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psa_util: improve convert_raw_to_der_single_int()

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Allow the function to support DER buffers than what it is nominally
required by the provided coordinates. In other words let's ignore
padding zeros in the raw number.

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
This commit is contained in:
Valerio Setti 2024-02-05 12:06:46 +01:00
parent 315e4afc0a
commit 954ef4bbd5
4 changed files with 33 additions and 16 deletions
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7
include/mbedtls/psa_util.h
View File

@ -191,7 +191,12 @@ static inline mbedtls_md_type_t mbedtls_md_type_from_psa_alg(psa_algorithm_t psa
* \param raw_len Length of \p raw in bytes.
* \param[out] der Buffer that will be filled with the converted DER
* output. It can overlap with raw buffer.
* \param der_size Size of \p der in bytes.
* \param der_size Size of \p der in bytes. Given \p bits parameter:
* * #MBEDTLS_ECDSA_MAX_SIG_LEN(\p bits) can be used
* to determine a large enough buffer for any
* \p raw input vector.
* * The minimum size might be smaller in case
* \p raw input vector contains padding zeros.
* \param[out] der_len On success it contains the amount of valid data
* (in bytes) written to \p der. It's undefined
* in case of failure.

25
library/psa_util.c
View File

@ -365,9 +365,21 @@ static int convert_raw_to_der_single_int(const unsigned char *raw_buf, size_t ra
unsigned char *der_buf_end)
{
unsigned char *p = der_buf_end;
int len = (int) raw_len;
int len;
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
/* ASN.1 DER encoding requires minimal length, so skip leading 0s.
* Provided input MPIs should not be 0, but as a failsafe measure, still
* detect that and return error in case. */
while (*raw_buf == 0x00) {
++raw_buf;
--raw_len;
if (raw_len == 0) {
return MBEDTLS_ERR_ASN1_INVALID_DATA;
}
}
len = (int) raw_len;
/* Copy the raw coordinate to the end of der_buf. */
if ((p - der_buf_start) < len) {
return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
@ -375,17 +387,6 @@ static int convert_raw_to_der_single_int(const unsigned char *raw_buf, size_t ra
p -= len;
memcpy(p, raw_buf, len);
/* ASN.1 DER encoding requires minimal length, so skip leading 0s.
* Provided input MPIs should not be 0, but as a failsafe measure, still
* detect that and return error in case. */
while (*p == 0x00) {
++p;
--len;
if (len == 0) {
return MBEDTLS_ERR_ASN1_INVALID_DATA;
}
}
/* If MSb is 1, ASN.1 requires that we prepend a 0. */
if (*p & 0x80) {
if ((p - der_buf_start) < 1) {

4
tests/suites/test_suite_psa_crypto_util.data
View File

@ -115,3 +115,7 @@ ecdsa_raw_to_der_incremental:512:"9111111111111111111111111111111111111111111111
ECDSA Raw -> DER, 521bit, Incremental DER buffer sizes
depends_on:PSA_WANT_ECC_SECP_R1_521
ecdsa_raw_to_der_incremental:528:"911111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222":"3081890243009111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111110242222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222"
ECDSA Raw -> DER, 256bit, DER buffer of minimal length (1 byte per integer)
depends_on:PSA_WANT_ECC_SECP_K1_256
ecdsa_raw_to_der_incremental:256:"00000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000002":"3006020101020102"

13
tests/suites/test_suite_psa_crypto_util.function
View File

@ -32,6 +32,7 @@ void ecdsa_raw_to_der_incremental(int key_bits, data_t *input, data_t *exp_resul
size_t ret_len;
size_t i;
/* Test with an output buffer smaller than required (expexted to fail). */
for (i = 1; i < tmp_buf_len; i++) {
TEST_CALLOC(tmp_buf, i);
TEST_ASSERT(mbedtls_ecdsa_raw_to_der(key_bits, input->x, input->len,
@ -39,10 +40,16 @@ void ecdsa_raw_to_der_incremental(int key_bits, data_t *input, data_t *exp_resul
mbedtls_free(tmp_buf);
tmp_buf = NULL;
}
/* Test with an output buffer larger/equal than required (expexted to
* succeed). */
for (i = tmp_buf_len; i < (2 * tmp_buf_len); i++) {
TEST_CALLOC(tmp_buf, i);
TEST_ASSERT(mbedtls_ecdsa_raw_to_der(key_bits, input->x, input->len,
tmp_buf, i, &ret_len) == 0);
mbedtls_free(tmp_buf);
tmp_buf = NULL;
}
TEST_CALLOC(tmp_buf, i);
TEST_EQUAL(mbedtls_ecdsa_raw_to_der(key_bits, input->x, input->len,
tmp_buf, i, &ret_len), 0);
exit:
mbedtls_free(tmp_buf);
}