/**
* mds — A micro-display server
* Copyright © 2014, 2015, 2016, 2017 Mattias Andrée (maandree@kth.se)
*
* 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 3 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, see <http://www.gnu.org/licenses/>.
*/
#include "mds-message.h"
#include "macros.h"
#include "util.h"
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/socket.h>
#define try(INSTRUCTION) do { if ((r = INSTRUCTION) < 0) return r; } while (0)
/**
* Initialise a message slot so that it can
* be used by `mds_message_read`
*
* @param this Memory slot in which to store the new message
* @return Non-zero on error, `errno` will be set accordingly.
* Destroy the message on error.
*/
int
mds_message_initialise(mds_message_t *restrict this)
{
this->headers = NULL;
this->header_count = 0;
this->payload = NULL;
this->payload_size = 0;
this->payload_ptr = 0;
this->buffer_size = 128;
this->buffer_ptr = 0;
this->stage = 0;
fail_if (xmalloc(this->buffer, this->buffer_size, char));
return 0;
fail:
return -1;
}
/**
* Zero initialise a message slot
*
* @param this Memory slot in which to store the new message
*/
void
mds_message_zero_initialise(mds_message_t *restrict this)
{
this->headers = NULL;
this->header_count = 0;
this->payload = NULL;
this->payload_size = 0;
this->payload_ptr = 0;
this->buffer = NULL;
this->buffer_size = 0;
this->buffer_ptr = 0;
this->stage = 0;
}
/**
* Release all resources in a message, should
* be done even if initialisation fails
*
* @param this The message
*/
void
mds_message_destroy(mds_message_t *restrict this)
{
size_t i;
if (this->headers)
xfree(this->headers, this->header_count);
free(this->payload), this->payload = NULL;
free(this->buffer), this->buffer = NULL;
}
/**
* Extend the header list's allocation
*
* @param this The message
* @param extent The number of additional entries
* @return Zero on success, -1 on error
*/
int
mds_message_extend_headers(mds_message_t *restrict this, size_t extent)
{
char **new_headers = this->headers;
fail_if (xrealloc(new_headers, this->header_count + extent, char*));
this->headers = new_headers;
return 0;
fail:
return -1;
}
/**
* Extend the read buffer by way of doubling
*
* @param this The message
* @return Zero on success, -1 on error
*/
static int __attribute__((nonnull))
mds_message_extend_buffer(mds_message_t *restrict this)
{
char *new_buf = this->buffer;
fail_if (xrealloc(new_buf, this->buffer_size << 1, char));
this->buffer = new_buf;
this->buffer_size <<= 1;
return 0;
fail:
return -1;
}
/**
* Reset the header list and the payload
*
* @param this The message
*/
static void __attribute__((nonnull))
reset_message(mds_message_t *restrict this)
{
size_t i;
if (this->headers)
xfree(this->headers, this->header_count);
this->header_count = 0;
free(this->payload);
this->payload = NULL;
this->payload_size = 0;
this->payload_ptr = 0;
}
/**
* Read the headers the message and determine, and store, its payload's length
*
* @param this The message
* @return Zero on success, negative on error (malformated message: unrecoverable state)
*/
static int __attribute__((pure, nonnull))
get_payload_length(mds_message_t *restrict this)
{
char *header;
size_t i;
for (i = 0; i < this->header_count; i++) {
if (strstr(this->headers[i], "Length: ") == this->headers[i]) {
/* Store the message length. */
header = this->headers[i] + strlen("Length: ");
this->payload_size = atoz(header);
/* Do not except a length that is not correctly formated. */
for (; *header; header++)
if (*header < '0' || '9' < *header)
return -2; /* Malformated value, enters unrecoverable state. */
/* Stop searching for the ‘Length’ header, we have found and parsed it. */
break;
}
}
return 0;
}
/**
* Verify that a header is correctly formatted
*
* @param header The header, must be NUL-terminated
* @param length The length of the header
* @return Zero if valid, negative if invalid (malformated message: unrecoverable state)
*/
static int __attribute__((pure, nonnull))
validate_header(const char *header, size_t length)
{
char *p = memchr(header, ':', length * sizeof(char));
if (verify_utf8(header, 0) < 0)
/* Either the string is not UTF-8, or your are under an UTF-8 attack,
let's just call this unrecoverable because the client will not correct. */
return -2;
if (!p || /* Buck you, rawmemchr should not segfault the program. */
p[1] != ' ') /* Also an invalid format. ' ' is mandated after the ':'. */
return -2;
return 0;
}
/**
* Remove the beginning of the read buffer
*
* @param this The message
* @param length The number of characters to remove
* @param update_ptr Whether to update the buffer pointer
*/
static void __attribute__((nonnull))
unbuffer_beginning(mds_message_t *restrict this, size_t length, int update_ptr)
{
memmove(this->buffer, this->buffer + length, (this->buffer_ptr - length) * sizeof(char));
if (update_ptr)
this->buffer_ptr -= length;
}
/**
* Remove the header–payload delimiter from the buffer,
* get the payload's size and allocate the payload
*
* @param this The message
* @return The return value follows the rules of `mds_message_read`
*/
static int __attribute__((nonnull))
initialise_payload(mds_message_t *restrict this)
{
/* Remove the \n (end of empty line) we found from the buffer. */
unbuffer_beginning(this, 1, 1);
/* Get the length of the payload. */
if (get_payload_length(this) < 0)
return -2; /* Malformated value, enters unrecoverable state. */
/* Allocate the payload buffer. */
if (this->payload_size > 0)
fail_if (xmalloc(this->payload, this->payload_size, char));
return 0;
fail:
return -1;
}
/**
* Create a header from the buffer and store it
*
* @param this The message
* @param length The length of the header, including LF-termination
* @return The return value follows the rules of `mds_message_read`
*/
static int __attribute__((nonnull))
store_header(mds_message_t *restrict this, size_t length)
{
char *header;
/* Allocate the header. */
fail_if (xmalloc(header, length, char)); /* Last char is a LF, which is substituted with NUL. */
/* Copy the header data into the allocated header, */
memcpy(header, this->buffer, length * sizeof(char));
/* and NUL-terminate it. */
header[length - 1] = '\0';
/* Remove the header data from the read buffer. */
unbuffer_beginning(this, length, 1);
/* Make sure the the header syntax is correct so that
the program does not need to care about it. */
if (validate_header(header, length)) {
free(header);
return -2;
}
/* Store the header in the header list. */
this->headers[this->header_count++] = header;
return 0;
fail:
return -1;
}
/**
* Continue reading from the socket into the buffer
*
* @param this The message
* @param fd The file descriptor of the socket
* @return The return value follows the rules of `mds_message_read`
*/
static int __attribute__((nonnull))
continue_read(mds_message_t *restrict this, int fd)
{
size_t n;
ssize_t got;
int r;
/* Figure out how much space we have left in the read buffer. */
n = this->buffer_size - this->buffer_ptr;
/* If we do not have too much left, */
if (n < 128) {
/* grow the buffer, */
try (mds_message_extend_buffer(this));
/* and recalculate how much space we have left. */
n = this->buffer_size - this->buffer_ptr;
}
/* Then read from the socket. */
errno = 0;
got = recv(fd, this->buffer + this->buffer_ptr, n, 0);
this->buffer_ptr += (size_t)(got < 0 ? 0 : got);
fail_if (errno);
if (!got)
fail_if ((errno = ECONNRESET));
return 0;
fail:
return -1;
}
/**
* Read the next message from a file descriptor of the socket
*
* @param this Memory slot in which to store the new message
* @param fd The file descriptor of the socket
* @return Non-zero on error or interruption, `errno` will be
* set accordingly. Destroy the message on error,
* be aware that the reading could have been
* interrupted by a signal rather than canonical error.
* If -2 is returned `errno` will not have been set,
* -2 indicates that the message is malformated,
* which is a state that cannot be recovered from.
*/
int
mds_message_read(mds_message_t *restrict this, int fd)
{
size_t header_commit_buffer = 0, length, need, move;
int r;
char *p;
/* If we are at stage 2, we are done and it is time to start over.
This is important because the function could have been interrupted. */
if (this->stage == 2) {
reset_message(this);
this->stage = 0;
}
/* Read from file descriptor until we have a full message. */
for (;;) {
/* Stage 0: headers. */
/* Read all headers that we have stored into the read buffer. */
while (!this->stage && ((p = memchr(this->buffer, '\n', this->buffer_ptr * sizeof(char))))) {
if ((length = (size_t)(p - this->buffer))) {
/* We have found a header. */
/* On every eighth header found with this function call,
we prepare the header list for eight more headers so
that it does not need to be reallocated again and again. */
if (!header_commit_buffer)
try (mds_message_extend_headers(this, header_commit_buffer = 8));
/* Create and store header. */
try (store_header(this, length + 1));
header_commit_buffer -= 1;
} else {
/* We have found an empty line, i.e. the end of the headers. */
/* Remove the header–payload delimiter from the buffer,
get the payload's size and allocate the payload. */
try (initialise_payload(this));
/* Mark end of stage, next stage is getting the payload. */
this->stage = 1;
}
}
/* Stage 1: payload. */
if (this->stage == 1 && this->payload_size > 0) {
/* How much of the payload that has not yet been filled. */
need = this->payload_size - this->payload_ptr;
/* How much we have of that what is needed. */
move = min(this->buffer_ptr, need);
/* Copy what we have, and remove it from the the read buffer. */
memcpy(this->payload + this->payload_ptr, this->buffer, move * sizeof(char));
unbuffer_beginning(this, move, 1);
/* Keep track of how much we have read. */
this->payload_ptr += move;
}
if (this->stage == 1 && this->payload_ptr == this->payload_size) {
/* If we have filled the payload (or there was no payload),
mark the end of this stage, i.e. that the message is
complete, and return with success. */
this->stage = 2;
return 0;
}
/* If stage 1 was not completed. */
/* Continue reading from the socket into the buffer. */
try (continue_read(this, fd));
}
}
/**
* Get the required allocation size for `data` of the
* function `mds_message_marshal`
*
* @param this The message
* @return The size of the message when marshalled
*/
size_t
mds_message_marshal_size(const mds_message_t *restrict this)
{
size_t i, rc = this->header_count + this->payload_size;
for (i = 0; i < this->header_count; i++)
rc += strlen(this->headers[i]);
rc *= sizeof(char);
rc += 4 * sizeof(size_t) + 2 * sizeof(int);
return rc;
}
/**
* Marshal a message for state serialisation
*
* @param this The message
* @param data Output buffer for the marshalled data
*/
void
mds_message_marshal(const mds_message_t *restrict this, char *restrict data)
{
size_t i, n;
buf_set_next(data, int, MDS_MESSAGE_T_VERSION);
buf_set_next(data, size_t, this->header_count);
buf_set_next(data, size_t, this->payload_size);
buf_set_next(data, size_t, this->payload_ptr);
buf_set_next(data, size_t, this->buffer_ptr);
buf_set_next(data, int, this->stage);
for (i = 0; i < this->header_count; i++) {
n = strlen(this->headers[i]) + 1;
memcpy(data, this->headers[i], n * sizeof(char));
buf_next(data, char, n);
}
memcpy(data, this->payload, this->payload_ptr * sizeof(char));
buf_next(data, char, this->payload_ptr);
memcpy(data, this->buffer, this->buffer_ptr * sizeof(char));
}
/**
* Unmarshal a message for state deserialisation
*
* @param this Memory slot in which to store the new message
* @param data In buffer with the marshalled data
* @return Non-zero on error, `errno` will be set accordingly.
* Destroy the message on error.
*/
int
mds_message_unmarshal(mds_message_t *restrict this, char *restrict data)
{
size_t i, n, header_count;
/* buf_get(data, int, 0, MDS_MESSAGE_T_VERSION); */
buf_next(data, int, 1);
this->header_count = 0;
buf_get_next(data, size_t, header_count);
buf_get_next(data, size_t, this->payload_size);
buf_get_next(data, size_t, this->payload_ptr);
buf_get_next(data, size_t, this->buffer_size = this->buffer_ptr);
buf_get_next(data, int, this->stage);
/* Make sure that the pointers are NULL so that they are
not freed without being allocated when the message is
destroyed if this function fails. */
this->headers = NULL;
this->payload = NULL;
this->buffer = NULL;
/* To 2-power-multiple of 128 bytes. */
this->buffer_size >>= 7;
if (!this->buffer_size) {
this->buffer_size = 1;
} else {
this->buffer_size -= 1;
this->buffer_size |= this->buffer_size >> 1;
this->buffer_size |= this->buffer_size >> 2;
this->buffer_size |= this->buffer_size >> 4;
this->buffer_size |= this->buffer_size >> 8;
this->buffer_size |= this->buffer_size >> 16;
#if SIZE_MAX == UINT64_MAX
this->buffer_size |= this->buffer_size >> 32;
#endif
this->buffer_size += 1;
}
this->buffer_size <<= 7;
/* Allocate header list, payload and read buffer. */
if (header_count > 0)
fail_if (xmalloc(this->headers, header_count, char*));
if (this->payload_size > 0)
fail_if (xmalloc(this->payload, this->payload_size, char));
fail_if (xmalloc(this->buffer, this->buffer_size, char));
/* Fill the header list, payload and read buffer. */
for (i = 0; i < header_count; i++) {
n = strlen(data) + 1;
fail_if (xmemdup(this->headers[i], data, n, char));
buf_next(data, char, n);
this->header_count++;
}
memcpy(this->payload, data, this->payload_ptr * sizeof(char));
buf_next(data, char, this->payload_ptr);
memcpy(this->buffer, data, this->buffer_ptr * sizeof(char));
return 0;
fail:
return -1;
}
/**
* Get the required allocation size for `data` of the
* function `mds_message_compose`
*
* @param this The message
* @return The size of the message when marshalled
*/
size_t
mds_message_compose_size(const mds_message_t *restrict this)
{
size_t rc = 1 + this->payload_size;
size_t i;
for (i = 0; i < this->header_count; i++)
rc += strlen(this->headers[i]) + 1;
return rc * sizeof(char);
}
/**
* Marshal a message for communication
*
* @param this The message
* @param data Output buffer for the marshalled data
*/
void
mds_message_compose(const mds_message_t *restrict this, char *restrict data)
{
size_t i, n;
for (i = 0; i < this->header_count; i++) {
n = strlen(this->headers[i]);
memcpy(data, this->headers[i], n * sizeof(char));
data += n;
buf_set_next(data, char, '\n');
}
buf_set_next(data, char, '\n');
if (this->payload_size > 0)
memcpy(data, this->payload, this->payload_size * sizeof(char));
}
#undef try
