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make sure RSA blinding works when the PRNG is not properly seeded;

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enable it automatically only for the built-in engine
This commit is contained in:
Bodo Möller 2003-03-19 18:58:55 +00:00
parent 5250725ba5
commit 84b1e84af1
4 changed files with 39 additions and 19 deletions
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14
CHANGES
View file

@ -4,12 +4,18 @@
Changes between 0.9.7a and 0.9.7b [xx XXX 2003]
*) Turn on RSA blinding by default, to avoid a timing attack. Applications
that don't want it can call RSA_blinding_off(). They would be ill-advised
to do so in most cases. The automatic enabling can also be turned off
by defining OPENSSL_FORCE_NO_RSA_BLINDING at compile-time.
*) 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]
*) Fixed a typo bug that would cause ENGINE_set_default() to set an
ENGINE as defaults for all supported algorithms irrespective of
the 'flags' parameter. 'flags' is now honoured, so applications

7
crypto/rsa/rsa.h
View file

@ -158,6 +158,11 @@ 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 0.9.7b; 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:
@ -170,6 +175,8 @@ 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

10
crypto/rsa/rsa_eay.c
View file

@ -208,7 +208,7 @@ static int rsa_eay_blinding(RSA *rsa, BN_CTX *ctx)
#define BLINDING_HELPER(rsa, ctx, err_instr) \
do { \
if(((rsa)->flags & RSA_FLAG_BLINDING) && \
if((!((rsa)->flags & RSA_FLAG_NO_BLINDING)) && \
((rsa)->blinding == NULL) && \
!rsa_eay_blinding(rsa, ctx)) \
err_instr \
@ -260,7 +260,7 @@ static int RSA_eay_private_encrypt(int flen, const unsigned char *from,
BLINDING_HELPER(rsa, ctx, goto err;);
if (rsa->flags & RSA_FLAG_BLINDING)
if (!(rsa->flags & RSA_FLAG_NO_BLINDING))
if (!BN_BLINDING_convert(&f,rsa->blinding,ctx)) goto err;
if ( (rsa->flags & RSA_FLAG_EXT_PKEY) ||
@ -275,7 +275,7 @@ static int RSA_eay_private_encrypt(int flen, const unsigned char *from,
if (!rsa->meth->bn_mod_exp(&ret,&f,rsa->d,rsa->n,ctx,NULL)) 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
@ -339,7 +339,7 @@ static int RSA_eay_private_decrypt(int flen, const unsigned char *from,
BLINDING_HELPER(rsa, ctx, goto err;);
if (rsa->flags & RSA_FLAG_BLINDING)
if (!(rsa->flags & RSA_FLAG_NO_BLINDING))
if (!BN_BLINDING_convert(&f,rsa->blinding,ctx)) goto err;
/* do the decrypt */
@ -356,7 +356,7 @@ 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;

19
crypto/rsa/rsa_lib.c
View file

@ -74,10 +74,6 @@ RSA *RSA_new(void)
{
RSA *r=RSA_new_method(NULL);
#ifndef OPENSSL_NO_FORCE_RSA_BLINDING
r->flags|=RSA_FLAG_BLINDING;
#endif
return r;
}
@ -313,7 +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)
@ -334,13 +331,23 @@ int RSA_blinding_on(RSA *rsa, BN_CTX *p_ctx)
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;
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: