1 files changed, 333 insertions, 0 deletions
diff --git a/src/common/scram.c b/src/common/scram.c
new file mode 100644
index 00000000..b39199de
--- /dev/null
+++ b/src/common/scram.c
@@ -0,0 +1,333 @@
+/* HexChat
+ * Copyright (C) 2023 Patrick Okraku
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
+ */
+
+#include "hexchat.h"
+
+#ifdef USE_OPENSSL
+
+#include "scram.h"
+#include <openssl/hmac.h>
+#include <openssl/rand.h>
+
+#define NONCE_LENGTH 18
+#define CLIENT_KEY "Client Key"
+#define SERVER_KEY "Server Key"
+
+// EVP_MD_CTX_create() and EVP_MD_CTX_destroy() were renamed in OpenSSL 1.1.0
+#if (OPENSSL_VERSION_NUMBER < 0x10100000L)
+#define EVP_MD_CTX_new(ctx) EVP_MD_CTX_create(ctx)
+#define EVP_MD_CTX_free(ctx) EVP_MD_CTX_destroy(ctx)
+#endif
+
+scram_session
+*scram_session_create (const char *digest, const char *username, const char *password)
+{
+	scram_session *session;
+	const EVP_MD *md;
+#if (OPENSSL_VERSION_NUMBER < 0x10100000L)
+	OpenSSL_add_all_algorithms ();
+#endif
+	md = EVP_get_digestbyname (digest);
+
+	if (md == NULL)
+	{
+		// Unknown message digest
+		return NULL;
+	}
+
+	session = g_new0 (scram_session, 1);
+	session->digest = md;
+	session->digest_size = EVP_MD_size (md);
+	session->username = g_strdup (username);
+	session->password = g_strdup (password);
+	return session;
+}
+
+void
+scram_session_free (scram_session *session)
+{
+	if (session == NULL)
+	{
+		return;
+	}
+
+	g_free (session->username);
+	g_free (session->password);
+	g_free (session->client_nonce_b64);
+	g_free (session->client_first_message_bare);
+	g_free (session->salted_password);
+	g_free (session->auth_message);
+	g_free (session->error);
+
+	g_free (session);
+}
+
+static int
+create_nonce (void *buffer, size_t length)
+{
+	return RAND_bytes (buffer, length);
+}
+
+static int
+create_SHA (scram_session *session, const unsigned char *input, size_t input_len,
+			unsigned char *output, unsigned int *output_len)
+{
+	EVP_MD_CTX *md_ctx = EVP_MD_CTX_new ();
+
+	if (!EVP_DigestInit_ex (md_ctx, session->digest, NULL))
+	{
+		session->error = g_strdup ("Message digest initialization failed");
+		EVP_MD_CTX_free (md_ctx);
+		return SCRAM_ERROR;
+	}
+
+	if (!EVP_DigestUpdate (md_ctx, input, input_len))
+	{
+		session->error = g_strdup ("Message digest update failed");
+		EVP_MD_CTX_free (md_ctx);
+		return SCRAM_ERROR;
+	}
+
+	if (!EVP_DigestFinal_ex (md_ctx, output, output_len))
+	{
+		session->error = g_strdup ("Message digest finalization failed");
+		EVP_MD_CTX_free (md_ctx);
+		return SCRAM_ERROR;
+	}
+
+	EVP_MD_CTX_free (md_ctx);
+	return SCRAM_IN_PROGRESS;
+}
+
+static scram_status
+process_client_first (scram_session *session, char **output, size_t *output_len)
+{
+	char nonce[NONCE_LENGTH];
+
+	if (!create_nonce (nonce, NONCE_LENGTH))
+	{
+		session->error = g_strdup ("Could not create client nonce");
+		return SCRAM_ERROR;
+	}
+
+	session->client_nonce_b64 = g_base64_encode ((guchar *) nonce, NONCE_LENGTH);
+	*output = g_strdup_printf ("n,,n=%s,r=%s", session->username, session->client_nonce_b64);
+	*output_len = strlen (*output);
+	session->client_first_message_bare = g_strdup (*output + 3);
+	session->step++;
+	return SCRAM_IN_PROGRESS;
+}
+
+static scram_status
+process_server_first (scram_session *session, const char *data, char **output,
+					  size_t *output_len)
+{
+	char **params, *client_final_message_without_proof, *salt, *server_nonce_b64,
+			*client_proof_b64;
+	unsigned char *client_key, stored_key[EVP_MAX_MD_SIZE], *client_signature, *client_proof;
+	unsigned int i, param_count, iteration_count, client_key_len, stored_key_len;
+	gsize salt_len = 0;
+	size_t client_nonce_len;
+
+	params = g_strsplit (data, ",", -1);
+	param_count = g_strv_length (params);
+
+	if (param_count < 3)
+	{
+		session->error = g_strdup_printf ("Invalid server-first-message: %s", data);
+		g_strfreev (params);
+		return SCRAM_ERROR;
+	}
+
+	server_nonce_b64 = NULL;
+	salt = NULL;
+	iteration_count = 0;
+
+	for (i = 0; i < param_count; i++)
+	{
+		if (!strncmp (params[i], "r=", 2))
+		{
+			g_free (server_nonce_b64);
+			server_nonce_b64 = g_strdup (params[i] + 2);
+		}
+		else if (!strncmp (params[i], "s=", 2))
+		{
+			g_free (salt);
+			salt = g_strdup (params[i] + 2);
+		}
+		else if (!strncmp (params[i], "i=", 2))
+		{
+			iteration_count = strtoul (params[i] + 2, NULL, 10);
+		}
+	}
+
+	g_strfreev (params);
+
+	if (server_nonce_b64 == NULL || *server_nonce_b64 == '\0' || salt == NULL ||
+		*salt == '\0' || iteration_count == 0)
+	{
+		session->error = g_strdup_printf ("Invalid server-first-message: %s", data);
+		g_free (server_nonce_b64);
+		g_free (salt);
+		return SCRAM_ERROR;
+	}
+
+	client_nonce_len = strlen (session->client_nonce_b64);
+
+	// The server can append his nonce to the client's nonce
+	if (strlen (server_nonce_b64) < client_nonce_len ||
+		strncmp (server_nonce_b64, session->client_nonce_b64, client_nonce_len))
+	{
+		session->error = g_strdup_printf ("Invalid server nonce: %s", server_nonce_b64);
+		return SCRAM_ERROR;
+	}
+
+	g_base64_decode_inplace ((gchar *) salt, &salt_len);
+
+	// SaltedPassword := Hi(Normalize(password), salt, i)
+	session->salted_password = g_malloc (session->digest_size);
+
+	PKCS5_PBKDF2_HMAC (session->password, strlen (session->password), (unsigned char *) salt,
+					   salt_len, iteration_count, session->digest, session->digest_size,
+					   session->salted_password);
+
+	// AuthMessage := client-first-message-bare + "," +
+	//                server-first-message + "," +
+	//                client-final-message-without-proof
+	client_final_message_without_proof = g_strdup_printf ("c=biws,r=%s", server_nonce_b64);
+
+	session->auth_message = g_strdup_printf ("%s,%s,%s", session->client_first_message_bare,
+											 data, client_final_message_without_proof);
+
+	// ClientKey := HMAC(SaltedPassword, "Client Key")
+	client_key = g_malloc0 (session->digest_size);
+
+	HMAC (session->digest, session->salted_password, session->digest_size,
+		  (unsigned char *) CLIENT_KEY, strlen (CLIENT_KEY), client_key, &client_key_len);
+
+	// StoredKey := H(ClientKey)
+	if (!create_SHA (session, client_key, session->digest_size, stored_key, &stored_key_len))
+	{
+		g_free (client_final_message_without_proof);
+		g_free (server_nonce_b64);
+		g_free (salt);
+		g_free (client_key);
+		return SCRAM_ERROR;
+	}
+
+	// ClientSignature := HMAC(StoredKey, AuthMessage)
+	client_signature = g_malloc0 (session->digest_size);
+	HMAC (session->digest, stored_key, stored_key_len, (unsigned char *) session->auth_message,
+		  strlen ((char *) session->auth_message), client_signature, NULL);
+
+	// ClientProof := ClientKey XOR ClientSignature
+	client_proof = g_malloc0 (client_key_len);
+
+	for (i = 0; i < client_key_len; i++)
+	{
+		client_proof[i] = client_key[i] ^ client_signature[i];
+	}
+
+	client_proof_b64 = g_base64_encode ((guchar *) client_proof, client_key_len);
+
+	*output = g_strdup_printf ("%s,p=%s", client_final_message_without_proof, client_proof_b64);
+	*output_len = strlen (*output);
+
+	g_free (server_nonce_b64);
+	g_free (salt);
+	g_free (client_final_message_without_proof);
+	g_free (client_key);
+	g_free (client_signature);
+	g_free (client_proof);
+	g_free (client_proof_b64);
+
+	session->step++;
+	return SCRAM_IN_PROGRESS;
+}
+
+static scram_status
+process_server_final (scram_session *session, const char *data)
+{
+	char *verifier;
+	unsigned char *server_key, *server_signature;
+	unsigned int server_key_len = 0, server_signature_len = 0;
+	gsize verifier_len = 0;
+
+	if (strlen (data) < 3 || (data[0] != 'v' && data[1] != '='))
+	{
+		return SCRAM_ERROR;
+	}
+
+	verifier = g_strdup (data + 2);
+	g_base64_decode_inplace (verifier, &verifier_len);
+
+	// ServerKey := HMAC(SaltedPassword, "Server Key")
+	server_key = g_malloc0 (session->digest_size);
+	HMAC (session->digest, session->salted_password, session->digest_size,
+		  (unsigned char *) SERVER_KEY, strlen (SERVER_KEY), server_key, &server_key_len);
+
+	// ServerSignature := HMAC(ServerKey, AuthMessage)
+	server_signature = g_malloc0 (session->digest_size);
+	HMAC (session->digest, server_key, session->digest_size,
+		  (unsigned char *) session->auth_message, strlen ((char *) session->auth_message),
+		  server_signature, &server_signature_len);
+
+	if (verifier_len == server_signature_len &&
+		memcmp (verifier, server_signature, verifier_len) == 0)
+	{
+		g_free (verifier);
+		g_free (server_key);
+		g_free (server_signature);
+		return SCRAM_SUCCESS;
+	}
+	else
+	{
+		g_free (verifier);
+		g_free (server_key);
+		g_free (server_signature);
+		return SCRAM_ERROR;
+	}
+}
+
+scram_status
+scram_process (scram_session *session, const char *input, char **output, size_t *output_len)
+{
+	scram_status status;
+
+	switch (session->step)
+	{
+		case 0:
+			status = process_client_first (session, output, output_len);
+			break;
+		case 1:
+			status = process_server_first (session, input, output, output_len);
+			break;
+		case 2:
+			status = process_server_final (session, input);
+			break;
+		default:
+			*output = NULL;
+			*output_len = 0;
+			status = SCRAM_ERROR;
+			break;
+	}
+
+	return status;
+}
+
+#endif
\ No newline at end of file