Allow importing Montgomery public keys in PSA Crypto
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>
diff --git a/ChangeLog.d/psa_curve25519_public_key_import.txt b/ChangeLog.d/psa_curve25519_public_key_import.txt
new file mode 100644
index 0000000..2ea11e2
--- /dev/null
+++ b/ChangeLog.d/psa_curve25519_public_key_import.txt
@@ -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.
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index 6e9d259..056e677 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -732,19 +732,34 @@
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. */
diff --git a/tests/suites/test_suite_psa_crypto.data b/tests/suites/test_suite_psa_crypto.data
index 6a28591..d1855fd 100644
--- a/tests/suites/test_suite_psa_crypto.data
+++ b/tests/suites/test_suite_psa_crypto.data
@@ -252,6 +252,10 @@
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
diff --git a/tests/suites/test_suite_psa_crypto.function b/tests/suites/test_suite_psa_crypto.function
index 4576b8b..f4b9a8f 100644
--- a/tests/suites/test_suite_psa_crypto.function
+++ b/tests/suites/test_suite_psa_crypto.function
@@ -961,14 +961,23 @@
#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 */