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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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25
library/psa_util.c
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@ -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) {