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Merge pull request #8062 from yanrayw/save_stack_usage_pkwrite

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pkwrite: use heap to save stack usage for writing keys in PEM string
This commit is contained in:
Bence Szépkúti 2023-10-13 14:27:13 +00:00 committed by GitHub
commit 195411bb17
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GPG key ID: 4AEE18F83AFDEB23
2 changed files with 37 additions and 16 deletions
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4
ChangeLog.d/pkwrite-pem-use-heap.txt Normal file
View file

@ -0,0 +1,4 @@
Changes
* Use heap memory to allocate DER encoded public/private key.
This reduces stack usage significantly for writing a public/private
key to a PEM string.

49
library/pkwrite.c
View file

@ -756,27 +756,38 @@ int mbedtls_pk_write_key_der(const mbedtls_pk_context *key, unsigned char *buf,
int mbedtls_pk_write_pubkey_pem(const mbedtls_pk_context *key, unsigned char *buf, size_t size) int mbedtls_pk_write_pubkey_pem(const 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[PUB_DER_MAX_BYTES]; unsigned char *output_buf = NULL;
output_buf = mbedtls_calloc(1, PUB_DER_MAX_BYTES);
if (output_buf == NULL) {
return MBEDTLS_ERR_PK_ALLOC_FAILED;
}
size_t olen = 0; size_t olen = 0;
if ((ret = mbedtls_pk_write_pubkey_der(key, output_buf, if ((ret = mbedtls_pk_write_pubkey_der(key, output_buf,
sizeof(output_buf))) < 0) { PUB_DER_MAX_BYTES)) < 0) {
return ret; goto cleanup;
} }
if ((ret = mbedtls_pem_write_buffer(PEM_BEGIN_PUBLIC_KEY, PEM_END_PUBLIC_KEY, if ((ret = mbedtls_pem_write_buffer(PEM_BEGIN_PUBLIC_KEY, PEM_END_PUBLIC_KEY,
output_buf + sizeof(output_buf) - ret, output_buf + PUB_DER_MAX_BYTES - ret,
ret, buf, size, &olen)) != 0) { ret, buf, size, &olen)) != 0) {
return ret; goto cleanup;
} }
return 0; ret = 0;
cleanup:
mbedtls_free(output_buf);
return ret;
} }
int mbedtls_pk_write_key_pem(const mbedtls_pk_context *key, unsigned char *buf, size_t size) int mbedtls_pk_write_key_pem(const 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 = mbedtls_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;
#if defined(MBEDTLS_PK_HAVE_ECC_KEYS) #if defined(MBEDTLS_PK_HAVE_ECC_KEYS)
@ -789,8 +800,8 @@ int mbedtls_pk_write_key_pem(const mbedtls_pk_context *key, unsigned char *buf,
int is_rsa_opaque = 0; int is_rsa_opaque = 0;
#endif #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) {
return ret; goto cleanup;
} }
#if defined(MBEDTLS_USE_PSA_CRYPTO) #if defined(MBEDTLS_USE_PSA_CRYPTO)
@ -833,15 +844,21 @@ int mbedtls_pk_write_key_pem(const mbedtls_pk_context *key, unsigned char *buf,
} }
} else } else
#endif /* MBEDTLS_PK_HAVE_ECC_KEYS */ #endif /* MBEDTLS_PK_HAVE_ECC_KEYS */
return MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE; {
ret = MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE;
if ((ret = mbedtls_pem_write_buffer(begin, end, goto cleanup;
output_buf + sizeof(output_buf) - ret,
ret, buf, size, &olen)) != 0) {
return ret;
} }
return 0; if ((ret = mbedtls_pem_write_buffer(begin, end,
output_buf + PRV_DER_MAX_BYTES - ret,
ret, buf, size, &olen)) != 0) {
goto cleanup;
}
ret = 0;
cleanup:
mbedtls_zeroize_and_free(output_buf, PRV_DER_MAX_BYTES);
return ret;
} }
#endif /* MBEDTLS_PEM_WRITE_C */ #endif /* MBEDTLS_PEM_WRITE_C */