fishlim: Implement correct handling of long and UTF-8 messages

9 files changed, 413 insertions, 66 deletions

diff --git a/plugins/fishlim/fish.c b/plugins/fishlim/fish.c
index 88f7caec..c2c2b9da 100644
--- a/plugins/fishlim/fish.c
+++ b/plugins/fishlim/fish.c
@@ -1,7 +1,7 @@
 /*
 
   Copyright (c) 2010 Samuel Lidén Borell <samuel@kodafritt.se>
-  Copyright (c) 2019 <bakasura@protonmail.ch>
+  Copyright (c) 2019-2020 <bakasura@protonmail.ch>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files (the "Software"), to deal
@@ -37,8 +37,11 @@
 
 #include "keystore.h"
 #include "fish.h"
+#include "utils.h"
 
 #define IB 64
+/* rfc 2812; 512 - CR-LF = 510 */
+static const int MAX_COMMAND_LENGTH = 510;
 static const char fish_base64[] = "./0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
 static const char base64_chars[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
 static const signed char fish_unbase64[256] = {
@@ -401,13 +404,40 @@ char *fish_decrypt_str(const char *key, size_t keylen, const char *data, enum fi
 }
 
 /**
- * Encrypts a message (see fish_decrypt). The key is searched for in the
- * key store.
+ * Determine if a nick have a key
+ *
+ * @param [in] nick  Nickname
+ * @return TRUE if have a key or FALSE if not
+ */
+gboolean fish_nick_has_key(const char *nick) {
+    gboolean has_key = FALSE;
+    char *key;
+    enum fish_mode mode;
+
+    key = keystore_get_key(nick, &mode);
+    if (key) {
+        has_key = TRUE;
+        g_free(key);
+    };
+
+    return has_key;
+}
+
+/**
+ * Encrypts a message (see fish_encrypt). The key is searched for in the key store
+ *
+ * @param [in] nick         Nickname
+ * @param [in] data         Plaintext to encrypt
+ * @param [out] omode       Mode of encryption
+ * @param [in] command_len  Length of command to use without the message part
+ * @return A list of encoded strings with the message encrypted or NULL if any error occurred
  */
-char *fish_encrypt_for_nick(const char *nick, const char *data, enum fish_mode *omode) {
+GSList *fish_encrypt_for_nick(const char *nick, const char *data, enum fish_mode *omode, size_t command_len) {
     char *key;
-    char *encrypted, *encrypted_cbc = NULL;
+    GSList *encrypted_list = NULL;
+    char *encrypted = NULL;
     enum fish_mode mode;
+    int max_len, max_chunks_len, chunks_len;
 
     /* Look for key */
     key = keystore_get_key(nick, &mode);
@@ -415,24 +445,40 @@ char *fish_encrypt_for_nick(const char *nick, const char *data, enum fish_mode *
 
     *omode = mode;
 
-    /* Encrypt */
-    encrypted = fish_encrypt(key, strlen(key), data, strlen(data), mode);
+    /* Calculate max length of each line */
+    max_len = MAX_COMMAND_LENGTH - command_len;
+    /* Add '*' */
+    if (mode == FISH_CBC_MODE) max_len--;
 
-    g_free(key);
+    max_chunks_len = max_text_command_len(max_len, mode);
 
-    if (encrypted == NULL || mode == FISH_ECB_MODE)
-        return encrypted;
+    const char *data_chunk = data;
 
-    /* Add '*' for CBC */
-    encrypted_cbc = g_strdup_printf("*%s",encrypted);
-    g_free(encrypted);
+    while(foreach_utf8_data_chunks(data_chunk, max_chunks_len, &chunks_len)) {
+        encrypted = fish_encrypt(key, strlen(key), data_chunk, chunks_len, mode);
 
-    return encrypted_cbc;
+        if (mode == FISH_CBC_MODE) {
+            /* Add '*' for CBC */
+            encrypted_list = g_slist_append(encrypted_list, g_strdup_printf("*%s", encrypted));
+            g_free(encrypted);
+        } else {
+            encrypted_list = g_slist_append(encrypted_list, encrypted);
+        }
+
+        /* Next chunk */
+        data_chunk += chunks_len;
+    }
+
+    return encrypted_list;
 }
 
 /**
- * Decrypts a message (see fish_decrypt). The key is searched for in the
- * key store.
+ * Decrypts a message (see fish_decrypt). The key is searched for in the key store
+ *
+ * @param [in] nick     Nickname
+ * @param [in] data     Plaintext to encrypt
+ * @param [out] omode   Mode of encryption
+ * @return Plaintext message or NULL if any error occurred
  */
 char *fish_decrypt_from_nick(const char *nick, const char *data, enum fish_mode *omode) {
     char *key;
diff --git a/plugins/fishlim/fish.h b/plugins/fishlim/fish.h
index daf17acf..6a2e911c 100644
--- a/plugins/fishlim/fish.h
+++ b/plugins/fishlim/fish.h
@@ -1,7 +1,7 @@
 /*
 
   Copyright (c) 2010 Samuel Lidén Borell <samuel@kodafritt.se>
-  Copyright (c) 2019 <bakasura@protonmail.ch>
+  Copyright (c) 2019-2020 <bakasura@protonmail.ch>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files (the "Software"), to deal
@@ -40,7 +40,8 @@ char *fish_base64_decode(const char *message, size_t *final_len);
 char *fish_encrypt(const char *key, size_t keylen, const char *message, size_t message_len, enum fish_mode mode);
 char *fish_decrypt(const char *key, size_t keylen, const char *data, enum fish_mode mode, size_t *final_len);
 char *fish_decrypt_str(const char *key, size_t keylen, const char *data, enum fish_mode mode);
-char *fish_encrypt_for_nick(const char *nick, const char *data, enum fish_mode *omode);
+gboolean fish_nick_has_key(const char *nick);
+GSList *fish_encrypt_for_nick(const char *nick, const char *data, enum fish_mode *omode, size_t command_len);
 char *fish_decrypt_from_nick(const char *nick, const char *data, enum fish_mode *omode);
 
 #endif
diff --git a/plugins/fishlim/fishlim.vcxproj b/plugins/fishlim/fishlim.vcxproj
index 43ae1df9..157c7928 100644
--- a/plugins/fishlim/fishlim.vcxproj
+++ b/plugins/fishlim/fishlim.vcxproj
@@ -55,6 +55,7 @@
   <ItemGroup>

     <ClInclude Include="dh1080.h" />

     <ClInclude Include="fish.h" />

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

     <ClInclude Include="irc.h" />

     <ClInclude Include="keystore.h" />

     <ClInclude Include="plugin_hexchat.h" />

@@ -62,6 +63,7 @@
   <ItemGroup>

     <ClCompile Include="dh1080.c" />

     <ClCompile Include="fish.c" />

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

     <ClCompile Include="irc.c" />

     <ClCompile Include="keystore.c" />

     <ClCompile Include="plugin_hexchat.c" />

diff --git a/plugins/fishlim/fishlim.vcxproj.filters b/plugins/fishlim/fishlim.vcxproj.filters
index 09649ec9..ee4e855a 100644
--- a/plugins/fishlim/fishlim.vcxproj.filters
+++ b/plugins/fishlim/fishlim.vcxproj.filters
@@ -29,6 +29,9 @@
     <ClInclude Include="fish.h">

       <Filter>Header Files</Filter>

     </ClInclude>

+    <ClInclude Include="utils.h">

+          <Filter>Header Files</Filter>

+        </ClInclude>

     <ClInclude Include="irc.h">

       <Filter>Header Files</Filter>

     </ClInclude>

@@ -46,6 +49,9 @@
     <ClCompile Include="fish.c">

       <Filter>Source Files</Filter>

     </ClCompile>

+    <ClCompile Include="utils.c">

+          <Filter>Source Files</Filter>

+        </ClCompile>

     <ClCompile Include="irc.c">

       <Filter>Source Files</Filter>

     </ClCompile>

diff --git a/plugins/fishlim/meson.build b/plugins/fishlim/meson.build
index 06cf5f9a..65ccc9ea 100644
--- a/plugins/fishlim/meson.build
+++ b/plugins/fishlim/meson.build
@@ -8,6 +8,7 @@ subdir('tests')
 fishlim_sources = [
   'dh1080.c',
   'fish.c',
+  'utils.c',
   'irc.c',
   'keystore.c',
   'plugin_hexchat.c'
diff --git a/plugins/fishlim/plugin_hexchat.c b/plugins/fishlim/plugin_hexchat.c
index ddb692da..83286e28 100644
--- a/plugins/fishlim/plugin_hexchat.c
+++ b/plugins/fishlim/plugin_hexchat.c
@@ -2,7 +2,7 @@
 
   Copyright (c) 2010-2011 Samuel Lidén Borell <samuel@kodafritt.se>
   Copyright (c) 2015 <the.cypher@gmail.com>
-  Copyright (c) 2019 <bakasura@protonmail.ch>
+  Copyright (c) 2019-2020 <bakasura@protonmail.ch>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files (the "Software"), to deal
@@ -29,7 +29,6 @@
 #include <glib.h>
 #include <stdlib.h>
 #include <string.h>
-
 #include "hexchat-plugin.h"
 
 #include "fish.h"
@@ -108,13 +107,14 @@ static hexchat_context *find_context_on_network (const char *name) {
 }
 
 /**
- * Retrive the prefix character for own nick in current context
- * @return @ or + or NULL
+ * Retrive the field for own user in current context
+ * @return the field value
  */
-char *get_my_own_prefix(void) {
+char *get_my_info(const char *field, gboolean find_in_other_context) {
     char *result = NULL;
     const char *own_nick;
     hexchat_list *list;
+    hexchat_context *ctx_current, *ctx_channel;
 
     /* Display message */
     own_nick = hexchat_get_info(ph, "nick");
@@ -122,12 +122,38 @@ char *get_my_own_prefix(void) {
     if (!own_nick)
         return NULL;
 
-    /* Get prefix for own nick if any */
-    list = hexchat_list_get (ph, "users");
+    /* Get field for own nick if any */
+    list = hexchat_list_get(ph, "users");
     if (list) {
         while (hexchat_list_next(ph, list)) {
             if (irc_nick_cmp(own_nick, hexchat_list_str(ph, list, "nick")) == 0)
-                result = g_strdup(hexchat_list_str(ph, list, "prefix"));
+                result = g_strdup(hexchat_list_str(ph, list, field));
+        }
+        hexchat_list_free(ph, list);
+    }
+
+    if (result) {
+        return result;
+    }
+
+    /* Try to get from a channel (we are outside a channel)  */
+    if (!find_in_other_context) {
+        return NULL;
+    }
+
+    list = hexchat_list_get(ph, "channels");
+    if (list) {
+        ctx_current = hexchat_get_context(ph);
+        while (hexchat_list_next(ph, list)) {
+            ctx_channel = (hexchat_context *) hexchat_list_str(ph, list, "context");
+
+            hexchat_set_context(ph, ctx_channel);
+            result = get_my_info(field, FALSE);
+            hexchat_set_context(ph, ctx_current);
+
+            if (result) {
+                break;
+            }
         }
         hexchat_list_free(ph, list);
     }
@@ -136,6 +162,45 @@ char *get_my_own_prefix(void) {
 }
 
 /**
+ * Retrive the prefix character for own nick in current context
+ * @return @ or + or NULL
+ */
+char *get_my_own_prefix(void) {
+    return get_my_info("prefix", FALSE);
+}
+
+/**
+ * Retrive the mask for own nick in current context
+ * @return Host name in the form: user@host (or NULL if not known)
+ */
+char *get_my_own_host(void) {
+    return get_my_info("host", TRUE);
+}
+
+/**
+ * Calculate the length of prefix for current user in current context
+ *
+ * @return Length of prefix
+ */
+int get_prefix_length(void) {
+    char *own_host;
+    int prefix_len = 0;
+
+    /* ':! ' + 'nick' + 'ident@host', e.g. ':user!~name@mynet.com ' */
+    prefix_len = 3 + strlen(hexchat_get_info(ph, "nick"));
+    own_host = get_my_own_host();
+    if (own_host) {
+        prefix_len += strlen(own_host);
+    } else {
+        /* https://stackoverflow.com/questions/8724954/what-is-the-maximum-number-of-characters-for-a-host-name-in-unix */
+        prefix_len += 64;
+    }
+    g_free(own_host);
+
+    return prefix_len;
+}
+
+/**
  * Try to decrypt the first occurrence of fish message
  * 
  * @param message  Message to decrypt
@@ -228,11 +293,23 @@ static int handle_outgoing(char *word[], char *word_eol[], void *userdata) {
     char *prefix;
     enum fish_mode mode;
     char *message;
-    /* Encrypt the message if possible */
+    GString *command;
+    GSList *encrypted_list, *encrypted_item;
+
     const char *channel = hexchat_get_info(ph, "channel");
-    char *encrypted = fish_encrypt_for_nick(channel, word_eol[1], &mode);
-    if (!encrypted) return HEXCHAT_EAT_NONE;
-    
+
+    /* Check if we can encrypt */
+    if (!fish_nick_has_key(channel)) return HEXCHAT_EAT_NONE;
+
+    command = g_string_new("");
+    g_string_printf(command, "PRIVMSG %s :+OK ", channel);
+
+    encrypted_list = fish_encrypt_for_nick(channel, word_eol[1], &mode, get_prefix_length() + command->len);
+    if (!encrypted_list) {
+        g_string_free(command, TRUE);
+        return HEXCHAT_EAT_NONE;
+    }
+
     /* Get prefix for own nick if any */
     prefix = get_my_own_prefix();
 
@@ -241,13 +318,21 @@ static int handle_outgoing(char *word[], char *word_eol[], void *userdata) {
 
     /* Display message */
     hexchat_emit_print(ph, "Your Message", hexchat_get_info(ph, "nick"), message, prefix, NULL);
-    g_free(prefix);
     g_free(message);
-    
-    /* Send message */
-    hexchat_commandf(ph, "PRIVMSG %s :+OK %s", channel, encrypted);
-    
-    g_free(encrypted);
+
+    /* Send encrypted messages */
+    encrypted_item = encrypted_list;
+    while (encrypted_item)
+    {
+        hexchat_commandf(ph, "%s%s", command->str, (char *)encrypted_item->data);
+
+        encrypted_item = encrypted_item->next;
+    }
+
+    g_free(prefix);
+    g_string_free(command, TRUE);
+    g_slist_free_full(encrypted_list, g_free);
+
     return HEXCHAT_EAT_HEXCHAT;
 }
 
@@ -498,8 +583,9 @@ static int handle_keyx(char *word[], char *word_eol[], void *userdata) {
 static int handle_crypt_topic(char *word[], char *word_eol[], void *userdata) {
     const char *target;
     const char *topic = word_eol[2];
-    char *buf;
     enum fish_mode mode;
+    GString *command;
+    GSList *encrypted_list;
 
     if (!*topic) {
         hexchat_print(ph, usage_topic);
@@ -512,44 +598,77 @@ static int handle_crypt_topic(char *word[], char *word_eol[], void *userdata) {
     }
 
     target = hexchat_get_info(ph, "channel");
-    buf = fish_encrypt_for_nick(target, topic, &mode);
-    if (buf == NULL) {
+
+    /* Check if we can encrypt */
+    if (!fish_nick_has_key(target)) {
         hexchat_printf(ph, "/topic+ error, no key found for %s", target);
         return HEXCHAT_EAT_ALL;
     }
 
-    hexchat_commandf(ph, "TOPIC %s +OK %s", target, buf);
-    g_free(buf);
-    return HEXCHAT_EAT_ALL;
+    command = g_string_new("");
+    g_string_printf(command, "TOPIC %s +OK ", target);
+
+    encrypted_list = fish_encrypt_for_nick(target, topic, &mode, get_prefix_length() + command->len);
+    if (!encrypted_list) {
+        g_string_free(command, TRUE);
+        hexchat_printf(ph, "/topic+ error, can't encrypt %s", target);
+        return HEXCHAT_EAT_ALL;
     }
 
+    hexchat_commandf(ph, "%s%s", command->str, (char *) encrypted_list->data);
+
+    g_string_free(command, TRUE);
+    g_slist_free_full(encrypted_list, g_free);
+
+    return HEXCHAT_EAT_ALL;
+}
+
 /**
  * Command handler for /notice+
  */
-static int handle_crypt_notice(char *word[], char *word_eol[], void *userdata)
-{
+static int handle_crypt_notice(char *word[], char *word_eol[], void *userdata) {
     const char *target = word[2];
     const char *notice = word_eol[3];
     char *notice_flag;
-    char *buf;
     enum fish_mode mode;
+    GString *command;
+    GSList *encrypted_list, *encrypted_item;
 
     if (!*target || !*notice) {
         hexchat_print(ph, usage_notice);
         return HEXCHAT_EAT_ALL;
     }
 
-    buf = fish_encrypt_for_nick(target, notice, &mode);
-    if (buf == NULL) {
+    /* Check if we can encrypt */
+    if (!fish_nick_has_key(target)) {
         hexchat_printf(ph, "/notice+ error, no key found for %s.", target);
         return HEXCHAT_EAT_ALL;
     }
 
-    hexchat_commandf(ph, "quote NOTICE %s :+OK %s", target, buf);
+    command = g_string_new("");
+    g_string_printf(command, "quote NOTICE %s :+OK ", target);
+
+    encrypted_list = fish_encrypt_for_nick(target, notice, &mode, get_prefix_length() + command->len);
+    if (!encrypted_list) {
+        g_string_free(command, TRUE);
+        hexchat_printf(ph, "/notice+ error, can't encrypt %s", target);
+        return HEXCHAT_EAT_ALL;
+    }
+
     notice_flag = g_strconcat("[", fish_modes[mode], "] ", notice, NULL);
     hexchat_emit_print(ph, "Notice Send", target, notice_flag);
+
+    /* Send encrypted messages */
+    encrypted_item = encrypted_list;
+    while (encrypted_item) {
+        hexchat_commandf(ph, "%s%s", command->str, (char *) encrypted_item->data);
+
+        encrypted_item = encrypted_item->next;
+    }
+
     g_free(notice_flag);
-    g_free(buf);
+    g_string_free(command, TRUE);
+    g_slist_free_full(encrypted_list, g_free);
 
     return HEXCHAT_EAT_ALL;
 }
@@ -563,21 +682,41 @@ static int handle_crypt_msg(char *word[], char *word_eol[], void *userdata) {
     char *message_flag;
     char *prefix;
     hexchat_context *query_ctx;
-    char *buf;
     enum fish_mode mode;
+    GString *command;
+    GSList *encrypted_list, *encrypted_item;
 
     if (!*target || !*message) {
         hexchat_print(ph, usage_msg);
         return HEXCHAT_EAT_ALL;
     }
 
-    buf = fish_encrypt_for_nick(target, message, &mode);
-    if (buf == NULL) {
+    /* Check if we can encrypt */
+    if (!fish_nick_has_key(target)) {
         hexchat_printf(ph, "/msg+ error, no key found for %s", target);
         return HEXCHAT_EAT_ALL;
     }
 
-    hexchat_commandf(ph, "PRIVMSG %s :+OK %s", target, buf);
+    command = g_string_new("");
+    g_string_printf(command, "PRIVMSG %s :+OK ", target);
+
+    encrypted_list = fish_encrypt_for_nick(target, message, &mode, get_prefix_length() + command->len);
+    if (!encrypted_list) {
+        g_string_free(command, TRUE);
+        hexchat_printf(ph, "/msg+ error, can't encrypt %s", target);
+        return HEXCHAT_EAT_ALL;
+    }
+
+    /* Send encrypted messages */
+    encrypted_item = encrypted_list;
+    while (encrypted_item) {
+        hexchat_commandf(ph, "%s%s", command->str, (char *) encrypted_item->data);
+
+        encrypted_item = encrypted_item->next;
+    }
+
+    g_string_free(command, TRUE);
+    g_slist_free_full(encrypted_list, g_free);
 
     query_ctx = find_context_on_network(target);
     if (query_ctx) {
@@ -587,33 +726,52 @@ static int handle_crypt_msg(char *word[], char *word_eol[], void *userdata) {
 
         /* Add encrypted flag */
         message_flag = g_strconcat("[", fish_modes[mode], "] ", message, NULL);
-        hexchat_emit_print(ph, "Your Message", hexchat_get_info(ph, "nick"),
-                           message_flag, prefix, NULL);
+        hexchat_emit_print(ph, "Your Message", hexchat_get_info(ph, "nick"), message_flag, prefix, NULL);
         g_free(prefix);
         g_free(message_flag);
     } else {
         hexchat_emit_print(ph, "Message Send", target, message);
     }
 
-    g_free(buf);
     return HEXCHAT_EAT_ALL;
 }
 
 static int handle_crypt_me(char *word[], char *word_eol[], void *userdata) {
-	const char *channel = hexchat_get_info(ph, "channel");
-	char *buf;
-	enum fish_mode mode;
+    const char *channel = hexchat_get_info(ph, "channel");
+    enum fish_mode mode;
+    GString *command;
+    GSList *encrypted_list, *encrypted_item;
 
-    buf = fish_encrypt_for_nick(channel, word_eol[2], &mode);
-	if (!buf)
+    /* Check if we can encrypt */
+    if (!fish_nick_has_key(channel)) {
         return HEXCHAT_EAT_NONE;
+    }
+
+    command = g_string_new("");
+    g_string_printf(command, "PRIVMSG %s :\001ACTION +OK ", channel);
+
+    /* 2 = ' \001' */
+    encrypted_list = fish_encrypt_for_nick(channel, word_eol[2], &mode, get_prefix_length() + command->len + 2);
+    if (!encrypted_list) {
+        g_string_free(command, TRUE);
+        hexchat_printf(ph, "/me error, can't encrypt %s", channel);
+        return HEXCHAT_EAT_ALL;
+    }
 
-	hexchat_commandf(ph, "PRIVMSG %s :\001ACTION +OK %s \001", channel, buf);
-	hexchat_emit_print(ph, "Your Action", hexchat_get_info(ph, "nick"),
-                       word_eol[2], NULL);
+    hexchat_emit_print(ph, "Your Action", hexchat_get_info(ph, "nick"), word_eol[2], NULL);
 
-	g_free(buf);
-	return HEXCHAT_EAT_ALL;
+    /* Send encrypted messages */
+    encrypted_item = encrypted_list;
+    while (encrypted_item) {
+        hexchat_commandf(ph, "%s%s \001", command->str, (char *) encrypted_item->data);
+
+        encrypted_item = encrypted_item->next;
+    }
+
+    g_string_free(command, TRUE);
+    g_slist_free_full(encrypted_list, g_free);
+
+    return HEXCHAT_EAT_ALL;
 }
 
 /**
diff --git a/plugins/fishlim/tests/tests.c b/plugins/fishlim/tests/tests.c
index 45dfd41c..bb841c5e 100644
--- a/plugins/fishlim/tests/tests.c
+++ b/plugins/fishlim/tests/tests.c
@@ -230,6 +230,54 @@ void __base64_cbc_len(void) {
     }
 }
 
+/**
+ * Check the calculation of length limit for a plaintext in each encryption mode
+ */
+void __max_text_command_len(void) {
+    int max_encoded_len, plaintext_len;
+    enum fish_mode mode;
+
+    for (max_encoded_len = 0; max_encoded_len < 10000; ++max_encoded_len) {
+        for (mode = FISH_ECB_MODE; mode <= FISH_CBC_MODE; ++mode) {
+            plaintext_len = max_text_command_len(max_encoded_len, mode);
+            g_assert_cmpuint(encoded_len(plaintext_len, mode), <= , max_encoded_len);
+        }
+    }
+}
+
+/**
+ * Check the calculation of length limit for a plaintext in each encryption mode
+ */
+void __foreach_utf8_data_chunks(void) {
+    GRand *rand = NULL;
+    GString *chunks = NULL;
+    int tests, max_chunks_len, chunks_len;
+    char ascii_message[1001];
+    char *data_chunk = NULL;
+
+    rand = g_rand_new();
+
+    for (tests = 0; tests < 1000; ++tests) {
+
+        max_chunks_len = g_rand_int_range(rand, 2, 301);
+        random_string(ascii_message, 1000);
+
+        data_chunk = ascii_message;
+
+        chunks = g_string_new(NULL);
+
+        while (foreach_utf8_data_chunks(data_chunk, max_chunks_len, &chunks_len)) {
+            g_string_append(chunks, g_strndup(data_chunk, chunks_len));
+            /* Next chunk */
+            data_chunk += chunks_len;
+        }
+        /* Check data loss */
+        g_assert_cmpstr(chunks->str, == , ascii_message);
+        g_string_free(chunks, TRUE);
+    }
+}
+
+
 int main(int argc, char *argv[]) {
 
     g_test_init(&argc, &argv, NULL);
@@ -240,6 +288,8 @@ int main(int argc, char *argv[]) {
     g_test_add_func("/fishlim/__base64_fish_len", __base64_fish_len);
     g_test_add_func("/fishlim/__base64_ecb_len", __base64_ecb_len);
     g_test_add_func("/fishlim/__base64_cbc_len", __base64_cbc_len);
+    g_test_add_func("/fishlim/__max_text_command_len", __max_text_command_len);
+    g_test_add_func("/fishlim/__foreach_utf8_data_chunks", __foreach_utf8_data_chunks);
 
     return g_test_run();
 }
diff --git a/plugins/fishlim/utils.c b/plugins/fishlim/utils.c
index 5af87404..4052995a 100644
--- a/plugins/fishlim/utils.c
+++ b/plugins/fishlim/utils.c
@@ -23,6 +23,7 @@
 */
 
 #include "utils.h"
+#include "fish.h"
 
 /**
  * Calculate the length of Base64-encoded string
@@ -67,4 +68,82 @@ unsigned long cbc_len(size_t plaintext_len) {
  */
 unsigned long ecb_len(size_t plaintext_len) {
     return base64_fish_len(plaintext_len);
+}
+
+/**
+ * Calculate the length of encrypted string in 'mode' mode
+ *
+ * @param plaintext_len Length of plaintext
+ * @param mode          Encryption mode
+ * @return Size of encoded string
+ */
+unsigned long encoded_len(size_t plaintext_len, enum fish_mode mode) {
+    switch (mode) {
+
+        case FISH_CBC_MODE:
+            return cbc_len(plaintext_len);
+            break;
+
+        case FISH_ECB_MODE:
+            return ecb_len(plaintext_len);
+    }
+
+    return 0;
+}
+
+/**
+ * Determine the maximum length of plaintext for a 'max_len' limit taking care the overload of encryption
+ *
+ * @param max_len   Limit for plaintext
+ * @param mode      Encryption mode
+ * @return Maximum allowed plaintext length
+ */
+int max_text_command_len(size_t max_len, enum fish_mode mode) {
+    int len;
+
+    for (len = max_len; encoded_len(len, mode) > max_len; --len);
+    return len;
+}
+
+/**
+ * Iterate over 'data' in chunks of 'max_chunk_len' taking care the UTF-8 characters
+ *
+ * @param data              Data to iterate
+ * @param max_chunk_len     Size of biggest chunk
+ * @param [out] chunk_len   Current chunk length
+ * @return Pointer to current chunk position or NULL if not have more chunks
+ */
+const char *foreach_utf8_data_chunks(const char *data, int max_chunk_len, int *chunk_len) {
+    int data_len, last_chunk_len = 0;
+
+    if (!*data) {
+        return NULL;
+    }
+
+    /* Last chunk of data */
+    data_len = strlen(data);
+    if (data_len <= max_chunk_len) {
+        *chunk_len = data_len;
+        return data;
+    }
+
+    *chunk_len = 0;
+    const char *utf8_character = data;
+
+    /* Not valid UTF-8, but maybe valid text, just split into max length */
+    if (!g_utf8_validate(data, -1, NULL)) {
+        *chunk_len = max_chunk_len;
+        return utf8_character;
+    }
+
+    while (*utf8_character && *chunk_len <= max_chunk_len) {
+        last_chunk_len = *chunk_len;
+        *chunk_len = (g_utf8_next_char(utf8_character) - data) * sizeof(*utf8_character);
+        utf8_character = g_utf8_next_char(utf8_character);
+    }
+
+    /* We need the previous length before overflow the limit */
+    *chunk_len = last_chunk_len;
+
+    return utf8_character;
 }
\ No newline at end of file
diff --git a/plugins/fishlim/utils.h b/plugins/fishlim/utils.h
index 9e2b3355..623c67a4 100644
--- a/plugins/fishlim/utils.h
+++ b/plugins/fishlim/utils.h
@@ -26,10 +26,14 @@
 #define PLUGIN_HEXCHAT_FISHLIM_UTILS_H
 
 #include <stddef.h>
+#include "fish.h"
 
 unsigned long base64_len(size_t plaintext_len);
 unsigned long base64_fish_len(size_t plaintext_len);
 unsigned long cbc_len(size_t plaintext_len);
 unsigned long ecb_len(size_t plaintext_len);
+unsigned long encoded_len(size_t plaintext_len, enum fish_mode mode);
+int max_text_command_len(size_t max_len, enum fish_mode mode);
+const char *foreach_utf8_data_chunks(const char *data, int max_chunk_len, int *chunk_len);
 
 #endif
\ No newline at end of file