{"id":18557,"date":"2009-12-31T12:21:49","date_gmt":"2009-12-31T06:51:49","guid":{"rendered":"http:\/\/froisa.com\/?p=192"},"modified":"2009-12-31T12:21:49","modified_gmt":"2009-12-31T06:51:49","slug":"nc-3","status":"publish","type":"post","link":"https:\/\/www.trueangle.org\/index.php\/2009\/12\/31\/nc-3\/","title":{"rendered":"nc – tcp\/ip swiss army knife"},"content":{"rendered":"

ABOUT nc<\/u><\/p>\n

\nNetcat (often abbreviated to nc) is a computer networking utility for reading from and writing to network connections using TCP or UDP. Netcat is designed to be a dependable back-end that can be used directly or easily driven by other programs and scripts. At the same time, it is a feature-rich network debugging and investigation tool, since it can produce almost any kind of connection its user could need and has a number of built-in capabilities.\n<\/pre>\n
TYPICAL COMMANDLINE RELATED<\/u>
\n[text]
\nWindow I Server<\/p>\n
$nc -l -p  3333
\nhello
\nhello
\nhow are you ?
\nfine
\nWindow II client<\/p>\n
$nc 127.0.0.1 3333
\nhello
\nhello
\nhow are you ?
\nfine
\n[\/text]<\/p>\n
Related Source Code Exposition<\/u>
\n[text]
\ndoexec (fd)
\n  int fd;
\n{
\n  register char * p;<\/p>\n
  dup2 (fd, 0);                         \/* the precise order of fiddlage *\/
\n  close (fd);                           \/* is apparently crucial; this is *\/
\n  dup2 (0, 1);                          \/* swiped directly out of "inetd". *\/<\/p>\n
  if (doexec_use_sh) {
\nDebug (("gonna exec "%s" using \/bin\/sh…", pr00gie))
\n    execl ("\/bin\/sh", "sh", "-c", pr00gie, NULL);
\n    bail ("exec %s failed", pr00gie);   \/* this gets sent out.  Hmm… *\/
\n  }<\/p>\n
  p = strrchr (pr00gie, ‘\/’);           \/* shorter argv[0] *\/
\n  if (p)
\n    p++;
\n  else
\n    p = pr00gie;
\nDebug (("gonna exec %s as %s…", pr00gie, p))
\n  execl (pr00gie, p, NULL);
\n  bail ("exec %s failed", pr00gie);     \/* this gets sent out.  Hmm… *\/
\n} \/* doexec *\/
\n[\/text]<\/p>\n
Source Code Highlight<\/u><\/p>\n
\nfiddle all  the file descriptors around, and  hand off to another prog.  Sort of like a one-off \"poor man's inetd\". This is the only section of code that would be security-critical, which  is\nwhy  it's ifdefed  out  by default.  Use at your own hairy risk; if you leave shells lying around\nbehind open listening ports  you deserve to lose!!\n<\/pre>\n
Related Knowledge<\/u><\/p>\n
\nIt has been suggested  that the open() system call should get   a  flag   which  would   cause  it   to\nselect  a non-sequential   file   descriptor   from   the   outset, eliminating   the   need   for   a\nseparate   call   to nonseqfd(). There are, however,  a number of system calls which  create file\ndescriptors but  which have  no flags parameter and  which, thus, will never be  able to return\nnon-sequential  file descriptors;  socket() is  a classic example. So there will still  be a need for a\nsystem call which can duplicate a file descriptor into the new space.\n<\/pre>\n
LINKS
\nhttp:\/\/lwn.net\/Articles\/236843\/<\/a>
\nhttp:\/\/www.g-loaded.eu\/2006\/11\/06\/netcat-a-couple-of-useful-examples\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
ABOUT nc Netcat (often abbreviated to nc) is a computer networking utility for reading from and writing to network connections using TCP or UDP. Netcat is designed to be a dependable back-end that can be used directly or easily driven by other programs and scripts. At the same time, it is a feature-rich network debugging … <\/p>\n
Continue reading “nc – tcp\/ip  swiss army knife”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":5243,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[19],"tags":[1149,1153,1523],"_links":{"self":[{"href":"https:\/\/www.trueangle.org\/index.php\/wp-json\/wp\/v2\/posts\/18557"}],"collection":[{"href":"https:\/\/www.trueangle.org\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.trueangle.org\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.trueangle.org\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.trueangle.org\/index.php\/wp-json\/wp\/v2\/comments?post=18557"}],"version-history":[{"count":0,"href":"https:\/\/www.trueangle.org\/index.php\/wp-json\/wp\/v2\/posts\/18557\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.trueangle.org\/index.php\/wp-json\/wp\/v2\/media\/5243"}],"wp:attachment":[{"href":"https:\/\/www.trueangle.org\/index.php\/wp-json\/wp\/v2\/media?parent=18557"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.trueangle.org\/index.php\/wp-json\/wp\/v2\/categories?post=18557"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.trueangle.org\/index.php\/wp-json\/wp\/v2\/tags?post=18557"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}