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compat-openssl098.8722
CVE-2014-0076.patch
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File CVE-2014-0076.patch of Package compat-openssl098.8722
Index: openssl-0.9.8j/crypto/bn/bn.h =================================================================== --- openssl-0.9.8j.orig/crypto/bn/bn.h +++ openssl-0.9.8j/crypto/bn/bn.h @@ -511,6 +511,8 @@ BIGNUM *BN_mod_inverse(BIGNUM *ret, 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, @@ -740,12 +742,22 @@ int RAND_pseudo_bytes(unsigned char *buf #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 #define bn_correct_top(a) \ Index: openssl-0.9.8j/crypto/bn/bn_lib.c =================================================================== --- openssl-0.9.8j.orig/crypto/bn/bn_lib.c +++ openssl-0.9.8j/crypto/bn/bn_lib.c @@ -824,3 +824,56 @@ int bn_cmp_part_words(const BN_ULONG *a, } 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 +} + Index: openssl-0.9.8j/crypto/ec/ec2_mult.c =================================================================== --- openssl-0.9.8j.orig/crypto/ec/ec2_mult.c +++ openssl-0.9.8j/crypto/ec/ec2_mult.c @@ -208,16 +208,18 @@ static int gf2m_Mxy(const EC_GROUP *grou /* Computes scalar*point and stores the result in r. * point can not equal r. - * Uses algorithm 2P of + * Uses a modified algorithm 2P of * Lopex, J. and Dahab, R. "Fast multiplication on elliptic curves over * GF(2^m) without precomputation". + * 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) { BIGNUM *x1, *x2, *z1, *z2; int ret = 0, i, j; - BN_ULONG mask; + BN_ULONG mask, word; if (r == point) { @@ -244,6 +246,11 @@ static int ec_GF2m_montgomery_point_mult 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 */ @@ -251,36 +258,33 @@ static int ec_GF2m_montgomery_point_mult if (!BN_GF2m_add(x2, x2, &group->b)) goto err; /* x2 = x^4 + b */ /* find top most bit and go one past it */ - i = scalar->top - 1; j = BN_BITS2 - 1; - mask = BN_TBIT; - while (!(scalar->d[i] & mask)) { mask >>= 1; j--; } - mask >>= 1; j--; + i = scalar->top - 1; + mask = BN_TBIT; + word = scalar->d[i]; + while (!(word & mask)) mask >>= 1; + mask >>= 1; /* if top most bit was at word break, go to next word */ - if (!mask) - { - i--; j = BN_BITS2 - 1; - mask = BN_TBIT; - } - - for (; i >= 0; i--) - { - for (; j >= 0; j--) - { - if (scalar->d[i] & 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; - } - mask >>= 1; - } - j = BN_BITS2 - 1; - mask = BN_TBIT; - } + if (!mask) + { + i--; + mask = BN_TBIT; + } + + for (; i >= 0; i--) + { + word = scalar->d[i]; + while (mask) + { + 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; + } /* convert out of "projective" coordinates */ i = gf2m_Mxy(group, &point->X, &point->Y, x1, z1, x2, z2, ctx);
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