Source-Changes-HG archive

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]

[src/trunk]: src/crypto/external/bsd/openssl/dist/crypto Add fix for CVE-2014...



details:   https://anonhg.NetBSD.org/src/rev/fa4c3efc9c74
branches:  trunk
changeset: 328414:fa4c3efc9c74
user:      tron <tron%NetBSD.org@localhost>
date:      Wed Apr 02 20:27:28 2014 +0000

description:
Add fix for CVE-2014-0076 taken from OpenSSL GIT repository:

Fix for the attack described in the paper "Recovering OpenSSL
ECDSA Nonces Using the FLUSH+RELOAD Cache Side-channel Attack"
by Yuval Yarom and Naomi Benger. Details can be obtained from:
http://eprint.iacr.org/2014/140

diffstat:

 crypto/external/bsd/openssl/dist/crypto/bn/bn.h       |  11 ++++
 crypto/external/bsd/openssl/dist/crypto/bn/bn_lib.c   |  52 +++++++++++++++++++
 crypto/external/bsd/openssl/dist/crypto/ec/ec2_mult.c |  27 +++++----
 3 files changed, 79 insertions(+), 11 deletions(-)

diffs (147 lines):

diff -r c94b27a54cc4 -r fa4c3efc9c74 crypto/external/bsd/openssl/dist/crypto/bn/bn.h
--- a/crypto/external/bsd/openssl/dist/crypto/bn/bn.h   Wed Apr 02 19:54:30 2014 +0000
+++ b/crypto/external/bsd/openssl/dist/crypto/bn/bn.h   Wed Apr 02 20:27:28 2014 +0000
@@ -538,6 +538,8 @@
 BIGNUM *BN_mod_sqrt(BIGNUM *ret,
        const BIGNUM *a, const BIGNUM *n,BN_CTX *ctx);
 
+void   BN_consttime_swap(BN_ULONG swap, BIGNUM *a, BIGNUM *b, int nwords);
+
 /* Deprecated versions */
 #ifndef OPENSSL_NO_DEPRECATED
 BIGNUM *BN_generate_prime(BIGNUM *ret,int bits,int safe,
@@ -774,11 +776,20 @@
 
 #define bn_fix_top(a)          bn_check_top(a)
 
+#define bn_check_size(bn, bits) bn_wcheck_size(bn, ((bits+BN_BITS2-1))/BN_BITS2)
+#define bn_wcheck_size(bn, words) \
+       do { \
+               const BIGNUM *_bnum2 = (bn); \
+               assert(words <= (_bnum2)->dmax && words >= (_bnum2)->top); \
+       } while(0)
+
 #else /* !BN_DEBUG */
 
 #define bn_pollute(a)
 #define bn_check_top(a)
 #define bn_fix_top(a)          bn_correct_top(a)
+#define bn_check_size(bn, bits)
+#define bn_wcheck_size(bn, words)
 
 #endif
 
diff -r c94b27a54cc4 -r fa4c3efc9c74 crypto/external/bsd/openssl/dist/crypto/bn/bn_lib.c
--- a/crypto/external/bsd/openssl/dist/crypto/bn/bn_lib.c       Wed Apr 02 19:54:30 2014 +0000
+++ b/crypto/external/bsd/openssl/dist/crypto/bn/bn_lib.c       Wed Apr 02 20:27:28 2014 +0000
@@ -824,3 +824,55 @@
                }
        return bn_cmp_words(a,b,cl);
        }
+
+/* 
+ * Constant-time conditional swap of a and b.  
+ * a and b are swapped if condition is not 0.  The code assumes that at most one bit of condition is set.
+ * nwords is the number of words to swap.  The code assumes that at least nwords are allocated in both a and b,
+ * and that no more than nwords are used by either a or b.
+ * a and b cannot be the same number
+ */
+void BN_consttime_swap(BN_ULONG condition, BIGNUM *a, BIGNUM *b, int nwords)
+       {
+       BN_ULONG t;
+       int i;
+
+       bn_wcheck_size(a, nwords);
+       bn_wcheck_size(b, nwords);
+
+       assert(a != b);
+       assert((condition & (condition - 1)) == 0);
+       assert(sizeof(BN_ULONG) >= sizeof(int));
+
+       condition = ((condition - 1) >> (BN_BITS2 - 1)) - 1;
+
+       t = (a->top^b->top) & condition;
+       a->top ^= t;
+       b->top ^= t;
+
+#define BN_CONSTTIME_SWAP(ind) \
+       do { \
+               t = (a->d[ind] ^ b->d[ind]) & condition; \
+               a->d[ind] ^= t; \
+               b->d[ind] ^= t; \
+       } while (0)
+
+
+       switch (nwords) {
+       default:
+               for (i = 10; i < nwords; i++) 
+                       BN_CONSTTIME_SWAP(i);
+               /* Fallthrough */
+       case 10: BN_CONSTTIME_SWAP(9); /* Fallthrough */
+       case 9: BN_CONSTTIME_SWAP(8); /* Fallthrough */
+       case 8: BN_CONSTTIME_SWAP(7); /* Fallthrough */
+       case 7: BN_CONSTTIME_SWAP(6); /* Fallthrough */
+       case 6: BN_CONSTTIME_SWAP(5); /* Fallthrough */
+       case 5: BN_CONSTTIME_SWAP(4); /* Fallthrough */
+       case 4: BN_CONSTTIME_SWAP(3); /* Fallthrough */
+       case 3: BN_CONSTTIME_SWAP(2); /* Fallthrough */
+       case 2: BN_CONSTTIME_SWAP(1); /* Fallthrough */
+       case 1: BN_CONSTTIME_SWAP(0);
+       }
+#undef BN_CONSTTIME_SWAP
+}
diff -r c94b27a54cc4 -r fa4c3efc9c74 crypto/external/bsd/openssl/dist/crypto/ec/ec2_mult.c
--- a/crypto/external/bsd/openssl/dist/crypto/ec/ec2_mult.c     Wed Apr 02 19:54:30 2014 +0000
+++ b/crypto/external/bsd/openssl/dist/crypto/ec/ec2_mult.c     Wed Apr 02 20:27:28 2014 +0000
@@ -208,11 +208,15 @@
        return ret;
        }
 
+
 /* Computes scalar*point and stores the result in r.
  * point can not equal r.
- * Uses algorithm 2P of
+ * Uses a modified algorithm 2P of
  *     Lopez, J. and Dahab, R.  "Fast multiplication on elliptic curves over 
  *     GF(2^m) without precomputation" (CHES '99, LNCS 1717).
+ *
+ * To protect against side-channel attack the function uses constant time swap,
+ * avoiding conditional branches.
  */
 static int ec_GF2m_montgomery_point_multiply(const EC_GROUP *group, EC_POINT *r, const BIGNUM *scalar,
        const EC_POINT *point, BN_CTX *ctx)
@@ -246,6 +250,11 @@
        x2 = &r->X;
        z2 = &r->Y;
 
+       bn_wexpand(x1, group->field.top);
+       bn_wexpand(z1, group->field.top);
+       bn_wexpand(x2, group->field.top);
+       bn_wexpand(z2, group->field.top);
+
        if (!BN_GF2m_mod_arr(x1, &point->X, group->poly)) goto err; /* x1 = x */
        if (!BN_one(z1)) goto err; /* z1 = 1 */
        if (!group->meth->field_sqr(group, z2, x1, ctx)) goto err; /* z2 = x1^2 = x^2 */
@@ -270,16 +279,12 @@
                word = scalar->d[i];
                while (mask)
                        {
-                       if (word & mask)
-                               {
-                               if (!gf2m_Madd(group, &point->X, x1, z1, x2, z2, ctx)) goto err;
-                               if (!gf2m_Mdouble(group, x2, z2, ctx)) goto err;
-                               }
-                       else
-                               {
-                               if (!gf2m_Madd(group, &point->X, x2, z2, x1, z1, ctx)) goto err;
-                               if (!gf2m_Mdouble(group, x1, z1, ctx)) goto err;
-                               }
+                       BN_consttime_swap(word & mask, x1, x2, group->field.top);
+                       BN_consttime_swap(word & mask, z1, z2, group->field.top);
+                       if (!gf2m_Madd(group, &point->X, x2, z2, x1, z1, ctx)) goto err;
+                       if (!gf2m_Mdouble(group, x1, z1, ctx)) goto err;
+                       BN_consttime_swap(word & mask, x1, x2, group->field.top);
+                       BN_consttime_swap(word & mask, z1, z2, group->field.top);
                        mask >>= 1;
                        }
                mask = BN_TBIT;



Home | Main Index | Thread Index | Old Index