TeamHepta/mbedtls
1
0
Fork 0
mirror of https://github.com/Mbed-TLS/mbedtls.git synced 2026-03-29 16:41:06 +02:00
Code Issues Packages Projects Releases Wiki Activity

Merge pull request #10592 from mpg/pkwrite-large-stack-buffer

Browse Source 
[3.6] PK write: avoid large stack buffer
This commit is contained in:
Valerio Setti
2026-02-11 05:02:04 +00:00
committed by GitHub
parent 25b5fcdcd3 6617ab467f
commit 5334c1dd14
2 changed files with 69 additions and 47 deletions
Download Patch File Download Diff File Expand all files Collapse all files

26
library/pkwrite.c
View File

@@ -64,22 +64,24 @@ static int pk_write_rsa_der(unsigned char **p, unsigned char *buf,
{
#if defined(MBEDTLS_USE_PSA_CRYPTO)
if (mbedtls_pk_get_type(pk) == MBEDTLS_PK_OPAQUE) {
uint8_t tmp[PSA_EXPORT_KEY_PAIR_MAX_SIZE];
size_t tmp_len = 0;
psa_status_t status;
size_t buf_size = (size_t) (*p - buf);
size_t key_len = 0;
if (psa_export_key(pk->priv_id, tmp, sizeof(tmp), &tmp_len) != PSA_SUCCESS) {
return MBEDTLS_ERR_PK_BAD_INPUT_DATA;
}
/* Ensure there's enough space in the provided buffer before copying data into it. */
if (tmp_len > (size_t) (*p - buf)) {
mbedtls_platform_zeroize(tmp, sizeof(tmp));
status = psa_export_key(pk->priv_id, buf, buf_size, &key_len);
if (status == PSA_ERROR_BUFFER_TOO_SMALL) {
return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
} else if (status != PSA_SUCCESS) {
return PSA_PK_RSA_TO_MBEDTLS_ERR(status);
}
*p -= tmp_len;
memcpy(*p, tmp, tmp_len);
mbedtls_platform_zeroize(tmp, sizeof(tmp));
return (int) tmp_len;
/* We wrote to the beginning of the buffer while
* we were supposed to write to its end. */
*p -= key_len;
memmove(*p, buf, key_len);
mbedtls_platform_zeroize(buf, *p - buf);
return (int) key_len;
}
#endif /* MBEDTLS_USE_PSA_CRYPTO */
return mbedtls_rsa_write_key(mbedtls_pk_rsa(*pk), buf, p);

90
tests/suites/test_suite_pkwrite.function
View File

@@ -66,15 +66,59 @@ static int pk_write_any_key(mbedtls_pk_context *pk, unsigned char **p,
return 0;
}
static int pk_write_check_context(mbedtls_pk_context *key,
int is_public_key, int is_der,
unsigned char *check_buf, size_t check_buf_len)
{
int ret = -1;
unsigned char *buf = NULL;
int expected_error = is_der ?
MBEDTLS_ERR_ASN1_BUF_TOO_SMALL :
MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL;
/* Test with:
* - buffer too small (all sizes)
* - buffer exactly the right size
* - buffer a bit larger - DER functions should write to the end of the
* buffer, and we can only tell the difference with a larger buffer
*/
for (size_t buf_size = 1; buf_size <= check_buf_len + 2; buf_size++) {
mbedtls_free(buf);
buf = NULL;
TEST_CALLOC(buf, buf_size);
unsigned char *start_buf = buf;
size_t out_len = buf_size;
int expected_result = buf_size < check_buf_len ? expected_error : 0;
mbedtls_test_set_step(buf_size);
TEST_EQUAL(pk_write_any_key(key, &start_buf, &out_len, is_public_key,
is_der), expected_result);
if (expected_result == 0) {
TEST_MEMORY_COMPARE(start_buf, out_len, check_buf, check_buf_len);
if (is_der) {
/* Data should be at the end of the buffer */
TEST_ASSERT(start_buf + out_len == buf + buf_size);
}
}
}
ret = 0;
exit:
mbedtls_free(buf);
return ret;
}
static void pk_write_check_common(char *key_file, int is_public_key, int is_der)
{
mbedtls_pk_context key;
mbedtls_pk_init(&key);
unsigned char *buf = NULL;
unsigned char *check_buf = NULL;
unsigned char *start_buf;
size_t buf_len, check_buf_len;
int expected_result;
size_t check_buf_len;
#if defined(MBEDTLS_USE_PSA_CRYPTO)
mbedtls_svc_key_id_t opaque_id = MBEDTLS_SVC_KEY_ID_INIT;
psa_key_attributes_t key_attr = PSA_KEY_ATTRIBUTES_INIT;
@@ -100,8 +144,6 @@ static void pk_write_check_common(char *key_file, int is_public_key, int is_der)
}
TEST_ASSERT(check_buf_len > 0);
TEST_CALLOC(buf, check_buf_len);
if (is_public_key) {
TEST_EQUAL(mbedtls_pk_parse_public_keyfile(&key, key_file), 0);
} else {
@@ -109,28 +151,14 @@ static void pk_write_check_common(char *key_file, int is_public_key, int is_der)
mbedtls_test_rnd_std_rand, NULL), 0);
}
start_buf = buf;
buf_len = check_buf_len;
if (is_der) {
expected_result = MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
} else {
expected_result = MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL;
if (pk_write_check_context(&key, is_public_key, is_der,
check_buf, check_buf_len) != 0) {
goto exit;
}
/* Intentionally pass a wrong size for the provided output buffer and check
* that the writing functions fails as expected. */
for (size_t i = 1; i < buf_len; i++) {
TEST_EQUAL(pk_write_any_key(&key, &start_buf, &i, is_public_key,
is_der), expected_result);
}
TEST_EQUAL(pk_write_any_key(&key, &start_buf, &buf_len, is_public_key,
is_der), 0);
TEST_MEMORY_COMPARE(start_buf, buf_len, check_buf, check_buf_len);
#if defined(MBEDTLS_USE_PSA_CRYPTO)
/* Verify that pk_write works also for opaque private keys */
if (!is_public_key) {
memset(buf, 0, check_buf_len);
/* Turn the key PK context into an opaque one.
* Note: set some practical usage for the key to make get_psa_attributes() happy. */
TEST_EQUAL(mbedtls_pk_get_psa_attributes(&key, PSA_KEY_USAGE_SIGN_MESSAGE, &key_attr), 0);
@@ -138,18 +166,11 @@ static void pk_write_check_common(char *key_file, int is_public_key, int is_der)
mbedtls_pk_free(&key);
mbedtls_pk_init(&key);
TEST_EQUAL(mbedtls_pk_setup_opaque(&key, opaque_id), 0);
start_buf = buf;
buf_len = check_buf_len;
/* Intentionally pass a wrong size for the provided output buffer and check
* that the writing functions fails as expected. */
for (size_t i = 1; i < buf_len; i++) {
TEST_EQUAL(pk_write_any_key(&key, &start_buf, &i, is_public_key,
is_der), expected_result);
}
TEST_EQUAL(pk_write_any_key(&key, &start_buf, &buf_len, is_public_key,
is_der), 0);
TEST_MEMORY_COMPARE(start_buf, buf_len, check_buf, check_buf_len);
if (pk_write_check_context(&key, is_public_key, is_der,
check_buf, check_buf_len) != 0) {
goto exit;
}
}
#endif /* MBEDTLS_USE_PSA_CRYPTO */
@@ -157,7 +178,6 @@ exit:
#if defined(MBEDTLS_USE_PSA_CRYPTO)
psa_destroy_key(opaque_id);
#endif /* MBEDTLS_USE_PSA_CRYPTO */
mbedtls_free(buf);
mbedtls_free(check_buf);
mbedtls_pk_free(&key);
USE_PSA_DONE();