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FEATURE: Allow email image embed with secure media (#10563)

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This PR introduces a few important changes to secure media redaction in emails. First of all, two new site settings have been introduced:

* `secure_media_allow_embed_images_in_emails`: If enabled we will embed secure images in emails instead of redacting them.
* `secure_media_max_email_embed_image_size_kb`: The cap to the size of the secure image we will embed, defaulting to 1mb, so the email does not become too big. Max is 10mb. Works in tandem with `email_total_attachment_size_limit_kb`.

`Email::Sender` will now attach images to the email based on these settings. The sender will also call `inline_secure_images` in `Email::Styles` after secure media is redacted and attachments are added to replace redaction messages with attached images. I went with attachment and `cid` URLs because base64 image support is _still_ flaky in email clients.

All redaction of secure media is now handled in `Email::Styles` and calls out to `PrettyText.strip_secure_media` to do the actual stripping and replacing with placeholders. `app/mailers/group_smtp_mailer.rb` and `app/mailers/user_notifications.rb` no longer do any stripping because they are earlier in the pipeline than `Email::Styles`.

Finally the redaction notice has been restyled and includes a link to the media that the user can click, which will show it to them if they have the necessary permissions.

![image](https://user-images.githubusercontent.com/920448/92341012-b9a2c380-f0ff-11ea-860e-b376b4528357.png)
This commit is contained in:
Martin Brennan 2020-09-10 09:50:16 +10:00 committed by GitHub
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commit dede942007
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11 changed files with 248 additions and 98 deletions
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15
app/mailers/group_smtp_mailer.rb
View File

@ -79,26 +79,13 @@ class GroupSmtpMailer < ActionMailer::Base
end
def email_post_markdown(post, add_posted_by = false)
result = +"#{post.with_secure_media? ? strip_secure_urls(post.raw) : post.raw}\n\n"
result = +"#{post.raw}\n\n"
if add_posted_by
result << "#{I18n.t('user_notifications.posted_by', username: post.username, post_date: post.created_at.strftime("%m/%d/%Y"))}\n\n"
end
result
end
def strip_secure_urls(raw)
urls = Set.new
raw.scan(Discourse::Utils::URI_REGEXP) { urls << $& }
urls.each do |url|
if (url.start_with?(Discourse.store.s3_upload_host) && FileHelper.is_supported_media?(url))
raw = raw.sub(url, "<p class='secure-media-notice'>#{I18n.t("emails.secure_media_placeholder")}</p>")
end
end
raw
end
def html_override(post, context_posts: nil)
UserNotificationRenderer.render(
template: 'email/notification',

15
app/mailers/user_notifications.rb
View File

@ -356,26 +356,13 @@ class UserNotifications < ActionMailer::Base
end
def email_post_markdown(post, add_posted_by = false)
result = +"#{post.with_secure_media? ? strip_secure_urls(post.raw) : post.raw}\n\n"
result = +"#{post.raw}\n\n"
if add_posted_by
result << "#{I18n.t('user_notifications.posted_by', username: post.username, post_date: post.created_at.strftime("%m/%d/%Y"))}\n\n"
end
result
end
def strip_secure_urls(raw)
urls = Set.new
raw.scan(Discourse::Utils::URI_REGEXP) { urls << $& }
urls.each do |url|
if (url.start_with?(Discourse.store.s3_upload_host) && FileHelper.is_supported_media?(url))
raw = raw.sub(url, "<p class='secure-media-notice'>#{I18n.t("emails.secure_media_placeholder")}</p>")
end
end
raw
end
def self.get_context_posts(post, topic_user, user)
if (user.user_option.email_previous_replies == UserOption.previous_replies_type[:never]) ||
SiteSetting.private_email?

5
config/locales/server.en.yml
View File

@ -125,7 +125,8 @@ en:
unsubscribe_not_allowed: "Happens when unsubscribing via email is not allowed for this user."
email_not_allowed: "Happens when the email address is not on the allowlist or is on the blocklist."
unrecognized_error: "Unrecognized Error"
secure_media_placeholder: "Redacted: this site has secure media enabled, visit the topic to see the attached image/audio/video."
secure_media_placeholder: "Redacted: This site has secure media enabled, visit the topic or click View Media to see the attached media."
view_redacted_media: "View Media"
errors: &errors
format: ! "%{attribute} %{message}"
@ -2116,6 +2117,8 @@ en:
prevent_anons_from_downloading_files: "Prevent anonymous users from downloading attachments. WARNING: this will prevent any non-image site assets posted as attachments from working."
secure_media: 'Limits access to ALL uploads (images, video, audio, text, pdfs, zips, and others). If “login required” is enabled, only logged-in users can access uploads. Otherwise, access will be limited only for media uploads in private messages and private categories. WARNING: This setting is complex and requires deep administrative understanding. See <a target="_blank" href="https://meta.discourse.org/t/secure-media-uploads/140017">the secure media topic on Meta</a> for details.'
secure_media_allow_embed_images_in_emails: "Allows embedding secure images that would normally be redacted in emails, if their size is smaller than the 'secure media max email embed image size kb' setting."
secure_media_max_email_embed_image_size_kb: "The size cutoff for secure images that will be embedded in emails if the 'secure media allow embed in emails' setting is enabled. Without that setting enabled, this setting has no effect."
slug_generation_method: "Choose a slug generation method. 'encoded' will generate percent encoding string. 'none' will disable slug at all."
enable_emoji: "Enable emoji"

6
config/site_settings.yml
View File

@ -1234,6 +1234,12 @@ files:
secure_media:
default: false
client: true
secure_media_allow_embed_images_in_emails:
default: false
secure_media_max_email_embed_image_size_kb:
default: 1024
min: 1
max: 10240
enable_s3_uploads:
default: false
client: true

27
lib/email/sender.rb
View File

@ -199,14 +199,25 @@ module Email
merge_json_x_header('X-MSYS-API', metadata: { message_id: @message.message_id })
end
# Parse the HTML again so we can make any final changes before
# sending
style = Email::Styles.new(@message.html_part.body.to_s)
# Suppress images from short emails
if SiteSetting.strip_images_from_short_emails &&
@message.html_part.body.to_s.bytesize <= SiteSetting.short_email_length &&
@message.html_part.body =~ /<img[^>]+>/
style = Email::Styles.new(@message.html_part.body.to_s)
@message.html_part.body = style.strip_avatars_and_emojis
style.strip_avatars_and_emojis
end
# Embeds any of the secure images that have been attached inline,
# removing the redaction notice.
if SiteSetting.secure_media_allow_embed_images_in_emails
style.inline_secure_images(@message.attachments)
end
@message.html_part.body = style.to_s
email_log.message_id = @message.message_id
DiscourseEvent.trigger(:before_email_send, @message, @email_type)
@ -249,7 +260,11 @@ module Email
email_size = 0
post.uploads.each do |upload|
next if FileHelper.is_supported_image?(upload.original_filename)
if FileHelper.is_supported_image?(upload.original_filename) &&
!should_attach_image?(upload)
next
end
next if email_size + upload.filesize > max_email_size
begin
@ -277,6 +292,12 @@ module Email
fix_parts_after_attachments!
end
def should_attach_image?(upload)
return if !SiteSetting.secure_media_allow_embed_images_in_emails || !upload.secure?
return if upload.filesize > SiteSetting.secure_media_max_email_embed_image_size_kb.kilobytes
true
end
#
# Two behaviors in the mail gem collide:
#

56
lib/email/styles.rb
View File

@ -198,7 +198,6 @@ module Email
style('code', 'background-color: #f1f1ff; padding: 2px 5px;')
style('pre code', 'display: block; background-color: #f1f1ff; padding: 5px;')
style('.featured-topic a', "text-decoration: none; font-weight: bold; color: #{SiteSetting.email_link_color}; line-height:1.5em;")
style('.secure-image-notice', 'font-style: italic; background-color: #f1f1ff; padding: 5px;')
style('.summary-email', "-moz-box-sizing:border-box;-ms-text-size-adjust:100%;-webkit-box-sizing:border-box;-webkit-text-size-adjust:100%;box-sizing:border-box;color:#0a0a0a;font-family:Helvetica,Arial,sans-serif;font-size:14px;font-weight:400;line-height:1.3;margin:0;min-width:100%;padding:0;width:100%")
style('.previous-discussion', 'font-size: 17px; color: #444; margin-bottom:10px;')
@ -237,10 +236,40 @@ module Email
@@plugin_callbacks.each { |block| block.call(@fragment, @opts) }
end
def inline_secure_images(attachments)
stripped_media = @fragment.css('[data-stripped-secure-media]')
upload_shas = {}
stripped_media.each do |div|
url = div['data-stripped-secure-media']
filename = File.basename(url)
sha1 = filename.gsub(File.extname(filename), "")
upload_shas[url] = sha1
end
uploads = Upload.select(:original_filename, :sha1).where(sha1: upload_shas.values)
stripped_media.each do |div|
upload = uploads.find { |upl| upl.sha1 == upload_shas[div['data-stripped-secure-media']] }
next if !upload
original_filename = upload.original_filename
if attachments[original_filename]
url = attachments[original_filename].url
div.add_next_sibling(
"<img src=\"#{url}\" data-embedded-secure-image=\"true\" style=\"max-width: 50%; max-height: 400px;\" />"
)
div.remove
end
end
end
def to_html
# needs to be before class + id strip because we need to style redacted
# media and also not double-redact already redacted from lower levels
replace_secure_media_urls
strip_classes_and_ids
replace_relative_urls
replace_secure_media_urls
if SiteSetting.preserve_email_structure_when_styling
@fragment.to_html
@ -249,6 +278,10 @@ module Email
end
end
def to_s
@fragment.to_s
end
def include_body?
@html =~ /<body>/i
end
@ -267,8 +300,6 @@ module Email
img.remove
end
end
@fragment.to_s
end
def make_all_links_absolute
@ -298,19 +329,12 @@ module Email
end
def replace_secure_media_urls
@fragment.css('[href]').each do |a|
if Upload.secure_media_url?(a['href'])
a.add_next_sibling "<p class='secure-media-notice'>#{I18n.t("emails.secure_media_placeholder")}</p>"
a.remove
end
end
# strip again, this can be done at a lower level like in the user
# notification template but that may not catch everything
PrettyText.strip_secure_media(@fragment)
@fragment.search('img[src]').each do |img|
if Upload.secure_media_url?(img['src'])
img.add_next_sibling "<p class='secure-media-notice'>#{I18n.t("emails.secure_media_placeholder")}</p>"
img.remove
end
end
style('div.secure-media-notice', 'border: 5px solid #e9e9e9; padding: 5px; display: inline-block;')
style('div.secure-media-notice a', "color: #{SiteSetting.email_link_color}")
end
def correct_first_body_margin

18
lib/pretty_text.rb
View File

@ -408,9 +408,25 @@ module PrettyText
doc.css("a[href]").each do |a|
if Upload.secure_media_url?(a["href"])
target = %w(video audio).include?(a&.parent&.name) ? a.parent : a
target.replace "<p class='secure-media-notice'>#{I18n.t("emails.secure_media_placeholder")}</p>"
next if target.to_s.include?("stripped-secure-view-media")
target.add_next_sibling secure_media_placeholder(doc, a['href'])
target.remove
end
end
doc.css('img[src]').each do |img|
if Upload.secure_media_url?(img['src'])
img.add_next_sibling secure_media_placeholder(doc, img['src'])
img.remove
end
end
end
def self.secure_media_placeholder(doc, url)
<<~HTML
<div class="secure-media-notice" data-stripped-secure-media="#{url}">
#{I18n.t('emails.secure_media_placeholder')} <a class='stripped-secure-view-media' href="#{url}">#{I18n.t("emails.view_redacted_media")}</a>.
</div>
HTML
end
def self.format_for_email(html, post = nil)

81
spec/components/email/sender_spec.rb
View File

@ -404,6 +404,87 @@ describe Email::Sender do
.to contain_exactly(*[small_pdf, large_pdf, csv_file].map(&:original_filename))
end
context "when secure media enabled" do
def enable_s3_uploads
SiteSetting.enable_s3_uploads = true
SiteSetting.s3_upload_bucket = "s3-upload-bucket"
SiteSetting.s3_access_key_id = "some key"
SiteSetting.s3_secret_access_key = "some secrets3_region key"
stub_request(:head, "https://#{SiteSetting.s3_upload_bucket}.s3.amazonaws.com/")
stub_request(
:put,
"https://#{SiteSetting.s3_upload_bucket}.s3.amazonaws.com/original/1X/#{image.sha1}.#{image.extension}?acl"
)
store = FileStore::S3Store.new
s3_helper = store.instance_variable_get(:@s3_helper)
client = Aws::S3::Client.new(stub_responses: true)
s3_helper.stubs(:s3_client).returns(client)
Discourse.stubs(:store).returns(store)
end
before do
enable_s3_uploads
SiteSetting.secure_media = true
SiteSetting.login_required = true
SiteSetting.email_total_attachment_size_limit_kb = 14_000
SiteSetting.secure_media_max_email_embed_image_size_kb = 5_000
Jobs.run_immediately!
Jobs::PullHotlinkedImages.any_instance.expects(:execute)
FileStore::S3Store.any_instance.expects(:has_been_uploaded?).returns(true).at_least_once
CookedPostProcessor.any_instance.stubs(:get_size).returns([244, 66])
@secure_image = UploadCreator.new(file_from_fixtures("logo.png", "images"), "logo.png")
.create_for(Discourse.system_user.id)
@secure_image.update_secure_status(secure_override_value: true)
@secure_image.update(access_control_post_id: reply.id)
reply.update(raw: reply.raw + "\n" + "#{UploadMarkdown.new(@secure_image).image_markdown}")
reply.rebake!
end
it "does not attach images when embedding them is not allowed" do
Email::Sender.new(message, :valid_type).send
expect(message.attachments.length).to eq(3)
end
context "when embedding secure images in email is allowed" do
before do
SiteSetting.secure_media_allow_embed_images_in_emails = true
end
it "does not attach images that are not marked as secure" do
Email::Sender.new(message, :valid_type).send
expect(message.attachments.length).to eq(4)
end
it "does not embed images that are too big" do
SiteSetting.secure_media_max_email_embed_image_size_kb = 1
Email::Sender.new(message, :valid_type).send
expect(message.attachments.length).to eq(3)
end
it "uses the email styles to inline secure images and attaches the secure image upload to the email" do
Email::Sender.new(message, :valid_type).send
expect(message.attachments.length).to eq(4)
expect(message.attachments.map(&:filename))
.to contain_exactly(*[small_pdf, large_pdf, csv_file, @secure_image].map(&:original_filename))
expect(message.html_part.body).to include("cid:")
expect(message.html_part.body).to include("embedded-secure-image")
expect(message.attachments.length).to eq(4)
end
end
end
it "adds only non-image uploads as attachments to the email and leaves the image intact with original source" do
SiteSetting.email_total_attachment_size_limit_kb = 10_000
Email::Sender.new(message, :valid_type).send
expect(message.attachments.length).to eq(3)
expect(message.attachments.map(&:filename))
.to contain_exactly(*[small_pdf, large_pdf, csv_file].map(&:original_filename))
expect(message.html_part.body).to include("<img src=\"#{Discourse.base_url}#{image.url}\"")
end
it "respects the size limit and attaches only files that fit into the max email size" do
SiteSetting.email_total_attachment_size_limit_kb = 40
Email::Sender.new(message, :valid_type).send

45
spec/components/email/styles_spec.rb
View File

@ -4,6 +4,7 @@ require 'rails_helper'
require 'email'
describe Email::Styles do
let(:attachments) { {} }
def basic_fragment(html)
styler = Email::Styles.new(html)
@ -186,23 +187,57 @@ describe Email::Styles do
end
end
context "replace_relative_urls" do
context "replace_secure_media_urls" do
let(:attachments) { { 'testimage.png' => stub(url: 'email/test.png') } }
it "replaces secure media within a link with a placeholder" do
frag = html_fragment("<a href=\"#{Discourse.base_url}\/secure-media-uploads/original/1X/testimage.png\"><img src=\"/secure-media-uploads/original/1X/testimage.png\"></a>")
expect(frag.at('p.secure-media-notice')).to be_present
expect(frag.at('img')).not_to be_present
expect(frag.at('a')).not_to be_present
expect(frag.to_s).to include("Redacted")
end
it "replaces secure images with a placeholder" do
frag = html_fragment("<img src=\"/secure-media-uploads/original/1X/testimage.png\">")
expect(frag.at('p.secure-media-notice')).to be_present
expect(frag.at('img')).not_to be_present
expect(frag.to_s).to include("Redacted")
end
it "does not replace topic links with secure-media-uploads in the name" do
frag = html_fragment("<a href=\"#{Discourse.base_url}\/t/secure-media-uploads/235723\">Visit Topic</a>")
expect(frag.at('p.secure-media-notice')).not_to be_present
expect(frag.to_s).not_to include("Redacted")
end
end
context "inline_secure_images" do
let(:attachments) { { 'testimage.png' => stub(url: 'cid:email/test.png') } }
fab!(:upload) { Fabricate(:upload, original_filename: 'testimage.png', secure: true, sha1: '123456') }
def strip_and_inline
html = "<a href=\"#{Discourse.base_url}\/secure-media-uploads/original/1X/123456.png\"><img src=\"/secure-media-uploads/original/1X/123456.png\"></a>"
# strip out the secure media
styler = Email::Styles.new(html)
styler.format_basic
styler.format_html
html = styler.to_html
# pass in the attachments to match uploads based on sha + original filename
styler = Email::Styles.new(html)
styler.inline_secure_images(attachments)
@frag = Nokogiri::HTML5.fragment(styler.to_s)
end
it "inlines attachments where stripped-secure-media data attr is present" do
strip_and_inline
expect(@frag.to_s).to include("cid:email/test.png")
expect(@frag.css('[data-stripped-secure-media]')).not_to be_present
end
it "does not inline anything if the upload cannot be found" do
upload.update(sha1: 'blah12')
strip_and_inline
expect(@frag.to_s).not_to include("cid:email/test.png")
expect(@frag.css('[data-stripped-secure-media]')).to be_present
end
end
end

34
spec/components/pretty_text_spec.rb
View File

@ -928,6 +928,40 @@ describe PrettyText do
expect(md.to_s).to match(I18n.t("emails.secure_media_placeholder"))
expect(md.to_s).not_to match(SiteSetting.Upload.s3_cdn_url)
end
it "replaces secure media within a link with a placeholder, keeping the url in an attribute" do
url = "#{Discourse.base_url}\/secure-media-uploads/original/1X/testimage.png"
html = <<~HTML
<a href=\"#{url}\"><img src=\"/secure-media-uploads/original/1X/testimage.png\"></a>
HTML
md = PrettyText.format_for_email(html, post)
expect(md).not_to include('<img')
expect(md).to include("Redacted")
expect(md).to include("data-stripped-secure-media=\"#{url}\"")
end
it "does not create nested redactions from double processing because of the view media link" do
url = "#{Discourse.base_url}\/secure-media-uploads/original/1X/testimage.png"
html = <<~HTML
<a href=\"#{url}\"><img src=\"/secure-media-uploads/original/1X/testimage.png\"></a>
HTML
md = PrettyText.format_for_email(html, post)
md = PrettyText.format_for_email(md, post)
expect(md.scan(/stripped-secure-view-media/).length).to eq(1)
expect(md.scan(/Redacted/).length).to eq(1)
end
it "replaces secure images with a placeholder, keeping the url in an attribute" do
url = "/secure-media-uploads/original/1X/testimage.png"
html = <<~HTML
<img src=\"#{url}\">
HTML
md = PrettyText.format_for_email(html, post)
expect(md).not_to include('<img')
expect(md).to include("Redacted")
expect(md).to include("data-stripped-secure-media=\"#{url}\"")
end
end
end

44
spec/mailers/user_notifications_spec.rb
View File

@ -699,50 +699,6 @@ describe UserNotifications do
expect(mail.body.to_s).to match(I18n.t("user_notifications.reached_limit", count: 2))
end
describe "secure media" do
let(:video_upload) { Fabricate(:upload, extension: "mov") }
let(:user) { Fabricate(:user) }
let(:post) { Fabricate(:post) }
before do
SiteSetting.s3_upload_bucket = "some-bucket-on-s3"
SiteSetting.s3_access_key_id = "s3-access-key-id"
SiteSetting.s3_secret_access_key = "s3-secret-access-key"
SiteSetting.s3_cdn_url = "https://s3.cdn.com"
SiteSetting.enable_s3_uploads = true
SiteSetting.secure_media = true
SiteSetting.login_required = true
video_upload.update!(url: "#{SiteSetting.s3_cdn_url}/#{Discourse.store.get_path_for_upload(video_upload)}")
user.email_logs.create!(
email_type: 'blah',
to_address: user.email,
user_id: user.id
)
end
it "replaces secure audio/video with placeholder" do
reply = Fabricate(:post, topic_id: post.topic_id, raw: "Video: #{video_upload.url}")
notification = Fabricate(
:notification,
topic_id: post.topic_id,
post_number: reply.post_number,
user: post.user,
data: { original_username: 'bob' }.to_json
)
mail = UserNotifications.user_replied(
user,
post: reply,
notification_type: notification.notification_type,
notification_data_hash: notification.data_hash
)
expect(mail.body.to_s).to match(I18n.t("emails.secure_media_placeholder"))
end
end
def expects_build_with(condition)
UserNotifications.any_instance.expects(:build_email).with(user.email, condition)
mailer = UserNotifications.public_send(