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Author SHA1 Message Date
Dominik Chilla
d01c98333e
Merge pull request #21 from chillout2k/devel
Security scanner badges
2020-12-13 16:32:42 +01:00
72a69d5d51 Security scanner badges 2020-12-13 16:32:17 +01:00
Dominik Chilla
5c626935a6
Create ossar-analysis.yml 2020-12-13 16:28:45 +01:00
Dominik Chilla
9eb62d9055
Create codeql-analysis.yml 2020-12-13 14:05:50 +01:00
Dominik Chilla
8562ce82d7
Merge pull request #18 from chillout2k/devel
Update README.md
2020-12-13 13:59:17 +01:00
Dominik Chilla
f7f3bab567
Update README.md
Some changes to the docs
2020-12-13 13:10:05 +01:00
3 changed files with 125 additions and 5 deletions

67
.github/workflows/codeql-analysis.yml vendored Normal file
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@ -0,0 +1,67 @@
# For most projects, this workflow file will not need changing; you simply need
# to commit it to your repository.
#
# You may wish to alter this file to override the set of languages analyzed,
# or to provide custom queries or build logic.
#
# ******** NOTE ********
# We have attempted to detect the languages in your repository. Please check
# the `language` matrix defined below to confirm you have the correct set of
# supported CodeQL languages.
#
name: "CodeQL"
on:
push:
branches: [ master ]
pull_request:
# The branches below must be a subset of the branches above
branches: [ master ]
schedule:
- cron: '39 12 * * 2'
jobs:
analyze:
name: Analyze
runs-on: ubuntu-latest
strategy:
fail-fast: false
matrix:
language: [ 'python' ]
# CodeQL supports [ 'cpp', 'csharp', 'go', 'java', 'javascript', 'python' ]
# Learn more:
# https://docs.github.com/en/free-pro-team@latest/github/finding-security-vulnerabilities-and-errors-in-your-code/configuring-code-scanning#changing-the-languages-that-are-analyzed
steps:
- name: Checkout repository
uses: actions/checkout@v2
# Initializes the CodeQL tools for scanning.
- name: Initialize CodeQL
uses: github/codeql-action/init@v1
with:
languages: ${{ matrix.language }}
# If you wish to specify custom queries, you can do so here or in a config file.
# By default, queries listed here will override any specified in a config file.
# Prefix the list here with "+" to use these queries and those in the config file.
# queries: ./path/to/local/query, your-org/your-repo/queries@main
# Autobuild attempts to build any compiled languages (C/C++, C#, or Java).
# If this step fails, then you should remove it and run the build manually (see below)
- name: Autobuild
uses: github/codeql-action/autobuild@v1
# Command-line programs to run using the OS shell.
# 📚 https://git.io/JvXDl
# ✏️ If the Autobuild fails above, remove it and uncomment the following three lines
# and modify them (or add more) to build your code if your project
# uses a compiled language
#- run: |
# make bootstrap
# make release
- name: Perform CodeQL Analysis
uses: github/codeql-action/analyze@v1

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.github/workflows/ossar-analysis.yml vendored Normal file
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# This workflow integrates a collection of open source static analysis tools
# with GitHub code scanning. For documentation, or to provide feedback, visit
# https://github.com/github/ossar-action
name: OSSAR
on:
push:
pull_request:
jobs:
OSSAR-Scan:
# OSSAR runs on windows-latest.
# ubuntu-latest and macos-latest support coming soon
runs-on: windows-latest
steps:
# Checkout your code repository to scan
- name: Checkout repository
uses: actions/checkout@v2
with:
# We must fetch at least the immediate parents so that if this is
# a pull request then we can checkout the head.
fetch-depth: 2
# If this run was triggered by a pull request event, then checkout
# the head of the pull request instead of the merge commit.
- run: git checkout HEAD^2
if: ${{ github.event_name == 'pull_request' }}
# Ensure a compatible version of dotnet is installed.
# The [Microsoft Security Code Analysis CLI](https://aka.ms/mscadocs) is built with dotnet v3.1.201.
# A version greater than or equal to v3.1.201 of dotnet must be installed on the agent in order to run this action.
# GitHub hosted runners already have a compatible version of dotnet installed and this step may be skipped.
# For self-hosted runners, ensure dotnet version 3.1.201 or later is installed by including this action:
# - name: Install .NET
# uses: actions/setup-dotnet@v1
# with:
# dotnet-version: '3.1.x'
# Run open source static analysis tools
- name: Run OSSAR
uses: github/ossar-action@v1
id: ossar
# Upload results to the Security tab
- name: Upload OSSAR results
uses: github/codeql-action/upload-sarif@v1
with:
sarif_file: ${{ steps.ossar.outputs.sarifFile }}

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@ -1,3 +1,7 @@
![CodeQL](https://github.com/chillout2k/ExOTA-Milter/workflows/CodeQL/badge.svg?branch=master)
![OSSAR](https://github.com/chillout2k/ExOTA-Milter/workflows/OSSAR/badge.svg?branch=master)
# ExOTA-Milter - Exchange Online Tenant Authorisation Milter (Mail-Filter)
The **ExOTA-[Milter](https://en.wikipedia.org/wiki/Milter)** application is written in python3 and derives from **[sdgathman´s pymilter](https://github.com/sdgathman/pymilter)**.
@ -9,7 +13,7 @@ The **ExOTA-Milter** is kind of an authentication helper which plays an essentia
So, the question is: *How can an Exchange-Online user/tenant be identified by a smarthost?*
# Identification possibilities provided by Microsoft
# Tenant identification options provided by Microsoft
## Client-IP ranges specified by Microsoft
Microsoft provides an ACL as [JSON file (ID: 10)](https://endpoints.office.com/endpoints/worldwide?clientrequestid=b10c5ed1-bad1-445f-b386-b919946339a7), which looks like this.
```
@ -37,10 +41,10 @@ Microsoft provides an ACL as [JSON file (ID: 10)](https://endpoints.office.com/e
[...]
```
The problem of this IP based ACL is that many other Exchange-Online customers/tenants are sending from the same IP-ranges as well! **This means that many smarthost configured to relay mails comming from Exchange-Online tends to be an open relay (for Microsoft customers) unless additional authentication mechanism on a higher layer than IP takes place! IP-address based ACLs are definitely not the right way to achieve this!**
The problem of IP based ACLs is that many other Exchange-Online customers/tenants are sending from the same IP-ranges as well! **This means that many smarthost configured to relay mails comming from Exchange-Online tend to act as open relays (for Microsoft customers) unless additional authentication mechanism on a higher layer than IP takes place! IP-address based ACLs are definitely not the right way to achieve this!**
## x509 client certificate presented by Exchange-Online
The Exchange-Online platform also *presents* a x509 client certificate to identitfy onself to the smarthost. Taking a closer look at the received header we´ll notice that the certificates common name (CN) *mail.protection.outlook.com* is not realy tenant specific. Although the certificate provides additional security regarding the identity of the client system, it does not provide identity regarding the tenant. **IMHO that´s stil not enough to permit relaying!**
The Exchange-Online platform also *presents* a x509 client certificate to identitfy onself to the smarthost. Taking a closer look at the received header shows on that the certificates common name (CN) *mail.protection.outlook.com* is not realy tenant specific. Although the certificate provides additional security regarding the identity of the client system, it does not provide identity regarding the tenant. **IMHO that´s stil not enough to permit relaying!**
```
Received: from DEU01-FR2-obe.outbound.protection.outlook.com (mail-fr2deu01lp2173.outbound.protection.outlook.com [104.47.11.173])
(using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits))
@ -48,7 +52,7 @@ Received: from DEU01-FR2-obe.outbound.protection.outlook.com (mail-fr2deu01lp217
by some.secure.smarthost.example.com (Postfix) with ESMTPS id 4CjqCQ2WRCzGjg6
for <blah.blubb@example.com>; Sat, 28 Nov 2020 12:34:26 +0100 (CET)
```
Client certificate verification is the job of the underlying MTA. So the **ExOTA-Milter** does not validate the client certificate itself, but it can be enabled (disabled per default) to match for the *expected* client CN. The emailserver [Postfix](http://postfix.org), for example, only provides the client CN to the milter API if the client certificate was successfully validated. Otherwise the **ExOTA-Milter** will not *see* the client CN over the milter protocol ([postfix milter macro](http://www.postfix.org/MILTER_README.html) `{cert_subject}`) which results in a milter reject action.
Client certificate verification is the job of the underlying MTA. So the **ExOTA-Milter** does not validate the client certificate itself, but it can be enabled (disabled per default) to match for the *expected* client CN. The mail server software [Postfix](http://postfix.org), for example, only presents the client CN to the milter API if the client certificate was successfully validated before. Otherwise the **ExOTA-Milter** will not *see* the client CN over the milter protocol ([postfix milter macro](http://www.postfix.org/MILTER_README.html#macros) `{cert_subject}`) which results in a milter reject action.
## DKIM - DomainKey Identified Message
Nevertheless, as [Microsoft supports DKIM-signing for outbound email traffic](https://docs.microsoft.com/de-de/microsoft-365/security/office-365-security/use-dkim-to-validate-outbound-email?view=o365-worldwide) the **ExOTA-Milter** can be used to authenticate sending tenants, respectively their sender domains, based on the cryptographic capabilities of [DKIM](https://tools.ietf.org/html/rfc6376). In fact the **ExOTA-Milter** does not validate the DKIM-signatures itself. Instead it simply parses DKIM-specific *Authentication-Results* headers produced by any previously DKIM-validating milter (like [OpenDKIM](http://www.opendkim.org/), [Rspamd](https://rspamd.com/) or [AMavis](https://www.ijs.si/software/amavisd/)) in the chain. I personally prefer OpenDKIM as it´s lightweight and fully focused on DKIM.
@ -118,4 +122,4 @@ The images are built on a weekly basis. The corresponding *Dockerfile* is locate
Take a look [here](OCI/README.md)
# How to test?
First of all please take a look at how to set up the testing environment, which is described [here](tests/README.md)
First of all please take a look at how to set up the testing environment, which is described [here](tests/README.md)