[Minor] Add ability to encrypt data using pubkey only

src/libcryptobox/keypair.c

@@ -978,6 +978,7 @@ rspamd_keypair_decrypt (struct rspamd_cryptobox_keypair *kp,
 
 	return TRUE;
 }
+
 gboolean
 rspamd_keypair_encrypt (struct rspamd_cryptobox_keypair *kp,
 						const guchar *in, gsize inlen,
@@ -1025,5 +1026,54 @@ rspamd_keypair_encrypt (struct rspamd_cryptobox_keypair *kp,
 		*outlen = olen;
 	}
 
+	return TRUE;
+}
+
+gboolean
+rspamd_pubkey_encrypt (struct rspamd_cryptobox_pubkey *pk,
+						const guchar *in, gsize inlen,
+						guchar **out, gsize *outlen,
+						GError **err)
+{
+	guchar *nonce, *mac, *data, *pubkey;
+	struct rspamd_cryptobox_keypair *local;
+	gsize olen;
+
+	g_assert (pk != NULL);
+	g_assert (in != NULL);
+
+	if (pk->type != RSPAMD_KEYPAIR_KEX) {
+		g_set_error (err, rspamd_keypair_quark (), EINVAL,
+				"invalid pubkey type");
+
+		return FALSE;
+	}
+
+	local = rspamd_keypair_new (pk->type, pk->alg);
+
+	olen = inlen + sizeof (encrypted_magic) +
+		   rspamd_cryptobox_pk_bytes (pk->alg) +
+		   rspamd_cryptobox_mac_bytes (pk->alg) +
+		   rspamd_cryptobox_nonce_bytes (pk->alg);
+	*out = g_malloc (olen);
+	memcpy (*out, encrypted_magic, sizeof (encrypted_magic));
+	pubkey = *out + sizeof (encrypted_magic);
+	mac = pubkey + rspamd_cryptobox_pk_bytes (pk->alg);
+	nonce = mac + rspamd_cryptobox_mac_bytes (pk->alg);
+	data = nonce + rspamd_cryptobox_nonce_bytes (pk->alg);
+
+	ottery_rand_bytes (nonce, rspamd_cryptobox_nonce_bytes (pk->alg));
+	memcpy (data, in, inlen);
+	memcpy (pubkey, rspamd_pubkey_get_pk (pk, NULL),
+			rspamd_cryptobox_pk_bytes (pk->alg));
+	rspamd_cryptobox_encrypt_inplace (data, inlen, nonce, pubkey,
+			rspamd_keypair_component (local, RSPAMD_KEYPAIR_COMPONENT_SK, NULL),
+			mac, pk->alg);
+	rspamd_keypair_unref (local);
+
+	if (outlen) {
+		*outlen = olen;
+	}
+
 	return TRUE;
 }

src/libcryptobox/keypair.h

@@ -303,6 +303,21 @@ gboolean rspamd_keypair_encrypt (struct rspamd_cryptobox_keypair *kp,
 								 const guchar *in, gsize inlen,
 								 guchar **out, gsize *outlen,
 								 GError **err);
-
+/**
+ * Encrypts data usign specific pubkey (must have KEX type).
+ * This method actually generates ephemeral local keypair, use public key from
+ * the remote keypair and encrypts data
+ * @param kp keypair
+ * @param in raw input
+ * @param inlen input length
+ * @param out output (allocated internally using g_malloc)
+ * @param outlen output size
+ * @param err pointer to error
+ * @return TRUE if encryption has been completed, out must be freed in this case
+ */
+gboolean rspamd_pubkey_encrypt (struct rspamd_cryptobox_pubkey *pk,
+								 const guchar *in, gsize inlen,
+								 guchar **out, gsize *outlen,
+								 GError **err);
 
 #endif /* SRC_LIBCRYPTOBOX_KEYPAIR_H_ */