fishlim: Add /keyx for DH1080 key exchange

Losely based upon work from PR #1440

Fixes #653

6 files changed, 416 insertions, 20 deletions

diff --git a/plugins/fishlim/Makefile.am b/plugins/fishlim/Makefile.am
index 95498bf5..fdf47051 100644
--- a/plugins/fishlim/Makefile.am
+++ b/plugins/fishlim/Makefile.am
@@ -1,9 +1,9 @@
-EXTRA_DIST = INSTALL LICENSE fish.h irc.h keystore.h plugin_hexchat.h
+EXTRA_DIST = INSTALL LICENSE fish.h irc.h keystore.h plugin_hexchat.h dh1080.h
 
 libdir = $(hexchatlibdir)
 
 lib_LTLIBRARIES = fishlim.la
-fishlim_la_SOURCES = fish.c irc.c keystore.c plugin_hexchat.c
+fishlim_la_SOURCES = fish.c irc.c keystore.c plugin_hexchat.c dh1080.c
 fishlim_la_LDFLAGS = $(PLUGIN_LDFLAGS) -module
 fishlim_la_LIBADD = $(GLIB_LIBS) $(OPENSSL_LIBS)
 fishlim_la_CPPFLAGS = -I$(top_srcdir)/src/common
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;
+}
diff --git a/plugins/fishlim/dh1080.h b/plugins/fishlim/dh1080.h
new file mode 100644
index 00000000..75662189
--- /dev/null
+++ b/plugins/fishlim/dh1080.h
@@ -0,0 +1,24 @@
+/* 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
+*/
+
+#pragma once
+
+int dh1080_generate_key (char **, char **);
+int dh1080_compute_key (const char *, const char *, char **);
+int dh1080_init (void);
+void dh1080_deinit (void);
+
diff --git a/plugins/fishlim/fishlim.vcxproj b/plugins/fishlim/fishlim.vcxproj
index 50eec873..43ae1df9 100644
--- a/plugins/fishlim/fishlim.vcxproj
+++ b/plugins/fishlim/fishlim.vcxproj
@@ -53,13 +53,14 @@
     <None Include="fishlim.def" />

   </ItemGroup>

   <ItemGroup>

-    <ClInclude Include="bool.h" />

+    <ClInclude Include="dh1080.h" />

     <ClInclude Include="fish.h" />

     <ClInclude Include="irc.h" />

     <ClInclude Include="keystore.h" />

     <ClInclude Include="plugin_hexchat.h" />

   </ItemGroup>

   <ItemGroup>

+    <ClCompile Include="dh1080.c" />

     <ClCompile Include="fish.c" />

     <ClCompile Include="irc.c" />

     <ClCompile Include="keystore.c" />

diff --git a/plugins/fishlim/irc.c b/plugins/fishlim/irc.c
index deba545b..19b810eb 100644
--- a/plugins/fishlim/irc.c
+++ b/plugins/fishlim/irc.c
@@ -50,7 +50,9 @@ gboolean irc_parse_message(const char *words[],
     if (command) *command = words[w];
     w++;
     
-    *parameters_offset = w;
+    if (parameters_offset)
+		*parameters_offset = w;
+
     return TRUE;
 }
 
diff --git a/plugins/fishlim/plugin_hexchat.c b/plugins/fishlim/plugin_hexchat.c
index 0afecd82..a163fd10 100644
--- a/plugins/fishlim/plugin_hexchat.c
+++ b/plugins/fishlim/plugin_hexchat.c
@@ -32,6 +32,7 @@
 #define HEXCHAT_MAX_WORDS 32
 
 #include "fish.h"
+#include "dh1080.h"
 #include "keystore.h"
 #include "irc.h"
 
@@ -41,8 +42,11 @@ static const char plugin_version[] = "0.0.17";
 
 static const char usage_setkey[] = "Usage: SETKEY [<nick or #channel>] <password>, sets the key for a channel or nick";
 static const char usage_delkey[] = "Usage: DELKEY <nick or #channel>, deletes the key for a channel or nick";
+static const char usage_keyx[] = "Usage: KEYX [<nick>], performs DH1080 key-exchange with <nick>";
+
 
 static hexchat_plugin *ph;
+static GHashTable *pending_exchanges;
 
 
 /**
@@ -58,6 +62,38 @@ gchar *get_config_filename(void) {
     return filename_fs;
 }
 
+static inline gboolean irc_is_query (const char *name) {
+    const char *chantypes = hexchat_list_str (ph, NULL, "chantypes");
+
+    return strchr (chantypes, name[0]) == NULL;
+}
+
+static hexchat_context *find_context_on_network (const char *name) {
+    hexchat_list *channels;
+    hexchat_context *ret = NULL;
+    int id;
+
+    if (hexchat_get_prefs(ph, "id", NULL, &id) != 2)
+        return NULL;
+
+    channels = hexchat_list_get(ph, "channels");
+    if (!channels)
+        return NULL;
+
+    while (hexchat_list_next(ph, channels)) {
+        int chan_id = hexchat_list_int(ph, channels, "id");
+        const char *chan_name = hexchat_list_str(ph, channels, "channel");
+
+        if (chan_id == id && chan_name && hexchat_nickcmp (ph, chan_name, name) == 0) {
+            ret = (hexchat_context*)hexchat_list_str(ph, channels, "context");
+            break;
+        }
+    };
+
+    hexchat_list_free(ph, channels);
+    return ret;
+}
+
 int irc_nick_cmp(const char *a, const char *b) {
 	return hexchat_nickcmp (ph, a, b);
 }
@@ -163,11 +199,11 @@ static int handle_incoming(char *word[], char *word_eol[], hexchat_event_attrs *
                 /* Prefix with colon, which gets stripped out otherwise */
                 g_string_append_c (message, ':');
             }
-            
+
             if (prefix_char) {
                 g_string_append_c (message, prefix_char);
             }
-            
+
         } else {
             /* Add unencrypted data (for example, a prefix from a bouncer or bot) */
             peice = word[uw];
@@ -176,7 +212,7 @@ static int handle_incoming(char *word[], char *word_eol[], hexchat_event_attrs *
         g_string_append (message, peice);
     }
     g_free(decrypted);
-    
+
     /* Simulate unencrypted message */
     /* hexchat_printf(ph, "simulating: %s\n", message->str); */
     hexchat_command(ph, message->str);
@@ -184,26 +220,103 @@ static int handle_incoming(char *word[], char *word_eol[], hexchat_event_attrs *
     g_string_free (message, TRUE);
     g_free(sender_nick);
     return HEXCHAT_EAT_HEXCHAT;
-  
+
   decrypt_error:
     g_free(decrypted);
     g_free(sender_nick);
     return HEXCHAT_EAT_NONE;
 }
 
+static int handle_keyx_notice(char *word[], char *word_eol[], void *userdata) {
+    const char *dh_message = word[4];
+    const char *dh_pubkey = word[5];
+    hexchat_context *query_ctx;
+    const char *prefix;
+    gboolean cbc;
+    char *sender, *secret_key, *priv_key = NULL;
+
+    if (!*dh_message || !*dh_pubkey || strlen(dh_pubkey) != 181)
+        return HEXCHAT_EAT_NONE;
+
+    if (!irc_parse_message((const char**)word, &prefix, NULL, NULL) || !prefix)
+        return HEXCHAT_EAT_NONE;
+
+    sender = irc_prefix_get_nick(prefix);
+    query_ctx = find_context_on_network(sender);
+    if (query_ctx)
+        hexchat_set_context(ph, query_ctx);
+
+    dh_message++; /* : prefix */
+    if (*dh_message == '+' || *dh_message == '-')
+        dh_message++; /* identify-msg */
+
+    cbc = g_strcmp0 (word[6], "CBC") == 0;
+
+    if (!strcmp(dh_message, "DH1080_INIT")) {
+        char *pub_key;
+
+        if (cbc) {
+            hexchat_print(ph, "Recieved key exchange for CBC mode which is not supported.");
+            goto cleanup;
+        }
+
+        hexchat_printf(ph, "Received public key from %s, sending mine...", sender);
+        if (dh1080_generate_key(&priv_key, &pub_key)) {
+            hexchat_commandf(ph, "quote NOTICE %s :DH1080_FINISH %s", sender, pub_key);
+            g_free(pub_key);
+        } else {
+            hexchat_print(ph, "Failed to generate keys");
+            goto cleanup;
+        }
+    } else if (!strcmp (dh_message, "DH1080_FINISH")) {
+        char *sender_lower = g_ascii_strdown(sender, -1);
+        /* FIXME: Properly respect irc casing */
+        priv_key = g_hash_table_lookup(pending_exchanges, sender_lower);
+        g_hash_table_steal(pending_exchanges, sender_lower);
+        g_free(sender_lower);
+
+        if (cbc) {
+            hexchat_print(ph, "Recieved key exchange for CBC mode which is not supported.");
+            goto cleanup;
+        }
+
+        if (!priv_key) {
+            hexchat_printf(ph, "Recieved a key exchange response for unknown user: %s", sender);
+            goto cleanup;
+        }
+    } else {
+        /* Regular notice */
+        g_free(sender);
+        return HEXCHAT_EAT_NONE;
+    }
+
+    if (dh1080_compute_key(priv_key, dh_pubkey, &secret_key)) {
+        keystore_store_key(sender, secret_key);
+        hexchat_printf(ph, "Stored new key for %s", sender);
+        g_free(secret_key);
+    } else {
+        hexchat_print(ph, "Failed to create secret key!");
+    }
+
+cleanup:
+    g_free(sender);
+    g_free(priv_key);
+    return HEXCHAT_EAT_ALL;
+}
+
 /**
  * Command handler for /setkey
  */
 static int handle_setkey(char *word[], char *word_eol[], void *userdata) {
     const char *nick;
     const char *key;
-    
+
     /* Check syntax */
     if (*word[2] == '\0') {
         hexchat_printf(ph, "%s\n", usage_setkey);
         return HEXCHAT_EAT_HEXCHAT;
     }
-    
+
     if (*word[3] == '\0') {
         /* /setkey password */
         nick = hexchat_get_info(ph, "channel");
@@ -213,14 +326,14 @@ static int handle_setkey(char *word[], char *word_eol[], void *userdata) {
         nick = word[2];
         key = word_eol[3];
     }
-    
+
     /* Set password */
     if (keystore_store_key(nick, key)) {
         hexchat_printf(ph, "Stored key for %s\n", nick);
     } else {
         hexchat_printf(ph, "\00305Failed to store key in addon_fishlim.conf\n");
     }
-    
+
     return HEXCHAT_EAT_HEXCHAT;
 }
 
@@ -229,25 +342,62 @@ static int handle_setkey(char *word[], char *word_eol[], void *userdata) {
  */
 static int handle_delkey(char *word[], char *word_eol[], void *userdata) {
     const char *nick;
-    
+
     /* Check syntax */
     if (*word[2] == '\0' || *word[3] != '\0') {
         hexchat_printf(ph, "%s\n", usage_delkey);
         return HEXCHAT_EAT_HEXCHAT;
     }
-    
+
     nick = g_strstrip (word_eol[2]);
-    
+
     /* Delete the given nick from the key store */
     if (keystore_delete_nick(nick)) {
         hexchat_printf(ph, "Deleted key for %s\n", nick);
     } else {
         hexchat_printf(ph, "\00305Failed to delete key in addon_fishlim.conf!\n");
     }
-    
+
     return HEXCHAT_EAT_HEXCHAT;
 }
 
+static int handle_keyx(char *word[], char *word_eol[], void *userdata) {
+    const char *target = word[2];
+    hexchat_context *query_ctx = NULL;
+    char *pub_key, *priv_key;
+    int ctx_type;
+
+    if (*target)
+        query_ctx = find_context_on_network(target);
+    else {
+        target = hexchat_get_info(ph, "channel");
+        query_ctx = hexchat_get_context (ph);
+    }
+
+    if (query_ctx) {
+        hexchat_set_context(ph, query_ctx);
+        ctx_type = hexchat_list_int(ph, NULL, "type");
+    }
+
+    if ((query_ctx && ctx_type != 3) || (!query_ctx && !irc_is_query(target))) {
+        hexchat_print(ph, "You can only exchange keys with individuals");
+        return HEXCHAT_EAT_ALL;
+    }
+
+    if (dh1080_generate_key(&priv_key, &pub_key)) {
+        g_hash_table_replace (pending_exchanges, g_ascii_strdown(target, -1), priv_key);
+
+        hexchat_commandf(ph, "quote NOTICE %s :DH1080_INIT %s", target, pub_key);
+        hexchat_printf(ph, "Sent public key to %s, waiting for reply...", target);
+
+        g_free(pub_key);
+    } else {
+        hexchat_print(ph, "Failed to generate keys");
+    }
+
+    return HEXCHAT_EAT_ALL;
+}
+
 /**
  * Returns the plugin name version information.
  */
@@ -267,30 +417,40 @@ int hexchat_plugin_init(hexchat_plugin *plugin_handle,
                       const char **version,
                       char *arg) {
     ph = plugin_handle;
-    
+
     /* Send our info to HexChat */
     *name = plugin_name;
     *desc = plugin_desc;
     *version = plugin_version;
-    
+
     /* Register commands */
     hexchat_hook_command(ph, "SETKEY", HEXCHAT_PRI_NORM, handle_setkey, usage_setkey, NULL);
     hexchat_hook_command(ph, "DELKEY", HEXCHAT_PRI_NORM, handle_delkey, usage_delkey, NULL);
-    
+    hexchat_hook_command(ph, "KEYX", HEXCHAT_PRI_NORM, handle_keyx, usage_keyx, NULL);
+
     /* Add handlers */
     hexchat_hook_command(ph, "", HEXCHAT_PRI_NORM, handle_outgoing, NULL, NULL);
+    hexchat_hook_server(ph, "NOTICE", HEXCHAT_PRI_HIGHEST, handle_keyx_notice, NULL);
     hexchat_hook_server_attrs(ph, "NOTICE", HEXCHAT_PRI_NORM, handle_incoming, NULL);
     hexchat_hook_server_attrs(ph, "PRIVMSG", HEXCHAT_PRI_NORM, handle_incoming, NULL);
     /* hexchat_hook_server(ph, "RAW LINE", HEXCHAT_PRI_NORM, handle_debug, NULL); */
     hexchat_hook_server_attrs(ph, "TOPIC", HEXCHAT_PRI_NORM, handle_incoming, NULL);
     hexchat_hook_server_attrs(ph, "332", HEXCHAT_PRI_NORM, handle_incoming, NULL);
-    
+
+    if (!dh1080_init())
+        return 0;
+
+    pending_exchanges = g_hash_table_new_full(g_str_hash, g_str_equal, g_free, g_free);
+
     hexchat_printf(ph, "%s plugin loaded\n", plugin_name);
     /* Return success */
     return 1;
 }
 
 int hexchat_plugin_deinit(void) {
+    g_clear_pointer(&pending_exchanges, g_hash_table_destroy);
+    dh1080_deinit();
+
     hexchat_printf(ph, "%s plugin unloaded\n", plugin_name);
     return 1;
 }