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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
parent d260e42c8a
commit dede942007
11 changed files with 248 additions and 98 deletions
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56
lib/email/styles.rb
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@@ -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