 +391,8 @@ static int RSA_eay_private_decrypt(int flen, const unsigned char *from,
unsigned char *p;
unsigned char *buf=NULL;
BN_CTX *ctx=NULL;
int local_blinding = 0;
BN_BLINDING *blinding = NULL;
BN_init(&f);
BN_init(&ret);
@ -356,9 +425,38 @@ static int RSA_eay_private_decrypt(int flen, const unsigned char *from,
}
BLINDING_HELPER(rsa, ctx, goto err;);
blinding = rsa->blinding;
/* Now unless blinding is disabled, 'blinding' is non-NULL.
* But the BN_BLINDING object may be owned by some other thread
* (we don't want to keep it constant and we don't want to use
* lots of locking to avoid race conditions, so only a single
* thread can use it; other threads have to use local blinding
* factors) */
if (!(rsa->flags & RSA_FLAG_NO_BLINDING))
if (!BN_BLINDING_convert(&f,rsa->blinding,ctx)) goto err;
{
if (blinding == NULL)
{
RSAerr(RSA_F_RSA_EAY_PRIVATE_DECRYPT, ERR_R_INTERNAL_ERROR);
goto err;
}
}
if (blinding != NULL)
{
if (blinding->thread_id != CRYPTO_thread_id())
{
/* we need a local one-time blinding factor */
blinding = setup_blinding(rsa, ctx);
if (blinding == NULL)
goto err;
local_blinding = 1;
}
}
if (blinding)
if (!BN_BLINDING_convert(&f, blinding, ctx)) goto err;
/* do the decrypt */
if ( (rsa->flags & RSA_FLAG_EXT_PKEY) ||
@ -376,8 +474,8 @@ static int RSA_eay_private_decrypt(int flen, const unsigned char *from,
goto err;
}
if (!(rsa->flags & RSA_FLAG_NO_BLINDING))
if (!BN_BLINDING_invert(&ret,rsa->blinding,ctx)) goto err;
if (blinding)
if (!BN_BLINDING_invert(&ret, blinding, ctx)) goto err;
p=buf;
j=BN_bn2bin(&ret,p); /* j is only used with no-padding mode */

11
crypto/rsa/rsa_lib.c
View File

@ -329,6 +329,10 @@ int RSA_blinding_on(RSA *rsa, BN_CTX *p_ctx)
if (rsa->blinding != NULL)
BN_BLINDING_free(rsa->blinding);
/* NB: similar code appears in setup_blinding (rsa_eay.c);
* this should be placed in a new function of its own, but for reasons
* of binary compatibility can't */
BN_CTX_start(ctx);
A = BN_CTX_get(ctx);
if ((RAND_status() == 0) && rsa->d != NULL && rsa->d->d != NULL)
@ -344,8 +348,11 @@ int RSA_blinding_on(RSA *rsa, BN_CTX *p_ctx)
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);
goto err;
if ((rsa->blinding=BN_BLINDING_new(A,Ai,rsa->n)) == NULL) goto err;
/* to make things thread-safe without excessive locking,
* rsa->blinding will be used just by the current thread: */
rsa->blinding->thread_id = CRYPTO_thread_id();
rsa->flags |= RSA_FLAG_BLINDING;
rsa->flags &= ~RSA_FLAG_NO_BLINDING;
BN_free(Ai);