[U-Boot] [PATCH 3/4] rsa: add support of padding pss
Simon Glass
sjg at chromium.org
Tue Oct 9 16:20:34 UTC 2018
Hi Philippe,
On 2 October 2018 at 10:32, Philippe Reynes
<philippe.reynes at softathome.com> wrote:
> We add the support of the padding pss for rsa signature.
> This new padding is often recommended instead of pkcs-1.5.
>
> Signed-off-by: Philippe Reynes <philippe.reynes at softathome.com>
> ---
> common/image-sig.c | 4 ++
> include/u-boot/rsa.h | 11 ++++
> lib/rsa/rsa-sign.c | 8 +++
> lib/rsa/rsa-verify.c | 173 +++++++++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 196 insertions(+)
Needs a doc update somewhere.
>
> diff --git a/common/image-sig.c b/common/image-sig.c
> index b7ca657..0aa1f2d 100644
> --- a/common/image-sig.c
> +++ b/common/image-sig.c
> @@ -76,6 +76,10 @@ struct padding_algo padding_algos[] = {
> .name = "pkcs-1.5",
> .verify = padding_pkcs_15_verify,
> },
> + {
> + .name = "pss",
> + .verify = padding_pss_verify,
> + }
I think this feature should be controlled by a new Kconfig option as
it presumably increases code size a bit.
> };
>
> struct checksum_algo *image_get_checksum_algo(const char *full_name)
> diff --git a/include/u-boot/rsa.h b/include/u-boot/rsa.h
> index 16b4c4c..6193c10 100644
> --- a/include/u-boot/rsa.h
> +++ b/include/u-boot/rsa.h
> @@ -101,6 +101,10 @@ int rsa_verify(struct image_sign_info *info,
> int padding_pkcs_15_verify(struct image_sign_info *info,
> uint8_t *msg, int msg_len,
> const uint8_t *hash, int hash_len);
> +
> +int padding_pss_verify(struct image_sign_info *info,
> + uint8_t *msg, int msg_len,
> + const uint8_t *hash, int hash_len);
> #else
> static inline int rsa_verify(struct image_sign_info *info,
> const struct image_region region[], int region_count,
> @@ -115,6 +119,13 @@ static inline int padding_pkcs_15_verify(struct image_sign_info *info,
> {
> return -ENXIO;
> }
> +
> +static inline int padding_pss_verify(struct image_sign_info *info,
> + uint8_t *msg, int msg_len,
> + const uint8_t *hash, int hash_len)
> +{
> + return -ENXIO;
> +}
> #endif
>
> #define RSA_DEFAULT_PADDING_NAME "pkcs-1.5"
> diff --git a/lib/rsa/rsa-sign.c b/lib/rsa/rsa-sign.c
> index 6aa0e2a..13c035e 100644
> --- a/lib/rsa/rsa-sign.c
> +++ b/lib/rsa/rsa-sign.c
> @@ -438,6 +438,14 @@ static int rsa_sign_with_key(RSA *rsa, struct padding_algo *padding_algo,
> goto err_sign;
> }
>
> + if (padding_algo && !strcmp(padding_algo->name, "pss")) {
> + if (EVP_PKEY_CTX_set_rsa_padding(ckey,
> + RSA_PKCS1_PSS_PADDING) <= 0) {
> + ret = rsa_err("Signer padding setup failed");
> + goto err_sign;
> + }
> + }
> +
> for (i = 0; i < region_count; i++) {
> if (!EVP_DigestSignUpdate(context, region[i].data,
> region[i].size)) {
> diff --git a/lib/rsa/rsa-verify.c b/lib/rsa/rsa-verify.c
> index 279a9ba..ca5c1fc 100644
> --- a/lib/rsa/rsa-verify.c
> +++ b/lib/rsa/rsa-verify.c
> @@ -80,6 +80,179 @@ int padding_pkcs_15_verify(struct image_sign_info *info,
> return 0;
> }
>
> +static void u32_i2osp(uint32_t val, uint8_t *buf)
> +{
> + buf[0] = (uint8_t)((val >> 24) & 0xff);
> + buf[1] = (uint8_t)((val >> 16) & 0xff);
> + buf[2] = (uint8_t)((val >> 8) & 0xff);
> + buf[3] = (uint8_t)((val >> 0) & 0xff);
> +}
> +
> +int mfg(struct checksum_algo *checksum, uint8_t *seed, int seed_len,
> + uint8_t *output, int output_len)
What is the name mfg? Can you make this a little longer please? Also,
did you mean to export it or should it be static? Finally, it needs a
function comment somewhere.
> +{
> + struct image_region region[2];
> + int ret = 0, i, i_output = 0, region_count = 2;
> + uint32_t counter = 0;
> + uint8_t buf_counter[4], *tmp;
> + int hash_len = checksum->checksum_len;
> +
> + memset(output, 0, output_len);
> +
> + region[0].data = seed;
> + region[0].size = seed_len;
> + region[1].data = &buf_counter[0];
> + region[1].size = 4;
> +
> + tmp = malloc(hash_len);
> + if (!tmp) {
> + debug("%s: can't allocate array tmp\n", __func__);
> + ret = -ENOMEM;
> + goto out;
> + }
> +
> + while (i_output < output_len) {
> + u32_i2osp(counter, &buf_counter[0]);
> +
> + ret = checksum->calculate(checksum->name,
> + region, region_count,
> + tmp);
> + if (ret < 0) {
> + debug("%s: Error in checksum calculation\n", __func__);
> + goto out;
> + }
> +
> + i = 0;
> + while ((i_output < output_len) && (i < hash_len)) {
> + output[i_output] = tmp[i];
> + i_output++;
> + i++;
> + }
> +
> + counter++;
> + }
> +
> +out:
> + free(tmp);
Please put a blank line before the final 'return' in a function.
> + return ret;
> +}
> +
> +int compute_hash_prime(struct checksum_algo *checksum,
> + uint8_t *pad, int pad_len,
> + uint8_t *hash, int hash_len,
> + uint8_t *salt, int salt_len,
> + uint8_t *hprime)
> +{
> + struct image_region region[3];
> + int ret, region_count = 3;
> +
> + region[0].data = pad;
> + region[0].size = pad_len;
> + region[1].data = hash;
> + region[1].size = hash_len;
> + region[2].data = salt;
> + region[2].size = salt_len;
> +
> + ret = checksum->calculate(checksum->name, region, region_count, hprime);
> + if (ret < 0) {
> + debug("%s: Error in checksum calculation\n", __func__);
> + goto out;
> + }
> +
> +out:
> + return ret;
> +}
> +
> +int padding_pss_verify(struct image_sign_info *info,
> + uint8_t *msg, int msg_len,
> + const uint8_t *hash, int hash_len)
> +{
> + uint8_t *masked_db = NULL;
> + int masked_db_len = msg_len - hash_len - 1;
> + uint8_t *h = NULL, *hprime = NULL;
> + int h_len = hash_len;
> + uint8_t *db_mask = NULL;
> + int db_mask_len = masked_db_len;
> + uint8_t *db = NULL, *salt = NULL;
> + int db_len = masked_db_len, salt_len = msg_len - hash_len - 2;
> + uint8_t pad_zero[8] = { 0 };
> + int ret, i, leftmost_bits = 1;
> + uint8_t leftmost_mask;
> + struct checksum_algo *checksum = info->checksum;
> +
> + /* first, allocate everything */
> + masked_db = malloc(masked_db_len);
> + h = malloc(h_len);
> + db_mask = malloc(db_mask_len);
> + db = malloc(db_len);
> + salt = malloc(salt_len);
> + hprime = malloc(hash_len);
> + if (!masked_db || !h || !db_mask || !db || !salt || !hprime) {
> + printf("%s: can't allocate some buffer\n", __func__);
> + ret = -ENOMEM;
> + goto out;
> + }
> +
> + /* step 4: check if the last byte is 0xbc */
> + if (msg[msg_len - 1] != 0xbc) {
> + printf("%s: invalid pss padding (0xbc is missing)\n", __func__);
> + ret = -EINVAL;
> + goto out;
> + }
> +
> + /* step 5 */
> + memcpy(masked_db, msg, masked_db_len);
> + memcpy(h, msg + masked_db_len, h_len);
> +
> + /* step 6 */
> + leftmost_mask = (0xff >> (8 - leftmost_bits)) << (8 - leftmost_bits);
> + if (masked_db[0] & leftmost_mask) {
> + printf("%s: invalid pss padding ", __func__);
> + printf("(leftmost bit of maskedDB not zero)\n");
> + ret = -EINVAL;
> + goto out;
> + }
> +
> + /* step 7 */
> + mfg(checksum, h, h_len, db_mask, db_mask_len);
> +
> + /* step 8 */
> + for (i = 0; i < db_len; i++)
> + db[i] = masked_db[i] ^ db_mask[i];
> +
> + /* step 9 */
> + db[0] &= 0xff >> leftmost_bits;
> +
> + /* step 10 */
> + if (db[0] != 0x01) {
> + printf("%s: invalid pss padding ", __func__);
> + printf("(leftmost byte of db isn't 0x01)\n");
> + ret = EINVAL;
> + goto out;
> + }
> +
> + /* step 11 */
> + memcpy(salt, &db[1], salt_len);
> +
> + /* step 12 & 13 */
> + compute_hash_prime(checksum, pad_zero, 8,
> + (uint8_t *)hash, hash_len,
> + salt, salt_len, hprime);
> +
> + /* step 14 */
> + ret = memcmp(h, hprime, hash_len);
> +
> +out:
> + free(hprime);
> + free(salt);
> + free(db);
> + free(db_mask);
> + free(h);
> + free(masked_db);
> +
> + return ret;
> +}
> +
> /**
> * rsa_verify_key() - Verify a signature against some data using RSA Key
> *
> --
> 2.7.4
>
Regards,
Simon
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