summaryrefslogtreecommitdiffhomepage
diff options
context:
space:
mode:
authorMatt Johnston <matt@ucc.asn.au>2014-02-22 18:02:09 +0800
committerMatt Johnston <matt@ucc.asn.au>2014-02-22 18:02:09 +0800
commitbb7934bf04128c8db9d129fd0c5db7f03b5311b8 (patch)
treef27c96fcf90b6365783314e4a8fa6359453de143
parentfb3c718963ea99225ad8419b260ace3ef5c5a9ba (diff)
A few fixes for cases where compression increases payload sizes, and
be more precise about maximum channel sizes
-rw-r--r--common-channel.c11
-rw-r--r--packet.c21
2 files changed, 19 insertions, 13 deletions
diff --git a/common-channel.c b/common-channel.c
index 4a6bdb4..9162980 100644
--- a/common-channel.c
+++ b/common-channel.c
@@ -59,6 +59,13 @@ static void close_chan_fd(struct Channel *channel, int fd, int how);
#define ERRFD_IS_READ(channel) ((channel)->extrabuf == NULL)
#define ERRFD_IS_WRITE(channel) (!ERRFD_IS_READ(channel))
+/* allow space for:
+ * 1 byte byte SSH_MSG_CHANNEL_DATA
+ * 4 bytes uint32 recipient channel
+ * 4 bytes string data
+ */
+#define RECV_MAX_CHANNEL_DATA_LEN (RECV_MAX_PAYLOAD_LEN-(1+4+4))
+
/* Initialise all the channels */
void chaninitialise(const struct ChanType *chantypes[]) {
@@ -165,7 +172,7 @@ static struct Channel* newchannel(unsigned int remotechan,
newchan->extrabuf = NULL; /* The user code can set it up */
newchan->recvdonelen = 0;
- newchan->recvmaxpacket = RECV_MAX_PAYLOAD_LEN;
+ newchan->recvmaxpacket = RECV_MAX_CHANNEL_DATA_LEN;
ses.channels[i] = newchan;
ses.chancount++;
@@ -1028,7 +1035,7 @@ int send_msg_channel_open_init(int fd, const struct ChanType *type) {
buf_putstring(ses.writepayload, type->name, strlen(type->name));
buf_putint(ses.writepayload, chan->index);
buf_putint(ses.writepayload, opts.recv_window);
- buf_putint(ses.writepayload, RECV_MAX_PAYLOAD_LEN);
+ buf_putint(ses.writepayload, RECV_MAX_CHANNEL_DATA_LEN);
TRACE(("leave send_msg_channel_open_init()"))
return DROPBEAR_SUCCESS;
diff --git a/packet.c b/packet.c
index 1b5ee93..b624c27 100644
--- a/packet.c
+++ b/packet.c
@@ -41,7 +41,11 @@ static void make_mac(unsigned int seqno, const struct key_context_directional *
unsigned char *output_mac);
static int checkmac();
-#define ZLIB_COMPRESS_INCR 100
+/* For exact details see http://www.zlib.net/zlib_tech.html
+ * 5 bytes per 16kB block, plus 6 bytes for the stream.
+ * We might allocate 5 unnecessary bytes here if it's an
+ * exact multiple. */
+#define ZLIB_COMPRESS_EXPANSION (((RECV_MAX_PAYLOAD_LEN/16384)+1)*5 + 6)
#define ZLIB_DECOMPRESS_INCR 1024
#ifndef DISABLE_ZLIB
static buffer* buf_decompress(buffer* buf, unsigned int len);
@@ -333,7 +337,7 @@ void decrypt_packet() {
/* payload length */
/* - 4 - 1 is for LEN and PADLEN values */
len = ses.readbuf->len - padlen - 4 - 1 - macsize;
- if ((len > RECV_MAX_PAYLOAD_LEN) || (len < 1)) {
+ if ((len > RECV_MAX_PAYLOAD_LEN+ZLIB_COMPRESS_EXPANSION) || (len < 1)) {
dropbear_exit("Bad packet size %d", len);
}
@@ -422,6 +426,8 @@ static buffer* buf_decompress(buffer* buf, unsigned int len) {
if (zstream->avail_out == 0) {
int new_size = 0;
if (ret->size >= RECV_MAX_PAYLOAD_LEN) {
+ /* Already been increased as large as it can go,
+ * yet didn't finish up the decompression */
dropbear_exit("bad packet, oversized decompressed");
}
new_size = MIN(RECV_MAX_PAYLOAD_LEN, ret->size + ZLIB_DECOMPRESS_INCR);
@@ -526,7 +532,7 @@ void encrypt_packet() {
+ mac_size
#ifndef DISABLE_ZLIB
/* some extra in case 'compression' makes it larger */
- + ZLIB_COMPRESS_INCR
+ + ZLIB_COMPRESS_EXPANSION
#endif
/* and an extra cleartext (stripped before transmission) byte for the
* packet type */
@@ -539,14 +545,7 @@ void encrypt_packet() {
#ifndef DISABLE_ZLIB
/* compression */
if (is_compress_trans()) {
- int compress_delta;
buf_compress(writebuf, ses.writepayload, ses.writepayload->len);
- compress_delta = (writebuf->len - PACKET_PAYLOAD_OFF) - ses.writepayload->len;
-
- /* Handle the case where 'compress' increased the size. */
- if (compress_delta > ZLIB_COMPRESS_INCR) {
- buf_resize(writebuf, writebuf->size + compress_delta);
- }
} else
#endif
{
@@ -694,7 +693,7 @@ static void buf_compress(buffer * dest, buffer * src, unsigned int len) {
/* the buffer has been filled, we must extend. This only happens in
* unusual circumstances where the data grows in size after deflate(),
* but it is possible */
- buf_resize(dest, dest->size + ZLIB_COMPRESS_INCR);
+ buf_resize(dest, dest->size + ZLIB_COMPRESS_EXPANSION);
}
TRACE2(("leave buf_compress"))