crypto: ecc - Actually remove stack VLA usage
On the quest to remove all VLAs from the kernel[1], this avoids VLAs
by just using the maximum allocation size (4 bytes) for stack arrays.
All the VLAs in ecc were either 3 or 4 bytes (or a multiple), so just
make it 4 bytes all the time. Initialization routines are adjusted to
check that ndigits does not end up larger than the arrays.
This includes a removal of the earlier attempt at this fix from
commit a963834b4742 ("crypto/ecc: Remove stack VLA usage")
[1] https://lkml.org/lkml/2018/3/7/621
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Kees Cook
Herbert Xu
parent
3a488aaec6
commit
d5c3b17898
3 changed files with 33 additions and 41 deletions
66
crypto/ecc.c
66
crypto/ecc.c
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@ -515,7 +515,7 @@ static void vli_mmod_fast_256(u64 *result, const u64 *product,
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static bool vli_mmod_fast(u64 *result, u64 *product,
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const u64 *curve_prime, unsigned int ndigits)
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{
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u64 tmp[2 * ndigits];
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u64 tmp[2 * ECC_MAX_DIGITS];
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switch (ndigits) {
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case 3:
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@ -536,7 +536,7 @@ static bool vli_mmod_fast(u64 *result, u64 *product,
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static void vli_mod_mult_fast(u64 *result, const u64 *left, const u64 *right,
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const u64 *curve_prime, unsigned int ndigits)
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{
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u64 product[2 * ndigits];
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u64 product[2 * ECC_MAX_DIGITS];
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vli_mult(product, left, right, ndigits);
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vli_mmod_fast(result, product, curve_prime, ndigits);
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@ -546,7 +546,7 @@ static void vli_mod_mult_fast(u64 *result, const u64 *left, const u64 *right,
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static void vli_mod_square_fast(u64 *result, const u64 *left,
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const u64 *curve_prime, unsigned int ndigits)
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{
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u64 product[2 * ndigits];
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u64 product[2 * ECC_MAX_DIGITS];
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vli_square(product, left, ndigits);
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vli_mmod_fast(result, product, curve_prime, ndigits);
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@ -560,8 +560,8 @@ static void vli_mod_square_fast(u64 *result, const u64 *left,
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static void vli_mod_inv(u64 *result, const u64 *input, const u64 *mod,
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unsigned int ndigits)
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{
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u64 a[ndigits], b[ndigits];
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u64 u[ndigits], v[ndigits];
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u64 a[ECC_MAX_DIGITS], b[ECC_MAX_DIGITS];
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u64 u[ECC_MAX_DIGITS], v[ECC_MAX_DIGITS];
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u64 carry;
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int cmp_result;
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@ -649,8 +649,8 @@ static void ecc_point_double_jacobian(u64 *x1, u64 *y1, u64 *z1,
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u64 *curve_prime, unsigned int ndigits)
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{
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/* t1 = x, t2 = y, t3 = z */
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u64 t4[ndigits];
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u64 t5[ndigits];
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u64 t4[ECC_MAX_DIGITS];
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u64 t5[ECC_MAX_DIGITS];
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if (vli_is_zero(z1, ndigits))
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return;
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@ -711,7 +711,7 @@ static void ecc_point_double_jacobian(u64 *x1, u64 *y1, u64 *z1,
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static void apply_z(u64 *x1, u64 *y1, u64 *z, u64 *curve_prime,
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unsigned int ndigits)
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{
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u64 t1[ndigits];
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u64 t1[ECC_MAX_DIGITS];
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vli_mod_square_fast(t1, z, curve_prime, ndigits); /* z^2 */
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vli_mod_mult_fast(x1, x1, t1, curve_prime, ndigits); /* x1 * z^2 */
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@ -724,7 +724,7 @@ static void xycz_initial_double(u64 *x1, u64 *y1, u64 *x2, u64 *y2,
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u64 *p_initial_z, u64 *curve_prime,
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unsigned int ndigits)
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{
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u64 z[ndigits];
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u64 z[ECC_MAX_DIGITS];
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vli_set(x2, x1, ndigits);
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vli_set(y2, y1, ndigits);
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@ -750,7 +750,7 @@ static void xycz_add(u64 *x1, u64 *y1, u64 *x2, u64 *y2, u64 *curve_prime,
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unsigned int ndigits)
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{
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/* t1 = X1, t2 = Y1, t3 = X2, t4 = Y2 */
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u64 t5[ndigits];
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u64 t5[ECC_MAX_DIGITS];
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/* t5 = x2 - x1 */
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vli_mod_sub(t5, x2, x1, curve_prime, ndigits);
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@ -791,9 +791,9 @@ static void xycz_add_c(u64 *x1, u64 *y1, u64 *x2, u64 *y2, u64 *curve_prime,
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unsigned int ndigits)
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{
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/* t1 = X1, t2 = Y1, t3 = X2, t4 = Y2 */
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u64 t5[ndigits];
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u64 t6[ndigits];
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u64 t7[ndigits];
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u64 t5[ECC_MAX_DIGITS];
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u64 t6[ECC_MAX_DIGITS];
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u64 t7[ECC_MAX_DIGITS];
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/* t5 = x2 - x1 */
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vli_mod_sub(t5, x2, x1, curve_prime, ndigits);
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@ -846,9 +846,9 @@ static void ecc_point_mult(struct ecc_point *result,
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unsigned int ndigits)
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{
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/* R0 and R1 */
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u64 rx[2][ndigits];
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u64 ry[2][ndigits];
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u64 z[ndigits];
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u64 rx[2][ECC_MAX_DIGITS];
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u64 ry[2][ECC_MAX_DIGITS];
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u64 z[ECC_MAX_DIGITS];
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int i, nb;
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int num_bits = vli_num_bits(scalar, ndigits);
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@ -943,13 +943,13 @@ int ecc_is_key_valid(unsigned int curve_id, unsigned int ndigits,
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int ecc_gen_privkey(unsigned int curve_id, unsigned int ndigits, u64 *privkey)
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{
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const struct ecc_curve *curve = ecc_get_curve(curve_id);
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u64 priv[ndigits];
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u64 priv[ECC_MAX_DIGITS];
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unsigned int nbytes = ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
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unsigned int nbits = vli_num_bits(curve->n, ndigits);
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int err;
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/* Check that N is included in Table 1 of FIPS 186-4, section 6.1.1 */
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if (nbits < 160)
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if (nbits < 160 || ndigits > ARRAY_SIZE(priv))
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return -EINVAL;
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/*
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@ -988,10 +988,10 @@ int ecc_make_pub_key(unsigned int curve_id, unsigned int ndigits,
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{
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int ret = 0;
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struct ecc_point *pk;
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u64 priv[ndigits];
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u64 priv[ECC_MAX_DIGITS];
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const struct ecc_curve *curve = ecc_get_curve(curve_id);
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if (!private_key || !curve) {
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if (!private_key || !curve || ndigits > ARRAY_SIZE(priv)) {
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ret = -EINVAL;
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goto out;
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}
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@ -1025,30 +1025,25 @@ int crypto_ecdh_shared_secret(unsigned int curve_id, unsigned int ndigits,
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{
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int ret = 0;
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struct ecc_point *product, *pk;
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u64 *priv, *rand_z;
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u64 priv[ECC_MAX_DIGITS];
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u64 rand_z[ECC_MAX_DIGITS];
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unsigned int nbytes;
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const struct ecc_curve *curve = ecc_get_curve(curve_id);
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if (!private_key || !public_key || !curve) {
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if (!private_key || !public_key || !curve ||
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ndigits > ARRAY_SIZE(priv) || ndigits > ARRAY_SIZE(rand_z)) {
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ret = -EINVAL;
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goto out;
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}
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priv = kmalloc_array(ndigits, sizeof(*priv), GFP_KERNEL);
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if (!priv) {
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ret = -ENOMEM;
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goto out;
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}
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nbytes = ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
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rand_z = kmalloc_array(ndigits, sizeof(*rand_z), GFP_KERNEL);
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if (!rand_z) {
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ret = -ENOMEM;
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goto kfree_out;
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}
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get_random_bytes(rand_z, nbytes);
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pk = ecc_alloc_point(ndigits);
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if (!pk) {
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ret = -ENOMEM;
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goto kfree_out;
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goto out;
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}
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product = ecc_alloc_point(ndigits);
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@ -1057,8 +1052,6 @@ int crypto_ecdh_shared_secret(unsigned int curve_id, unsigned int ndigits,
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goto err_alloc_product;
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}
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get_random_bytes(rand_z, ndigits << ECC_DIGITS_TO_BYTES_SHIFT);
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ecc_swap_digits(public_key, pk->x, ndigits);
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ecc_swap_digits(&public_key[ndigits], pk->y, ndigits);
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ecc_swap_digits(private_key, priv, ndigits);
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@ -1073,9 +1066,6 @@ int crypto_ecdh_shared_secret(unsigned int curve_id, unsigned int ndigits,
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ecc_free_point(product);
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err_alloc_product:
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ecc_free_point(pk);
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kfree_out:
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kzfree(priv);
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kzfree(rand_z);
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out:
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return ret;
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}
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@ -26,7 +26,9 @@
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#ifndef _CRYPTO_ECC_H
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#define _CRYPTO_ECC_H
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#define ECC_MAX_DIGITS 4 /* 256 */
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#define ECC_CURVE_NIST_P192_DIGITS 3
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#define ECC_CURVE_NIST_P256_DIGITS 4
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#define ECC_MAX_DIGITS ECC_CURVE_NIST_P256_DIGITS
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#define ECC_DIGITS_TO_BYTES_SHIFT 3
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@ -30,8 +30,8 @@ static inline struct ecdh_ctx *ecdh_get_ctx(struct crypto_kpp *tfm)
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static unsigned int ecdh_supported_curve(unsigned int curve_id)
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{
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switch (curve_id) {
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case ECC_CURVE_NIST_P192: return 3;
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case ECC_CURVE_NIST_P256: return 4;
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case ECC_CURVE_NIST_P192: return ECC_CURVE_NIST_P192_DIGITS;
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case ECC_CURVE_NIST_P256: return ECC_CURVE_NIST_P256_DIGITS;
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default: return 0;
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}
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}
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