New function mbedtls_pk_copy_public_from_psa
Document and implement mbedtls_pk_copy_public_from_psa() to export the
public key of a PSA key into PK.
Unit-test it alongside mbedtls_pk_copy_from_psa().
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/ChangeLog.d/8709.txt b/ChangeLog.d/8709.txt
index a9b2751..e0bea44 100644
--- a/ChangeLog.d/8709.txt
+++ b/ChangeLog.d/8709.txt
@@ -1,3 +1,4 @@
Features
- * The new function mbedtls_pk_copy_from_psa() provides a way to set up a PK
- context with the same content as a PSA key.
+ * The new functions mbedtls_pk_copy_from_psa() and
+ mbedtls_pk_copy_public_from_psa() provide ways to set up a PK context
+ with the same content as a PSA key.
diff --git a/include/mbedtls/pk.h b/include/mbedtls/pk.h
index c1fb605..d2e8674 100644
--- a/include/mbedtls/pk.h
+++ b/include/mbedtls/pk.h
@@ -426,6 +426,39 @@
* parameters are not correct.
*/
int mbedtls_pk_copy_from_psa(mbedtls_svc_key_id_t key_id, mbedtls_pk_context *pk);
+
+/**
+ * \brief Create a PK context for the public key of a PSA key.
+ *
+ * The key must be an RSA or ECC key. It can be either a
+ * public key or a key pair, and only the public key is copied.
+ * The resulting PK object will be a transparent type:
+ * - #MBEDTLS_PK_RSA for RSA keys or
+ * - #MBEDTLS_PK_ECKEY for EC keys.
+ *
+ * Once this functions returns the PK object will be completely
+ * independent from the original PSA key that it was generated
+ * from.
+ * Calling mbedtls_pk_verify() or
+ * mbedtls_pk_encrypt() on the resulting
+ * PK context will perform the corresponding algorithm for that
+ * PK context type.
+ *
+ * For an RSA key, the output PK context will allow both
+ * encrypt and verify regardless of the original key's policy.
+ * The original key's policy determines the output key's padding
+ * mode: PCKS1 v2.1 is set if the PSA key policy is OAEP or PSS,
+ * otherwise PKCS1 v1.5 is set.
+ *
+ * \param key_id The key identifier of the key stored in PSA.
+ * \param pk The PK context that will be filled. It must be initialized,
+ * but not set up.
+ *
+ * \return 0 on success.
+ * \return MBEDTLS_ERR_PK_BAD_INPUT_DATA in case the provided input
+ * parameters are not correct.
+ */
+int mbedtls_pk_copy_public_from_psa(mbedtls_svc_key_id_t key_id, mbedtls_pk_context *pk);
#endif /* MBEDTLS_PSA_CRYPTO_C */
#if defined(MBEDTLS_PK_RSA_ALT_SUPPORT)
diff --git a/library/pk.c b/library/pk.c
index 4345ea2..7bc1da8 100644
--- a/library/pk.c
+++ b/library/pk.c
@@ -1379,7 +1379,9 @@
}
#if defined(MBEDTLS_PSA_CRYPTO_C)
-int mbedtls_pk_copy_from_psa(mbedtls_svc_key_id_t key_id, mbedtls_pk_context *pk)
+static int copy_from_psa(mbedtls_svc_key_id_t key_id,
+ mbedtls_pk_context *pk,
+ int public_only)
{
psa_status_t status;
psa_key_attributes_t key_attr = PSA_KEY_ATTRIBUTES_INIT;
@@ -1400,13 +1402,20 @@
return MBEDTLS_ERR_PK_BAD_INPUT_DATA;
}
- status = psa_export_key(key_id, exp_key, sizeof(exp_key), &exp_key_len);
+ if (public_only) {
+ status = psa_export_public_key(key_id, exp_key, sizeof(exp_key), &exp_key_len);
+ } else {
+ status = psa_export_key(key_id, exp_key, sizeof(exp_key), &exp_key_len);
+ }
if (status != PSA_SUCCESS) {
ret = PSA_PK_TO_MBEDTLS_ERR(status);
goto exit;
}
key_type = psa_get_key_type(&key_attr);
+ if (public_only) {
+ key_type = PSA_KEY_TYPE_PUBLIC_KEY_OF_KEY_PAIR(key_type);
+ }
key_bits = psa_get_key_bits(&key_attr);
alg_type = psa_get_key_algorithm(&key_attr);
@@ -1485,6 +1494,19 @@
return ret;
}
+
+
+int mbedtls_pk_copy_from_psa(mbedtls_svc_key_id_t key_id,
+ mbedtls_pk_context *pk)
+{
+ return copy_from_psa(key_id, pk, 0);
+}
+
+int mbedtls_pk_copy_public_from_psa(mbedtls_svc_key_id_t key_id,
+ mbedtls_pk_context *pk)
+{
+ return copy_from_psa(key_id, pk, 1);
+}
#endif /* MBEDTLS_PSA_CRYPTO_C */
#endif /* MBEDTLS_PK_C */
diff --git a/tests/suites/test_suite_pk.function b/tests/suites/test_suite_pk.function
index 75dc4ac..d955ab6 100644
--- a/tests/suites/test_suite_pk.function
+++ b/tests/suites/test_suite_pk.function
@@ -322,6 +322,83 @@
expected_usage |= PSA_KEY_USAGE_EXPORT | PSA_KEY_USAGE_COPY;
return expected_usage;
}
+
+#define RSA_WRITE_PUBKEY_MAX_SIZE \
+ PSA_KEY_EXPORT_RSA_PUBLIC_KEY_MAX_SIZE(PSA_VENDOR_RSA_MAX_KEY_BITS)
+#define ECP_WRITE_PUBKEY_MAX_SIZE \
+ PSA_KEY_EXPORT_ECC_PUBLIC_KEY_MAX_SIZE(PSA_VENDOR_ECC_MAX_CURVE_BITS)
+static int pk_public_same(const mbedtls_pk_context *pk1,
+ const mbedtls_pk_context *pk2)
+{
+ int ok = 0;
+
+ mbedtls_pk_type_t type = mbedtls_pk_get_type(pk1);
+ TEST_EQUAL(type, mbedtls_pk_get_type(pk2));
+
+ switch (type) {
+#if defined(MBEDTLS_RSA_C)
+ case MBEDTLS_PK_RSA:
+ {
+ const mbedtls_rsa_context *rsa1 = mbedtls_pk_rsa(*pk1);
+ const mbedtls_rsa_context *rsa2 = mbedtls_pk_rsa(*pk2);
+ TEST_EQUAL(mbedtls_rsa_get_padding_mode(rsa1),
+ mbedtls_rsa_get_padding_mode(rsa2));
+ TEST_EQUAL(mbedtls_rsa_get_md_alg(rsa1),
+ mbedtls_rsa_get_md_alg(rsa2));
+ unsigned char buf1[RSA_WRITE_PUBKEY_MAX_SIZE];
+ unsigned char *p1 = buf1 + sizeof(buf1);
+ int len1 = mbedtls_rsa_write_pubkey(rsa1, buf1, &p1);
+ TEST_LE_U(0, len1);
+ unsigned char buf2[RSA_WRITE_PUBKEY_MAX_SIZE];
+ unsigned char *p2 = buf2 + sizeof(buf2);
+ int len2 = mbedtls_rsa_write_pubkey(rsa2, buf2, &p2);
+ TEST_LE_U(0, len2);
+ TEST_MEMORY_COMPARE(p1, len1, p2, len2);
+ break;
+ }
+#endif /* MBEDTLS_RSA_C */
+
+#if defined(MBEDTLS_PK_HAVE_ECC_KEYS)
+ case MBEDTLS_PK_ECKEY:
+ case MBEDTLS_PK_ECKEY_DH:
+ case MBEDTLS_PK_ECDSA:
+ {
+#if defined(MBEDTLS_PK_USE_PSA_EC_DATA)
+ TEST_MEMORY_COMPARE(pk1->pub_raw, pk1->pub_raw_len,
+ pk2->pub_raw, pk2->pub_raw_len);
+ TEST_EQUAL(pk1->ec_family, pk2->ec_family);
+ TEST_EQUAL(pk1->ec_bits, pk2->ec_bits);
+
+#else /* MBEDTLS_PK_USE_PSA_EC_DATA */
+ const mbedtls_ecp_keypair *ec1 = mbedtls_pk_ec_ro(*pk1);
+ const mbedtls_ecp_keypair *ec2 = mbedtls_pk_ec_ro(*pk2);
+ TEST_EQUAL(mbedtls_ecp_keypair_get_group_id(ec1),
+ mbedtls_ecp_keypair_get_group_id(ec2));
+ unsigned char buf1[ECP_WRITE_PUBKEY_MAX_SIZE];
+ size_t len1 = 99999991;
+ TEST_EQUAL(mbedtls_ecp_write_public_key(
+ ec1, MBEDTLS_ECP_PF_UNCOMPRESSED,
+ &len1, buf1, sizeof(buf1)), 0);
+ unsigned char buf2[ECP_WRITE_PUBKEY_MAX_SIZE];
+ size_t len2 = 99999992;
+ TEST_EQUAL(mbedtls_ecp_write_public_key(
+ ec2, MBEDTLS_ECP_PF_UNCOMPRESSED,
+ &len2, buf2, sizeof(buf2)), 0);
+ TEST_MEMORY_COMPARE(buf1, len1, buf2, len2);
+#endif /* MBEDTLS_PK_USE_PSA_EC_DATA */
+ }
+ break;
+#endif /* MBEDTLS_PK_HAVE_ECC_KEYS */
+
+ default:
+ TEST_FAIL("Unsupported pk type in pk_public_same");
+ }
+
+ ok = 1;
+
+exit:
+ return ok;
+}
#endif /* MBEDTLS_PSA_CRYPTO_C */
#if defined(MBEDTLS_RSA_C)
@@ -2322,16 +2399,21 @@
/* Null pk pointer. */
TEST_EQUAL(mbedtls_pk_copy_from_psa(key_id, NULL),
MBEDTLS_ERR_PK_BAD_INPUT_DATA);
+ TEST_EQUAL(mbedtls_pk_copy_public_from_psa(key_id, NULL),
+ MBEDTLS_ERR_PK_BAD_INPUT_DATA);
/* Invalid key ID. */
TEST_EQUAL(mbedtls_pk_copy_from_psa(mbedtls_svc_key_id_make(0, 0), &pk_ctx),
MBEDTLS_ERR_PK_BAD_INPUT_DATA);
+ TEST_EQUAL(mbedtls_pk_copy_public_from_psa(mbedtls_svc_key_id_make(0, 0), &pk_ctx),
+ MBEDTLS_ERR_PK_BAD_INPUT_DATA);
#if defined(PSA_WANT_KEY_TYPE_DH_KEY_PAIR_GENERATE)
/* Generate a key type that is not handled by the PK module. */
PSA_ASSERT(pk_psa_genkey_generic(PSA_KEY_TYPE_DH_KEY_PAIR(PSA_DH_FAMILY_RFC7919), 2048,
PSA_KEY_USAGE_EXPORT, PSA_ALG_NONE, &key_id));
TEST_EQUAL(mbedtls_pk_copy_from_psa(key_id, &pk_ctx), MBEDTLS_ERR_PK_BAD_INPUT_DATA);
+ TEST_EQUAL(mbedtls_pk_copy_public_from_psa(key_id, &pk_ctx), MBEDTLS_ERR_PK_BAD_INPUT_DATA);
psa_destroy_key(key_id);
#endif /* PSA_WANT_KEY_TYPE_DH_KEY_PAIR_GENERATE */
@@ -2382,7 +2464,7 @@
psa_algorithm_t key_alg = key_alg_arg;
psa_key_usage_t key_usage = PSA_KEY_USAGE_SIGN_HASH | PSA_KEY_USAGE_VERIFY_HASH |
PSA_KEY_USAGE_EXPORT | PSA_KEY_USAGE_COPY;
- mbedtls_pk_context pk_priv, pk_pub;
+ mbedtls_pk_context pk_priv, pk_priv_copy_public, pk_pub, pk_pub_copy_public;
mbedtls_svc_key_id_t priv_key_id = MBEDTLS_SVC_KEY_ID_INIT;
mbedtls_svc_key_id_t pub_key_id = MBEDTLS_SVC_KEY_ID_INIT;
unsigned char *in_buf = NULL;
@@ -2392,7 +2474,9 @@
size_t out_buf_len, out_buf2_len;
mbedtls_pk_init(&pk_priv);
+ mbedtls_pk_init(&pk_priv_copy_public);
mbedtls_pk_init(&pk_pub);
+ mbedtls_pk_init(&pk_pub_copy_public);
PSA_INIT();
if (key_type == PSA_KEY_TYPE_RSA_KEY_PAIR) {
@@ -2404,9 +2488,11 @@
key_type, key_usage, key_alg, &priv_key_id));
pub_key_id = psa_pub_key_from_priv(priv_key_id);
- /* Create 2 PK contexts starting from the PSA keys we just created. */
+ /* Create 4 PK contexts starting from the PSA keys we just created. */
TEST_EQUAL(mbedtls_pk_copy_from_psa(priv_key_id, &pk_priv), 0);
+ TEST_EQUAL(mbedtls_pk_copy_public_from_psa(pub_key_id, &pk_priv_copy_public), 0);
TEST_EQUAL(mbedtls_pk_copy_from_psa(pub_key_id, &pk_pub), 0);
+ TEST_EQUAL(mbedtls_pk_copy_public_from_psa(pub_key_id, &pk_pub_copy_public), 0);
/* Destoy both PSA keys to prove that generated PK contexts are independent
* from them. */
@@ -2534,10 +2620,19 @@
}
}
+ /* Test that the keys from mbedtls_pk_copy_public_from_psa() are identical
+ * to the public key from mbedtls_pk_copy_from_psa(). */
+ mbedtls_test_set_step(1);
+ TEST_ASSERT(pk_public_same(&pk_pub, &pk_priv_copy_public));
+ mbedtls_test_set_step(2);
+ TEST_ASSERT(pk_public_same(&pk_pub, &pk_pub_copy_public));
+
exit:
mbedtls_free(in_buf);
mbedtls_pk_free(&pk_priv);
+ mbedtls_pk_free(&pk_priv_copy_public);
mbedtls_pk_free(&pk_pub);
+ mbedtls_pk_free(&pk_pub_copy_public);
psa_destroy_key(priv_key_id);
psa_destroy_key(pub_key_id);
PSA_DONE();