Commit 0dcb9d21 authored by Diego Louzán's avatar Diego Louzán

feat: SMIME signed notification emails

- Add mail interceptor the signs outgoing email with SMIME
- Add lib and helpers to work with SMIME data
- New configuration params for setting up SMIME key and cert files
parent d8966abd
......@@ -75,6 +75,8 @@ eslint-report.html
/.rspec
/plugins/*
/.gitlab_pages_secret
/.gitlab_smime_key
/.gitlab_smime_cert
package-lock.json
/junit_*.xml
/coverage-frontend/
......
---
title: Notification emails can be signed with SMIME
merge_request: 30644
author: Diego Louzán
type: added
......@@ -95,6 +95,15 @@ production: &base
email_display_name: GitLab
email_reply_to: noreply@example.com
email_subject_suffix: ''
email_smime:
# Uncomment and set to true if you need to enable email S/MIME signing (default: false)
# enabled: false
# S/MIME private key file in PEM format, unencrypted
# Default is '.gitlab_smime_key' relative to Rails.root (i.e. root of the GitLab app).
# key_file: /home/git/gitlab/.gitlab_smime_key
# S/MIME public certificate key in PEM format, will be attached to signed messages
# Default is '.gitlab_smime_cert' relative to Rails.root (i.e. root of the GitLab app).
# cert_file: /home/git/gitlab/.gitlab_smime_cert
# Email server smtp settings are in config/initializers/smtp_settings.rb.sample
......
require_relative '../settings'
require_relative '../object_store_settings'
require_relative '../smime_signature_settings'
# Default settings
Settings['ldap'] ||= Settingslogic.new({})
......@@ -171,6 +172,7 @@ Settings.gitlab['email_from'] ||= ENV['GITLAB_EMAIL_FROM'] || "gitlab@#{Settings
Settings.gitlab['email_display_name'] ||= ENV['GITLAB_EMAIL_DISPLAY_NAME'] || 'GitLab'
Settings.gitlab['email_reply_to'] ||= ENV['GITLAB_EMAIL_REPLY_TO'] || "noreply@#{Settings.gitlab.host}"
Settings.gitlab['email_subject_suffix'] ||= ENV['GITLAB_EMAIL_SUBJECT_SUFFIX'] || ""
Settings.gitlab['email_smime'] = SmimeSignatureSettings.parse(Settings.gitlab['email_smime'])
Settings.gitlab['base_url'] ||= Settings.__send__(:build_base_gitlab_url)
Settings.gitlab['url'] ||= Settings.__send__(:build_gitlab_url)
Settings.gitlab['user'] ||= 'git'
......
......@@ -10,3 +10,8 @@ ActionMailer::Base.register_interceptors(
)
ActionMailer::Base.register_observer(::Gitlab::Email::Hook::DeliveryMetricsObserver)
if Gitlab.config.gitlab.email_enabled && Gitlab.config.gitlab.email_smime.enabled
ActionMailer::Base.register_interceptor(::Gitlab::Email::Hook::SmimeSignatureInterceptor)
Gitlab::AppLogger.debug "S/MIME signing of outgoing emails enabled"
end
# Set default values for email_smime settings
class SmimeSignatureSettings
def self.parse(email_smime)
email_smime ||= Settingslogic.new({})
email_smime['enabled'] = false unless email_smime['enabled']
email_smime['key_file'] ||= Rails.root.join('.gitlab_smime_key')
email_smime['cert_file'] ||= Rails.root.join('.gitlab_smime_cert')
email_smime
end
end
......@@ -64,6 +64,7 @@ Learn how to install, configure, update, and maintain your GitLab instance.
- [External Classification Policy Authorization](../user/admin_area/settings/external_authorization.md) **(PREMIUM ONLY)**
- [Upload a license](../user/admin_area/license.md): Upload a license to unlock features that are in paid tiers of GitLab. **(STARTER ONLY)**
- [Admin Area](../user/admin_area/index.md): for self-managed instance-wide configuration and maintenance.
- [S/MIME Signing](smime_signing_email.md): how to sign all outgoing notification emails with S/MIME
#### Customizing GitLab's appearance
......
# Signing outgoing email with S/MIME
Notification emails sent by Gitlab can be signed with S/MIME for improved
security.
> **Note:**
Please be aware that S/MIME certificates and TLS/SSL certificates are not the
same and are used for different purposes: TLS creates a secure channel, whereas
S/MIME signs and/or encrypts the message itself
## Enable S/MIME signing
This setting must be explicitly enabled and a single pair of key and certificate
files must be provided in `gitlab.rb` or `gitlab.yml` if you are using Omnibus
GitLab or installed GitLab from source respectively:
```yaml
email_smime:
enabled: true
key_file: /etc/pki/smime/private/gitlab.key
cert_file: /etc/pki/smime/certs/gitlab.crt
```
- Both files must be provided PEM-encoded.
- The key file must be unencrypted so that Gitlab can read it without user
intervention.
NOTE: **Note:** Be mindful of the access levels for your private keys and visibility to
third parties.
### How to convert S/MIME PKCS#12 / PFX format to PEM encoding
Typically S/MIME certificates are handled in binary PKCS#12 format (`.pfx` or `.p12`
extensions), which contain the following in a single encrypted file:
- Server certificate
- Intermediate certificates (if any)
- Private key
In order to export the required files in PEM encoding from the PKCS#12 file,
the `openssl` command can be used:
```bash
#-- Extract private key in PEM encoding (no password, unencrypted)
$ openssl pkcs12 -in gitlab.p12 -nocerts -nodes -out gitlab.key
#-- Extract certificates in PEM encoding (full certs chain including CA)
$ openssl pkcs12 -in gitlab.p12 -nokeys -out gitlab.crt
```
......@@ -5,6 +5,10 @@
To view rendered emails "sent" in your development instance, visit
[`/rails/letter_opener`](http://localhost:3000/rails/letter_opener).
Please note that [S/MIME signed](../administration/smime_signing_email.md) emails
[cannot be currently previewed](https://github.com/fgrehm/letter_opener_web/issues/96) with
`letter_opener`.
## Mailer previews
Rails provides a way to preview our mailer templates in HTML and plaintext using
......
# frozen_string_literal: true
module Gitlab
module Email
module Hook
class SmimeSignatureInterceptor
# Sign emails with SMIME if enabled
class << self
def delivering_email(message)
signed_message = Gitlab::Email::Smime::Signer.sign(
cert: certificate.cert,
key: certificate.key,
data: message.encoded)
signed_email = Mail.new(signed_message)
overwrite_body(message, signed_email)
overwrite_headers(message, signed_email)
end
private
def certificate
@certificate ||= Gitlab::Email::Smime::Certificate.from_files(key_path, cert_path)
end
def key_path
Gitlab.config.gitlab.email_smime.key_file
end
def cert_path
Gitlab.config.gitlab.email_smime.cert_file
end
def overwrite_body(message, signed_email)
# since this is a multipart email, assignment to nil is important,
# otherwise Message#body will add a new mail part
message.body = nil
message.body = signed_email.body.encoded
end
def overwrite_headers(message, signed_email)
message.content_disposition = signed_email.content_disposition
message.content_transfer_encoding = signed_email.content_transfer_encoding
message.content_type = signed_email.content_type
end
end
end
end
end
end
# frozen_string_literal: true
module Gitlab
module Email
module Smime
class Certificate
include OpenSSL
attr_reader :key, :cert
def key_string
@key.to_s
end
def cert_string
@cert.to_pem
end
def self.from_strings(key_string, cert_string)
key = PKey::RSA.new(key_string)
cert = X509::Certificate.new(cert_string)
new(key, cert)
end
def self.from_files(key_path, cert_path)
from_strings(File.read(key_path), File.read(cert_path))
end
def initialize(key, cert)
@key = key
@cert = cert
end
end
end
end
end
# frozen_string_literal: true
require 'openssl'
module Gitlab
module Email
module Smime
# Tooling for signing and verifying data with SMIME
class Signer
include OpenSSL
def self.sign(cert:, key:, data:)
signed_data = PKCS7.sign(cert, key, data, nil, PKCS7::DETACHED)
PKCS7.write_smime(signed_data)
end
# return nil if data cannot be verified, otherwise the signed content data
def self.verify_signature(cert:, ca_cert: nil, signed_data:)
store = X509::Store.new
store.set_default_paths
store.add_cert(ca_cert) if ca_cert
signed_smime = PKCS7.read_smime(signed_data)
signed_smime if signed_smime.verify([cert], store)
end
end
end
end
end
require 'fast_spec_helper'
describe SmimeSignatureSettings do
describe '.parse' do
let(:default_smime_key) { Rails.root.join('.gitlab_smime_key') }
let(:default_smime_cert) { Rails.root.join('.gitlab_smime_cert') }
it 'sets correct default values to disabled' do
parsed_settings = described_class.parse(nil)
expect(parsed_settings['enabled']).to be(false)
expect(parsed_settings['key_file']).to eq(default_smime_key)
expect(parsed_settings['cert_file']).to eq(default_smime_cert)
end
context 'when providing custom values' do
it 'sets correct default values to disabled' do
custom_settings = Settingslogic.new({})
parsed_settings = described_class.parse(custom_settings)
expect(parsed_settings['enabled']).to be(false)
expect(parsed_settings['key_file']).to eq(default_smime_key)
expect(parsed_settings['cert_file']).to eq(default_smime_cert)
end
it 'enables smime with default key and cert' do
custom_settings = Settingslogic.new({
'enabled' => true
})
parsed_settings = described_class.parse(custom_settings)
expect(parsed_settings['enabled']).to be(true)
expect(parsed_settings['key_file']).to eq(default_smime_key)
expect(parsed_settings['cert_file']).to eq(default_smime_cert)
end
it 'enables smime with custom key and cert' do
custom_key = '/custom/key'
custom_cert = '/custom/cert'
custom_settings = Settingslogic.new({
'enabled' => true,
'key_file' => custom_key,
'cert_file' => custom_cert
})
parsed_settings = described_class.parse(custom_settings)
expect(parsed_settings['enabled']).to be(true)
expect(parsed_settings['key_file']).to eq(custom_key)
expect(parsed_settings['cert_file']).to eq(custom_cert)
end
end
end
end
require 'spec_helper'
describe 'ActionMailer hooks' do
describe 'smime signature interceptor' do
before do
class_spy(ActionMailer::Base).as_stubbed_const
end
it 'is disabled by default' do
load Rails.root.join('config/initializers/action_mailer_hooks.rb')
expect(ActionMailer::Base).not_to(
have_received(:register_interceptor).with(Gitlab::Email::Hook::SmimeSignatureInterceptor))
end
describe 'interceptor testbed' do
where(:email_enabled, :email_smime_enabled, :smime_interceptor_enabled) do
[
[false, false, false],
[false, true, false],
[true, false, false],
[true, true, true]
]
end
with_them do
before do
stub_config_setting(email_enabled: email_enabled)
stub_config_setting(email_smime: { enabled: email_smime_enabled })
end
it 'is enabled depending on settings' do
load Rails.root.join('config/initializers/action_mailer_hooks.rb')
if smime_interceptor_enabled
expect(ActionMailer::Base).to(
have_received(:register_interceptor).with(Gitlab::Email::Hook::SmimeSignatureInterceptor))
else
expect(ActionMailer::Base).not_to(
have_received(:register_interceptor).with(Gitlab::Email::Hook::SmimeSignatureInterceptor))
end
end
end
end
end
end
......@@ -13,9 +13,6 @@ describe Gitlab::Email::Hook::DisableEmailInterceptor do
end
after do
# Removing interceptor from the list because unregister_interceptor is
# implemented in later version of mail gem
# See: https://github.com/mikel/mail/pull/705
Mail.unregister_interceptor(described_class)
end
......
require 'spec_helper'
describe Gitlab::Email::Hook::SmimeSignatureInterceptor do
include SmimeHelper
# cert generation is an expensive operation and they are used read-only,
# so we share them as instance variables in all tests
before :context do
@root_ca = generate_root
@cert = generate_cert(root_ca: @root_ca)
end
let(:root_certificate) do
Gitlab::Email::Smime::Certificate.new(@root_ca[:key], @root_ca[:cert])
end
let(:certificate) do
Gitlab::Email::Smime::Certificate.new(@cert[:key], @cert[:cert])
end
let(:mail) do
ActionMailer::Base.mail(to: 'test@example.com', from: 'info@example.com', body: 'signed hello')
end
before do
allow(Gitlab::Email::Smime::Certificate).to receive_messages(from_files: certificate)
Mail.register_interceptor(described_class)
mail.deliver_now
end
after do
Mail.unregister_interceptor(described_class)
end
it 'signs the email appropriately with SMIME' do
expect(mail.header['To'].value).to eq('test@example.com')
expect(mail.header['From'].value).to eq('info@example.com')
expect(mail.header['Content-Type'].value).to match('multipart/signed').and match('protocol="application/x-pkcs7-signature"')
# verify signature and obtain pkcs7 encoded content
p7enc = Gitlab::Email::Smime::Signer.verify_signature(
cert: certificate.cert,
ca_cert: root_certificate.cert,
signed_data: mail.encoded)
# envelope in a Mail object and obtain the body
decoded_mail = Mail.new(p7enc.data)
expect(decoded_mail.body.encoded).to eq('signed hello')
end
end
# frozen_string_literal: true
require 'spec_helper'
describe Gitlab::Email::Smime::Certificate do
include SmimeHelper
# cert generation is an expensive operation and they are used read-only,
# so we share them as instance variables in all tests
before :context do
@root_ca = generate_root
@cert = generate_cert(root_ca: @root_ca)
end
describe 'testing environment setup' do
describe 'generate_root' do
subject { @root_ca }
it 'generates a root CA that expires a long way in the future' do
expect(subject[:cert].not_after).to be > 999.years.from_now
end
end
describe 'generate_cert' do
subject { @cert }
it 'generates a cert properly signed by the root CA' do
expect(subject[:cert].issuer).to eq(@root_ca[:cert].subject)
end
it 'generates a cert that expires soon' do
expect(subject[:cert].not_after).to be < 60.minutes.from_now
end
it 'generates a cert intended for email signing' do
expect(subject[:cert].extensions).to include(an_object_having_attributes(oid: 'extendedKeyUsage', value: match('E-mail Protection')))
end
context 'passing in INFINITE_EXPIRY' do
subject { generate_cert(root_ca: @root_ca, expires_in: SmimeHelper::INFINITE_EXPIRY) }
it 'generates a cert that expires a long way in the future' do
expect(subject[:cert].not_after).to be > 999.years.from_now
end
end
end
end
describe '.from_strings' do
it 'parses correctly a certificate and key' do
parsed_cert = described_class.from_strings(@cert[:key].to_s, @cert[:cert].to_pem)
common_cert_tests(parsed_cert, @cert, @root_ca)
end
end
describe '.from_files' do
it 'parses correctly a certificate and key' do
allow(File).to receive(:read).with('a_key').and_return(@cert[:key].to_s)
allow(File).to receive(:read).with('a_cert').and_return(@cert[:cert].to_pem)
parsed_cert = described_class.from_files('a_key', 'a_cert')
common_cert_tests(parsed_cert, @cert, @root_ca)
end
end
def common_cert_tests(parsed_cert, cert, root_ca)
expect(parsed_cert.cert).to be_a(OpenSSL::X509::Certificate)
expect(parsed_cert.cert.subject).to eq(cert[:cert].subject)
expect(parsed_cert.cert.issuer).to eq(root_ca[:cert].subject)
expect(parsed_cert.cert.not_before).to eq(cert[:cert].not_before)
expect(parsed_cert.cert.not_after).to eq(cert[:cert].not_after)
expect(parsed_cert.cert.extensions).to include(an_object_having_attributes(oid: 'extendedKeyUsage', value: match('E-mail Protection')))
expect(parsed_cert.key).to be_a(OpenSSL::PKey::RSA)
end
end
# frozen_string_literal: true
require 'spec_helper'
describe Gitlab::Email::Smime::Signer do
include SmimeHelper
it 'signs data appropriately with SMIME' do
root_certificate = generate_root
certificate = generate_cert(root_ca: root_certificate)
signed_content = described_class.sign(
cert: certificate[:cert],
key: certificate[:key],
data: 'signed content')
expect(signed_content).not_to be_nil
p7enc = described_class.verify_signature(
cert: certificate[:cert],
ca_cert: root_certificate[:cert],
signed_data: signed_content)
expect(p7enc).not_to be_nil
expect(p7enc.data).to eq('signed content')
end
end
module SmimeHelper
include OpenSSL
INFINITE_EXPIRY = 1000.years
SHORT_EXPIRY = 30.minutes
def generate_root
issue(signed_by: nil, expires_in: INFINITE_EXPIRY, certificate_authority: true)
end
def generate_cert(root_ca:, expires_in: SHORT_EXPIRY)
issue(signed_by: root_ca, expires_in: expires_in, certificate_authority: false)
end
# returns a hash { key:, cert: } containing a generated key, cert pair
def issue(email_address: 'test@example.com', signed_by:, expires_in:, certificate_authority:)
key = OpenSSL::PKey::RSA.new(4096)
public_key = key.public_key
subject = if certificate_authority
X509::Name.parse("/CN=EU")
else
X509::Name.parse("/CN=#{email_address}")
end
cert = X509::Certificate.new
cert.subject = subject
cert.issuer = signed_by&.fetch(:cert, nil)&.subject || subject
cert.not_before = Time.now
cert.not_after = expires_in.from_now
cert.public_key = public_key
cert.serial = 0x0
cert.version = 2
extension_factory = X509::ExtensionFactory.new
if certificate_authority
extension_factory.subject_certificate = cert
extension_factory.issuer_certificate = cert
cert.add_extension(extension_factory.create_extension('subjectKeyIdentifier', 'hash'))
cert.add_extension(extension_factory.create_extension('basicConstraints', 'CA:TRUE', true))
cert.add_extension(extension_factory.create_extension('keyUsage', 'cRLSign,keyCertSign', true))
else
cert.add_extension(extension_factory.create_extension('subjectAltName', "email:#{email_address}", false))
cert.add_extension(extension_factory.create_extension('basicConstraints', 'CA:FALSE', true))
cert.add_extension(extension_factory.create_extension('keyUsage', 'digitalSignature,keyEncipherment', true))
cert.add_extension(extension_factory.create_extension('extendedKeyUsage', 'clientAuth,emailProtection', false))
end
cert.sign(signed_by&.fetch(:key, nil) || key, Digest::SHA256.new)
{ key: key, cert: cert }
end
end
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