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-rw-r--r--src/libmdsclient/inbound.c483
-rw-r--r--src/libmdsclient/inbound.h126
2 files changed, 609 insertions, 0 deletions
diff --git a/src/libmdsclient/inbound.c b/src/libmdsclient/inbound.c
new file mode 100644
index 0000000..35e7ca5
--- /dev/null
+++ b/src/libmdsclient/inbound.c
@@ -0,0 +1,483 @@
+/**
+ * mds — A micro-display server
+ * Copyright © 2014, 2015 Mattias Andrée (maandree@member.fsf.org)
+ *
+ * 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 "inbound.h"
+
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <sys/socket.h>
+
+
+#define try(INSTRUCTION) if ((r = INSTRUCTION) < 0) return r
+
+
+
+/**
+ * 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 libmds_message_initialise(libmds_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;
+ this->buffer = malloc(this->buffer_size * sizeof(char));
+ return this->buffer == NULL ? -1 : 0;
+}
+
+
+/**
+ * Release all resources in a message, should
+ * be done even if initialisation fails
+ *
+ * @param this The message
+ */
+void libmds_message_destroy(libmds_message_t* restrict this)
+{
+ size_t i, n = this->header_count;
+ if (this->headers != NULL)
+ for (i = 0; i < n; i++)
+ free(this->headers[i]);
+
+ free(this->headers), this->headers = NULL;
+ free(this->payload), this->payload = NULL;
+ free(this->buffer), this->buffer = NULL;
+}
+
+
+/**
+ * Check whether a NUL-terminated string is encoded in UTF-8
+ *
+ * @param string The string
+ * @param allow_modified_nul Whether Modified UTF-8 is allowed, which allows a two-byte encoding for NUL
+ * @return Zero if good, -1 on encoding error
+ */
+__attribute__((nonnull))
+static int verify_utf8(const char* string, int allow_modified_nul) /* Cannibalised from <libmdsserver/util.h> */
+{
+ static long BYTES_TO_MIN_BITS[] = {0, 0, 8, 12, 17, 22, 37};
+ static long BYTES_TO_MAX_BITS[] = {0, 7, 11, 16, 21, 26, 31};
+ long bytes = 0, read_bytes = 0, bits = 0, c, character;
+
+ /* min bits max bits
+ 0....... 0 7
+ 110..... 10...... 8 11
+ 1110.... 10...... 10...... 12 16
+ 11110... 10...... 10...... 10...... 17 21
+ 111110.. 10...... 10...... 10...... 10...... 22 26
+ 1111110. 10...... 10...... 10...... 10...... 10...... 27 31
+ */
+
+ while ((c = (long)(*string++)))
+ if (read_bytes == 0)
+ {
+ /* First byte of the character. */
+
+ if ((c & 0x80) == 0x00)
+ /* Single-byte character. */
+ continue;
+
+ if ((c & 0xC0) == 0x80)
+ /* Single-byte character marked as multibyte, or
+ a non-first byte in a multibyte character. */
+ return -1;
+
+ /* Multibyte character. */
+ while ((c & 0x80))
+ bytes++, c <<= 1;
+ read_bytes = 1;
+ character = c & 0x7F;
+ if (bytes > 6)
+ /* 31-bit characters can be encoded with 6-bytes,
+ and UTF-8 does not cover higher code points. */
+ return -1;
+ }
+ else
+ {
+ /* Not first byte of the character. */
+
+ if ((c & 0xC0) != 0x80)
+ /* Beginning of new character before a
+ multibyte character has ended. */
+ return -1;
+
+ character = (character << 6) | (c & 0x7F);
+
+ if (++read_bytes < bytes)
+ /* Not at last byte yet. */
+ continue;
+
+ /* Check that the character is not unnecessarily long. */
+ while (character)
+ character >>= 1, bits++;
+ bits = ((bits == 0) && (bytes == 2) && allow_modified_nul) ? 8 : bits;
+ if ((bits < BYTES_TO_MIN_BITS[bytes]) || (BYTES_TO_MAX_BITS[bytes] < bits))
+ return -1;
+
+ read_bytes = bytes = bits = 0;
+ }
+
+ /* Make sure we did not stop at the middle of a multibyte character. */
+ return read_bytes == 0 ? 0 : -1;
+}
+
+
+
+/**
+ * Extend the header list's allocation
+ *
+ * @param this The message
+ * @param extent The number of additional entries
+ * @return Zero on success, -1 on error
+ */
+__attribute__((nonnull))
+static int extend_headers(libmds_message_t* restrict this, size_t extent)
+{
+ char** new_headers = realloc(this->headers, (this->header_count + extent) * sizeof(char*));
+ if (new_headers == NULL)
+ return -1;
+ this->headers = new_headers;
+ return 0;
+}
+
+
+/**
+ * Extend the read buffer by way of doubling
+ *
+ * @param this The message
+ * @return Zero on success, -1 on error
+ */
+__attribute__((nonnull))
+static int extend_buffer(libmds_message_t* restrict this)
+{
+ char* new_buf = realloc(this->buffer, (this->buffer_size << 1) * sizeof(char));
+ if (new_buf == NULL)
+ return -1;
+ this->buffer = new_buf;
+ this->buffer_size <<= 1;
+ return 0;
+}
+
+/**
+ * Reset the header list and the payload
+ *
+ * @param this The message
+ */
+__attribute__((nonnull))
+static void reset_message(libmds_message_t* restrict this)
+{
+ size_t i, n = this->header_count;
+ if (this->headers != NULL)
+ {
+ for (i = 0; i < n; i++)
+ free(this->headers[i]);
+ free(this->headers);
+ this->headers = NULL;
+ }
+ 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)
+ */
+__attribute__((pure, nonnull))
+static int get_payload_length(libmds_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 = (size_t)atoll(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)
+ */
+__attribute__((pure, nonnull))
+static int 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,
+ lets just call this unrecoverable because the client will not correct. */
+ return -2;
+
+ if ((p == NULL) || /* 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
+ */
+__attribute__((nonnull))
+static void unbuffer_beginning(libmds_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`
+ */
+__attribute__((nonnull))
+static int initialise_payload(libmds_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)
+ if ((this->payload = malloc(this->payload_size * sizeof(char))) == NULL)
+ return -1;
+
+ return 0;
+}
+
+
+/**
+ * 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`
+ */
+__attribute__((nonnull))
+static int store_header(libmds_message_t* restrict this, size_t length)
+{
+ char* header;
+
+ /* Allocate the header. */
+ header = malloc(length * sizeof(char)); /* Last char is a LF, which is substituted with NUL. */
+ if (header == NULL)
+ return -1;
+ /* 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;
+}
+
+
+/**
+ * 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`
+ */
+__attribute__((nonnull))
+static int continue_read(libmds_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 (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);
+ if (errno)
+ return -1;
+ if (got == 0)
+ return errno = ECONNRESET, -1;
+
+ return 0;
+}
+
+
+/**
+ * Read the next message from a file descriptor
+ *
+ * @param this Memory slot in which to store the new message
+ * @param fd The file descriptor
+ * @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 libmds_message_read(libmds_message_t* restrict this, int fd)
+{
+ size_t header_commit_buffer = 0;
+ int r;
+
+ /* 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 (;;)
+ {
+ char* p;
+ size_t length;
+
+ /* Stage 0: headers. */
+ /* Read all headers that we have stored into the read buffer. */
+ while ((this->stage == 0) &&
+ ((p = memchr(this->buffer, '\n', this->buffer_ptr * sizeof(char))) != NULL))
+ 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 == 0)
+ try (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. */
+ size_t need = this->payload_size - this->payload_ptr;
+ /* How much we have of that what is needed. */
+ size_t move = this->buffer_ptr < need ? 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));
+ }
+}
+
diff --git a/src/libmdsclient/inbound.h b/src/libmdsclient/inbound.h
new file mode 100644
index 0000000..a127c3e
--- /dev/null
+++ b/src/libmdsclient/inbound.h
@@ -0,0 +1,126 @@
+/**
+ * mds — A micro-display server
+ * Copyright © 2014, 2015 Mattias Andrée (maandree@member.fsf.org)
+ *
+ * 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/>.
+ */
+#ifndef MDS_LIBMDSCLIENT_INBOUND_H
+#define MDS_LIBMDSCLIENT_INBOUND_H
+/* This module is eerily similar to <libmdsserver/mds-message.h>,
+ * somethings have been removed, some things have been added. */
+
+
+#include <stddef.h>
+
+
+
+/**
+ * Message passed between a server and a client or between two of either
+ */
+typedef struct libmds_message
+{
+ /**
+ * The headers in the message, each element in this list
+ * as an unparsed header, it consists of both the header
+ * name and its associated value, joined by ": ". A header
+ * cannot be `NULL` (unless its memory allocation failed,)
+ * but `headers` itself is `NULL` if there are no headers.
+ * The "Length" header should be included in this list.
+ */
+ char** headers;
+
+ /**
+ * The number of headers in the message
+ */
+ size_t header_count;
+
+ /**
+ * The payload of the message, `NULL` if none (of zero-length)
+ */
+ char* payload;
+
+ /**
+ * The size of the payload
+ */
+ size_t payload_size;
+
+ /**
+ * How much of the payload that has been stored (internal data)
+ */
+ size_t payload_ptr;
+
+ /**
+ * Internal buffer for the reading function (internal data)
+ */
+ char* buffer;
+
+ /**
+ * The size allocated to `buffer` (internal data)
+ */
+ size_t buffer_size;
+
+ /**
+ * The number of bytes used in `buffer` (internal data)
+ */
+ size_t buffer_ptr;
+
+ /**
+ * 0 while reading headers, 1 while reading payload, and 2 when done (internal data)
+ */
+ int stage;
+
+} libmds_message_t;
+
+
+
+/**
+ * Initialise a message slot so that it can
+ * be used by `libmds_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.
+ */
+__attribute__((nonnull))
+int libmds_message_initialise(libmds_message_t* restrict this);
+
+/**
+ * Release all resources in a message, should
+ * be done even if initialisation fails
+ *
+ * @param this The message
+ */
+__attribute__((nonnull))
+void libmds_message_destroy(libmds_message_t* restrict this);
+
+/**
+ * Read the next message from a file descriptor
+ *
+ * @param this Memory slot in which to store the new message
+ * @param fd The file descriptor
+ * @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.
+ */
+__attribute__((nonnull))
+int libmds_message_read(libmds_message_t* restrict this, int fd);
+
+
+
+#endif
+
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