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Make sockets temporarily blocking in ncat_send and ncat_broadcast.

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It is possible to send so quickly that we start getting EAGAIN on sends.
In listen mode, this means that some sends can get lost. This patch,
adapted from one by Alex Weber, makes sockets blocking for the duration
of the send. This is not as nice as retrying the send through an event
mechanism, but should at least be correct.

http://seclists.org/nmap-dev/2012/q3/670

Compare a similar patch in r13552, which applied to --exec mode.
This commit is contained in:
david
2012-09-06 18:17:27 +00:00
parent 39f2e06d42
commit 3ae9ba63be
2 changed files with 22 additions and 2 deletions
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4
CHANGELOG
View File

@@ -1,5 +1,9 @@
# Nmap Changelog ($Id$); -*-text-*-
o [Ncat] Applied a blocking-socket workaround for a bug that could
prevent some sends from working in listen mode. The problem was
reported by Jonas Wielicki. [Alex Weber, David Fifield]
o Protocol scan (-sO) probes for TCP, UDP, and SCTP now go to ports
80, 40125, and 80 respectively, instead of being randomly generated
or going to the same port as the source port. [David Fifield]

20
ncat/ncat_core.c
View File

@@ -291,6 +291,22 @@ int fdinfo_send(struct fdinfo *fdn, const char *buf, size_t size)
return send(fdn->fd, buf, size, 0);
}
/* If we are sending a large amount of data, we might momentarily run out of send
space and get an EAGAIN when we send. Temporarily convert a socket to
blocking more, do the send, and unblock it again. Assumes that the socket was
in nonblocking mode to begin with; it has the side effect of leaving the
socket nonblocking on return. */
static int blocking_fdinfo_send(struct fdinfo *fdn, const char *buf, size_t size)
{
int ret;
block_socket(fdn->fd);
ret = fdinfo_send(fdn, buf, size);
unblock_socket(fdn->fd);
return ret;
}
int ncat_send(struct fdinfo *fdn, const char *buf, size_t size)
{
int n;
@@ -298,7 +314,7 @@ int ncat_send(struct fdinfo *fdn, const char *buf, size_t size)
if (o.recvonly)
return size;
n = fdinfo_send(fdn, buf, size);
n = blocking_fdinfo_send(fdn, buf, size);
if (n <= 0)
return n;
@@ -323,7 +339,7 @@ int ncat_broadcast(fd_set *fds, const fd_list_t *fdlist, const char *msg, size_t
continue;
fdn = get_fdinfo(fdlist, i);
if (fdinfo_send(fdn, msg, size) <= 0) {
if (blocking_fdinfo_send(fdn, msg, size) <= 0) {
if (o.debug > 1)
logdebug("Error sending to fd %d: %s.\n", i, socket_strerror(socket_errno()));
ret = -1;