Return smaller of ret and f.

[openssl.git] / crypto / rsa / rsa_eay.c

diff --git a/crypto/rsa/rsa_eay.c b/crypto/rsa/rsa_eay.c
index 325efb95c7799d9e87797792e42373f2aed2440b..64c23f7cdbcc336ab7a3526b779b015c342c8ed4 100644 (file)
--- a/crypto/rsa/rsa_eay.c
+++ b/crypto/rsa/rsa_eay.c
@@ -334,45 +334,51 @@ static BN_BLINDING *rsa_get_blinding(RSA *rsa, int *local, BN_CTX *ctx)
        return ret;
 }
 
-static int rsa_blinding_convert(BN_BLINDING *b, int local, BIGNUM *f,
-       BIGNUM *r, BN_CTX *ctx)
-{
-       if (local)
+static int rsa_blinding_convert(BN_BLINDING *b, BIGNUM *f, BIGNUM *unblind,
+       BN_CTX *ctx)
+       {
+       if (unblind == NULL)
+               /* Local blinding: store the unblinding factor
+                * in BN_BLINDING. */
                return BN_BLINDING_convert_ex(f, NULL, b, ctx);
        else
                {
-               int ret;
-               CRYPTO_r_lock(CRYPTO_LOCK_RSA_BLINDING);
-               ret = BN_BLINDING_convert_ex(f, r, b, ctx);
-               CRYPTO_r_unlock(CRYPTO_LOCK_RSA_BLINDING);
-               return ret;
-               }
-}
-
-static int rsa_blinding_invert(BN_BLINDING *b, int local, BIGNUM *f,
-       BIGNUM *r, BN_CTX *ctx)
-{
-       if (local)
-               return BN_BLINDING_invert_ex(f, NULL, b, ctx);
-       else
-               {
+               /* Shared blinding: store the unblinding factor
+                * outside BN_BLINDING. */
                int ret;
                CRYPTO_w_lock(CRYPTO_LOCK_RSA_BLINDING);
-               ret = BN_BLINDING_invert_ex(f, r, b, ctx);
+               ret = BN_BLINDING_convert_ex(f, unblind, b, ctx);
                CRYPTO_w_unlock(CRYPTO_LOCK_RSA_BLINDING);
                return ret;
                }
-}
+       }
+
+static int rsa_blinding_invert(BN_BLINDING *b, BIGNUM *f, BIGNUM *unblind,
+       BN_CTX *ctx)
+       {
+       /* For local blinding, unblind is set to NULL, and BN_BLINDING_invert_ex
+        * will use the unblinding factor stored in BN_BLINDING.
+        * If BN_BLINDING is shared between threads, unblind must be non-null:
+        * BN_BLINDING_invert_ex will then use the local unblinding factor,
+        * and will only read the modulus from BN_BLINDING.
+        * In both cases it's safe to access the blinding without a lock.
+        */
+       return BN_BLINDING_invert_ex(f, unblind, b, ctx);
+       }
 
 /* signing */
 static int RSA_eay_private_encrypt(int flen, const unsigned char *from,
             unsigned char *to, RSA *rsa, int padding)
        {
-       BIGNUM *f, *ret, *br, *res;
+       BIGNUM *f, *ret, *res;
        int i,j,k,num=0,r= -1;
        unsigned char *buf=NULL;
        BN_CTX *ctx=NULL;
        int local_blinding = 0;
+       /* Used only if the blinding structure is shared. A non-NULL unblind
+        * instructs rsa_blinding_convert() and rsa_blinding_invert() to store
+        * the unblinding factor outside the blinding structure. */
+       BIGNUM *unblind = NULL;
        BN_BLINDING *blinding = NULL;
 
 #ifdef OPENSSL_FIPS
@@ -393,7 +399,6 @@ static int RSA_eay_private_encrypt(int flen, const unsigned char *from,
        if ((ctx=BN_CTX_new()) == NULL) goto err;
        BN_CTX_start(ctx);
        f   = BN_CTX_get(ctx);
-       br  = BN_CTX_get(ctx);
        ret = BN_CTX_get(ctx);
        num = BN_num_bytes(rsa->n);
        buf = OPENSSL_malloc(num);
@@ -441,8 +446,15 @@ static int RSA_eay_private_encrypt(int flen, const unsigned char *from,
                }
        
        if (blinding != NULL)
-               if (!rsa_blinding_convert(blinding, local_blinding, f, br, ctx))
+               {
+               if (!local_blinding && ((unblind = BN_CTX_get(ctx)) == NULL))
+                       {
+                       RSAerr(RSA_F_RSA_EAY_PRIVATE_ENCRYPT,ERR_R_MALLOC_FAILURE);
+                       goto err;
+                       }
+               if (!rsa_blinding_convert(blinding, f, unblind, ctx))
                        goto err;
+               }
 
        if ( (rsa->flags & RSA_FLAG_EXT_PKEY) ||
                ((rsa->p != NULL) &&
@@ -476,13 +488,13 @@ static int RSA_eay_private_encrypt(int flen, const unsigned char *from,
                }
 
        if (blinding)
-               if (!rsa_blinding_invert(blinding, local_blinding, ret, br, ctx))
+               if (!rsa_blinding_invert(blinding, ret, unblind, ctx))
                        goto err;
 
        if (padding == RSA_X931_PADDING)
                {
                BN_sub(f, rsa->n, ret);
-               if (BN_cmp(ret, f))
+               if (BN_cmp(ret, f) > 0)
                        res = f;
                else
                        res = ret;
@@ -515,12 +527,16 @@ err:
 static int RSA_eay_private_decrypt(int flen, const unsigned char *from,
             unsigned char *to, RSA *rsa, int padding)
        {
-       BIGNUM *f, *ret, *br;
+       BIGNUM *f, *ret;
        int j,num=0,r= -1;
        unsigned char *p;
        unsigned char *buf=NULL;
        BN_CTX *ctx=NULL;
        int local_blinding = 0;
+       /* Used only if the blinding structure is shared. A non-NULL unblind
+        * instructs rsa_blinding_convert() and rsa_blinding_invert() to store
+        * the unblinding factor outside the blinding structure. */
+       BIGNUM *unblind = NULL;
        BN_BLINDING *blinding = NULL;
 
 #ifdef OPENSSL_FIPS
@@ -541,7 +557,6 @@ static int RSA_eay_private_decrypt(int flen, const unsigned char *from,
        if((ctx = BN_CTX_new()) == NULL) goto err;
        BN_CTX_start(ctx);
        f   = BN_CTX_get(ctx);
-       br  = BN_CTX_get(ctx);
        ret = BN_CTX_get(ctx);
        num = BN_num_bytes(rsa->n);
        buf = OPENSSL_malloc(num);
@@ -579,8 +594,15 @@ static int RSA_eay_private_decrypt(int flen, const unsigned char *from,
                }
        
        if (blinding != NULL)
-               if (!rsa_blinding_convert(blinding, local_blinding, f, br, ctx))
+               {
+               if (!local_blinding && ((unblind = BN_CTX_get(ctx)) == NULL))
+                       {
+                       RSAerr(RSA_F_RSA_EAY_PRIVATE_DECRYPT,ERR_R_MALLOC_FAILURE);
                        goto err;
+                       }
+               if (!rsa_blinding_convert(blinding, f, unblind, ctx))
+                       goto err;
+               }
 
        /* do the decrypt */
        if ( (rsa->flags & RSA_FLAG_EXT_PKEY) ||
@@ -614,7 +636,7 @@ static int RSA_eay_private_decrypt(int flen, const unsigned char *from,
                }
 
        if (blinding)
-               if (!rsa_blinding_invert(blinding, local_blinding, ret, br, ctx))
+               if (!rsa_blinding_invert(blinding, ret, unblind, ctx))
                        goto err;
 
        p=buf;