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SUSE:SLE-12-SP5:GA
openssl.9335
openssl-CVE-2018-5407-PortSmash.patch
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File openssl-CVE-2018-5407-PortSmash.patch of Package openssl.9335
commit b18162a7c9bbfb57112459a4d6631fa258fd8c0c Author: Billy Brumley <bbrumley@gmail.com> Date: Thu Nov 8 13:57:54 2018 +0200 CVE-2018-5407 fix: ECC ladder Reviewed-by: Matt Caswell <matt@openssl.org> Reviewed-by: Paul Dale <paul.dale@oracle.com> Reviewed-by: Nicola Tuveri <nic.tuv@gmail.com> (Merged from https://github.com/openssl/openssl/pull/7593) Index: openssl-1.0.2j/crypto/bn/bn_lib.c =================================================================== --- openssl-1.0.2j.orig/crypto/bn/bn_lib.c 2018-11-12 16:36:13.932939169 +0100 +++ openssl-1.0.2j/crypto/bn/bn_lib.c 2018-11-12 16:36:54.601186017 +0100 @@ -879,6 +879,33 @@ void BN_consttime_swap(BN_ULONG conditio a->top ^= t; b->top ^= t; + t = (a->neg ^ b->neg) & condition; + a->neg ^= t; + b->neg ^= t; + + /*- + * BN_FLG_STATIC_DATA: indicates that data may not be written to. Intention + * is actually to treat it as it's read-only data, and some (if not most) + * of it does reside in read-only segment. In other words observation of + * BN_FLG_STATIC_DATA in BN_consttime_swap should be treated as fatal + * condition. It would either cause SEGV or effectively cause data + * corruption. + * + * BN_FLG_MALLOCED: refers to BN structure itself, and hence must be + * preserved. + * + * BN_FLG_SECURE: must be preserved, because it determines how x->d was + * allocated and hence how to free it. + * + * BN_FLG_CONSTTIME: sufficient to mask and swap + */ + +#define BN_CONSTTIME_SWAP_FLAGS (BN_FLG_CONSTTIME) + + t = ((a->flags ^ b->flags) & BN_CONSTTIME_SWAP_FLAGS) & condition; + a->flags ^= t; + b->flags ^= t; + #define BN_CONSTTIME_SWAP(ind) \ do { \ t = (a->d[ind] ^ b->d[ind]) & condition; \ Index: openssl-1.0.2j/crypto/ec/ec_mult.c =================================================================== --- openssl-1.0.2j.orig/crypto/ec/ec_mult.c 2018-11-12 16:36:13.932939169 +0100 +++ openssl-1.0.2j/crypto/ec/ec_mult.c 2018-11-12 16:36:22.716992487 +0100 @@ -306,6 +306,224 @@ static signed char *compute_wNAF(const B return r; } +#define EC_POINT_BN_set_flags(P, flags) do { \ + BN_set_flags(&(P)->X, (flags)); \ + BN_set_flags(&(P)->Y, (flags)); \ + BN_set_flags(&(P)->Z, (flags)); \ +} while(0) + +/*- + * This functions computes (in constant time) a point multiplication over the + * EC group. + * + * At a high level, it is Montgomery ladder with conditional swaps. + * + * It performs either a fixed scalar point multiplication + * (scalar * generator) + * when point is NULL, or a generic scalar point multiplication + * (scalar * point) + * when point is not NULL. + * + * scalar should be in the range [0,n) otherwise all constant time bets are off. + * + * NB: This says nothing about EC_POINT_add and EC_POINT_dbl, + * which of course are not constant time themselves. + * + * The product is stored in r. + * + * Returns 1 on success, 0 otherwise. + */ +static int ec_mul_consttime(const EC_GROUP *group, EC_POINT *r, + const BIGNUM *scalar, const EC_POINT *point, + BN_CTX *ctx) +{ + int i, cardinality_bits, group_top, kbit, pbit, Z_is_one; + EC_POINT *s = NULL; + BIGNUM *k = NULL; + BIGNUM *lambda = NULL; + BIGNUM *cardinality = NULL; + BN_CTX *new_ctx = NULL; + int ret = 0; + + if (ctx == NULL && (ctx = new_ctx = BN_CTX_new()) == NULL) + return 0; + + BN_CTX_start(ctx); + + s = EC_POINT_new(group); + if (s == NULL) + goto err; + + if (point == NULL) { + if (!EC_POINT_copy(s, group->generator)) + goto err; + } else { + if (!EC_POINT_copy(s, point)) + goto err; + } + + EC_POINT_BN_set_flags(s, BN_FLG_CONSTTIME); + + cardinality = BN_CTX_get(ctx); + lambda = BN_CTX_get(ctx); + k = BN_CTX_get(ctx); + if (k == NULL || !BN_mul(cardinality, &group->order, &group->cofactor, ctx)) + goto err; + + /* + * Group cardinalities are often on a word boundary. + * So when we pad the scalar, some timing diff might + * pop if it needs to be expanded due to carries. + * So expand ahead of time. + */ + cardinality_bits = BN_num_bits(cardinality); + group_top = cardinality->top; + if ((bn_wexpand(k, group_top + 2) == NULL) + || (bn_wexpand(lambda, group_top + 2) == NULL)) + goto err; + + if (!BN_copy(k, scalar)) + goto err; + + BN_set_flags(k, BN_FLG_CONSTTIME); + + if ((BN_num_bits(k) > cardinality_bits) || (BN_is_negative(k))) { + /*- + * this is an unusual input, and we don't guarantee + * constant-timeness + */ + if (!BN_nnmod(k, k, cardinality, ctx)) + goto err; + } + + if (!BN_add(lambda, k, cardinality)) + goto err; + BN_set_flags(lambda, BN_FLG_CONSTTIME); + if (!BN_add(k, lambda, cardinality)) + goto err; + /* + * lambda := scalar + cardinality + * k := scalar + 2*cardinality + */ + kbit = BN_is_bit_set(lambda, cardinality_bits); + BN_consttime_swap(kbit, k, lambda, group_top + 2); + + group_top = group->field.top; + if ((bn_wexpand(&s->X, group_top) == NULL) + || (bn_wexpand(&s->Y, group_top) == NULL) + || (bn_wexpand(&s->Z, group_top) == NULL) + || (bn_wexpand(&r->X, group_top) == NULL) + || (bn_wexpand(&r->Y, group_top) == NULL) + || (bn_wexpand(&r->Z, group_top) == NULL)) + goto err; + + /* top bit is a 1, in a fixed pos */ + if (!EC_POINT_copy(r, s)) + goto err; + + EC_POINT_BN_set_flags(r, BN_FLG_CONSTTIME); + + if (!EC_POINT_dbl(group, s, s, ctx)) + goto err; + + pbit = 0; + +#define EC_POINT_CSWAP(c, a, b, w, t) do { \ + BN_consttime_swap(c, &(a)->X, &(b)->X, w); \ + BN_consttime_swap(c, &(a)->Y, &(b)->Y, w); \ + BN_consttime_swap(c, &(a)->Z, &(b)->Z, w); \ + t = ((a)->Z_is_one ^ (b)->Z_is_one) & (c); \ + (a)->Z_is_one ^= (t); \ + (b)->Z_is_one ^= (t); \ +} while(0) + + /*- + * The ladder step, with branches, is + * + * k[i] == 0: S = add(R, S), R = dbl(R) + * k[i] == 1: R = add(S, R), S = dbl(S) + * + * Swapping R, S conditionally on k[i] leaves you with state + * + * k[i] == 0: T, U = R, S + * k[i] == 1: T, U = S, R + * + * Then perform the ECC ops. + * + * U = add(T, U) + * T = dbl(T) + * + * Which leaves you with state + * + * k[i] == 0: U = add(R, S), T = dbl(R) + * k[i] == 1: U = add(S, R), T = dbl(S) + * + * Swapping T, U conditionally on k[i] leaves you with state + * + * k[i] == 0: R, S = T, U + * k[i] == 1: R, S = U, T + * + * Which leaves you with state + * + * k[i] == 0: S = add(R, S), R = dbl(R) + * k[i] == 1: R = add(S, R), S = dbl(S) + * + * So we get the same logic, but instead of a branch it's a + * conditional swap, followed by ECC ops, then another conditional swap. + * + * Optimization: The end of iteration i and start of i-1 looks like + * + * ... + * CSWAP(k[i], R, S) + * ECC + * CSWAP(k[i], R, S) + * (next iteration) + * CSWAP(k[i-1], R, S) + * ECC + * CSWAP(k[i-1], R, S) + * ... + * + * So instead of two contiguous swaps, you can merge the condition + * bits and do a single swap. + * + * k[i] k[i-1] Outcome + * 0 0 No Swap + * 0 1 Swap + * 1 0 Swap + * 1 1 No Swap + * + * This is XOR. pbit tracks the previous bit of k. + */ + + for (i = cardinality_bits - 1; i >= 0; i--) { + kbit = BN_is_bit_set(k, i) ^ pbit; + EC_POINT_CSWAP(kbit, r, s, group_top, Z_is_one); + if (!EC_POINT_add(group, s, r, s, ctx)) + goto err; + if (!EC_POINT_dbl(group, r, r, ctx)) + goto err; + /* + * pbit logic merges this cswap with that of the + * next iteration + */ + pbit ^= kbit; + } + /* one final cswap to move the right value into r */ + EC_POINT_CSWAP(pbit, r, s, group_top, Z_is_one); +#undef EC_POINT_CSWAP + + ret = 1; + + err: + EC_POINT_free(s); + BN_CTX_end(ctx); + BN_CTX_free(new_ctx); + + return ret; +} + +#undef EC_POINT_BN_set_flags + /* * TODO: table should be optimised for the wNAF-based implementation, * sometimes smaller windows will give better performance (thus the @@ -365,6 +583,34 @@ int ec_wNAF_mul(const EC_GROUP *group, E return EC_POINT_set_to_infinity(group, r); } + if (!BN_is_zero(&group->order) && !BN_is_zero(&group->cofactor)) { + /*- + * Handle the common cases where the scalar is secret, enforcing a constant + * time scalar multiplication algorithm. + */ + if ((scalar != NULL) && (num == 0)) { + /*- + * In this case we want to compute scalar * GeneratorPoint: this + * codepath is reached most prominently by (ephemeral) key generation + * of EC cryptosystems (i.e. ECDSA keygen and sign setup, ECDH + * keygen/first half), where the scalar is always secret. This is why + * we ignore if BN_FLG_CONSTTIME is actually set and we always call the + * constant time version. + */ + return ec_mul_consttime(group, r, scalar, NULL, ctx); + } + if ((scalar == NULL) && (num == 1)) { + /*- + * In this case we want to compute scalar * GenericPoint: this codepath + * is reached most prominently by the second half of ECDH, where the + * secret scalar is multiplied by the peer's public point. To protect + * the secret scalar, we ignore if BN_FLG_CONSTTIME is actually set and + * we always call the constant time version. + */ + return ec_mul_consttime(group, r, scalars[0], points[0], ctx); + } + } + for (i = 0; i < num; i++) { if (group->meth != points[i]->meth) { ECerr(EC_F_EC_WNAF_MUL, EC_R_INCOMPATIBLE_OBJECTS);
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