Libssh2 + ssh-brute support by edeirme-zz · Pull Request #910 · nmap/nmap

edeirme-zz · 2017-06-16T21:31:17Z

This pull request is a collaborative effort of Devin Bjelland, Sergey Khegay and me. This request introduces the ssh-brute script and various other ssh scripts.

More specifically this pull request includes the following scripts:
ssh-brute
ssh-run
ssh-auth-methods
ssh-publickey-acceptance

The following libraries have been included:

libssh2 1.8.0
zlib 1.2.8

dmiller-nmap · 2017-06-20T02:25:23Z

Can you please clean this up by removing the build directories (Debug_lib and Release_lib) from zlib? This is probably easiest done by adding them to the .gitignore file, as we have done with Debug and Release directories throughout. Generally speaking, we would like to reduce the amount of zlib included as much as is allowable by their license. Removing the contrib directory, the documentation, etc. may be possibilities. The same goes for libssh2.

edeirme-zz · 2017-06-20T16:51:35Z

Removed a lot of files. We are down from 711 to 382 added/changed files.

From libssh2, the directories docs, examples, test were removed.
From libz, the directories Debug_lib, Release_lib, docs, examples were removed.

The .gitignore file was also updated to include the Debug_lib and Release_lib directories.

I cannot remove the contrib directory of libz since the visual studio files are contained in that directory.

I haven't removed the test directory from libz. The compilation was failing without it. More changes will need to be performed to the library in order to exclude that directory.

dmiller-nmap · 2017-06-20T19:44:08Z

Some findings from the check script:

scripts/ssh-brute.nse:61: Found unrequired NSE library "libssh2".
scripts/ssh-brute.nse:86: Found bad indexed global "methods".
scripts/ssh-brute.nse:85: Found bad set global "methods".
scripts/ssh-publickey-acceptance.nse:69: Found unrequired NSE library "string".
scripts/ssh-publickey-acceptance.nse:56: Found bad indexed global "username".
scripts/ssh-run.nse:78: Found unrequired NSE library "table".

The one about "username" is causing a script crash when I try ssh-publickey-acceptance against localhost with a single username and single public key file. More comments coming soon.

dmiller-nmap · 2017-06-20T19:48:55Z

nse_utility.h

@@ -8,9 +8,9 @@ class Target;
 #include "nmap_config.h"
 #endif

-#if HAVE_STDINT_H
+//#if HAVE_STDINT_H


Don't change this; instead add this to nmap_winconfig.h:

diff --git a/nmap_winconfig.h b/nmap_winconfig.h index bb59dfa..912d790 100644 --- a/nmap_winconfig.h +++ b/nmap_winconfig.h @@ -144,6 +144,8 @@ #define HAVE_OPENSSL 1 #define HAVE_SSL_SET_TLSEXT_HOST_NAME 1 +/* Since MSVC 2010, stdint.h is included as part of C99 compatibility */ +#define HAVE_STDINT_H 1 #define LUA_INCLUDED 1 #undef PCAP_INCLUDED

It doesn't seem to compile in windows when adding the HAVE_STDINT_H flag in nmap_winconfig.h

Ah, we need to include nmap_winconfig.h here.

#ifdef HAVE_CONFIG_H #include "nmap_config.h" #else #ifdef WIN32 #include "nmap_winconfig.h" #endif /* WIN32 */ #endif /* HAVE_CONFIG_H */

dmiller-nmap · 2017-06-20T19:55:25Z

Can we add library version output for libssh2 and zlib just like we do for openssl, libpcre, etc.? See display_nmap_version in nmap.cc. This will make it easier to check whether different configure options are being respected.

dmiller-nmap · 2017-06-21T02:49:55Z

Compiler warning (LLDB on OS X):

nse_libssh2.cc:733:9: warning: variable 'buf' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
    if (lua_isstring(L, 3))
        ^~~~~~~~~~~~~~~~~~
nse_libssh2.cc:738:50: note: uninitialized use occurs here
    while ((rc = libssh2_channel_write(*channel, buf, buflen)) == LIBSSH2_ERROR_EAGAIN) {
                                                 ^~~
./libssh2/include/libssh2.h:819:43: note: expanded from macro 'libssh2_channel_write'
  libssh2_channel_write_ex((channel), 0, (buf), (buflen))
                                          ^
nse_libssh2.cc:733:5: note: remove the 'if' if its condition is always true
    if (lua_isstring(L, 3))
    ^~~~~~~~~~~~~~~~~~~~~~~
nse_libssh2.cc:729:20: note: initialize the variable 'buf' to silence this warning
    const char *buf;
                   ^
                    = NULL
1 warning generated.

EDIT: This is caused because clang doesn't know that luaL_error is not a returning function. You can avoid it by using return luaL_error("...") so that the compiler knows that execution will not continue.

dmiller-nmap · 2017-06-21T04:20:32Z

Breaks on OS X due to libssh2's configure script ignoring the --with-openssl=X option. Its version is --with-libssl-prefix=X. I found this hack to work OK:

diff --git a/configure.ac b/configure.ac
index 5ba1a04..47e98f0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -355,6 +355,7 @@ AC_HELP_STRING([--with-openssl=DIR],[Use optional openssl libs and includes from
     ;;
   *)
     specialssldir="$with_openssl"
+    ac_configure_args="$ac_configure_args '--with-libssl-prefix=$with_openssl'"
     CPPFLAGS="$CPPFLAGS -I$with_openssl/include"
     LDFLAGS="$LDFLAGS -L$with_openssl/lib"
     ;;

and of course run autoconf to regenerate configure.

Of note, this is probably the right solution for nmap/ncrack#1, not making modifications to opensshlib as was done to close that issue.

edeirme-zz · 2017-06-21T19:27:47Z

Fixed the check script warnings.
Added libssh2 and libz versioning (For some reason, the output is in parenthesis, will investigate later e.g. openssl-1.1.0f libssh2-(1.8.0) libz-(1.2.8) nmap-libpcre-7.6 ).
The compiler warning in LLDB OSX should be gone.
Updated the autoconfig file to support your changes for the OSX build.
Added a small fix for ssh-publickey-acceptance.nse

dmiller-nmap · 2017-06-23T19:50:18Z

nse_libssh2.cc

+    struct ssh_userdata *sshu = NULL;
+
+    sshu = (struct ssh_userdata *) nseU_checkudata(L, 1, SSH2_UDATA, "ssh2");
+    if (sshu) {


This condition should also cover the closing of the sockets below, otherwise if sshu is NULL then it's a null pointer dereference. This line could be written as if (!sshu) { return 0; } to avoid indenting the rest of the function, or even return luaL_error(L, "some error");, though I am not sure what the exact sequence of events would have to be in order for it to be NULL.

dmiller-nmap · 2017-06-23T21:20:02Z

nselib/libssh2.luadoc

@@ -0,0 +1,120 @@
+--


This needs to be --- (3 hyphens) in order for this block to be parsed as NSEdoc.

dmiller-nmap · 2017-06-23T21:20:42Z

nselib/libssh2.luadoc

+--
+-- @author Devin Bjelland
+-- @author Sergey Khegay
+-- @copyright same as Nmap


Please use the exact "Same as Nmap--See https://nmap.org/book/man-legal.html" string here.

dmiller-nmap · 2017-06-23T21:24:01Z

nselib/libssh2-utility.lua

+  while not libssh2.channel_eof(channel) do
+    data = libssh2.channel_read(self.session, channel)
+    if data then
+      buff = buff .. data


Concatenation within a loop is potentially dangerous (CPU sink due to repeated memory allocation and copy). Make buff a table and append to it, then return the concatenation of the table.

dmiller-nmap · 2017-06-23T21:26:08Z

nselib/libssh2-utility.lua

+-- @return true on success or false on failure.
+function SSHConnection:publickey_auth(username, privatekey_file, passphrase)
+  if not passphrase then
+    local passphrase = ""


This local variable goes out of scope in the very next line. Probably this block doesn't need to be here. libssh2.userauth_publickey should understand a nil passphrase to mean no passphrase.

dmiller-nmap · 2017-06-23T21:31:47Z

nselib/libssh2-utility.lua

+end
+
+
+function SSHConnection:list(username)


Need NSEdoc for the rest of these functions and complete NSEdoc for a few of the others.

dmiller-nmap · 2017-06-23T21:35:09Z

nselib/libssh2-utility.lua

+-- @param username A username to authenticate as.
+-- @param password A password to authenticate as.
+-- @return true on success or false on failure.
+function SSHConnection:password_auth(username, password)


After this is committed, it will be important to add keyboard_interactive auth also.

Do you want this to be added in the nse_libssh2.cc and the libssh2-utility.lua as a function or as a part of the ssh scripts as well?

Don't worry about it until this PR is merged first. But the goal would be for ssh-brute to use either one transparently, since many users don't/can't perceive a difference. Logic would look something like:

If password auth is supported, do that.

If not, but keyboard-interactive auth is supported, try to see if it's a password prompt.

If it's a password prompt, continue brute forcing over keyboard-interactive.

Keyboard-interactive can be other things, though, so maybe we'll have to add different script-args to enable other kinds of prompts, but the most common is a simple PAM password prompt. I'd guess (though haven't researched that part of the protocol) that the API would be something like handing the script a socket connected to the other end, and let the script do prompt detection (like telnet-brute does) and actual authentication.

Another fun thing might be a script to grab the "banner" of keyboard-interactive auth (OpenSSH's sshd_config uses the Banner directive for this).

dmiller-nmap · 2017-06-23T21:48:29Z

That's all the comments I have. It would be nice to have trailing whitespace cleaned up and check for proper indentation: https://secwiki.org/w/Nmap/Code_Standards

edeirme-zz · 2017-06-25T21:16:11Z

Made most of the changes.
Added documentation.
Removed buggy/redundant code.
Used the lua-format scripts for the added lua files.

dmiller-nmap · 2017-06-26T13:37:11Z

I'm satisfied with this. If your mentor agrees, please merge and commit to SVN.

Evangelos Deirmentzoglou and others added 12 commits June 14, 2017 14:12

ssh support

dc88554

autoconf

08773e1

rebasing libz & libssh2

cb24db2

Working build for windows and kali

b93fb42

fixes

ce2652e

visual studio files

5a8c78c

updated ssh scripts to use wrapper

ce40346

updated to use libssh2 wrapper

55bfbef

updating libssh2 wrapper

a12ae0a

removed disconnect

dadaa4e

removed ssh-vuln-hostkey

1a11bd8

cleaning up

f0d6458

edeirme-zz changed the title ~~ssh~~ Libssh2 + ssh-brute support Jun 16, 2017

Evangelos Deirmentzoglou and others added 5 commits June 20, 2017 19:27

cleaning libssh2

fb4b6b0

cleaning up libssh2 vol2

9dc80a7

cleaning up libz vol1

1903f69

cleaning up libz vol2

1119c06

cleaning libz vol3

0f2875d

dmiller-nmap reviewed Jun 20, 2017

View reviewed changes

Evangelos Deirmentzoglou and others added 5 commits June 21, 2017 09:22

check script fixes

1a08560

OSX config

f39f746

check script fixes vol2

59fd38e

adding versioning for libssh2

1fcbb7a

added versioning for zlib

349b435

Evangelos Deirmentzoglou added 5 commits June 21, 2017 15:18

removed compiler warning

8714af0

libz versioning

18357ce

bug fix

2b295e8

added HAVE_STDINT in nmap_winconfig

29e3544

adding zlib versioning for windows

3966674

dmiller-nmap reviewed Jun 23, 2017

View reviewed changes

edeirme and others added 5 commits June 25, 2017 12:47

added libssh2 documentation

629f04e

fixed null pointer dereference

b9d7463

removed redundant code

db76c9c

used tables instead of loop concatenation

319b73e

lua-format'ed scripts

da8a523

root added 2 commits June 26, 2017 18:24

versioning fixes

ddbb438

removed redundant files

194e561

nmap-bot closed this in 0c14233 Jun 29, 2017

jungle-boogie mentioned this pull request Jul 3, 2017

no make target rule - build-libssh2 #929

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edeirme-zz commented Jun 16, 2017

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dmiller-nmap commented Jun 20, 2017

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dmiller-nmap commented Jun 20, 2017

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dmiller-nmap commented Jun 23, 2017

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edeirme-zz commented Jun 25, 2017

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dmiller-nmap commented Jun 21, 2017 •

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