CVE-2017-18026 (Ruby, published 2018-01-10T09:29Z)
Description: value: Redmine before 3.2.9, 3.3.x before 3.3.6, and 3.4.x before 3.4.4 does not block the --config and --debugger flags to the Mercurial hg program, which allows remote attackers to execute arbitrary commands (through the Mercurial adapter) via vectors involving a branch whose name begins with a --config= or --debugger= substring, a related issue to CVE-2017-17536.
Severity: MEDIUM (CVSS v3 base score: 8.8)
Weakness: NVD-CWE-noinfo \u2014 Insufficient Information
There is insufficient information about the issue to classify it; details are unkown or unspecified.
Repository: https://github.com/redmine/redmine
Files changed:
lib/redmine/scm/adapters/mercurial_adapter.rb
test/unit/lib/redmine/scm/adapters/mercurial_adapter_test.rb
Commit message: mercurial: reject malicious command argument (#27516)

We've got a security report from the Phabricator team, which basically says
--config and --debugger arguments can be injected anywhere to lead to an
arbitrary command execution.

https://secure.phabricator.com/rPa7921a4448093d00defa8bd18f35b8c8f8bf3314

This is a fundamental issue of the argument parsing rules in Mercurial, which
allows extensions to populate their parsing rules and such extensions can be
loaded by "--config extensions.<name>=". There's a chicken and egg problem.
We're working on hardening the parsing rules, but which won't come in by
default as it would be a behavior change.

This patch adds a verification to reject malicious command arguments as a
last ditch. The subsequent patches will fix the problem in more appropriate
way.

Contributed by Yuya Nishihara.

git-svn-id: http://svn.redmine.org/redmine/trunk@17060 e93f8b46-1217-0410-a6f0-8f06a7374b81


Vulnerable code:

Fixed code:
        # raised if bad command argument detected before executing hg.
        class HgCommandArgumentError < CommandFailed; end
        # command options which may be processed earlier, by faulty parser in hg
        HG_EARLY_BOOL_ARG = /^--(debugger|profile|traceback)$/
        HG_EARLY_LIST_ARG = /^(--(config|cwd|repo(sitory)?)\b|-R)/
        private_constant :HG_EARLY_BOOL_ARG, :HG_EARLY_LIST_ARG

          # as of hg 4.4.1, early parsing of bool options is not terminated at '--'
          if args.any? { |s| s =~ HG_EARLY_BOOL_ARG }
            raise HgCommandArgumentError, "malicious command argument detected"
          end
          if args.take_while { |s| s != '--' }.any? { |s| s =~ HG_EARLY_LIST_ARG }
            raise HgCommandArgumentError, "malicious command argument detected"
          end

  HgCommandArgumentError = Redmine::Scm::Adapters::MercurialAdapter::HgCommandArgumentError
    def test_bad_early_options
      assert_raise HgCommandArgumentError do
        @adapter.diff('sources/welcome_controller.rb', '--config=alias.rhdiff=!xterm')
      end
      assert_raise HgCommandArgumentError do
        @adapter.entries('--debugger')
      end
      assert_raise HgCommandArgumentError do
        @adapter.revisions(nil, nil, nil, limit: '--repo=otherrepo')
      end
      assert_raise HgCommandArgumentError do
        @adapter.nodes_in_branch('default', limit: '--repository=otherrepo')
      end
      assert_raise HgCommandArgumentError do
        @adapter.nodes_in_branch('-Rotherrepo')
      end
    end