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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 217416a76e
commit 7bbca1363f
1 changed files with 14 additions and 4 deletions
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18
library/pkwrite.c
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@ -601,14 +601,19 @@ int mbedtls_pk_write_pubkey_pem(mbedtls_pk_context *key, unsigned char *buf, siz
int mbedtls_pk_write_key_pem(mbedtls_pk_context *key, unsigned char *buf, size_t size) int mbedtls_pk_write_key_pem(mbedtls_pk_context *key, unsigned char *buf, size_t size)
{ {
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; 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; const char *begin, *end;
size_t olen = 0; size_t olen = 0;
PK_VALIDATE_RET(key != NULL); PK_VALIDATE_RET(key != NULL);
PK_VALIDATE_RET(buf != NULL || size == 0); PK_VALIDATE_RET(buf != NULL || size == 0);
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; return ret;
} }
@ -624,14 +629,19 @@ int mbedtls_pk_write_key_pem(mbedtls_pk_context *key, unsigned char *buf, size_t
end = PEM_END_PRIVATE_KEY_EC; end = PEM_END_PRIVATE_KEY_EC;
} else } else
#endif #endif
return MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE; {
free(output_buf);
return MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE;
}
if ((ret = mbedtls_pem_write_buffer(begin, end, 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) { ret, buf, size, &olen)) != 0) {
free(output_buf);
return ret; return ret;
} }
free(output_buf);
return 0; return 0;
} }
#endif /* MBEDTLS_PEM_WRITE_C */ #endif /* MBEDTLS_PEM_WRITE_C */