/******************************************************************************
- Channel Payload
+ Channel Message Payload
******************************************************************************/
-/* Channel Payload structure. Contents of this structure is parsed
+/* Channel Message Payload structure. Contents of this structure is parsed
from SILC packets. */
struct SilcChannelPayloadStruct {
unsigned short data_len;
unsigned char *data;
- unsigned short iv_len;
+ unsigned char *mac;
unsigned char *iv;
};
-/* Parses channel payload returning new channel payload structure */
+/* Parses channel payload returning new channel payload structure. This
+ also decrypts it and checks the MAC. */
-SilcChannelPayload silc_channel_payload_parse(SilcBuffer buffer)
+SilcChannelPayload silc_channel_payload_parse(SilcBuffer buffer,
+ SilcCipher cipher,
+ SilcHmac hmac)
{
SilcChannelPayload new;
int ret;
+ unsigned int iv_len, mac_len;
+ unsigned char *mac, mac2[32];
SILC_LOG_DEBUG(("Parsing channel payload"));
+ /* Decrypt the channel message. First push the IV out of the packet.
+ The IV is used in the decryption process. Then decrypt the message.
+ After decyprtion, take the MAC from the decrypted packet, compute MAC
+ and compare the MACs. If they match, the decryption was successfull
+ and we have the channel message ready to be displayed. */
+
+ /* Push the IV out of the packet (it will be in buffer->tail) */
+ iv_len = silc_cipher_get_block_len(cipher);
+ silc_buffer_push_tail(buffer, iv_len);
+
+ /* Decrypt the channel message */
+ silc_cipher_decrypt(cipher, buffer->data, buffer->data,
+ buffer->len, buffer->tail);
+
+ /* Take the MAC */
+ mac_len = silc_hmac_len(hmac);
+ silc_buffer_push_tail(buffer, mac_len);
+ mac = buffer->tail;
+
+ /* Check the MAC of the message */
+ SILC_LOG_DEBUG(("Checking channel message MACs"));
+ silc_hmac_make(hmac, buffer->data, buffer->len, mac2, &mac_len);
+ if (memcmp(mac, mac2, mac_len)) {
+ SILC_LOG_DEBUG(("Channel message MACs does not match"));
+ return NULL;
+ }
+ SILC_LOG_DEBUG(("MAC is Ok"));
+ silc_buffer_pull_tail(buffer, iv_len + mac_len);
+
new = silc_calloc(1, sizeof(*new));
- /* Parse the Channel Payload. Ignore padding and IV, we don't need
- them. */
+ /* Parse the Channel Payload. Ignore the padding. */
ret = silc_buffer_unformat(buffer,
- SILC_STR_UI16_NSTRING_ALLOC(&new->data,
- &new->data_len),
- SILC_STR_UI16_NSTRING_ALLOC(NULL, NULL),
+ SILC_STR_UI16_NSTRING(&new->data,
+ &new->data_len),
+ SILC_STR_UI16_NSTRING(NULL, NULL),
+ SILC_STR_UI_XNSTRING(&new->mac, mac_len),
+ SILC_STR_UI_XNSTRING(&new->iv, iv_len),
SILC_STR_END);
if (ret == -1)
goto err;
return new;
err:
- if (new->data)
- silc_free(new->data);
- if (new->iv)
- silc_free(new->iv);
silc_free(new);
return NULL;
}
unsigned char *data,
unsigned short iv_len,
unsigned char *iv,
+ SilcCipher cipher,
+ SilcHmac hmac,
SilcRng rng)
{
int i;
SilcBuffer buffer;
- unsigned int len, pad_len;
+ unsigned int len, pad_len, mac_len;
unsigned char pad[SILC_PACKET_MAX_PADLEN];
+ unsigned char mac[32];
SILC_LOG_DEBUG(("Encoding channel payload"));
/* Calculate length of padding. IV is not included into the calculation
since it is not encrypted. */
- len = 2 + data_len + 2;
+ mac_len = silc_hmac_len(hmac);
+ len = 4 + data_len + mac_len;
pad_len = SILC_PACKET_PADLEN((len + 2));
/* Allocate channel payload buffer */
- len += pad_len;
- buffer = silc_buffer_alloc(len + iv_len);
- silc_buffer_pull_tail(buffer, SILC_BUFFER_END(buffer));
+ len += pad_len + iv_len;
+ buffer = silc_buffer_alloc(len);
/* Generate padding */
for (i = 0; i < pad_len; i++) pad[i] = silc_rng_get_byte(rng);
/* Encode the Channel Payload */
+ silc_buffer_pull_tail(buffer, 4 + data_len + pad_len);
silc_buffer_format(buffer,
SILC_STR_UI_SHORT(data_len),
SILC_STR_UI_XNSTRING(data, data_len),
SILC_STR_UI_SHORT(pad_len),
SILC_STR_UI_XNSTRING(pad, pad_len),
+ SILC_STR_END);
+
+ /* Compute the MAC of the channel message data */
+ silc_hmac_make(hmac, buffer->data, buffer->len, mac, &mac_len);
+
+ /* Put rest of the data to the payload */
+ silc_buffer_pull_tail(buffer, mac_len + iv_len);
+ silc_buffer_pull(buffer, 4 + data_len + pad_len);
+ silc_buffer_format(buffer,
+ SILC_STR_UI_XNSTRING(mac, mac_len),
SILC_STR_UI_XNSTRING(iv, iv_len),
SILC_STR_END);
+ silc_buffer_push(buffer, 4 + data_len + pad_len);
+
+ /* Encrypt payload of the packet. This is encrypted with the channel key. */
+ silc_cipher_encrypt(cipher, buffer->data, buffer->data,
+ buffer->len - iv_len, iv);
+
+ memset(pad, 0, sizeof(pad));
+ memset(mac, 0, sizeof(mac));
- memset(pad, 0, pad_len);
return buffer;
}
void silc_channel_payload_free(SilcChannelPayload payload)
{
- if (payload) {
- if (payload->data)
- silc_free(payload->data);
- if (payload->iv)
- silc_free(payload->iv);
+ if (payload)
silc_free(payload);
- }
}
/* Return data */
return payload->data;
}
-/* Return initial vector */
+/* Return MAC. The caller knows the length of the MAC */
-unsigned char *silc_channel_get_iv(SilcChannelPayload payload,
- unsigned int *iv_len)
+unsigned char *silc_channel_get_mac(SilcChannelPayload payload)
{
- if (iv_len)
- *iv_len = payload->iv_len;
+ return payload->mac;
+}
+
+/* Return IV. The caller knows the length of the IV */
+unsigned char *silc_channel_get_iv(SilcChannelPayload payload)
+{
return payload->iv;
}
projects / silc.git / blobdiff