###############################################################################
# SPDX-License-Identifier: GPL-3.0-only
# PURPOSE: Apache user enumeration
###############################################################################

sub nikto_apacheusers_init {
    my $id = {
            name        => "apacheusers",
            full_name   => "Apache Users",
            author      => "Javier Fernandez-Sanguinoi Pena",
            description => "Checks whether we can enumerate usernames directly from the web server",
            hooks       => { scan => { method => \&nikto_apacheusers, }, },
            copyright   => "2008 Chris Sullo",
            options     => {
                         enumerate  => "Flag to indicate whether to attempt to enumerate users",
                         dictionary => "Filename for a dictionary file of users",
                         size       => "Maximum size of username if bruteforcing",
                         home       => "Look for ~user to enumerate",
                         cgiwrap    => "User cgi-bin/cgiwrap to enumerate"
                         }
              };
    return $id;
}

sub nikto_apacheusers {
    my ($mark, $parameters) = @_;
    return if $mark->{'terminate'};
    my $apacheusers = 0;

    # If we haven't been asked to enumerate users then return
    return unless (defined $parameters->{'enumerate'}
                   && $parameters->{'enumerate'} == 1);

    # First ensure that the server is vulnerable
    my ($res, $content, $error, $request, $response) = nfetch($mark, "/~bin", "GET", "", "", "", "apacheusers: known user");

    if ($content =~ /forbidden/i)    # good on "bin"
    {
        my ($res, $content, $errors, $request, $response) =
          nfetch($mark, "/~" . LW2::utils_randstr(8),
                 "GET", "", "", "", "apacheusers: invalid user");

        if ($content !~ /forbidden/i)    # Good, it gave an error instead of forbidden
        {
            add_vulnerability(
                $mark,
                "/~bin: Enumeration of users is possible by requesting ~username (responds with 'Forbidden' for users and 'not found' for non-existent users).",
                999999,
                "CVE-2001-1013",
                "GET",
                "/~bin",
                $request,
                $response
                );
        }
        $apacheusers = 1;
    }

    # If we can't enumerate users then return
    return unless ($apacheusers == 1);

    # Now we can attempt to enumerate the users
    my ($url, $dictfile, $size);
    my @cgiwraps;
    my @CFGCGI = split(/ /, $VARIABLES{"\@CGIDIRS"});

    if (defined $parameters->{'dictionary'}) {
        $dictfile = $parameters->{'dictionary'};
    }
    if (defined $parameters->{'size'}) {
        $size = $parameters->{'size'} if $parameters->{'size'} =~ /^\d+$/;
    }

    # Set the URL according to the parameters
    if (defined $parameters->{'cgiwrap'}) {

        # Check for existence of cgiwrap
        foreach my $cgidir (@CFGCGI) {
            my $curl = "$cgidir" . "cgiwrap";
            my ($response, $content) =
              nfetch($mark, $curl, "GET", "", "", "", "user_enum_apache: cgiwrap");
            if ($content =~ /check your URL/i) {
                push(@cgiwraps, "$curl");
            }
        }

        foreach my $cgiwrap (@cgiwraps) {
            $url = "$cgiwrap/~";

            # First check whether we use a dictionary attack of brute force it
            if (defined $dictfile) {

                # We have options - assume it is a dictionary attack
                nikto_user_enum_apache_dictionary($url, $mark, $dictfile);
            }
            else {
                nikto_user_enum_apache_brute($url, $mark, $size);
            }
        }
    }
    if (defined $parameters->{'home'}) {
        $url = "/~";

        # First check whether we use a dictionary attack of brute force it
        if (defined $dictfile) {

            # We have options - assume it is a dictionary attack
            nikto_user_enum_apache_dictionary($url, $mark, $dictfile);
        }
        else {
            nikto_user_enum_apache_brute($url, $mark, $size);
        }
    }
}

sub nikto_user_enum_apache_brute {

    # Note1: This script only generates names with letters A-Z (no numbers)
    #
    # Note2: this script will generate SUM(26^n)(n=$min to $max)
    # it's probably faster to write this to a file than to generate it
    # on the fly BTW.
    #
    # Of course, it could be optimized to skip some "strange"
    # combinations of usernames, but hey, then it wouldn't
    # be 'brute force' would it? (jfs)

    my ($url, $mark, $size) = @_;
    $size //= 5;
    nprint("- Enumerating Apache users (1 to $size characters).", "v", "apacheusers");

    my $text    = "a";
    my $ctr     = 0;
    my $message = "Valid users found via Apache enumeration: ";
    my ($response, $content);
    my @foundusers = ();
    while (length($text) <= $size) {
        return if $mark->{'terminate'};
        if (($ctr % 500) == 0) {
            nprint("- User enumeration guess $ctr ($text)", "v", "apacheusers");
        }
        my ($res, $content, $errors, $request, $response) =
          nfetch($mark, $url . $text, "HEAD", "", "", "", "user_enum_apache: enumeration");
        my $user = nikto_user_enum_apache_check($response, $text);
        if (defined $user && $user ne "") {
            push(@foundusers, $user);
        }
        $text++;
        $ctr++;
    }
    if (scalar(@foundusers)) {
        my $u = join(', ', @foundusers);
        add_vulnerability($mark, $message . $u,
                          "000479", "CVE-2001-1013", "HEAD", "/", $request, $response);
    }
}

sub nikto_user_enum_apache_dictionary {
    my ($url, $mark, $filename) = @_;
    my $message    = "Valid users found via Apache enumeration: ";
    my @foundusers = ();
    my ($response, $content);
    my $ctr = 0;

    nprint("- Enumerating Apache users (using dictionary $filename).", "v", "apacheusers");
    open(my $fh, "<", $filename)
      or do { nprint("+ ERROR: Unable to open dictionary file $filename: $!."); return; };

    # Now attempt on each entry
    while (<$fh>) {
        return if $mark->{'terminate'};
        chomp;
        s/\#.*$//;

        # remove preceding ~ just in case
        s/^~//;
        if ($_ eq "")          { next }
        if (($ctr % 500) == 0) { nprint("- User enumeration guess $ctr ($_)", "v", "apacheusers"); }
        my($res, $content, $errors, $request, $response) =
          nfetch($mark, $url . $_, "HEAD", "", "", "", "user_enum_apache: dictionary");
        my $user = nikto_user_enum_apache_check($response, $_);
        if ($user) {
            push(@foundusers, $user);
        }
        $ctr++;
    }
    close($fh);
    if (scalar(@foundusers)) {
        my $u = join(', ', @foundusers);
        add_vulnerability($mark, $message . $u,
                          "000478", "CVE-2001-1013", "HEAD", "/", $request, $response);
    }
}

sub nikto_user_enum_apache_check {
    (my $code, my $user) = @_;
    my $response = "";

    foreach my $found (split(/ /, $VARIABLES{"\@HTTPFOUND"})) {
        if ($code eq $found) {
            $response = $user;
            last;
        }
    }

    return $response;
}

1;