4 files changed, 861 insertions, 3 deletions

diff --git a/toxcore/Messenger.c b/toxcore/Messenger.c
index 21cb2671..3d96f6ca 100644
--- a/toxcore/Messenger.c
+++ b/toxcore/Messenger.c
@@ -42,6 +42,7 @@
 static void set_friend_status(Messenger *m, int32_t friendnumber, uint8_t status);
 static int write_cryptpacket_id(const Messenger *m, int32_t friendnumber, uint8_t packet_id, const uint8_t *data,
                                 uint32_t length, uint8_t congestion_control);
+static int send_avatar_data_control(const Messenger *m, const uint32_t friendnumber, uint8_t op);
 
 // friend_not_valid determines if the friendnumber passed is valid in the Messenger object
 static uint8_t friend_not_valid(const Messenger *m, int32_t friendnumber)
@@ -247,6 +248,10 @@ int32_t m_addfriend(Messenger *m, const uint8_t *address, const uint8_t *data, u
             m->friendlist[i].statusmessage = calloc(1, 1);
             m->friendlist[i].statusmessage_length = 1;
             m->friendlist[i].userstatus = USERSTATUS_NONE;
+            m->friendlist[i].avatar_info_sent = 0;
+            m->friendlist[i].avatar_recv_data = NULL;
+            m->friendlist[i].avatar_send_data.bytes_sent = 0;
+            m->friendlist[i].avatar_send_data.last_reset = 0;
             m->friendlist[i].is_typing = 0;
             memcpy(m->friendlist[i].info, data, length);
             m->friendlist[i].info_size = length;
@@ -299,6 +304,10 @@ int32_t m_addfriend_norequest(Messenger *m, const uint8_t *client_id)
             m->friendlist[i].statusmessage = calloc(1, 1);
             m->friendlist[i].statusmessage_length = 1;
             m->friendlist[i].userstatus = USERSTATUS_NONE;
+            m->friendlist[i].avatar_info_sent = 0;
+            m->friendlist[i].avatar_recv_data = NULL;
+            m->friendlist[i].avatar_send_data.bytes_sent = 0;
+            m->friendlist[i].avatar_send_data.last_reset = 0;
             m->friendlist[i].is_typing = 0;
             m->friendlist[i].message_id = 0;
             m->friendlist[i].receives_read_receipts = 1; /* Default: YES. */
@@ -330,6 +339,7 @@ int m_delfriend(Messenger *m, int32_t friendnumber)
     onion_delfriend(m->onion_c, m->friendlist[friendnumber].onion_friendnum);
     crypto_kill(m->net_crypto, m->friendlist[friendnumber].crypt_connection_id);
     free(m->friendlist[friendnumber].statusmessage);
+    free(m->friendlist[friendnumber].avatar_recv_data);
     remove_request_received(&(m->fr), m->friendlist[friendnumber].client_id);
     memset(&(m->friendlist[friendnumber]), 0, sizeof(Friend));
     uint32_t i;
@@ -564,6 +574,131 @@ int m_set_userstatus(Messenger *m, uint8_t status)
     return 0;
 }
 
+int m_set_avatar(Messenger *m, uint8_t format, const uint8_t *data, uint32_t length)
+{
+    if (length > MAX_AVATAR_DATA_LENGTH)
+        return -1;
+
+    if (format == AVATARFORMAT_NONE) {
+        free(m->avatar_data);
+        m->avatar_data = NULL;
+        m->avatar_data_length = 0;
+        m->avatar_format = format;
+        memset(m->avatar_hash, 0, AVATAR_HASH_LENGTH);
+    } else {
+        if (length == 0 || data == NULL)
+            return -1;
+
+        uint8_t *tmp = realloc(m->avatar_data, length);
+
+        if (tmp == NULL)
+            return -1;
+
+        m->avatar_format = format;
+        m->avatar_data = tmp;
+        m->avatar_data_length = length;
+        memcpy(m->avatar_data, data, length);
+
+        m_avatar_hash(m->avatar_hash, m->avatar_data, m->avatar_data_length);
+    }
+
+    uint32_t i;
+
+    for (i = 0; i < m->numfriends; ++i)
+        m->friendlist[i].avatar_info_sent = 0;
+
+    return 0;
+}
+
+int m_get_self_avatar(const Messenger *m, uint8_t *format, uint8_t *buf, uint32_t *length, uint32_t maxlen,
+                      uint8_t *hash)
+{
+    if (format)
+        *format = m->avatar_format;
+
+    if (length)
+        *length = m->avatar_data_length;
+
+    if (hash)
+        memcpy(hash, m->avatar_hash, AVATAR_HASH_LENGTH);
+
+    if (buf != NULL && maxlen > 0) {
+        if (m->avatar_data_length <= maxlen)
+            memcpy(buf, m->avatar_data, m->avatar_data_length);
+        else
+            return -1;
+    }
+
+    return 0;
+}
+
+int m_avatar_hash(uint8_t *hash, const uint8_t *data, const uint32_t datalen)
+{
+    if (hash == NULL)
+        return -1;
+
+    crypto_hash_sha256(hash, data, datalen);
+    return 0;
+}
+
+
+int m_request_avatar_info(const Messenger *m, const int32_t friendnumber)
+{
+    if (friend_not_valid(m, friendnumber))
+        return -1;
+
+    if (write_cryptpacket_id(m, friendnumber, PACKET_ID_AVATAR_INFO_REQ, 0, 0, 0))
+        return 0;
+    else
+        return -1;
+}
+
+int m_send_avatar_info(const Messenger *m, const int32_t friendnumber)
+{
+    if (friend_not_valid(m, friendnumber))
+        return -1;
+
+    uint8_t data[sizeof(uint8_t) + AVATAR_HASH_LENGTH];
+    data[0] = m->avatar_format;
+    memcpy(data + 1, m->avatar_hash, AVATAR_HASH_LENGTH);
+
+    if (write_cryptpacket_id(m, friendnumber, PACKET_ID_AVATAR_INFO, data, sizeof(data), 0))
+        return 0;
+    else
+        return -1;
+}
+
+int m_request_avatar_data(const Messenger *m, const int32_t friendnumber)
+{
+    if (friend_not_valid(m, friendnumber))
+        return -1;
+
+    AVATARRECEIVEDATA *avrd = m->friendlist[friendnumber].avatar_recv_data;
+
+    if (avrd == NULL) {
+        avrd = calloc(sizeof(AVATARRECEIVEDATA), 1);
+
+        if (avrd == NULL)
+            return -1;
+
+        avrd->started = 0;
+        m->friendlist[friendnumber].avatar_recv_data = avrd;
+    }
+
+    if (avrd->started) {
+        LOGGER_DEBUG("Resetting already started data request. "
+                     "friendnumber == %u", friendnumber);
+    }
+
+    avrd->started = 0;
+    avrd->bytes_received = 0;
+    avrd->total_length = 0;
+    avrd->format = AVATARFORMAT_NONE;
+
+    return send_avatar_data_control(m, friendnumber, AVATARDATACONTROL_REQ);
+}
+
+
 /* return the size of friendnumber's user status.
  * Guaranteed to be at most MAX_STATUSMESSAGE_LENGTH.
  */
@@ -806,6 +941,20 @@ void m_callback_connectionstatus_internal_av(Messenger *m, void (*function)(Mess
     m->friend_connectionstatuschange_internal_userdata = userdata;
 }
 
+void m_callback_avatar_info(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t, uint8_t *, void *),
+                            void *userdata)
+{
+    m->avatar_info_recv = function;
+    m->avatar_info_recv_userdata = userdata;
+}
+
+void m_callback_avatar_data(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t, uint8_t *, uint8_t *,
+                            uint32_t, void *), void *userdata)
+{
+    m->avatar_data_recv = function;
+    m->avatar_data_recv_userdata = userdata;
+}
+
 static void break_files(const Messenger *m, int32_t friendnumber);
 static void check_friend_connectionstatus(Messenger *m, int32_t friendnumber, uint8_t status)
 {
@@ -1857,6 +2006,9 @@ Messenger *new_messenger(Messenger_Options *options)
         m->net = new_networking(ip, TOX_PORT_DEFAULT);
     }
 
+    m->avatar_format = AVATARFORMAT_NONE;
+    m->avatar_data = NULL;
+
     if (m->net == NULL) {
         free(m);
         return NULL;
@@ -1930,10 +2082,11 @@ void kill_messenger(Messenger *m)
     kill_networking(m->net);
 
     for (i = 0; i < m->numfriends; ++i) {
-        if (m->friendlist[i].statusmessage)
-            free(m->friendlist[i].statusmessage);
+        free(m->friendlist[i].statusmessage);
+        free(m->friendlist[i].avatar_recv_data);
     }
 
+    free(m->avatar_data);
     free(m->friendlist);
     free(m);
 }
@@ -1973,11 +2126,287 @@ static int handle_status(void *object, int i, uint8_t status)
         if (m->friendlist[i].status == FRIEND_ONLINE) {
             set_friend_status(m, i, FRIEND_CONFIRMED);
         }
+
+        /* Clear avatar transfer state */
+        if (m->friendlist[i].avatar_recv_data) {
+            free(m->friendlist[i].avatar_recv_data);
+            m->friendlist[i].avatar_recv_data = NULL;
+        }
     }
 
     return 0;
 }
 
+
+/* Sends an avatar data control packet to the peer. Usually to return status
+ * values or request data.
+ */
+static int send_avatar_data_control(const Messenger *m, const uint32_t friendnumber,
+                                    uint8_t op)
+{
+    int ret = write_cryptpacket_id(m, friendnumber, PACKET_ID_AVATAR_DATA_CONTROL,
+                                   &op, sizeof(op), 0);
+    LOGGER_DEBUG("friendnumber = %u, op = %u, ret = %d",
+                 friendnumber, op, ret);
+    return ret ? 0 : -1;
+}
+
+
+static int handle_avatar_data_control(Messenger *m, uint32_t friendnumber,
+                                      uint8_t *data, uint32_t data_length)
+{
+    if (data_length != 1) {
+        LOGGER_DEBUG("Error: PACKET_ID_AVATAR_DATA_CONTROL with bad "
+                     "data_length = %u, friendnumber = %u",
+                     data_length, friendnumber);
+        send_avatar_data_control(m, friendnumber, AVATARDATACONTROL_ERROR);
+        return -1;  /* Error */
+    }
+
+    LOGGER_DEBUG("friendnumber = %u, op = %u", friendnumber, data[0]);
+
+    switch (data[0]) {
+        case AVATARDATACONTROL_REQ: {
+
+            /* Check data transfer limits for this friend */
+            AVATARSENDDATA *const avsd = &(m->friendlist[friendnumber].avatar_send_data);
+
+            if (avsd->bytes_sent >= AVATAR_DATA_TRANSFER_LIMIT) {
+                /* User reached data limit. Check timeout */
+                uint64_t now = unix_time();
+
+                if (avsd->last_reset > 0
+                        && (avsd->last_reset + AVATAR_DATA_TRANSFER_TIMEOUT < now)) {
+                    avsd->bytes_sent = 0;
+                    avsd->last_reset = now;
+                } else {
+                    /* Friend still rate-limitted. Send an error and stops. */
+                    LOGGER_DEBUG("Avatar data transfer limit reached. "
+                                 "friendnumber = %u", friendnumber);
+                    send_avatar_data_control(m, friendnumber, AVATARDATACONTROL_ERROR);
+                    return 0;
+                }
+            }
+
+            /* Start the transmission with a DATA_START message. Format:
+             *  uint8_t format
+             *  uint8_t hash[AVATAR_HASH_LENGTH]
+             *  uint32_t total_length
+             */
+            LOGGER_DEBUG("Sending start msg to friend number %u. "
+                         "m->avatar_format = %u, m->avatar_data_length = %u",
+                         friendnumber, m->avatar_format, m->avatar_data_length);
+            uint8_t start_data[1 + AVATAR_HASH_LENGTH + sizeof(uint32_t)];
+            uint32_t avatar_len = htonl(m->avatar_data_length);
+
+            start_data[0] = m->avatar_format;
+            memcpy(start_data + 1, m->avatar_hash, AVATAR_HASH_LENGTH);
+            memcpy(start_data + 1 + AVATAR_HASH_LENGTH, &avatar_len, sizeof(uint32_t));
+
+            avsd->bytes_sent += sizeof(start_data);  /* For rate limit */
+
+            int ret = write_cryptpacket_id(m, friendnumber, PACKET_ID_AVATAR_DATA_START,
+                                           start_data, sizeof(start_data), 0);
+
+            if (!ret) {
+                /* Something went wrong, try to signal the error so the friend
+                 * can clear up the state. */
+                send_avatar_data_control(m, friendnumber, AVATARDATACONTROL_ERROR);
+                return 0;
+            }
+
+            /* User have no avatar data, nothing more to do. */
+            if (m->avatar_format == AVATARFORMAT_NONE)
+                return 0;
+
+            /* Send the actual avatar data. */
+            uint32_t offset = 0;
+
+            while (offset < m->avatar_data_length) {
+                uint32_t chunk_len = m->avatar_data_length - offset;
+
+                if (chunk_len > AVATAR_DATA_MAX_CHUNK_SIZE)
+                    chunk_len = AVATAR_DATA_MAX_CHUNK_SIZE;
+
+                uint8_t chunk[AVATAR_DATA_MAX_CHUNK_SIZE];
+                memcpy(chunk, m->avatar_data + offset, chunk_len);
+                offset += chunk_len;
+                avsd->bytes_sent += chunk_len;  /* For rate limit */
+
+                int ret = write_cryptpacket_id(m, friendnumber,
+                                               PACKET_ID_AVATAR_DATA_PUSH,
+                                               chunk, chunk_len, 0);
+
+                if (!ret) {
+                    LOGGER_DEBUG("write_cryptpacket_id failed. ret = %d, "
+                                 "friendnumber = %u, offset = %u",
+                                 ret, friendnumber, offset);
+                    send_avatar_data_control(m, friendnumber, AVATARDATACONTROL_ERROR);
+                    return -1;
+                }
+            }
+
+            return 0;
+        }
+
+        case AVATARDATACONTROL_ERROR: {
+            if (m->friendlist[friendnumber].avatar_recv_data) {
+                /* We were receiving the data, sender detected an error
+                  (eg. changing avatar) and asked us to stop. */
+                free(m->friendlist[friendnumber].avatar_recv_data);
+                m->friendlist[friendnumber].avatar_recv_data = NULL;
+            }
+
+            return 0;
+        }
+    }
+
+    return -1;
+}
+
+
+static int handle_avatar_data_start(Messenger *m, uint32_t friendnumber,
+                                    uint8_t *data, uint32_t data_length)
+{
+    LOGGER_DEBUG("data_length = %u, friendnumber = %u", data_length, friendnumber);
+
+    if (data_length != 1 + AVATAR_HASH_LENGTH + sizeof(uint32_t)) {
+        LOGGER_DEBUG("Invalid msg length = %u, friendnumber = %u",
+                     data_length, friendnumber);
+        return -1;
+    }
+
+    AVATARRECEIVEDATA *avrd = m->friendlist[friendnumber].avatar_recv_data;
+
+    if (avrd == NULL) {
+        LOGGER_DEBUG("Received an unrequested DATA_START, friendnumber = %u",
+                     friendnumber);
+        return -1;
+    }
+
+    if (avrd->started) {
+        /* Already receiving data from this friend. Must be an error
+         * or an malicious request, because we zeroed the started bit
+         * when we requested the data. */
+        LOGGER_DEBUG("Received an unrequested duplicated DATA_START, "
+                     "friendnumber = %u", friendnumber);
+        return -1;
+    }
+
+    /* Copy data from message to our control structure */
+    avrd->started = 1;
+    avrd->format = data[0];
+    memcpy(avrd->hash, data + 1, AVATAR_HASH_LENGTH);
+    uint32_t tmp_len;
+    memcpy(&tmp_len, data + 1 + AVATAR_HASH_LENGTH, sizeof(uint32_t));
+    avrd->total_length = ntohl(tmp_len);
+    avrd->bytes_received = 0;
+
+    LOGGER_DEBUG("friendnumber = %u, avrd->format = %u, "
+                 "avrd->total_length = %u, avrd->bytes_received = %u",
+                 friendnumber, avrd->format, avrd->total_length,
+                 avrd->bytes_received);
+
+    if (avrd->total_length > MAX_AVATAR_DATA_LENGTH) {
+        /* Invalid data length. Stops. */
+        LOGGER_DEBUG("Error: total_length > MAX_AVATAR_DATA_LENGTH, "
+                     "friendnumber = %u", friendnumber);
+        free(avrd);
+        avrd = NULL;
+        m->friendlist[friendnumber].avatar_recv_data = NULL;
+        return 0;
+    }
+
+    if (avrd->format == AVATARFORMAT_NONE || avrd->total_length == 0) {
+        /* No real data to receive. Run callback function and finish. */
+        LOGGER_DEBUG("format == NONE, friendnumber = %u", friendnumber);
+
+        if (m->avatar_data_recv) {
+            memset(avrd->hash, 0, AVATAR_HASH_LENGTH);
+            (m->avatar_data_recv)(m, friendnumber, avrd->format, avrd->hash,
+                                  NULL, 0, m->avatar_data_recv_userdata);
+        }
+
+        free(avrd);
+        avrd = NULL;
+        m->friendlist[friendnumber].avatar_recv_data = NULL;
+        return 0;
+    }
+
+    /* Waits for more data to be received */
+    return 0;
+}
+
+
+static int handle_avatar_data_push(Messenger *m, uint32_t friendnumber,
+                                   uint8_t *data, uint32_t data_length)
+{
+    LOGGER_DEBUG("friendnumber = %u, data_length = %u", friendnumber, data_length);
+
+    AVATARRECEIVEDATA *avrd = m->friendlist[friendnumber].avatar_recv_data;
+
+    if (avrd == NULL) {
+        /* No active transfer. It must be an error or a malicious request,
+         * because we set the avatar_recv_data on the first DATA_START. */
+        LOGGER_DEBUG("Error: avrd == NULL, friendnumber = %u", friendnumber);
+        return -1;  /* Error */
+    }
+
+    if (avrd->started == 0) {
+        /* Receiving data for a non-started request. Must be an error
+         * or an malicious request. */
+        LOGGER_DEBUG("Received an data push for a yet non started data "
+                     "request. friendnumber = %u", friendnumber);
+        return -1;  /* Error */
+    }
+
+    uint32_t new_length = avrd->bytes_received + data_length;
+
+    if (new_length > avrd->total_length
+            || new_length >= MAX_AVATAR_DATA_LENGTH) {
+        /* Invalid data length due to error or malice. Stops. */
+        LOGGER_DEBUG("Invalid data length. friendnumber = %u, "
+                     "new_length = %u, avrd->total_length = %u",
+                     friendnumber, new_length,  avrd->total_length);
+        free(avrd);
+        m->friendlist[friendnumber].avatar_recv_data = NULL;
+        return 0;
+    }
+
+    memcpy(avrd->data + avrd->bytes_received, data, data_length);
+    avrd->bytes_received += data_length;
+
+    if (avrd->bytes_received == avrd->total_length) {
+        LOGGER_DEBUG("All data received. friendnumber = %u", friendnumber);
+
+        /* All data was received. Check if the hashes match. It the
+         * requester's responsability to do this. The sender may have done
+         * anything with its avatar data between the DATA_START and now.
+         */
+        uint8_t cur_hash[AVATAR_HASH_LENGTH];
+        m_avatar_hash(cur_hash, avrd->data, avrd->bytes_received);
+
+        if (memcmp(cur_hash, avrd->hash, AVATAR_HASH_LENGTH) == 0) {
+            /* Avatar successfuly received! */
+            if (m->avatar_data_recv) {
+                (m->avatar_data_recv)(m, friendnumber, avrd->format, cur_hash,
+                                      avrd->data, avrd->bytes_received, m->avatar_data_recv_userdata);
+            }
+        } else {
+            LOGGER_DEBUG("Avatar hash error. friendnumber = %u", friendnumber);
+        }
+
+        free(avrd);
+        m->friendlist[friendnumber].avatar_recv_data = NULL;
+        return 0;
+    }
+
+    /* Waits for more data to be received */
+    return 0;
+}
+
+
+
 static int handle_packet(void *object, int i, uint8_t *temp, uint16_t len)
 {
     if (len == 0)
@@ -2115,6 +2544,42 @@ static int handle_packet(void *object, int i, uint8_t *temp, uint16_t len)
             break;
         }
 
+        case PACKET_ID_AVATAR_INFO_REQ: {
+            /* Send our avatar information */
+            m_send_avatar_info(m, i);
+            break;
+        }
+
+        case PACKET_ID_AVATAR_INFO: {
+            if (m->avatar_info_recv) {
+                /*
+                 * A malicious user may send an incomplete avatar info message.
+                 * Check if it have the correct size for the format:
+                 * [1 uint8_t: avatar format] [32 uint8_t: hash]
+                 */
+                if (data_length == AVATAR_HASH_LENGTH + 1) {
+                    (m->avatar_info_recv)(m, i, data[0], data + 1, m->avatar_info_recv_userdata);
+                }
+            }
+
+            break;
+        }
+
+        case PACKET_ID_AVATAR_DATA_CONTROL: {
+            handle_avatar_data_control(m, i, data, data_length);
+            break;
+        }
+
+        case PACKET_ID_AVATAR_DATA_START: {
+            handle_avatar_data_start(m, i, data, data_length);
+            break;
+        }
+
+        case PACKET_ID_AVATAR_DATA_PUSH: {
+            handle_avatar_data_push(m, i, data, data_length);
+            break;
+        }
+
         case PACKET_ID_RECEIPT: {
             uint32_t msgid;
 
@@ -2343,6 +2808,11 @@ void do_friends(Messenger *m)
                     m->friendlist[i].userstatus_sent = 1;
             }
 
+            if (m->friendlist[i].avatar_info_sent == 0) {
+                if (m_send_avatar_info(m, i) == 0)
+                    m->friendlist[i].avatar_info_sent = 1;
+            }
+
             if (m->friendlist[i].user_istyping_sent == 0) {
                 if (send_user_istyping(m, i, m->friendlist[i].user_istyping))
                     m->friendlist[i].user_istyping_sent = 1;
diff --git a/toxcore/Messenger.h b/toxcore/Messenger.h
index 6c641a9a..a107d80f 100644
--- a/toxcore/Messenger.h
+++ b/toxcore/Messenger.h
@@ -36,6 +36,9 @@
 #define MAX_NAME_LENGTH 128
 /* TODO: this must depend on other variable. */
 #define MAX_STATUSMESSAGE_LENGTH 1007
+#define MAX_AVATAR_DATA_LENGTH 16384
+#define AVATAR_HASH_LENGTH 32
+
 
 #define FRIEND_ADDRESS_SIZE (crypto_box_PUBLICKEYBYTES + sizeof(uint32_t) + sizeof(uint16_t))
 
@@ -46,6 +49,11 @@
 #define PACKET_ID_STATUSMESSAGE 49
 #define PACKET_ID_USERSTATUS 50
 #define PACKET_ID_TYPING 51
+#define PACKET_ID_AVATAR_INFO_REQ 52
+#define PACKET_ID_AVATAR_INFO 53
+#define PACKET_ID_AVATAR_DATA_CONTROL 54
+#define PACKET_ID_AVATAR_DATA_START 55
+#define PACKET_ID_AVATAR_DATA_PUSH 56
 #define PACKET_ID_RECEIPT 63
 #define PACKET_ID_MESSAGE 64
 #define PACKET_ID_ACTION 65
@@ -109,6 +117,13 @@ enum {
 /* If no packets are received from friend in this time interval, kill the connection. */
 #define FRIEND_CONNECTION_TIMEOUT (FRIEND_PING_INTERVAL * 3)
 
+/* Must be < MAX_CRYPTO_DATA_SIZE */
+#define AVATAR_DATA_MAX_CHUNK_SIZE (MAX_CRYPTO_DATA_SIZE-1)
+
+/* Per-friend data limit for avatar data requests */
+#define AVATAR_DATA_TRANSFER_LIMIT  (10*MAX_AVATAR_DATA_LENGTH)
+#define AVATAR_DATA_TRANSFER_TIMEOUT    (60) /* 164kB every 60 seconds is not a lot */
+
 
 /* USERSTATUS -
  * Represents userstatuses someone can have.
@@ -122,6 +137,42 @@ typedef enum {
 }
 USERSTATUS;
 
+/* AVATARFORMAT -
+ * Data formats for user avatar images
+ */
+typedef enum {
+    AVATARFORMAT_NONE,
+    AVATARFORMAT_PNG
+}
+AVATARFORMAT;
+
+/* AVATARDATACONTROL
+ * To control avatar data requests (PACKET_ID_AVATAR_DATA_CONTROL)
+ */
+typedef enum {
+    AVATARDATACONTROL_REQ,
+    AVATARDATACONTROL_ERROR
+}
+AVATARDATACONTROL;
+
+typedef struct {
+    uint8_t started;
+    AVATARFORMAT format;
+    uint8_t hash[AVATAR_HASH_LENGTH];
+    uint32_t total_length;
+    uint32_t bytes_received;
+    uint8_t data[MAX_AVATAR_DATA_LENGTH];
+}
+AVATARRECEIVEDATA;
+
+typedef struct {
+    /* Fields only used to limit the network usage from a given friend */
+    uint32_t bytes_sent;    /* Total bytes send to this user */
+    uint64_t last_reset;    /* Time the data counter was last reset */
+}
+AVATARSENDDATA;
+
+
 struct File_Transfers {
     uint64_t size;
     uint64_t transferred;
@@ -163,6 +214,7 @@ typedef struct {
     uint8_t statusmessage_sent;
     USERSTATUS userstatus;
     uint8_t userstatus_sent;
+    uint8_t avatar_info_sent;
     uint8_t user_istyping;
     uint8_t user_istyping_sent;
     uint8_t is_typing;
@@ -178,6 +230,9 @@ typedef struct {
     int invited_groups[MAX_INVITED_GROUPS];
     uint16_t invited_groups_num;
 
+    AVATARSENDDATA avatar_send_data;
+    AVATARRECEIVEDATA *avatar_recv_data;    // We are receiving avatar data from this friend.
+
     struct {
         int (*function)(void *object, const uint8_t *data, uint32_t len);
         void *object;
@@ -209,6 +264,11 @@ typedef struct Messenger {
 
     USERSTATUS userstatus;
 
+    AVATARFORMAT avatar_format;
+    uint8_t *avatar_data;
+    uint32_t avatar_data_length;
+    uint8_t avatar_hash[AVATAR_HASH_LENGTH];
+
     Friend *friendlist;
     uint32_t numfriends;
 
@@ -243,6 +303,10 @@ typedef struct Messenger {
     void *friend_connectionstatuschange_userdata;
     void (*friend_connectionstatuschange_internal)(struct Messenger *m, int32_t, uint8_t, void *);
     void *friend_connectionstatuschange_internal_userdata;
+    void *avatar_info_recv_userdata;
+    void (*avatar_info_recv)(struct Messenger *m, int32_t, uint8_t, uint8_t *, void *);
+    void *avatar_data_recv_userdata;
+    void (*avatar_data_recv)(struct Messenger *m, int32_t, uint8_t, uint8_t *, uint8_t *, uint32_t, void *);
 
     void (*group_invite)(struct Messenger *m, int32_t, const uint8_t *, void *);
     void *group_invite_userdata;
@@ -437,6 +501,94 @@ int m_copy_self_statusmessage(const Messenger *m, uint8_t *buf, uint32_t maxlen)
 uint8_t m_get_userstatus(const Messenger *m, int32_t friendnumber);
 uint8_t m_get_self_userstatus(const Messenger *m);
 
+
+/* Set the user avatar image data.
+ * This should be made before connecting, so we will not announce that the user have no avatar
+ * before setting and announcing a new one, forcing the peers to re-download it.
+ *
+ * Notice that the library treats the image as raw data and does not interpret it by any way.
+ *
+ * Arguments:
+ *  format - Avatar image format or NONE for user with no avatar (see AVATARFORMAT);
+ *  data - pointer to the avatar data (may be NULL it the format is NONE);
+ *  length - length of image data. Must be <= MAX_AVATAR_DATA_LENGTH.
+ *
+ * returns 0 on success
+ * returns -1 on failure.
+ */
+int m_set_avatar(Messenger *m, uint8_t format, const uint8_t *data, uint32_t length);
+
+/* Get avatar data from the current user.
+ * Copies the current user avatar data to the destination buffer and sets the image format
+ * accordingly.
+ *
+ * If the avatar format is NONE, the buffer 'buf' isleft uninitialized, 'hash' is zeroed, and
+ * 'length' is set to zero.
+ *
+ * If any of the pointers format, buf, length, and hash are NULL, that particular field will be ignored.
+ *
+ * Arguments:
+ *   format - destination pointer to the avatar image format (see AVATARFORMAT);
+ *   buf - destination buffer to the image data. Must have at least 'maxlen' bytes;
+ *   length - destination pointer to the image data length;
+ *   maxlen - length of the destination buffer 'buf';
+ *   hash - destination pointer to the avatar hash (it must be exactly AVATAR_HASH_LENGTH bytes long).
+ *
+ * returns 0 on success;
+ * returns -1 on failure.
+ *
+ */
+int m_get_self_avatar(const Messenger *m, uint8_t *format, uint8_t *buf, uint32_t *length, uint32_t maxlen,
+                      uint8_t *hash);
+
+/* Generates a cryptographic hash of the given avatar data.
+ * This function is a wrapper to internal message-digest functions and specifically provided
+ * to generate hashes from user avatars that may be memcmp()ed with the values returned by the
+ * other avatar functions. It is specially important to validate cached avatars.
+ *
+ * Arguments:
+ *  hash - destination buffer for the hash data, it must be exactly AVATAR_HASH_LENGTH bytes long.
+ *  data - avatar image data;
+ *  datalen - length of the avatar image data; it must be <= MAX_AVATAR_DATA_LENGTH.
+ *
+ * returns 0 on success
+ * returns -1 on failure.
+ */
+int m_avatar_hash(uint8_t *hash, const uint8_t *data, const uint32_t datalen);
+
+/* Request avatar information from a friend.
+ * Asks a friend to provide their avatar information (image format and hash). The friend may
+ * or may not answer this request and, if answered, the information will be provided through
+ * the callback 'avatar_info'.
+ *
+ * returns 0 on success
+ * returns -1 on failure.
+ */
+int m_request_avatar_info(const Messenger *m, const int32_t friendnumber);
+
+/* Send an unrequested avatar information to a friend.
+ * Sends our avatar format and hash to a friend; he/she can use this information to validate
+ * an avatar from the cache and may (or not) reply with an avatar data request.
+ *
+ * Notice: it is NOT necessary to send these notification after changing the avatar or
+ * connecting. The library already does this.
+ *
+ * returns 0 on success
+ * returns -1 on failure.
+ */
+int m_send_avatar_info(const Messenger *m, const int32_t friendnumber);
+
+
+/* Request the avatar data from a friend.
+ * Ask a friend to send their avatar data. The friend may or may not answer this request and,
+ * if answered, the information will be provided in callback 'avatar_data'.
+ *
+ * returns 0 on sucess
+ * returns -1 on failure.
+ */
+int m_request_avatar_data(const Messenger *m, const int32_t friendnumber);
+
+
 /* returns timestamp of last time friendnumber was seen online, or 0 if never seen.
  * returns -1 on error.
  */
@@ -533,6 +685,49 @@ void m_callback_connectionstatus(Messenger *m, void (*function)(Messenger *m, in
 void m_callback_connectionstatus_internal_av(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t, void *),
         void *userdata);
 
+
+/* Set the callback function for avatar information.
+ * This callback will be called when avatar information are received from friends. These events
+ * can arrive at anytime, but are usually received uppon connection and in reply of avatar
+ * information requests.
+ *
+ * Function format is:
+ *  function(Tox *tox, int32_t friendnumber, uint8_t format, uint8_t *hash, void *userdata)
+ *
+ * where 'format' is the avatar image format (see AVATARFORMAT) and 'hash' is the hash of
+ * the avatar data for caching purposes and it is exactly AVATAR_HASH_LENGTH long. If the
+ * image format is NONE, the hash is zeroed.
+ *
+ */
+void m_callback_avatar_info(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t, uint8_t *, void *),
+                            void *userdata);
+
+
+/* Set the callback function for avatar data.
+ * This callback will be called when the complete avatar data was correctly received from a
+ * friend. This only happens in reply of a avatar data request (see tox_request_avatar_data);
+ *
+ * Function format is:
+ *  function(Tox *tox, int32_t friendnumber, uint8_t format, uint8_t *hash, uint8_t *data, uint32_t datalen, void *userdata)
+ *
+ * where 'format' is the avatar image format (see AVATARFORMAT); 'hash' is the
+ * locally-calculated cryptographic hash of the avatar data and it is exactly
+ * AVATAR_HASH_LENGTH long; 'data' is the avatar image data and 'datalen' is the length
+ * of such data.
+ *
+ * If format is NONE, 'data' is NULL, 'datalen' is zero, and the hash is zeroed. The hash is
+ * always validated locally with the function tox_avatar_hash and ensured to match the image
+ * data, so this value can be safely used to compare with cached avatars.
+ *
+ * WARNING: users MUST treat all avatar image data received from another peer as untrusted and
+ * potentially malicious. The library only ensures that the data which arrived is the same the
+ * other user sent, and does not interpret or validate any image data.
+ */
+void m_callback_avatar_data(Messenger *m, void (*function)(Messenger *m, int32_t, uint8_t, uint8_t *, uint8_t *,
+                            uint32_t, void *), void *userdata);
+
+
+
 /**********GROUP CHATS************/
 
 /* Set the callback for group invites.
diff --git a/toxcore/tox.c b/toxcore/tox.c
index a4413c4f..b44f0ee6 100644
--- a/toxcore/tox.c
+++ b/toxcore/tox.c
@@ -798,6 +798,57 @@ uint64_t tox_file_data_remaining(const Tox *tox, int32_t friendnumber, uint8_t f
     return file_dataremaining(m, friendnumber, filenumber, send_receive);
 }
 
+
+/****************AVATAR FUNCTIONS*****************/
+
+void tox_callback_avatar_info(Tox *tox, void (*function)(Tox *tox, int32_t, uint8_t, uint8_t *, void *), void *userdata)
+{
+    Messenger *m = tox;
+    m_callback_avatar_info(m, function, userdata);
+}
+
+void tox_callback_avatar_data(Tox *tox, void (*function)(Tox *tox, int32_t, uint8_t, uint8_t *, uint8_t *, uint32_t,
+                              void *), void *userdata)
+{
+    Messenger *m = tox;
+    m_callback_avatar_data(m, function, userdata);
+}
+
+int tox_set_avatar(Tox *tox, uint8_t format, const uint8_t *data, uint32_t length)
+{
+    Messenger *m = tox;
+    return m_set_avatar(m, format, data, length);
+}
+
+int tox_get_self_avatar(const Tox *tox, uint8_t *format, uint8_t *buf, uint32_t *length, uint32_t maxlen, uint8_t *hash)
+{
+    const Messenger *m = tox;
+    return m_get_self_avatar(m, format, buf, length, maxlen, hash);
+}
+
+int tox_avatar_hash(const Tox *tox, uint8_t *hash, const uint8_t *data, const uint32_t datalen)
+{
+    return m_avatar_hash(hash, data, datalen);
+}
+
+int tox_request_avatar_info(const Tox *tox, const int32_t friendnumber)
+{
+    const Messenger *m = tox;
+    return m_request_avatar_info(m, friendnumber);
+}
+
+int tox_send_avatar_info(Tox *tox, const int32_t friendnumber)
+{
+    const Messenger *m = tox;
+    return m_send_avatar_info(m, friendnumber);
+}
+
+int tox_request_avatar_data(const Tox *tox, const int32_t friendnumber)
+{
+    const Messenger *m = tox;
+    return m_request_avatar_data(m, friendnumber);
+}
+
 /***************END OF FILE SENDING FUNCTIONS******************/
 
 /* Like tox_bootstrap_from_address but for TCP relays only.
diff --git a/toxcore/tox.h b/toxcore/tox.h
index 278a19cd..a5efee34 100644
--- a/toxcore/tox.h
+++ b/toxcore/tox.h
@@ -37,6 +37,8 @@ extern "C" {
 #define TOX_MAX_MESSAGE_LENGTH 1368
 #define TOX_MAX_STATUSMESSAGE_LENGTH 1007
 #define TOX_CLIENT_ID_SIZE 32
+#define TOX_MAX_AVATAR_DATA_LENGTH 16384
+#define TOX_AVATAR_HASH_LENGTH 32
 
 #define TOX_FRIEND_ADDRESS_SIZE (TOX_CLIENT_ID_SIZE + sizeof(uint32_t) + sizeof(uint16_t))
 
@@ -70,6 +72,16 @@ typedef enum {
 }
 TOX_USERSTATUS;
 
+
+/* AVATARFORMAT -
+ * Data formats for user avatar images
+ */
+typedef enum {
+    TOX_AVATARFORMAT_NONE,
+    TOX_AVATARFORMAT_PNG
+}
+TOX_AVATARFORMAT;
+
 #ifndef __TOX_DEFINED__
 #define __TOX_DEFINED__
 typedef struct Tox Tox;
@@ -242,7 +254,6 @@ int tox_get_self_status_message(const Tox *tox, uint8_t *buf, uint32_t maxlen);
 uint8_t tox_get_user_status(const Tox *tox, int32_t friendnumber);
 uint8_t tox_get_self_user_status(const Tox *tox);
 
-
 /* returns timestamp of last time friendnumber was seen online, or 0 if never seen.
  * returns -1 on error.
  */
@@ -517,6 +528,137 @@ uint32_t tox_count_chatlist(const Tox *tox);
  * of out_list will be truncated to list_size. */
 uint32_t tox_get_chatlist(const Tox *tox, int *out_list, uint32_t list_size);
 
+/****************AVATAR FUNCTIONS*****************/
+
+/* Set the callback function for avatar information.
+ * This callback will be called when avatar information are received from friends. These events
+ * can arrive at anytime, but are usually received uppon connection and in reply of avatar
+ * information requests.
+ *
+ * Function format is:
+ *  function(Tox *tox, int32_t friendnumber, uint8_t format, uint8_t *hash, void *userdata)
+ *
+ * where 'format' is the avatar image format (see TOX_AVATARFORMAT) and 'hash' is the hash of
+ * the avatar data for caching purposes and it is exactly TOX_AVATAR_HASH_LENGTH long. If the
+ * image format is NONE, the hash is zeroed.
+ *
+ */
+void tox_callback_avatar_info(Tox *tox, void (*function)(Tox *tox, int32_t, uint8_t, uint8_t *, void *),
+                              void *userdata);
+
+
+/* Set the callback function for avatar data.
+ * This callback will be called when the complete avatar data was correctly received from a
+ * friend. This only happens in reply of a avatar data request (see tox_request_avatar_data);
+ *
+ * Function format is:
+ *  function(Tox *tox, int32_t friendnumber, uint8_t format, uint8_t *hash, uint8_t *data, uint32_t datalen, void *userdata)
+ *
+ * where 'format' is the avatar image format (see TOX_AVATARFORMAT); 'hash' is the
+ * locally-calculated cryptographic hash of the avatar data and it is exactly
+ * TOX_AVATAR_HASH_LENGTH long; 'data' is the avatar image data and 'datalen' is the length
+ * of such data.
+ *
+ * If format is NONE, 'data' is NULL, 'datalen' is zero, and the hash is zeroed. The hash is
+ * always validated locally with the function tox_avatar_hash and ensured to match the image
+ * data, so this value can be safely used to compare with cached avatars.
+ *
+ * WARNING: users MUST treat all avatar image data received from another peer as untrusted and
+ * potentially malicious. The library only ensures that the data which arrived is the same the
+ * other user sent, and does not interpret or validate any image data.
+ */
+void tox_callback_avatar_data(Tox *tox, void (*function)(Tox *tox, int32_t, uint8_t, uint8_t *, uint8_t *, uint32_t,
+                              void *), void *userdata);
+
+/* Set the user avatar image data.
+ * This should be made before connecting, so we will not announce that the user have no avatar
+ * before setting and announcing a new one, forcing the peers to re-download it.
+ *
+ * Notice that the library treats the image as raw data and does not interpret it by any way.
+ *
+ * Arguments:
+ *  format - Avatar image format or NONE for user with no avatar (see TOX_AVATARFORMAT);
+ *  data - pointer to the avatar data (may be NULL it the format is NONE);
+ *  length - length of image data. Must be <= TOX_MAX_AVATAR_DATA_LENGTH.
+ *
+ * returns 0 on success
+ * returns -1 on failure.
+ */
+int tox_set_avatar(Tox *tox, uint8_t format, const uint8_t *data, uint32_t length);
+
+
+/* Get avatar data from the current user.
+ * Copies the current user avatar data to the destination buffer and sets the image format
+ * accordingly.
+ *
+ * If the avatar format is NONE, the buffer 'buf' isleft uninitialized, 'hash' is zeroed, and
+ * 'length' is set to zero.
+ *
+ * If any of the pointers format, buf, length, and hash are NULL, that particular field will be ignored.
+ *
+ * Arguments:
+ *   format - destination pointer to the avatar image format (see TOX_AVATARFORMAT);
+ *   buf - destination buffer to the image data. Must have at least 'maxlen' bytes;
+ *   length - destination pointer to the image data length;
+ *   maxlen - length of the destination buffer 'buf';
+ *   hash - destination pointer to the avatar hash (it must be exactly TOX_AVATAR_HASH_LENGTH bytes long).
+ *
+ * returns 0 on success;
+ * returns -1 on failure.
+ *
+ */
+int tox_get_self_avatar(const Tox *tox, uint8_t *format, uint8_t *buf, uint32_t *length, uint32_t maxlen,
+                        uint8_t *hash);
+
+
+/* Generates a cryptographic hash of the given avatar data.
+ * This function is a wrapper to internal message-digest functions and specifically provided
+ * to generate hashes from user avatars that may be memcmp()ed with the values returned by the
+ * other avatar functions. It is specially important to validate cached avatars.
+ *
+ * Arguments:
+ *  hash - destination buffer for the hash data, it must be exactly TOX_AVATAR_HASH_LENGTH bytes long.
+ *  data - avatar image data;
+ *  datalen - length of the avatar image data; it must be <= TOX_MAX_AVATAR_DATA_LENGTH.
+ *
+ * returns 0 on success
+ * returns -1 on failure.
+ */
+int tox_avatar_hash(const Tox *tox, uint8_t *hash, const uint8_t *data, const uint32_t datalen);
+
+
+/* Request avatar information from a friend.
+ * Asks a friend to provide their avatar information (image format and hash). The friend may
+ * or may not answer this request and, if answered, the information will be provided through
+ * the callback 'avatar_info'.
+ *
+ * returns 0 on success
+ * returns -1 on failure.
+ */
+int tox_request_avatar_info(const Tox *tox, const int32_t friendnumber);
+
+
+/* Send an unrequested avatar information to a friend.
+ * Sends our avatar format and hash to a friend; he/she can use this information to validate
+ * an avatar from the cache and may (or not) reply with an avatar data request.
+ *
+ * Notice: it is NOT necessary to send these notification after changing the avatar or
+ * connecting. The library already does this.
+ *
+ * returns 0 on success
+ * returns -1 on failure.
+ */
+int tox_send_avatar_info(Tox *tox, const int32_t friendnumber);
+
+
+/* Request the avatar data from a friend.
+ * Ask a friend to send their avatar data. The friend may or may not answer this request and,
+ * if answered, the information will be provided in callback 'avatar_data'.
+ *
+ * returns 0 on sucess
+ * returns -1 on failure.
+ */
+int tox_request_avatar_data(const Tox *tox, const int32_t friendnumber);
 
 /****************FILE SENDING FUNCTIONS*****************/
 /* NOTE: This how to will be updated.