pk: move ECC setters to a separate file
- These functions are used both in pkparse.c for key parsing
as well as pk.c for managing copy_from_psa(). As as consequence
they should belong to pk.c, but that would make that module
messier, so that's why a new separate module is added.
- Their guard can be changed from PKPARSE_C to PK_C.
Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/library/pk_ecc.c b/library/pk_ecc.c
new file mode 100644
index 0000000..a103f46
--- /dev/null
+++ b/library/pk_ecc.c
@@ -0,0 +1,304 @@
+#include "common.h"
+
+#include "mbedtls/pk.h"
+#include "mbedtls/error.h"
+#include "mbedtls/ecp.h"
+#include "pk_internal.h"
+
+/***********************************************************************
+ *
+ * ECC setters
+ *
+ * 1. This is an abstraction layer around MBEDTLS_PK_USE_PSA_EC_DATA:
+ * this macro will not appear outside this section.
+ * 2. All inputs are raw (no metadata).
+ *
+ **********************************************************************/
+
+#if defined(MBEDTLS_PK_C) && defined(MBEDTLS_PK_HAVE_ECC_KEYS)
+
+/*
+ * Set the group used by this key.
+ *
+ * [in/out] pk: in: must have been pk_setup() to an ECC type
+ * out: will have group (curve) information set
+ * [in] grp_in: a supported group ID (not NONE)
+ */
+int mbedtls_pk_ecc_set_group(mbedtls_pk_context *pk, mbedtls_ecp_group_id grp_id)
+{
+#if defined(MBEDTLS_PK_USE_PSA_EC_DATA)
+ size_t ec_bits;
+ psa_ecc_family_t ec_family = mbedtls_ecc_group_to_psa(grp_id, &ec_bits);
+
+ /* group may already be initialized; if so, make sure IDs match */
+ if ((pk->ec_family != 0 && pk->ec_family != ec_family) ||
+ (pk->ec_bits != 0 && pk->ec_bits != ec_bits)) {
+ return MBEDTLS_ERR_PK_KEY_INVALID_FORMAT;
+ }
+
+ /* set group */
+ pk->ec_family = ec_family;
+ pk->ec_bits = ec_bits;
+
+ return 0;
+#else /* MBEDTLS_PK_USE_PSA_EC_DATA */
+ mbedtls_ecp_keypair *ecp = mbedtls_pk_ec_rw(*pk);
+
+ /* grp may already be initialized; if so, make sure IDs match */
+ if (mbedtls_pk_ec_ro(*pk)->grp.id != MBEDTLS_ECP_DP_NONE &&
+ mbedtls_pk_ec_ro(*pk)->grp.id != grp_id) {
+ return MBEDTLS_ERR_PK_KEY_INVALID_FORMAT;
+ }
+
+ /* set group */
+ return mbedtls_ecp_group_load(&(ecp->grp), grp_id);
+#endif /* MBEDTLS_PK_USE_PSA_EC_DATA */
+}
+
+/*
+ * Set the private key material
+ *
+ * [in/out] pk: in: must have the group set already, see mbedtls_pk_ecc_set_group().
+ * out: will have the private key set.
+ * [in] key, key_len: the raw private key (no ASN.1 wrapping).
+ */
+int mbedtls_pk_ecc_set_key(mbedtls_pk_context *pk, unsigned char *key, size_t key_len)
+{
+#if defined(MBEDTLS_PK_USE_PSA_EC_DATA)
+ psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
+ psa_key_usage_t flags;
+ psa_status_t status;
+
+ psa_set_key_type(&attributes, PSA_KEY_TYPE_ECC_KEY_PAIR(pk->ec_family));
+ if (pk->ec_family == PSA_ECC_FAMILY_MONTGOMERY) {
+ /* Do not set algorithm here because Montgomery keys cannot do ECDSA and
+ * the PK module cannot do ECDH. When the key will be used in TLS for
+ * ECDH, it will be exported and then re-imported with proper flags
+ * and algorithm. */
+ flags = PSA_KEY_USAGE_EXPORT;
+ } else {
+ psa_set_key_algorithm(&attributes,
+ MBEDTLS_PK_PSA_ALG_ECDSA_MAYBE_DET(PSA_ALG_ANY_HASH));
+ flags = PSA_KEY_USAGE_SIGN_HASH | PSA_KEY_USAGE_SIGN_MESSAGE |
+ PSA_KEY_USAGE_EXPORT;
+ }
+ psa_set_key_usage_flags(&attributes, flags);
+
+ status = psa_import_key(&attributes, key, key_len, &pk->priv_id);
+ return psa_pk_status_to_mbedtls(status);
+
+#else /* MBEDTLS_PK_USE_PSA_EC_DATA */
+
+ mbedtls_ecp_keypair *eck = mbedtls_pk_ec_rw(*pk);
+ int ret = mbedtls_ecp_read_key(eck->grp.id, eck, key, key_len);
+ if (ret != 0) {
+ return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_PK_KEY_INVALID_FORMAT, ret);
+ }
+ return 0;
+#endif /* MBEDTLS_PK_USE_PSA_EC_DATA */
+}
+
+/*
+ * Derive a public key from its private counterpart.
+ * Computationally intensive, only use when public key is not available.
+ *
+ * [in/out] pk: in: must have the private key set, see mbedtls_pk_ecc_set_key().
+ * out: will have the public key set.
+ * [in] prv, prv_len: the raw private key (see note below).
+ * [in] f_rng, p_rng: RNG function and context.
+ *
+ * Note: the private key information is always available from pk,
+ * however for convenience the serialized version is also passed,
+ * as it's available at each calling site, and useful in some configs
+ * (as otherwise we would have to re-serialize it from the pk context).
+ *
+ * There are three implementations of this function:
+ * 1. MBEDTLS_PK_USE_PSA_EC_DATA,
+ * 2. MBEDTLS_USE_PSA_CRYPTO but not MBEDTLS_PK_USE_PSA_EC_DATA,
+ * 3. not MBEDTLS_USE_PSA_CRYPTO.
+ */
+int mbedtls_pk_ecc_set_pubkey_from_prv(mbedtls_pk_context *pk,
+ const unsigned char *prv, size_t prv_len,
+ int (*f_rng)(void *, unsigned char *, size_t), void *p_rng)
+{
+#if defined(MBEDTLS_PK_USE_PSA_EC_DATA)
+
+ (void) f_rng;
+ (void) p_rng;
+ (void) prv;
+ (void) prv_len;
+ psa_status_t status;
+
+ status = psa_export_public_key(pk->priv_id, pk->pub_raw, sizeof(pk->pub_raw),
+ &pk->pub_raw_len);
+ return psa_pk_status_to_mbedtls(status);
+
+#elif defined(MBEDTLS_USE_PSA_CRYPTO) /* && !MBEDTLS_PK_USE_PSA_EC_DATA */
+
+ (void) f_rng;
+ (void) p_rng;
+ psa_status_t status;
+
+ mbedtls_ecp_keypair *eck = (mbedtls_ecp_keypair *) pk->pk_ctx;
+ size_t curve_bits;
+ psa_ecc_family_t curve = mbedtls_ecc_group_to_psa(eck->grp.id, &curve_bits);
+
+ /* Import private key into PSA, from serialized input */
+ mbedtls_svc_key_id_t key_id = MBEDTLS_SVC_KEY_ID_INIT;
+ psa_key_attributes_t key_attr = PSA_KEY_ATTRIBUTES_INIT;
+ psa_set_key_type(&key_attr, PSA_KEY_TYPE_ECC_KEY_PAIR(curve));
+ psa_set_key_usage_flags(&key_attr, PSA_KEY_USAGE_EXPORT);
+ status = psa_import_key(&key_attr, prv, prv_len, &key_id);
+ if (status != PSA_SUCCESS) {
+ return psa_pk_status_to_mbedtls(status);
+ }
+
+ /* Export public key from PSA */
+ unsigned char pub[MBEDTLS_PSA_MAX_EC_PUBKEY_LENGTH];
+ size_t pub_len;
+ status = psa_export_public_key(key_id, pub, sizeof(pub), &pub_len);
+ psa_status_t destruction_status = psa_destroy_key(key_id);
+ if (status != PSA_SUCCESS) {
+ return psa_pk_status_to_mbedtls(status);
+ } else if (destruction_status != PSA_SUCCESS) {
+ return psa_pk_status_to_mbedtls(destruction_status);
+ }
+
+ /* Load serialized public key into ecp_keypair structure */
+ return mbedtls_ecp_point_read_binary(&eck->grp, &eck->Q, pub, pub_len);
+
+#else /* MBEDTLS_USE_PSA_CRYPTO */
+
+ (void) prv;
+ (void) prv_len;
+
+ mbedtls_ecp_keypair *eck = (mbedtls_ecp_keypair *) pk->pk_ctx;
+ return mbedtls_ecp_mul(&eck->grp, &eck->Q, &eck->d, &eck->grp.G, f_rng, p_rng);
+
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
+}
+
+#if defined(MBEDTLS_PK_USE_PSA_EC_DATA)
+/*
+ * Set the public key: fallback using ECP_LIGHT in the USE_PSA_EC_DATA case.
+ *
+ * Normally, when MBEDTLS_PK_USE_PSA_EC_DATA is enabled, we only use PSA
+ * functions to handle keys. However, currently psa_import_key() does not
+ * support compressed points. In case that support was explicitly requested,
+ * this fallback uses ECP functions to get the job done. This is the reason
+ * why MBEDTLS_PK_PARSE_EC_COMPRESSED auto-enables MBEDTLS_ECP_LIGHT.
+ *
+ * [in/out] pk: in: must have the group set, see mbedtls_pk_ecc_set_group().
+ * out: will have the public key set.
+ * [in] pub, pub_len: the public key as an ECPoint,
+ * in any format supported by ECP.
+ *
+ * Return:
+ * - 0 on success;
+ * - MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE if the format is potentially valid
+ * but not supported;
+ * - another error code otherwise.
+ */
+static int pk_ecc_set_pubkey_psa_ecp_fallback(mbedtls_pk_context *pk,
+ const unsigned char *pub,
+ size_t pub_len)
+{
+#if !defined(MBEDTLS_PK_PARSE_EC_COMPRESSED)
+ (void) pk;
+ (void) pub;
+ (void) pub_len;
+ return MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE;
+#else /* MBEDTLS_PK_PARSE_EC_COMPRESSED */
+ mbedtls_ecp_keypair ecp_key;
+ mbedtls_ecp_group_id ecp_group_id;
+ int ret;
+
+ ecp_group_id = mbedtls_ecc_group_from_psa(pk->ec_family, pk->ec_bits);
+
+ mbedtls_ecp_keypair_init(&ecp_key);
+ ret = mbedtls_ecp_group_load(&(ecp_key.grp), ecp_group_id);
+ if (ret != 0) {
+ goto exit;
+ }
+ ret = mbedtls_ecp_point_read_binary(&(ecp_key.grp), &ecp_key.Q,
+ pub, pub_len);
+ if (ret != 0) {
+ goto exit;
+ }
+ ret = mbedtls_ecp_point_write_binary(&(ecp_key.grp), &ecp_key.Q,
+ MBEDTLS_ECP_PF_UNCOMPRESSED,
+ &pk->pub_raw_len, pk->pub_raw,
+ sizeof(pk->pub_raw));
+
+exit:
+ mbedtls_ecp_keypair_free(&ecp_key);
+ return ret;
+#endif /* MBEDTLS_PK_PARSE_EC_COMPRESSED */
+}
+#endif /* MBEDTLS_PK_USE_PSA_EC_DATA */
+
+/*
+ * Set the public key.
+ *
+ * [in/out] pk: in: must have its group set, see mbedtls_pk_ecc_set_group().
+ * out: will have the public key set.
+ * [in] pub, pub_len: the raw public key (an ECPoint).
+ *
+ * Return:
+ * - 0 on success;
+ * - MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE if the format is potentially valid
+ * but not supported;
+ * - another error code otherwise.
+ */
+int mbedtls_pk_ecc_set_pubkey(mbedtls_pk_context *pk, const unsigned char *pub, size_t pub_len)
+{
+#if defined(MBEDTLS_PK_USE_PSA_EC_DATA)
+
+ /* Load the key */
+ if (!PSA_ECC_FAMILY_IS_WEIERSTRASS(pk->ec_family) || *pub == 0x04) {
+ /* Format directly supported by PSA:
+ * - non-Weierstrass curves that only have one format;
+ * - uncompressed format for Weierstrass curves. */
+ if (pub_len > sizeof(pk->pub_raw)) {
+ return MBEDTLS_ERR_PK_BUFFER_TOO_SMALL;
+ }
+ memcpy(pk->pub_raw, pub, pub_len);
+ pk->pub_raw_len = pub_len;
+ } else {
+ /* Other format, try the fallback */
+ int ret = pk_ecc_set_pubkey_psa_ecp_fallback(pk, pub, pub_len);
+ if (ret != 0) {
+ return ret;
+ }
+ }
+
+ /* Validate the key by trying to import it */
+ mbedtls_svc_key_id_t key_id = MBEDTLS_SVC_KEY_ID_INIT;
+ psa_key_attributes_t key_attrs = PSA_KEY_ATTRIBUTES_INIT;
+
+ psa_set_key_usage_flags(&key_attrs, 0);
+ psa_set_key_type(&key_attrs, PSA_KEY_TYPE_ECC_PUBLIC_KEY(pk->ec_family));
+ psa_set_key_bits(&key_attrs, pk->ec_bits);
+
+ if ((psa_import_key(&key_attrs, pk->pub_raw, pk->pub_raw_len,
+ &key_id) != PSA_SUCCESS) ||
+ (psa_destroy_key(key_id) != PSA_SUCCESS)) {
+ return MBEDTLS_ERR_PK_INVALID_PUBKEY;
+ }
+
+ return 0;
+
+#else /* MBEDTLS_PK_USE_PSA_EC_DATA */
+
+ int ret;
+ mbedtls_ecp_keypair *ec_key = (mbedtls_ecp_keypair *) pk->pk_ctx;
+ ret = mbedtls_ecp_point_read_binary(&ec_key->grp, &ec_key->Q, pub, pub_len);
+ if (ret != 0) {
+ return ret;
+ }
+ return mbedtls_ecp_check_pubkey(&ec_key->grp, &ec_key->Q);
+
+#endif /* MBEDTLS_PK_USE_PSA_EC_DATA */
+}
+
+#endif /* MBEDTLS_PK_C && MBEDTLS_PK_HAVE_ECC_KEYS */