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sftp_packet_read: handle partial reads of the length field

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SFTP packets come as [32 bit length][payload] and the code didn't
previously handle that the initial 32 bit field was read only partially
when it was read.
This commit is contained in:
Daniel Stenberg 2010-11-02 19:14:33 +01:00
parent 73be9fab04
commit 6395a738fd
2 changed files with 39 additions and 35 deletions
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72
src/sftp.c
View File

@ -167,10 +167,8 @@ sftp_packet_read(LIBSSH2_SFTP *sftp)
{ {
LIBSSH2_CHANNEL *channel = sftp->channel; LIBSSH2_CHANNEL *channel = sftp->channel;
LIBSSH2_SESSION *session = channel->session; LIBSSH2_SESSION *session = channel->session;
unsigned char buffer[4]; /* To store the packet length */
unsigned char *packet; unsigned char *packet;
size_t packet_len, packet_received; size_t packet_len, packet_received;
ssize_t bytes_received;
int rc; int rc;
_libssh2_debug(session, LIBSSH2_TRACE_SFTP, "recv packet"); _libssh2_debug(session, LIBSSH2_TRACE_SFTP, "recv packet");
@ -187,62 +185,66 @@ sftp_packet_read(LIBSSH2_SFTP *sftp)
"partial read cont, len: %lu", packet_len); "partial read cont, len: %lu", packet_len);
} }
else { else {
rc = _libssh2_channel_read(channel, 0, (char *) buffer, 4); /* each packet starts with a 32 bit length field */
if (rc == LIBSSH2_ERROR_EAGAIN) { rc = _libssh2_channel_read(channel, 0,
(char *)&sftp->partial_size[
sftp->partial_size_len],
4 - sftp->partial_size_len);
if (rc == LIBSSH2_ERROR_EAGAIN)
return rc; return rc;
} else if (rc < 0)
else if (4 != rc) { return _libssh2_error(session, rc, "channel read");
/* TODO: this is stupid since we can in fact get 1-3 bytes in a
legitimate working case as well if the connection happens to be sftp->partial_size_len += rc;
super slow or something */
return _libssh2_error(session, LIBSSH2_ERROR_CHANNEL_FAILURE, if(4 != sftp->partial_size_len)
"Read part of packet"); /* we got a short read for the length part */
} return LIBSSH2_ERROR_EAGAIN;
packet_len = _libssh2_ntohu32(sftp->partial_size);
/* make sure we don't proceed if the packet size is unreasonably
large */
if (packet_len > LIBSSH2_SFTP_PACKET_MAXLEN)
return _libssh2_error(session,
LIBSSH2_ERROR_CHANNEL_PACKET_EXCEEDED,
"SFTP packet too large");
packet_len = _libssh2_ntohu32(buffer);
_libssh2_debug(session, LIBSSH2_TRACE_SFTP, _libssh2_debug(session, LIBSSH2_TRACE_SFTP,
"Data begin - Packet Length: %lu", packet_len); "Data begin - Packet Length: %lu", packet_len);
if (packet_len > LIBSSH2_SFTP_PACKET_MAXLEN) {
return _libssh2_error(session, LIBSSH2_ERROR_CHANNEL_PACKET_EXCEEDED,
"SFTP packet too large");
}
packet = LIBSSH2_ALLOC(session, packet_len); packet = LIBSSH2_ALLOC(session, packet_len);
if (!packet) { if (!packet)
return _libssh2_error(session, LIBSSH2_ERROR_ALLOC, return _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
"Unable to allocate SFTP packet"); "Unable to allocate SFTP packet");
} sftp->partial_size_len = 0;
packet_received = 0; packet_received = 0;
} }
/* Read as much of the packet as we can */ /* Read as much of the packet as we can */
while (packet_len > packet_received) { while (packet_len > packet_received) {
bytes_received = rc = _libssh2_channel_read(channel, 0,
_libssh2_channel_read(channel, 0, (char *) packet + packet_received,
(char *) packet + packet_received, packet_len - packet_received);
packet_len - packet_received);
if (bytes_received == LIBSSH2_ERROR_EAGAIN) { if (rc == LIBSSH2_ERROR_EAGAIN) {
/* /*
* We received EAGAIN, save what we have and * We received EAGAIN, save what we have and return EAGAIN to the
* return to EAGAIN to the caller * caller
*/ */
sftp->partial_packet = packet; sftp->partial_packet = packet;
sftp->partial_len = packet_len; sftp->partial_len = packet_len;
sftp->partial_received = packet_received; sftp->partial_received = packet_received;
packet = NULL; return rc;
return bytes_received;
} }
else if (bytes_received < 0) { else if (rc < 0) {
LIBSSH2_FREE(session, packet); LIBSSH2_FREE(session, packet);
return _libssh2_error(session, bytes_received, return _libssh2_error(session, rc,
"Receive error waiting for SFTP packet"); "Error waiting for SFTP packet");
} }
packet_received += bytes_received; packet_received += rc;
} }
sftp->partial_packet = NULL;
rc = sftp_packet_add(sftp, packet, packet_len); rc = sftp_packet_add(sftp, packet, packet_len);
if (rc) { if (rc) {
LIBSSH2_FREE(session, packet); LIBSSH2_FREE(session, packet);

2
src/sftp.h
View File

@ -114,6 +114,8 @@ struct _LIBSSH2_SFTP
uint32_t last_errno; uint32_t last_errno;
/* Holder for partial packet, use in libssh2_sftp_packet_read() */ /* Holder for partial packet, use in libssh2_sftp_packet_read() */
unsigned char partial_size[4]; /* buffer for size field */
size_t partial_size_len; /* size field length */
unsigned char *partial_packet; /* The data */ unsigned char *partial_packet; /* The data */
size_t partial_len; /* Desired number of bytes */ size_t partial_len; /* Desired number of bytes */
size_t partial_received; /* Bytes received so far */ size_t partial_received; /* Bytes received so far */