Linux: Read SSHd configuration (KB)

# SPDX-FileCopyrightText: 2020 Greenbone AG
# Some text descriptions might be excerpted from (a) referenced
# source(s), and are Copyright (C) by the respective right holder(s).
#
# SPDX-License-Identifier: GPL-2.0-only

if(description)
{
  script_oid("1.3.6.1.4.1.25623.1.0.150065");
  script_version("2023-07-28T16:09:07+0000");
  script_tag(name:"last_modification", value:"2023-07-28 16:09:07 +0000 (Fri, 28 Jul 2023)");
  script_tag(name:"creation_date", value:"2020-01-13 14:24:40 +0100 (Mon, 13 Jan 2020)");
  script_tag(name:"cvss_base", value:"0.0");
  script_tag(name:"cvss_base_vector", value:"AV:L/AC:H/Au:S/C:N/I:N/A:N");
  script_tag(name:"qod", value:"97");

  script_name("Linux: Read SSHd configuration (KB)");

  script_category(ACT_GATHER_INFO);
  script_copyright("Copyright (C) 2020 Greenbone AG");
  script_family("Policy");
  script_dependencies("gather-package-list.nasl", "compliance_tests.nasl");
  script_mandatory_keys("Compliance/Launch");
  script_exclude_keys("ssh/no_linux_shell");

  script_xref(name:"URL", value:"https://linux.die.net/man/5/sshd_config");

  script_tag(name:"summary", value:"sshd reads configuration data from /etc/ssh/sshd_config (or the
file specified with -f on the command line). The file contains keyword-argument pairs, one per line.
Lines starting with '#' and empty lines are interpreted as comments. Arguments may optionally be
enclosed in double quotes in order to represent arguments containing spaces.

Note: This script only stores information for other Policy Controls.");

  exit(0);
}

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

if(!get_kb_item("login/SSH/success") || !sock = ssh_login_or_reuse_connection()){
  set_kb_item(name:"Policy/linux/sshd_config/ERROR", value:TRUE);
  set_kb_item(name:"Policy/linux/sshd_config/stat/ERROR", value:TRUE);
  exit(0);
}

# Information about sshd_config file
stat_cmd = "stat /etc/ssh/sshd_config";
stat_ret = ssh_cmd(socket:sock, cmd:stat_cmd, return_erros:FALSE);
if(!stat_ret){
  set_kb_item(name:"Policy/linux/sshd_config/stat/ERROR", value:TRUE);
  exit(0);
}
set_kb_item(name:"Policy/linux/sshd_config/stat", value:stat_ret);

cat_cmd = "cat /etc/ssh/sshd_config";
cat_ret = ssh_cmd(socket:sock, cmd:cat_cmd, return_erros:FALSE);
if(!cat_ret){
  set_kb_item(name:"Policy/linux/sshd_config/ERROR", value:TRUE);
  exit(0);
}
set_kb_item(name:"Policy/linux/sshd_config", value:cat_ret);

ret_split = split(cat_ret, keep:FALSE);
foreach line (ret_split){
  # filter comments or empty lines
  if(line =~ "^\s*#" || line =~ "^\s*$")
    continue;

  line = ereg_replace(string:line, pattern:"\s+", replace:" ");
  replace_first_whitespace = str_replace(string:line, find:" ", replace:"|", count:1);
  # bar = eregmatch(string:baz, pattern:"(.*)\|(.*)");
  reg_match = eregmatch(string:replace_first_whitespace, pattern:"(.*)\|(.*)");
  set_kb_item(name:"Policy/linux/sshd_config/" + tolower(reg_match[1]), value:reg_match[2]);
}

# information about SSH private host key files
policy_access_permission_regex(filepath:"/etc/ssh/ssh_host_*_key", socket:sock);

# information about SSH public host key files
policy_access_permission_regex(filepath:"/etc/ssh/ssh_host_*_key.pub", socket:sock);

exit(0);