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Allow importing Montgomery public keys in PSA Crypto

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PSA Crypto was checking the byte length of a to-be-imported public ECP key
against the expected length for Weierstrass keys, forgetting that
Curve25519/Curve448 exists.

Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
This commit is contained in:
Steven Cooreman 2020-07-30 15:04:07 +02:00
parent 7f39187d6b
commit 3fa684ed91
4 changed files with 49 additions and 18 deletions
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3
ChangeLog.d/psa_curve25519_public_key_import.txt Normal file
View file

@ -0,0 +1,3 @@
Bugfix
* PSA key import will now correctly import a Curve25519/Curve448 public key
instead of erroring out. Contributed by Steven Cooreman in #3492.

35
library/psa_crypto.c
View file

@ -732,19 +732,34 @@ static psa_status_t psa_load_ecp_representation( const uint8_t *buffer,
mbedtls_ecp_group_id grp_id = MBEDTLS_ECP_DP_NONE;
psa_status_t status;
mbedtls_ecp_keypair *ecp = NULL;
size_t curve_size = size;
size_t curve_size;
if( PSA_KEY_TYPE_IS_PUBLIC_KEY( type ) )
{
/* A public key is represented as:
* - The byte 0x04;
* - `x_P` as a `ceiling(m/8)`-byte string, big-endian;
* - `y_P` as a `ceiling(m/8)`-byte string, big-endian.
* So its data length is 2m+1 where n is the key size in bits.
*/
if( ( size & 1 ) == 0 )
return( PSA_ERROR_INVALID_ARGUMENT );
curve_size = size / 2;
if( PSA_KEY_TYPE_ECC_GET_FAMILY( type ) == PSA_ECC_FAMILY_MONTGOMERY )
{
/* A Montgomery public key is represented as its raw
* compressed public point.
*/
curve_size = size;
}
else
{
/* A Weierstrass public key is represented as:
* - The byte 0x04;
* - `x_P` as a `ceiling(m/8)`-byte string, big-endian;
* - `y_P` as a `ceiling(m/8)`-byte string, big-endian.
* So its data length is 2m+1 where n is the key size in bits.
*/
if( ( size & 1 ) == 0 )
return( PSA_ERROR_INVALID_ARGUMENT );
curve_size = size / 2;
}
}
else
{
/* Private keys are represented as the raw private value */
curve_size = size;
}
/* Allocate and initialize a key representation. */

4
tests/suites/test_suite_psa_crypto.data
View file

@ -252,6 +252,10 @@ PSA import/export EC brainpoolP256r1 public key: good
depends_on:MBEDTLS_PK_PARSE_C:MBEDTLS_PK_WRITE_C:MBEDTLS_ECP_C:MBEDTLS_ECP_DP_BP256R1_ENABLED
import_export:"04768c8cae4abca6306db0ed81b0c4a6215c378066ec6d616c146e13f1c7df809b96ab6911c27d8a02339f0926840e55236d3d1efbe2669d090e4c4c660fada91d":PSA_KEY_TYPE_ECC_PUBLIC_KEY(PSA_ECC_FAMILY_BRAINPOOL_P_R1):PSA_KEY_USAGE_EXPORT:PSA_ALG_ECDSA_ANY:256:0:PSA_SUCCESS:1
PSA import/export curve25519 public key: good
depends_on:MBEDTLS_PK_PARSE_C:MBEDTLS_PK_WRITE_C:MBEDTLS_ECP_C:MBEDTLS_ECP_DP_CURVE25519_ENABLED
import_export:"8520f0098930a754748b7ddcb43ef75a0dbf3a0d26381af4eba4a98eaa9b4e6a":PSA_KEY_TYPE_ECC_PUBLIC_KEY(PSA_ECC_FAMILY_MONTGOMERY):PSA_KEY_USAGE_EXPORT:PSA_ALG_ECDH:255:0:PSA_SUCCESS:1
PSA import/export AES key: policy forbids export
depends_on:MBEDTLS_AES_C:MBEDTLS_CIPHER_MODE_CTR
import_export:"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa":PSA_KEY_TYPE_AES:PSA_KEY_USAGE_ENCRYPT | PSA_KEY_USAGE_DECRYPT:PSA_ALG_CTR:128:0:PSA_ERROR_NOT_PERMITTED:1

25
tests/suites/test_suite_psa_crypto.function
View file

@ -961,14 +961,23 @@ static int exported_key_sanity_check( psa_key_type_t type, size_t bits,
#if defined(MBEDTLS_ECP_C)
if( PSA_KEY_TYPE_IS_ECC_PUBLIC_KEY( type ) )
{
/* The representation of an ECC public key is:
* - The byte 0x04;
* - `x_P` as a `ceiling(m/8)`-byte string, big-endian;
* - `y_P` as a `ceiling(m/8)`-byte string, big-endian;
* - where m is the bit size associated with the curve.
*/
TEST_EQUAL( p + 1 + 2 * PSA_BITS_TO_BYTES( bits ), end );
TEST_EQUAL( p[0], 4 );
if( PSA_KEY_TYPE_ECC_GET_FAMILY( type ) == PSA_ECC_FAMILY_MONTGOMERY )
{
/* The representation of an ECC Montgomery public key is
* the raw compressed point */
TEST_EQUAL( p + PSA_BITS_TO_BYTES( bits ), end );
}
else
{
/* The representation of an ECC Weierstrass public key is:
* - The byte 0x04;
* - `x_P` as a `ceiling(m/8)`-byte string, big-endian;
* - `y_P` as a `ceiling(m/8)`-byte string, big-endian;
* - where m is the bit size associated with the curve.
*/
TEST_EQUAL( p + 1 + 2 * PSA_BITS_TO_BYTES( bits ), end );
TEST_EQUAL( p[0], 4 );
}
}
else
#endif /* MBEDTLS_ECP_C */