Re: [PATCH v2] crypto/ecc: Actually remove stack VLA usage

[Herbert Xu]

On Fri, Mar 30, 2018 at 09:55:44AM -0700, Kees Cook wrote:
> 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 

Patch applied.  Thanks.
-- 
Email: Herbert Xu 
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [PATCH v2] crypto/ecc: Actually remove stack VLA usage

[Herbert Xu]

On Fri, Mar 30, 2018 at 09:55:44AM -0700, Kees Cook wrote:
> 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 

Patch applied.  Thanks.
-- 
Email: Herbert Xu 
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [PATCH v2] crypto/ecc: Actually remove stack VLA usage

[Kees Cook]

On Fri, Mar 30, 2018 at 9:55 AM, Kees Cook  wrote:
> 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 

Friendly ping. Please apply to fix a963834b4742 ("crypto/ecc: Remove
stack VLA usage").

Thanks!

-Kees

> ---
> v2:
> - Squash revert (herbert)
> ---
>  crypto/ecc.c  | 66 
> +--
>  crypto/ecc.h  |  4 +++-
>  crypto/ecdh.c |  4 ++--
>  3 files changed, 33 insertions(+), 41 deletions(-)
>
> diff --git a/crypto/ecc.c b/crypto/ecc.c
> index 9c066b5ac12d..815541309a95 100644
> --- a/crypto/ecc.c
> +++ b/crypto/ecc.c
> @@ -515,7 +515,7 @@ static void vli_mmod_fast_256(u64 *result, const u64 
> *product,
>  static bool vli_mmod_fast(u64 *result, u64 *product,
>   const u64 *curve_prime, unsigned int ndigits)
>  {
> -   u64 tmp[2 * ndigits];
> +   u64 tmp[2 * ECC_MAX_DIGITS];
>
> switch (ndigits) {
> case 3:
> @@ -536,7 +536,7 @@ static bool vli_mmod_fast(u64 *result, u64 *product,
>  static void vli_mod_mult_fast(u64 *result, const u64 *left, const u64 *right,
>   const u64 *curve_prime, unsigned int ndigits)
>  {
> -   u64 product[2 * ndigits];
> +   u64 product[2 * ECC_MAX_DIGITS];
>
> vli_mult(product, left, right, ndigits);
> vli_mmod_fast(result, product, curve_prime, ndigits);
> @@ -546,7 +546,7 @@ static void vli_mod_mult_fast(u64 *result, const u64 
> *left, const u64 *right,
>  static void vli_mod_square_fast(u64 *result, const u64 *left,
> const u64 *curve_prime, unsigned int ndigits)
>  {
> -   u64 product[2 * ndigits];
> +   u64 product[2 * ECC_MAX_DIGITS];
>
> vli_square(product, left, ndigits);
> vli_mmod_fast(result, product, curve_prime, ndigits);
> @@ -560,8 +560,8 @@ static void vli_mod_square_fast(u64 *result, const u64 
> *left,
>  static void vli_mod_inv(u64 *result, const u64 *input, const u64 *mod,
> unsigned int ndigits)
>  {
> -   u64 a[ndigits], b[ndigits];
> -   u64 u[ndigits], v[ndigits];
> +   u64 a[ECC_MAX_DIGITS], b[ECC_MAX_DIGITS];
> +   u64 u[ECC_MAX_DIGITS], v[ECC_MAX_DIGITS];
> u64 carry;
> int cmp_result;
>
> @@ -649,8 +649,8 @@ static void ecc_point_double_jacobian(u64 *x1, u64 *y1, 
> u64 *z1,
>   u64 *curve_prime, unsigned int ndigits)
>  {
> /* t1 = x, t2 = y, t3 = z */
> -   u64 t4[ndigits];
> -   u64 t5[ndigits];
> +   u64 t4[ECC_MAX_DIGITS];
> +   u64 t5[ECC_MAX_DIGITS];
>
> if (vli_is_zero(z1, ndigits))
> return;
> @@ -711,7 +711,7 @@ static void ecc_point_double_jacobian(u64 *x1, u64 *y1, 
> u64 *z1,
>  static void apply_z(u64 *x1, u64 *y1, u64 *z, u64 *curve_prime,
> unsigned int ndigits)
>  {
> -   u64 t1[ndigits];
> +   u64 t1[ECC_MAX_DIGITS];
>
> vli_mod_square_fast(t1, z, curve_prime, ndigits);/* z^2 */
> vli_mod_mult_fast(x1, x1, t1, curve_prime, ndigits); /* x1 * z^2 */
> @@ -724,7 +724,7 @@ static void xycz_initial_double(u64 *x1, u64 *y1, u64 
> *x2, u64 *y2,
> u64 *p_initial_z, u64 *curve_prime,
> unsigned int ndigits)
>  {
> -   u64 z[ndigits];
> +   u64 z[ECC_MAX_DIGITS];
>
> vli_set(x2, x1, ndigits);
> vli_set(y2, y1, ndigits);
> @@ -750,7 +750,7 @@ static void xycz_add(u64 *x1, u64 *y1, u64 *x2, u64 *y2, 
> u64 *curve_prime,
>  unsigned int ndigits)
>  {
> /* t1 = X1, t2 = Y1, t3 = X2, t4 = Y2 */
> -   u64 t5[ndigits];
> +   u64 t5[ECC_MAX_DIGITS];
>
> /* t5 = x2 - x1 */
> vli_mod_sub(t5, x2, x1, curve_prime, ndigits);
> @@ -791,9 +791,9 @@ static void xycz_add_c(u64 *x1, u64 *y1, u64 *x2, u64 
> *y2, u64 *curve_prime,
>unsigned int ndigits)
>  {
> /* t1 = X1, t2 = Y1, t3 = X2, t4 = Y2 */
> -   u64 t5[ndigits];
> -   u64 t6[ndigits];
> -   u64 t7[ndigits];
> +   u64 t5[ECC_MAX_DIGITS];
> +   u64 t6[ECC_MAX_DIGITS];
> +   u64 t7[ECC_MAX_DIGITS];
>
> /* t5 = x2 - x1 */
> vli_mod_sub(t5, x2, x1, curve_prime, ndigits);
> @@ -846,9 +846,9 @@ static void ecc_point_mult(struct ecc_point *result,
>unsigned int ndigits)
>  {
> /* R0 and R1 */
> -   u64 rx[2][ndigits];
> -   u64 

Re: [PATCH v2] crypto/ecc: Actually remove stack VLA usage

[Kees Cook]

On Fri, Mar 30, 2018 at 9:55 AM, Kees Cook  wrote:
> 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 

Friendly ping. Please apply to fix a963834b4742 ("crypto/ecc: Remove
stack VLA usage").

Thanks!

-Kees

> ---
> v2:
> - Squash revert (herbert)
> ---
>  crypto/ecc.c  | 66 
> +--
>  crypto/ecc.h  |  4 +++-
>  crypto/ecdh.c |  4 ++--
>  3 files changed, 33 insertions(+), 41 deletions(-)
>
> diff --git a/crypto/ecc.c b/crypto/ecc.c
> index 9c066b5ac12d..815541309a95 100644
> --- a/crypto/ecc.c
> +++ b/crypto/ecc.c
> @@ -515,7 +515,7 @@ static void vli_mmod_fast_256(u64 *result, const u64 
> *product,
>  static bool vli_mmod_fast(u64 *result, u64 *product,
>   const u64 *curve_prime, unsigned int ndigits)
>  {
> -   u64 tmp[2 * ndigits];
> +   u64 tmp[2 * ECC_MAX_DIGITS];
>
> switch (ndigits) {
> case 3:
> @@ -536,7 +536,7 @@ static bool vli_mmod_fast(u64 *result, u64 *product,
>  static void vli_mod_mult_fast(u64 *result, const u64 *left, const u64 *right,
>   const u64 *curve_prime, unsigned int ndigits)
>  {
> -   u64 product[2 * ndigits];
> +   u64 product[2 * ECC_MAX_DIGITS];
>
> vli_mult(product, left, right, ndigits);
> vli_mmod_fast(result, product, curve_prime, ndigits);
> @@ -546,7 +546,7 @@ static void vli_mod_mult_fast(u64 *result, const u64 
> *left, const u64 *right,
>  static void vli_mod_square_fast(u64 *result, const u64 *left,
> const u64 *curve_prime, unsigned int ndigits)
>  {
> -   u64 product[2 * ndigits];
> +   u64 product[2 * ECC_MAX_DIGITS];
>
> vli_square(product, left, ndigits);
> vli_mmod_fast(result, product, curve_prime, ndigits);
> @@ -560,8 +560,8 @@ static void vli_mod_square_fast(u64 *result, const u64 
> *left,
>  static void vli_mod_inv(u64 *result, const u64 *input, const u64 *mod,
> unsigned int ndigits)
>  {
> -   u64 a[ndigits], b[ndigits];
> -   u64 u[ndigits], v[ndigits];
> +   u64 a[ECC_MAX_DIGITS], b[ECC_MAX_DIGITS];
> +   u64 u[ECC_MAX_DIGITS], v[ECC_MAX_DIGITS];
> u64 carry;
> int cmp_result;
>
> @@ -649,8 +649,8 @@ static void ecc_point_double_jacobian(u64 *x1, u64 *y1, 
> u64 *z1,
>   u64 *curve_prime, unsigned int ndigits)
>  {
> /* t1 = x, t2 = y, t3 = z */
> -   u64 t4[ndigits];
> -   u64 t5[ndigits];
> +   u64 t4[ECC_MAX_DIGITS];
> +   u64 t5[ECC_MAX_DIGITS];
>
> if (vli_is_zero(z1, ndigits))
> return;
> @@ -711,7 +711,7 @@ static void ecc_point_double_jacobian(u64 *x1, u64 *y1, 
> u64 *z1,
>  static void apply_z(u64 *x1, u64 *y1, u64 *z, u64 *curve_prime,
> unsigned int ndigits)
>  {
> -   u64 t1[ndigits];
> +   u64 t1[ECC_MAX_DIGITS];
>
> vli_mod_square_fast(t1, z, curve_prime, ndigits);/* z^2 */
> vli_mod_mult_fast(x1, x1, t1, curve_prime, ndigits); /* x1 * z^2 */
> @@ -724,7 +724,7 @@ static void xycz_initial_double(u64 *x1, u64 *y1, u64 
> *x2, u64 *y2,
> u64 *p_initial_z, u64 *curve_prime,
> unsigned int ndigits)
>  {
> -   u64 z[ndigits];
> +   u64 z[ECC_MAX_DIGITS];
>
> vli_set(x2, x1, ndigits);
> vli_set(y2, y1, ndigits);
> @@ -750,7 +750,7 @@ static void xycz_add(u64 *x1, u64 *y1, u64 *x2, u64 *y2, 
> u64 *curve_prime,
>  unsigned int ndigits)
>  {
> /* t1 = X1, t2 = Y1, t3 = X2, t4 = Y2 */
> -   u64 t5[ndigits];
> +   u64 t5[ECC_MAX_DIGITS];
>
> /* t5 = x2 - x1 */
> vli_mod_sub(t5, x2, x1, curve_prime, ndigits);
> @@ -791,9 +791,9 @@ static void xycz_add_c(u64 *x1, u64 *y1, u64 *x2, u64 
> *y2, u64 *curve_prime,
>unsigned int ndigits)
>  {
> /* t1 = X1, t2 = Y1, t3 = X2, t4 = Y2 */
> -   u64 t5[ndigits];
> -   u64 t6[ndigits];
> -   u64 t7[ndigits];
> +   u64 t5[ECC_MAX_DIGITS];
> +   u64 t6[ECC_MAX_DIGITS];
> +   u64 t7[ECC_MAX_DIGITS];
>
> /* t5 = x2 - x1 */
> vli_mod_sub(t5, x2, x1, curve_prime, ndigits);
> @@ -846,9 +846,9 @@ static void ecc_point_mult(struct ecc_point *result,
>unsigned int ndigits)
>  {
> /* R0 and R1 */
> -   u64 rx[2][ndigits];
> -   u64 ry[2][ndigits];
> -   u64 z[ndigits];
> +