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From: Guilhem Moulin <guilhem@debian.org>
Date: Mon, 22 Oct 2018 04:15:52 +0200
Subject: destination port list
---
nc.1 | 26 ++++++++++++++++---
netcat.c | 86 ++++++++++++++++++++++++++++++++-------------------------------
2 files changed, 68 insertions(+), 44 deletions(-)
--- a/nc.1
+++ b/nc.1
@@ -414,15 +414,35 @@ The
flag can be used to tell
.Nm
to report open ports,
-rather than initiate a connection.
+rather than initiate a connection. Usually it's useful to turn on verbose
+output to stderr by use this option in conjunction with
+.Fl v
+option.
+.Pp
For example:
.Bd -literal -offset indent
-$ nc -z host.example.com 20-30
+$ nc \-zv host.example.com 20-30
Connection to host.example.com 22 port [tcp/ssh] succeeded!
Connection to host.example.com 25 port [tcp/smtp] succeeded!
.Ed
.Pp
-The port range was specified to limit the search to ports 20 \- 30.
+The port range was specified to limit the search to ports 20 \- 30, and is
+scanned by increasing order (unless the
+.Fl r
+flag is set).
+.Pp
+You can also specify a list of ports to scan, for example:
+.Bd -literal -offset indent
+$ nc \-zv host.example.com http 20 22-23
+nc: connect to host.example.com 80 (tcp) failed: Connection refused
+nc: connect to host.example.com 20 (tcp) failed: Connection refused
+Connection to host.example.com port [tcp/ssh] succeeded!
+nc: connect to host.example.com 23 (tcp) failed: Connection refused
+.Ed
+.Pp
+The ports are scanned by the order you given (unless the
+.Fl r
+flag is set).
.Pp
Alternatively, it might be useful to know which server software
is running, and which versions.
--- a/netcat.c
+++ b/netcat.c
@@ -192,7 +192,7 @@ int minttl = -1;
void atelnet(int, unsigned char *, unsigned int);
int strtoport(char *portstr, int udp);
-void build_ports(char *);
+void build_ports(char **);
void help(void) __attribute__((noreturn));
int local_listen(const char *, const char *, struct addrinfo);
# if defined(TLS)
@@ -244,7 +244,7 @@ int
main(int argc, char *argv[])
{
int ch, s = -1, ret, socksv;
- char *host, *uport;
+ char *host, **uport;
struct addrinfo hints;
struct servent *sv;
socklen_t len;
@@ -525,11 +525,11 @@ main(int argc, char *argv[])
} else if (argv[0] && !argv[1]) {
if (!lflag)
usage(1);
- uport = argv[0];
+ uport = &argv[0];
host = NULL;
} else if (argv[0] && argv[1]) {
host = argv[0];
- uport = argv[1];
+ uport = &argv[1];
} else
usage(1);
@@ -716,7 +716,7 @@ main(int argc, char *argv[])
else
s = unix_listen(host);
} else
- s = local_listen(host, uport, hints);
+ s = local_listen(host, *uport, hints);
if (s < 0)
err(1, NULL);
@@ -1766,57 +1766,61 @@ strtoport(char *portstr, int udp)
* that we should try to connect to.
*/
void
-build_ports(char *p)
+build_ports(char **p)
{
struct servent *sv;
char *n;
int hi, lo, cp;
int x = 0;
+ int i;
char *proto = proto_name(uflag, dccpflag);
- sv = getservbyname(p, proto);
- if (sv) {
- if (asprintf(&portlist[0], "%d", ntohs(sv->s_port)) < 0)
- err(1, "asprintf");
- } else if ((n = strchr(p, '-')) != NULL) {
- *n = '\0';
- n++;
-
- /* Make sure the ports are in order: lowest->highest. */
- hi = strtoport(n, uflag);
- lo = strtoport(p, uflag);
- if (lo > hi) {
- cp = hi;
- hi = lo;
- lo = cp;
- }
-
- /*
- * Initialize portlist with a random permutation. Based on
- * Knuth, as in ip_randomid() in sys/netinet/ip_id.c.
- */
- if (rflag) {
- for (x = 0; x <= hi - lo; x++) {
- cp = arc4random_uniform(x + 1);
- portlist[x] = portlist[cp];
- if (asprintf(&portlist[cp], "%d", x + lo) < 0)
- err(1, "asprintf");
+ for (i = 0; p[i] != NULL; i++) {
+ sv = getservbyname(p[i], proto);
+ if (sv) {
+ if (asprintf(&portlist[x], "%d", ntohs(sv->s_port)) < 0)
+ err(1, "asprintf");
+ x++;
+ } else if ((n = strchr(p[i], '-')) != NULL) {
+ *n = '\0';
+ n++;
+
+ /* Make sure the ports are in order: lowest->highest. */
+ hi = strtoport(n, uflag);
+ lo = strtoport(p[i], uflag);
+ if (lo > hi) {
+ cp = hi;
+ hi = lo;
+ lo = cp;
}
- } else { /* Load ports sequentially. */
+
+ /* Load ports sequentially. */
for (cp = lo; cp <= hi; cp++) {
if (asprintf(&portlist[x], "%d", cp) < 0)
err(1, "asprintf");
x++;
}
+ } else {
+ hi = strtoport(p[i], uflag);
+ if (asprintf(&portlist[x], "%d", hi) < 0)
+ err(1, "asprintf");
+ x++;
}
- } else {
- char *tmp;
+ }
- hi = strtoport(p, uflag);
- if (asprintf(&tmp, "%d", hi) != -1)
- portlist[0] = tmp;
- else
- err(1, NULL);
+ /*
+ * Initialize portlist with a random permutation using
+ * Fisher–Yates shuffle.
+ */
+ if (rflag) {
+ for (i = x-1; i > 0; i--) {
+ cp = arc4random_uniform(i+1);
+ if (cp != i) {
+ n = portlist[i];
+ portlist[i] = portlist[cp];
+ portlist[cp] = n;
+ }
+ }
}
}
|
