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

enable it automatically only for the built-in engine

diff --git a/CHANGES b/CHANGES
index 6ab49d23a1bbd3ce0a5a0f0ee3982dd9fa104253..73ca1e18a5ecd8a23c67a1282e210a32cd460b58 100644 (file)
--- a/CHANGES
+++ b/CHANGES
@@ -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

diff --git a/crypto/rsa/rsa.h b/crypto/rsa/rsa.h
index b2e25e4e7c714a73449f437a107a002ab983c941..264d929fcd538babc4841ca55c8c70150ac7b8eb 100644 (file)
--- a/crypto/rsa/rsa.h
+++ b/crypto/rsa/rsa.h
@@ -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

diff --git a/crypto/rsa/rsa_eay.c b/crypto/rsa/rsa_eay.c
index e4bcf499d064a6bdc8cb37e2a7bd19fb5bce00a4..d9b2925b1bcd9665794802433f6ecdba04364914 100644 (file)
--- a/crypto/rsa/rsa_eay.c
+++ b/crypto/rsa/rsa_eay.c
@@ -208,10 +208,10 @@ static int rsa_eay_blinding(RSA *rsa, BN_CTX *ctx)
 
 #define BLINDING_HELPER(rsa, ctx, err_instr) \
        do { \
-               if(((rsa)->flags & RSA_FLAG_BLINDING) && \
-                               ((rsa)->blinding == NULL) && \
-                               !rsa_eay_blinding(rsa, ctx)) \
-                       err_instr \
+               if((!((rsa)->flags & RSA_FLAG_NO_BLINDING)) && \
+                   ((rsa)->blinding == NULL) && \
+                   !rsa_eay_blinding(rsa, ctx)) \
+                   err_instr \
        } while(0)
 
 /* signing */
@@ -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;

diff --git a/crypto/rsa/rsa_lib.c b/crypto/rsa/rsa_lib.c
index f234ae0748cad7acb855abcfdc1ca5a4347ddb46..33ca8330c9939640953a1d258a4f9ebabbc52478 100644 (file)
--- a/crypto/rsa/rsa_lib.c
+++ b/crypto/rsa/rsa_lib.c
@@ -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 (!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: