From c559611a8bb1df04128ab3f6ccedc88d441b0d47 Mon Sep 17 00:00:00 2001 From: Oswaldo Ferreira Date: Tue, 20 Aug 2019 17:36:57 -0300 Subject: Avoid exposing unaccessible repo data upon GFM processing When post-processing relative links to absolute links RelativeLinkFilter didn't take into consideration that internal repository data could be exposed for users that do not have repository access to the project. This commit solves that by checking whether the user can `download_code` at this repository, avoiding any processing of this filter if the user can't. Additionally, if we're processing for a group ( no project was given), we check if the user can read it in order to expand the href as an extra. That doesn't seem necessarily a breach now, but an extra check doesn't hurt as after all the user needs to be able to `read_group`. --- .../unreleased/security-exposed-default-branch.yml | 5 ++ lib/banzai/filter/relative_link_filter.rb | 16 +++++ .../lib/banzai/filter/relative_link_filter_spec.rb | 72 +++++++++++++++++++++- 3 files changed, 91 insertions(+), 2 deletions(-) create mode 100644 changelogs/unreleased/security-exposed-default-branch.yml diff --git a/changelogs/unreleased/security-exposed-default-branch.yml b/changelogs/unreleased/security-exposed-default-branch.yml new file mode 100644 index 00000000000..bf32617ee8a --- /dev/null +++ b/changelogs/unreleased/security-exposed-default-branch.yml @@ -0,0 +1,5 @@ +--- +title: Avoid exposing unaccessible repo data upon GFM post processing +merge_request: +author: +type: security diff --git a/lib/banzai/filter/relative_link_filter.rb b/lib/banzai/filter/relative_link_filter.rb index bf84d7cddae..114b0cf5daf 100644 --- a/lib/banzai/filter/relative_link_filter.rb +++ b/lib/banzai/filter/relative_link_filter.rb @@ -9,6 +9,7 @@ module Banzai # Context options: # :commit # :group + # :current_user # :project # :project_wiki # :ref @@ -18,6 +19,7 @@ module Banzai def call return doc if context[:system_note] + return doc unless visible_to_user? @uri_types = {} clear_memoization(:linkable_files) @@ -166,6 +168,16 @@ module Banzai Gitlab.config.gitlab.relative_url_root.presence || '/' end + def visible_to_user? + if project + Ability.allowed?(current_user, :download_code, project) + elsif group + Ability.allowed?(current_user, :read_group, group) + else # Objects detached from projects or groups, e.g. Personal Snippets. + true + end + end + def ref context[:ref] || project.default_branch end @@ -178,6 +190,10 @@ module Banzai context[:project] end + def current_user + context[:current_user] + end + def repository @repository ||= project&.repository end diff --git a/spec/lib/banzai/filter/relative_link_filter_spec.rb b/spec/lib/banzai/filter/relative_link_filter_spec.rb index a714fa50f5f..0fe070608d4 100644 --- a/spec/lib/banzai/filter/relative_link_filter_spec.rb +++ b/spec/lib/banzai/filter/relative_link_filter_spec.rb @@ -5,6 +5,7 @@ describe Banzai::Filter::RelativeLinkFilter do contexts.reverse_merge!({ commit: commit, project: project, + current_user: user, group: group, project_wiki: project_wiki, ref: ref, @@ -31,7 +32,8 @@ describe Banzai::Filter::RelativeLinkFilter do %(
#{element}
) end - let(:project) { create(:project, :repository) } + let(:project) { create(:project, :repository, :public) } + let(:user) { create(:user) } let(:group) { nil } let(:project_path) { project.full_path } let(:ref) { 'markdown' } @@ -73,6 +75,11 @@ describe Banzai::Filter::RelativeLinkFilter do include_examples :preserve_unchanged end + context 'without project repository access' do + let(:project) { create(:project, :repository, repository_access_level: ProjectFeature::PRIVATE) } + include_examples :preserve_unchanged + end + it 'does not raise an exception on invalid URIs' do act = link("://foo") expect { filter(act) }.not_to raise_error @@ -280,6 +287,37 @@ describe Banzai::Filter::RelativeLinkFilter do let(:relative_path) { "/#{project.full_path}#{upload_path}" } context 'to a project upload' do + context 'without project repository access' do + let(:project) { create(:project, :repository, repository_access_level: ProjectFeature::PRIVATE) } + + it 'does not rebuild relative URL for a link' do + doc = filter(link(upload_path)) + expect(doc.at_css('a')['href']).to eq(upload_path) + + doc = filter(nested(link(upload_path))) + expect(doc.at_css('a')['href']).to eq(upload_path) + end + + it 'does not rebuild relative URL for an image' do + doc = filter(image(upload_path)) + expect(doc.at_css('img')['src']).to eq(upload_path) + + doc = filter(nested(image(upload_path))) + expect(doc.at_css('img')['src']).to eq(upload_path) + end + + context 'with an absolute URL' do + let(:absolute_path) { Gitlab.config.gitlab.url + relative_path } + let(:only_path) { false } + + it 'does not rewrite the link' do + doc = filter(link(upload_path)) + + expect(doc.at_css('a')['href']).to eq(upload_path) + end + end + end + context 'with an absolute URL' do let(:absolute_path) { Gitlab.config.gitlab.url + relative_path } let(:only_path) { false } @@ -329,11 +367,41 @@ describe Banzai::Filter::RelativeLinkFilter do end context 'to a group upload' do - let(:upload_link) { link('/uploads/e90decf88d8f96fe9e1389afc2e4a91f/test.jpg') } + let(:upload_path) { '/uploads/e90decf88d8f96fe9e1389afc2e4a91f/test.jpg' } + let(:upload_link) { link(upload_path) } let(:group) { create(:group) } let(:project) { nil } let(:relative_path) { "/groups/#{group.full_path}/-/uploads/e90decf88d8f96fe9e1389afc2e4a91f/test.jpg" } + context 'without group read access' do + let(:group) { create(:group, :private) } + + it 'does not rewrite the link' do + doc = filter(upload_link) + + expect(doc.at_css('a')['href']).to eq(upload_path) + end + + it 'does not rewrite the link for subgroup' do + group.update!(parent: create(:group)) + + doc = filter(upload_link) + + expect(doc.at_css('a')['href']).to eq(upload_path) + end + + context 'with an absolute URL' do + let(:absolute_path) { Gitlab.config.gitlab.url + relative_path } + let(:only_path) { false } + + it 'does not rewrite the link' do + doc = filter(upload_link) + + expect(doc.at_css('a')['href']).to eq(upload_path) + end + end + end + context 'with an absolute URL' do let(:absolute_path) { Gitlab.config.gitlab.url + relative_path } let(:only_path) { false } -- cgit v1.2.3