fishlim: Add /keyx for DH1080 key exchange

Losely based upon work from PR #1440

Fixes #653

1 files changed, 209 insertions, 0 deletions

diff --git a/plugins/fishlim/dh1080.c b/plugins/fishlim/dh1080.c
new file mode 100644
index 00000000..41b65844
--- /dev/null
+++ b/plugins/fishlim/dh1080.c
@@ -0,0 +1,209 @@
+/* HexChat
+*
+* 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
+*/
+
+/*
+ * For Diffie-Hellman key-exchange a 1080bit germain prime is used, the
+ * generator g=2 renders a field Fp from 1 to p-1. Therefore breaking it
+ * means to solve a discrete logarithm problem with no less than 1080bit.
+ *
+ * Base64 format is used to send the public keys over IRC.
+ *
+ * The calculated secret key is hashed with SHA-256, the result is converted
+ * to base64 for final use with blowfish.
+ */
+
+#include "dh1080.h"
+
+#include <openssl/bn.h>
+#include <openssl/dh.h>
+#include <openssl/sha.h>
+
+#include <string.h>
+#include <glib.h>
+
+#define DH1080_PRIME_BITS 1080
+#define DH1080_PRIME_BYTES 135
+#define SHA256_DIGEST_LENGTH 32
+#define B64ABC "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
+#define MEMZERO(x) memset(x, 0x00, (sizeof(x)/sizeof(*x)) )
+
+/* All clients must use the same prime number to be able to keyx */
+static const guchar prime1080[DH1080_PRIME_BYTES] =
+{
+	0xFB, 0xE1, 0x02, 0x2E, 0x23, 0xD2, 0x13, 0xE8, 0xAC, 0xFA, 0x9A, 0xE8, 0xB9, 0xDF, 0xAD, 0xA3, 0xEA,
+	0x6B, 0x7A, 0xC7, 0xA7, 0xB7, 0xE9, 0x5A, 0xB5, 0xEB, 0x2D, 0xF8, 0x58, 0x92, 0x1F, 0xEA, 0xDE, 0x95,
+	0xE6, 0xAC, 0x7B, 0xE7, 0xDE, 0x6A, 0xDB, 0xAB, 0x8A, 0x78, 0x3E, 0x7A, 0xF7, 0xA7, 0xFA, 0x6A, 0x2B,
+	0x7B, 0xEB, 0x1E, 0x72, 0xEA, 0xE2, 0xB7, 0x2F, 0x9F, 0xA2, 0xBF, 0xB2, 0xA2, 0xEF, 0xBE, 0xFA, 0xC8,
+	0x68, 0xBA, 0xDB, 0x3E, 0x82, 0x8F, 0xA8, 0xBA, 0xDF, 0xAD, 0xA3, 0xE4, 0xCC, 0x1B, 0xE7, 0xE8, 0xAF,
+	0xE8, 0x5E, 0x96, 0x98, 0xA7, 0x83, 0xEB, 0x68, 0xFA, 0x07, 0xA7, 0x7A, 0xB6, 0xAD, 0x7B, 0xEB, 0x61,
+	0x8A, 0xCF, 0x9C, 0xA2, 0x89, 0x7E, 0xB2, 0x8A, 0x61, 0x89, 0xEF, 0xA0, 0x7A, 0xB9, 0x9A, 0x8A, 0x7F,
+	0xA9, 0xAE, 0x29, 0x9E, 0xFA, 0x7B, 0xA6, 0x6D, 0xEA, 0xFE, 0xFB, 0xEF, 0xBF, 0x0B, 0x7D, 0x8B
+};
+
+static DH *g_dh;
+
+int
+dh1080_init (void)
+{
+	g_return_val_if_fail (g_dh == NULL, 0);
+
+	if ((g_dh = DH_new()))
+	{
+		int codes;
+
+		g_dh->p = BN_bin2bn (prime1080, DH1080_PRIME_BYTES, NULL);
+		g_dh->g = BN_new ();
+
+		g_assert (g_dh->p != NULL && g_dh->g != NULL);
+		BN_set_word(g_dh->g, 2);
+
+		if (DH_check (g_dh, &codes))
+			return codes == 0;
+	}
+
+	return 0;
+}
+
+void
+dh1080_deinit (void)
+{
+	g_clear_pointer (&g_dh, DH_free);
+}
+
+static inline int
+DH_verifyPubKey (BIGNUM *pk)
+{
+	int codes;
+	return DH_check_pub_key (g_dh, pk, &codes) && codes == 0;
+}
+
+static guchar *
+dh1080_decode_b64 (const char *data, gsize *out_len)
+{
+	GString *str = g_string_new (data);
+	guchar *ret;
+
+	if (str->len % 4 == 1 && str->str[str->len - 1] == 'A')
+		g_string_truncate (str, str->len - 1);
+
+	while (str->len % 4 != 0)
+		g_string_append_c (str, '=');
+
+	ret = g_base64_decode_inplace (str->str, out_len);
+	g_string_free (str, FALSE);
+  	return ret;
+}
+
+static char *
+dh1080_encode_b64 (const guchar *data, gsize data_len)
+{
+	char *ret = g_base64_encode (data, data_len);
+	char *p;
+
+	if (!(p = strchr (ret, '=')))
+	{
+		char *new_ret = g_new(char, strlen(ret) + 2);
+		strcpy (new_ret, ret);
+		strcat (new_ret, "A");
+		g_free (ret);
+		ret = new_ret;
+	}
+	else
+	{
+		*p = '\0';
+	}
+
+  	return ret;
+}
+
+int
+dh1080_generate_key (char **priv_key, char **pub_key)
+{
+	guchar buf[DH1080_PRIME_BYTES];
+	int len;
+	DH *dh;
+
+  	g_assert (priv_key != NULL);
+	g_assert (pub_key != NULL);
+
+  	dh = DHparams_dup (g_dh);
+	if (!dh)
+		return 0;
+
+	if (!DH_generate_key (dh))
+	{
+		DH_free (dh);
+		return 0;
+	}
+
+	MEMZERO (buf);
+	len = BN_bn2bin (dh->priv_key, buf);
+	*priv_key = dh1080_encode_b64 (buf, len);
+
+	MEMZERO (buf);
+	len = BN_bn2bin(dh->pub_key, buf);
+	*pub_key = dh1080_encode_b64 (buf, len);
+
+	OPENSSL_cleanse (buf, sizeof (buf));
+	DH_free (dh);
+	return 1;
+}
+
+int
+dh1080_compute_key (const char *priv_key, const char *pub_key, char **secret_key)
+{
+	char *pub_key_data;
+	gsize pub_key_len;
+	BIGNUM *pk;
+	DH *dh;
+
+  	g_assert (secret_key != NULL);
+
+	/* Verify base64 strings */
+	if (strspn (priv_key, B64ABC) != strlen (priv_key)
+	    || strspn (pub_key, B64ABC) != strlen (pub_key))
+		return 0;
+
+	dh = DHparams_dup (g_dh);
+
+	pub_key_data = dh1080_decode_b64 (pub_key, &pub_key_len);
+	pk = BN_bin2bn (pub_key_data, pub_key_len, NULL);
+
+	if (DH_verifyPubKey (pk))
+	{
+		guchar shared_key[DH1080_PRIME_BYTES] = { 0 };
+		guchar sha256[SHA256_DIGEST_LENGTH] = { 0 };
+		char *priv_key_data;
+		gsize priv_key_len;
+		int shared_len;
+
+	  	priv_key_data = dh1080_decode_b64 (priv_key, &priv_key_len);
+		dh->priv_key = BN_bin2bn(priv_key_data, priv_key_len, NULL);
+
+		shared_len = DH_compute_key (shared_key, pk, dh);
+		SHA256(shared_key, shared_len, sha256);
+		*secret_key = dh1080_encode_b64 (sha256, sizeof(sha256));
+
+		OPENSSL_cleanse (priv_key_data, priv_key_len);
+	  	g_free (priv_key_data);
+	}
+
+	BN_free (pk);
+	DH_free (dh);
+	g_free (pub_key_data);
+	return 1;
+}