Add read_ssh_blocking

[jjnicola]

What:
Extend nasl_ssh_shell_read()

Jira: SC-452

Why:
The function receives now a new parameter timeout.
If a timeout is given, enables the blocking ssh read until it gives the timeout or there is no bytes left to read.
Otherwise, it does a non-blocking ssh read as before.

How:

To test, run the following script (it should be a debian based OS, with dpkg cmd)

time sudo openvas-nasl -X -B -d -i /home/jjnicola/install/var/lib/openvas/plugins -t 192.168.0.1 ssh_shell_gather_package_list_ssh_read_timeout.nasl

if(description)
{
  script_oid("1.3.6.1.4.1.25623.1.0.ssh1");
  script_version("2020-11-12T09:50:32+0000");
  script_tag(name:"last_modification", value:"2021-11-17 11:25:00 +0000 (Mon, 17 May 2021)");
  script_tag(name:"creation_date", value:"2021-11-17 11:25:00 +0000 (Mon, 17 May 2021)");
  script_tag(name:"cvss_base", value:"0.0");
  script_tag(name:"cvss_base_vector", value:"AV:N/AC:L/Au:N/C:N/I:N/A:N");
  script_name("SSH shell 1");
  script_category(ACT_GATHER_INFO);
  script_copyright("Copyright (C) 2007-2012 Greenbone Networks GmbH");
  script_family("General");

  script_tag(name:"summary", value:"This script tries to login with provided credentials.

  If the login was successful, it marks this port as available for any authenticated tests.");

  script_tag(name:"qod_type", value:"remote_banner");

  exit(0);
}

include("ssh_func.inc");
include("misc_func.inc");

port = 22;
user = 'USER';
pass = 'PASS';
priv_user = 'root';
priv_pass = 'ROOT_PASS';

function clean_buffer(sess) {
  while( TRUE ) {
    c = ssh_shell_read(sess);
    if( strlen( c ) <= 0 ) break;
  }
};

soc = open_sock_tcp( port );
if( ! soc ) exit( 0 );
display (soc);

display("Open connection");
sess = ssh_connect( socket:soc );
display("User Auth");
prompt = ssh_userauth(sess, login:user, password:pass);

display("Open shell");
sess = ssh_shell_open (sess, pty:1);
clean_buffer (sess);

cmd1 = "whoami" + '\n';
sh_wr = ssh_shell_write(sess, cmd:cmd1);
ret = "";
ret = ssh_shell_read(sess, timeout: 1000);
display("Return whoami before priv login: ", ret);

display("Changing to root");
cmd1 = 'su - ' + priv_user  + '\n';
sh_wr = ssh_shell_write(sess, cmd:cmd1);

ret = "";
ret = ssh_shell_read(sess, timeout: 1000);
   display(ret);

if (strstr(ret, "Password")){
   cmd1 = priv_pass + '\n';
   sh_wr = ssh_shell_write(sess, cmd:cmd1);
   clean_buffer(sess);
}

cmd1 = 'dpkg -l' + '\n';
sh_wr = ssh_shell_write(sess, cmd:cmd1);

ret = ssh_shell_read(sess, timeout: 1000);
display("Return whoami after priv login: ", ret);

ssh_shell_close(sess);
ssh_disconnect(sess);
display("Finished, close, disconnect script 1");

Checklist:

• Tests
• PR merge commit message adjusted