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pkwrite.c: save stack usage for pk_write_key_pem

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mbedtls_pk_write_key_pem would allocate 5679 bytes in writing a DER
encoded RSA private key. To save stack usage significantly, we use
heap memory instead.

Signed-off-by: Yanray Wang <yanray.wang@arm.com>
This commit is contained in:
Yanray Wang 2023-08-11 15:33:07 +08:00
parent 45ad306fbf
commit c84086e55c
1 changed files with 14 additions and 4 deletions
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18
library/pkwrite.c
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@ -786,7 +786,11 @@ int mbedtls_pk_write_pubkey_pem(const mbedtls_pk_context *key, unsigned char *bu
int mbedtls_pk_write_key_pem(const mbedtls_pk_context *key, unsigned char *buf, size_t size)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
unsigned char output_buf[PRV_DER_MAX_BYTES];
unsigned char *output_buf = NULL;
output_buf = calloc(1, PRV_DER_MAX_BYTES);
if (output_buf == NULL) {
return MBEDTLS_ERR_PK_ALLOC_FAILED;
}
const char *begin, *end;
size_t olen = 0;
#if defined(MBEDTLS_PK_HAVE_ECC_KEYS)
@ -799,7 +803,8 @@ int mbedtls_pk_write_key_pem(const mbedtls_pk_context *key, unsigned char *buf,
int is_rsa_opaque = 0;
#endif
if ((ret = mbedtls_pk_write_key_der(key, output_buf, sizeof(output_buf))) < 0) {
if ((ret = mbedtls_pk_write_key_der(key, output_buf, PRV_DER_MAX_BYTES)) < 0) {
free(output_buf);
return ret;
}
@ -843,14 +848,19 @@ int mbedtls_pk_write_key_pem(const mbedtls_pk_context *key, unsigned char *buf,
}
} else
#endif /* MBEDTLS_PK_HAVE_ECC_KEYS */
return MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE;
{
free(output_buf);
return MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE;
}
if ((ret = mbedtls_pem_write_buffer(begin, end,
output_buf + sizeof(output_buf) - ret,
output_buf + PRV_DER_MAX_BYTES - ret,
ret, buf, size, &olen)) != 0) {
free(output_buf);
return ret;
}
free(output_buf);
return 0;
}
#endif /* MBEDTLS_PEM_WRITE_C */