Add key management utilities to p256-m

Those will be needed in order for the driver to implement all the PSA
key management entry points (currently only implements key generation).

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>

3rdparty/p256-m/p256-m/p256-m.c

@@ -1468,4 +1468,49 @@ int p256_ecdsa_verify(const uint8_t sig[64], const uint8_t pub[64],
     return P256_INVALID_SIGNATURE;
 }
 
+/**********************************************************************
+ *
+ * Key management utilities
+ *
+ **********************************************************************/
+
+int p256_validate_pubkey(const uint8_t pub[64])
+{
+    uint32_t x[8], y[8];
+    int ret = point_from_bytes(x, y, pub);
+
+    return ret == 0 ? P256_SUCCESS : P256_INVALID_PUBKEY;
+}
+
+int p256_validate_privkey(const uint8_t priv[32])
+{
+    uint32_t s[8];
+    int ret = scalar_from_bytes(s, priv);
+    zeroize(s, sizeof(s));
+
+    return ret == 0 ? P256_SUCCESS : P256_INVALID_PRIVKEY;
+}
+
+int p256_public_from_private(uint8_t pub[64], const uint8_t priv[32])
+{
+    int ret;
+    uint32_t s[8];
+
+    ret = scalar_from_bytes(s, priv);
+    if (ret != 0)
+        return P256_INVALID_PRIVKEY;
+
+    /* compute and ouput the associated public key */
+    uint32_t x[8], y[8];
+    scalar_mult(x, y, p256_gx, p256_gy, s);
+
+    /* the associated public key is not a secret, the scalar was */
+    CT_UNPOISON(x, 32);
+    CT_UNPOISON(y, 32);
+    zeroize(s, sizeof(s));
+
+    point_to_bytes(pub, x, y);
+    return P256_SUCCESS;
+}
+
 #endif

3rdparty/p256-m/p256-m/p256-m.h

@@ -89,6 +89,45 @@ int p256_ecdsa_sign(uint8_t sig[64], const uint8_t priv[32],
 int p256_ecdsa_verify(const uint8_t sig[64], const uint8_t pub[64],
                       const uint8_t *hash, size_t hlen);
 
+/*
+ * Public key validation
+ *
+ * Note: you never need to call this function, as all other function always
+ * validate their input; however it's availabe if you want to validate the key
+ * without performing an operation.
+ *
+ * [in] pub: the public key, as two big-endian integers
+ *
+ * return:  P256_SUCCESS if the key is valid
+ *          P256_INVALID_PUBKEY if pub is invalid
+ */
+int p256_validate_pubkey(const uint8_t pub[64]);
+
+/*
+ * Private key validation
+ *
+ * Note: you never need to call this function, as all other function always
+ * validate their input; however it's availabe if you want to validate the key
+ * without performing an operation.
+ *
+ * [in] priv: the private key, as a big-endian integer
+ *
+ * return:  P256_SUCCESS if the key is valid
+ *          P256_INVALID_PRIVKEY if priv is invalid
+ */
+int p256_validate_privkey(const uint8_t priv[32]);
+
+/*
+ * Compute public key from private key
+ *
+ * [out] pub: the associated public key, as two big-endian integers
+ * [in] priv: the private key, as a big-endian integer
+ *
+ * return:  P256_SUCCESS on success
+ *          P256_INVALID_PRIVKEY if priv is invalid
+ */
+int p256_public_from_private(uint8_t pub[64], const uint8_t priv[32]);
+
 #ifdef __cplusplus
 }
 #endif