/* Copyright (c) 2013-2018 Dovecot authors, see the included COPYING file */
#include "lib.h"
#include "buffer.h"
#include "base64.h"
#include "istream-private.h"
#include "message-parser.h"
#include "istream-binary-converter.h"
#define BASE64_BLOCK_INPUT_SIZE 3
#define BASE64_BLOCK_SIZE 4
#define BASE64_BLOCKS_PER_LINE (76/BASE64_BLOCK_SIZE)
#define MAX_HDR_BUFFER_SIZE (1024*32)
struct binary_converter_istream {
struct istream_private istream;
pool_t pool;
struct message_parser_ctx *parser;
struct message_part *convert_part;
char base64_delayed[BASE64_BLOCK_INPUT_SIZE-1];
unsigned int base64_delayed_len;
unsigned int base64_block_pos;
buffer_t *hdr_buf;
size_t cte_header_len;
bool content_type_seen:1;
};
static void stream_add_data(struct binary_converter_istream *bstream,
const void *data, size_t size);
static bool part_can_convert(const struct message_part *part)
{
/* some MUAs use "c-t-e: binary" for multiparts.
we don't want to convert them. */
return (part->flags & MESSAGE_PART_FLAG_MULTIPART) == 0;
}
static void
stream_finish_convert_decision(struct binary_converter_istream *bstream)
{
buffer_t *buf = bstream->hdr_buf;
const unsigned char *data;
bstream->hdr_buf = NULL;
if (!part_can_convert(bstream->convert_part)) {
bstream->convert_part = NULL;
stream_add_data(bstream, buf->data, buf->used);
} else {
stream_add_data(bstream,
"Content-Transfer-Encoding: base64\r\n", 35);
data = CONST_PTR_OFFSET(buf->data, bstream->cte_header_len);
stream_add_data(bstream, data,
buf->used - bstream->cte_header_len);
}
buffer_free(&buf);
}
static void stream_add_data(struct binary_converter_istream *bstream,
const void *data, size_t size)
{
if (size == 0)
return;
if (bstream->hdr_buf != NULL) {
if (bstream->hdr_buf->used + size <= MAX_HDR_BUFFER_SIZE) {
buffer_append(bstream->hdr_buf, data, size);
return;
}
/* buffer is getting too large. just finish the decision. */
stream_finish_convert_decision(bstream);
}
memcpy(i_stream_alloc(&bstream->istream, size), data, size);
bstream->istream.pos += size;
}
static void stream_encode_base64(struct binary_converter_istream *bstream,
const void *_data, size_t size)
{
struct istream_private *stream = &bstream->istream;
const unsigned char *data = _data;
buffer_t buf;
void *dest;
size_t encode_size, max_encoded_size;
unsigned char base64_block[BASE64_BLOCK_INPUT_SIZE];
unsigned int base64_block_len, missing_len, encode_blocks;
if (bstream->base64_delayed_len > 0) {
if (bstream->base64_delayed_len == 1 && size == 1) {
bstream->base64_delayed[1] = data[0];
bstream->base64_delayed_len++;
return;
}
memcpy(base64_block, bstream->base64_delayed,
bstream->base64_delayed_len);
base64_block_len = bstream->base64_delayed_len;
if (size == 0) {
/* finish base64 */
} else {
missing_len = BASE64_BLOCK_INPUT_SIZE - base64_block_len;
i_assert(size >= missing_len);
memcpy(base64_block + base64_block_len,
data, missing_len);
data += missing_len;
size -= missing_len;
base64_block_len = BASE64_BLOCK_INPUT_SIZE;
}
if (bstream->base64_block_pos == BASE64_BLOCKS_PER_LINE) {
memcpy(i_stream_alloc(stream, 2), "\r\n", 2);
stream->pos += 2;
bstream->base64_block_pos = 0;
}
dest = i_stream_alloc(stream, BASE64_BLOCK_SIZE);
buffer_create_from_data(&buf, dest, BASE64_BLOCK_SIZE);
base64_encode(base64_block, base64_block_len, &buf);
stream->pos += buf.used;
bstream->base64_block_pos++;
bstream->base64_delayed_len = 0;
}
while (size >= BASE64_BLOCK_INPUT_SIZE) {
if (bstream->base64_block_pos == BASE64_BLOCKS_PER_LINE) {
memcpy(i_stream_alloc(stream, 2), "\r\n", 2);
stream->pos += 2;
bstream->base64_block_pos = 0;
}
/* try to encode one full line of base64 blocks */
encode_size = I_MIN(size, BASE64_BLOCKS_PER_LINE*BASE64_BLOCK_SIZE);
if (encode_size % BASE64_BLOCK_INPUT_SIZE != 0)
encode_size -= encode_size % BASE64_BLOCK_INPUT_SIZE;
encode_blocks = encode_size/BASE64_BLOCK_INPUT_SIZE;
if (bstream->base64_block_pos + encode_blocks > BASE64_BLOCKS_PER_LINE) {
encode_blocks = BASE64_BLOCKS_PER_LINE -
bstream->base64_block_pos;
encode_size = encode_blocks * BASE64_BLOCK_INPUT_SIZE;
}
max_encoded_size = MAX_BASE64_ENCODED_SIZE(encode_size);
dest = i_stream_alloc(stream, max_encoded_size);
buffer_create_from_data(&buf, dest, max_encoded_size);
base64_encode(data, encode_size, &buf);
stream->pos += buf.used;
bstream->base64_block_pos += encode_blocks;
data += encode_size;
size -= encode_size;
}
if (size > 0) {
/* encode these when more data is available */
i_assert(size < BASE64_BLOCK_INPUT_SIZE);
memcpy(bstream->base64_delayed, data, size);
bstream->base64_delayed_len = size;
}
}
static void stream_add_hdr(struct binary_converter_istream *bstream,
const struct message_header_line *hdr)
{
if (!hdr->continued) {
stream_add_data(bstream, hdr->name, hdr->name_len);
stream_add_data(bstream, hdr->middle, hdr->middle_len);
}
stream_add_data(bstream, hdr->value, hdr->value_len);
if (!hdr->no_newline)
stream_add_data(bstream, "\r\n", 2);
}
static ssize_t i_stream_binary_converter_read(struct istream_private *stream)
{
/* @UNSAFE */
struct binary_converter_istream *bstream =
(struct binary_converter_istream *)stream;
struct message_block block;
size_t old_size, new_size;
if (stream->pos - stream->skip >= i_stream_get_max_buffer_size(&stream->istream))
return -2;
old_size = stream->pos - stream->skip;
switch (message_parser_parse_next_block(bstream->parser, &block)) {
case -1:
/* done / error */
if (bstream->convert_part != NULL &&
bstream->base64_delayed_len > 0) {
/* flush any pending base64 output */
stream_encode_base64(bstream, "", 0);
new_size = stream->pos - stream->skip;
i_assert(old_size != new_size);
return new_size - old_size;
}
stream->istream.eof = TRUE;
stream->istream.stream_errno = stream->parent->stream_errno;
return -1;
case 0:
/* need more data */
return 0;
default:
break;
}
if (block.part != bstream->convert_part &&
bstream->convert_part != NULL) {
/* end of base64 encoded part */
stream_encode_base64(bstream, "", 0);
}
if (block.hdr != NULL) {
/* parsing a header */
if (strcasecmp(block.hdr->name, "Content-Type") == 0)
bstream->content_type_seen = TRUE;
if (strcasecmp(block.hdr->name, "Content-Transfer-Encoding") == 0 &&
!block.hdr->continued && !block.hdr->continues &&
block.hdr->value_len == 6 &&
i_memcasecmp(block.hdr->value, "binary", 6) == 0 &&
part_can_convert(block.part) &&
bstream->convert_part != block.part) {
/* looks like we want to convert this body part to
base64, but if we haven't seen Content-Type yet
delay the decision until we've read the rest of
the header */
i_assert(block.part != NULL);
bstream->convert_part = block.part;
bstream->base64_block_pos = 0;
if (!bstream->content_type_seen) {
i_assert(bstream->hdr_buf == NULL);
bstream->hdr_buf = buffer_create_dynamic(default_pool, 512);
stream_add_hdr(bstream, block.hdr);
bstream->cte_header_len = bstream->hdr_buf->used;
} else {
stream_add_data(bstream,
"Content-Transfer-Encoding: base64\r\n", 35);
}
} else if (block.hdr->eoh && bstream->hdr_buf != NULL) {
/* finish the decision about decoding */
stream_finish_convert_decision(bstream);
stream_add_data(bstream, "\r\n", 2);
} else {
stream_add_hdr(bstream, block.hdr);
}
} else if (block.size == 0) {
/* end of header */
if (bstream->hdr_buf != NULL) {
/* message has no body */
bstream->convert_part = NULL;
stream_add_data(bstream, bstream->hdr_buf->data,
bstream->hdr_buf->used);
buffer_free(&bstream->hdr_buf);
}
bstream->content_type_seen = FALSE;
} else if (block.part == bstream->convert_part) {
/* convert body part to base64 */
stream_encode_base64(bstream, block.data, block.size);
} else {
stream_add_data(bstream, block.data, block.size);
}
new_size = stream->pos - stream->skip;
if (new_size == old_size)
return i_stream_binary_converter_read(stream);
return new_size - old_size;
}
static void i_stream_binary_converter_close(struct iostream_private *stream,
bool close_parent)
{
struct binary_converter_istream *bstream =
(struct binary_converter_istream *)stream;
struct message_part *parts;
if (bstream->parser != NULL) {
message_parser_deinit(&bstream->parser, &parts);
}
pool_unref(&bstream->pool);
if (close_parent)
i_stream_close(bstream->istream.parent);
}
struct istream *i_stream_create_binary_converter(struct istream *input)
{
struct binary_converter_istream *bstream;
bstream = i_new(struct binary_converter_istream, 1);
bstream->istream.max_buffer_size = input->real_stream->max_buffer_size;
bstream->istream.read = i_stream_binary_converter_read;
bstream->istream.iostream.close = i_stream_binary_converter_close;
bstream->istream.istream.readable_fd = FALSE;
bstream->istream.istream.blocking = input->blocking;
bstream->istream.istream.seekable = FALSE;
bstream->pool = pool_alloconly_create("istream binary converter", 128);
bstream->parser = message_parser_init(bstream->pool, input, 0,
MESSAGE_PARSER_FLAG_INCLUDE_MULTIPART_BLOCKS |
MESSAGE_PARSER_FLAG_INCLUDE_BOUNDARIES);
return i_stream_create(&bstream->istream, input,
i_stream_get_fd(input), 0);
}