Added toxdns.

toxdns currently contains functions to make it easier for clients
to create tox dns3 requests and handle tox dns3 responses: an
encrypted way of querying Tox DNS id servers for Tox ids from
usernames.

1 files changed, 224 insertions, 0 deletions

diff --git a/toxdns/toxdns.c b/toxdns/toxdns.c
new file mode 100644
index 00000000..20a4486c
--- /dev/null
+++ b/toxdns/toxdns.c
@@ -0,0 +1,224 @@
+/* toxdns.c
+ *
+ * Tox secure username DNS toxid resolving functions.
+ *
+ *  Copyright (C) 2013 Tox project All Rights Reserved.
+ *
+ *  This file is part of Tox.
+ *
+ *  Tox 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 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  Tox 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 Tox.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "../toxcore/Messenger.h"
+
+static const char base32[32] = {"abcdefghijklmnopqrstuvwxyz012345"};
+
+#define _encode(a, b, c) \
+{ \
+uint8_t i = 0; \
+    while(i != c) { \
+        *a++ = base32[((b[0] >> bits) | (b[1] << (8 - bits))) & 0x1F]; \
+        bits += 5; \
+        if(bits >= 8) { \
+            bits -= 8; \
+            b++; \
+            i++; \
+        } \
+    } \
+} \
+ 
+typedef struct {
+    uint8_t temp_pk[crypto_box_PUBLICKEYBYTES];
+    uint8_t temp_sk[crypto_box_SECRETKEYBYTES];
+    uint8_t server_public_key[crypto_box_PUBLICKEYBYTES];
+    uint8_t shared_key[crypto_box_KEYBYTES];
+    uint32_t nonce;
+    uint32_t nonce_start;
+} DNS_Object;
+
+static void dns_new_temp_keys(DNS_Object *d)
+{
+    d->nonce = d->nonce_start = random_int();
+    crypto_box_keypair(d->temp_pk, d->temp_sk);
+    encrypt_precompute(d->server_public_key, d->temp_sk, d->shared_key);
+}
+
+/* Create a new tox_dns3 object for server with server_public_key.
+ *
+ * return Null on failure.
+ * return pointer object on success.
+ */
+void *tox_dns3_new(uint8_t *server_public_key)
+{
+    DNS_Object *d = malloc(sizeof(DNS_Object));
+
+    if (d == NULL)
+        return NULL;
+
+    memcpy(d->server_public_key, server_public_key, crypto_box_PUBLICKEYBYTES);
+    dns_new_temp_keys(d);
+    return d;
+}
+
+/* Destroy the tox dns3 object.
+ */
+void tox_dns3_kill(void *dns3_object)
+{
+    memset(dns3_object, 0, sizeof(DNS_Object));
+    free(dns3_object);
+}
+
+/* Generate a dns3 string of string_max_len used to query the dns server reffered to by to
+ * dns3_object for a tox id registered to user with name of name_len.
+ *
+ * This is what the string returned looks like:
+ * 4haaaaipr1o3mz0bxweox541airydbovqlbju51mb4p0ebxq.rlqdj4kkisbep2ks3fj2nvtmk4daduqiueabmexqva1jc
+ *
+ * returns length of string on sucess.
+ * returns -1 on failure.
+ */
+int tox_generate_dns3_string(void *dns3_object, uint8_t *string, uint16_t string_max_len, uint8_t *name,
+                             uint8_t name_len)
+{
+#define DOT_INTERVAL (6 * 5)
+    int base = (sizeof(uint32_t) + crypto_box_PUBLICKEYBYTES + name_len + crypto_box_MACBYTES);
+    int end_len = ((base * 8) / 5) + (base / DOT_INTERVAL) + !!(base % 5);
+
+    if (end_len > string_max_len)
+        return -1;
+
+    DNS_Object *d = dns3_object;
+    uint8_t buffer[1024];
+    uint8_t nonce[crypto_box_NONCEBYTES] = {0};
+    memcpy(nonce, &d->nonce, sizeof(uint32_t));
+    memcpy(buffer, &d->nonce, sizeof(uint32_t));
+    memcpy(buffer + sizeof(uint32_t), d->temp_pk, crypto_box_PUBLICKEYBYTES);
+    int len = encrypt_data_symmetric(d->shared_key, nonce, name, name_len,
+                                     buffer + sizeof(uint32_t) + crypto_box_PUBLICKEYBYTES);
+
+    if (len == -1)
+        return -1;
+
+    int total_len = len + sizeof(uint32_t) + crypto_box_PUBLICKEYBYTES;
+    uint8_t *buff = buffer, *old_str = string;
+    buffer[total_len] = 0;
+    uint8_t bits = 0;
+    int i;
+
+    for (i = 0; i < (total_len / DOT_INTERVAL); ++i) {
+        _encode(string, buff, DOT_INTERVAL);
+        *string = '.';
+        ++string;
+    }
+
+    _encode(string, buff, total_len % DOT_INTERVAL);
+#undef DOT_INTERVAL
+    ++d->nonce;
+
+    if (d->nonce == d->nonce_start) {
+        dns_new_temp_keys(d);
+    }
+
+    if (end_len != string - old_str) {
+        printf("tox_generate_dns3_string Fail\n");
+        return -1;
+    }
+
+    return string - old_str;
+}
+
+
+static int decode(uint8_t *dest, uint8_t *src)
+{
+    uint8_t *p = src, *op = dest, bits = 0;
+    *op = 0;
+
+    while (*p) {
+        uint8_t ch = *p++;
+
+        switch (ch) {
+            case 'A' ... 'Z': {
+                ch = ch - 'A';
+                break;
+            }
+
+            case 'a' ... 'z': {
+                ch = ch - 'a';
+                break;
+            }
+
+            case '0' ... '5': {
+                ch = ch - '0' + 26;
+                break;
+            }
+
+            default: {
+                return - 1;
+            }
+        }
+
+        *op |= (ch << bits);
+        bits += 5;
+
+        if (bits >= 8) {
+            bits -= 8;
+            ++op;
+            *op = (ch >> (5 - bits));
+        }
+    }
+
+    return op - dest;
+}
+
+/* Decode and decrypt the id_record returned of length id_record_len into
+ * tox_id (needs to be at least TOX_FRIEND_ADDRESS_SIZE).
+ *
+ * the id_record passed to this function should look somewhat like this:
+ * 4haaaa2vgcxuycbuctvauik3plsv3d3aadv4zfjfhi3thaizwxinelrvigchv0ah3qjcsx5qhmaksb2lv2hm5cwbtx0yp
+ *
+ * returns -1 on failure.
+ * returns 0 on success.
+ *
+ */
+int tox_decrypt_dns3_TXT(void *dns3_object, uint8_t *tox_id, uint8_t *id_record, uint32_t id_record_len)
+{
+    DNS_Object *d = dns3_object;
+
+    if (id_record_len != 93)
+        return -1;
+
+    /*if (id_record_len > 255 || id_record_len <= (sizeof(uint32_t) + crypto_box_MACBYTES))
+        return -1;*/
+
+    uint8_t data[id_record_len];
+    int length = decode(data, id_record);
+
+    if (length == -1)
+        return -1;
+
+    uint8_t nonce[crypto_box_NONCEBYTES] = {0};
+    memcpy(nonce, data, sizeof(uint32_t));
+    nonce[sizeof(uint32_t)] = 1;
+    int len = decrypt_data_symmetric(d->shared_key, nonce, data + sizeof(uint32_t), length - sizeof(uint32_t), tox_id);
+
+    if (len != FRIEND_ADDRESS_SIZE)
+        return -1;
+
+    return 0;
+}
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