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67
.github/workflows/codeql-analysis.yml
vendored
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67
.github/workflows/codeql-analysis.yml
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# For most projects, this workflow file will not need changing; you simply need
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# to commit it to your repository.
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#
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# You may wish to alter this file to override the set of languages analyzed,
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# or to provide custom queries or build logic.
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#
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# ******** NOTE ********
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# We have attempted to detect the languages in your repository. Please check
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# the `language` matrix defined below to confirm you have the correct set of
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# supported CodeQL languages.
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#
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name: "CodeQL"
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on:
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push:
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branches: [ master ]
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pull_request:
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# The branches below must be a subset of the branches above
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branches: [ master ]
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schedule:
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- cron: '39 12 * * 2'
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jobs:
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analyze:
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name: Analyze
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runs-on: ubuntu-latest
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strategy:
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fail-fast: false
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matrix:
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language: [ 'python' ]
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# CodeQL supports [ 'cpp', 'csharp', 'go', 'java', 'javascript', 'python' ]
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# Learn more:
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# 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
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steps:
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- name: Checkout repository
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uses: actions/checkout@v2
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# Initializes the CodeQL tools for scanning.
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- name: Initialize CodeQL
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uses: github/codeql-action/init@v1
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with:
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languages: ${{ matrix.language }}
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# If you wish to specify custom queries, you can do so here or in a config file.
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# By default, queries listed here will override any specified in a config file.
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# Prefix the list here with "+" to use these queries and those in the config file.
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# queries: ./path/to/local/query, your-org/your-repo/queries@main
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# Autobuild attempts to build any compiled languages (C/C++, C#, or Java).
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# If this step fails, then you should remove it and run the build manually (see below)
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- name: Autobuild
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uses: github/codeql-action/autobuild@v1
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# ℹ️ Command-line programs to run using the OS shell.
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# 📚 https://git.io/JvXDl
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# ✏️ If the Autobuild fails above, remove it and uncomment the following three lines
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# and modify them (or add more) to build your code if your project
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# uses a compiled language
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#- run: |
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# make bootstrap
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# make release
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- name: Perform CodeQL Analysis
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uses: github/codeql-action/analyze@v1
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49
.github/workflows/ossar-analysis.yml
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.github/workflows/ossar-analysis.yml
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# This workflow integrates a collection of open source static analysis tools
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# with GitHub code scanning. For documentation, or to provide feedback, visit
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# https://github.com/github/ossar-action
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name: OSSAR
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on:
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push:
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pull_request:
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jobs:
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OSSAR-Scan:
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# OSSAR runs on windows-latest.
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# ubuntu-latest and macos-latest support coming soon
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runs-on: windows-latest
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steps:
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# Checkout your code repository to scan
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- name: Checkout repository
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uses: actions/checkout@v2
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with:
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# We must fetch at least the immediate parents so that if this is
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# a pull request then we can checkout the head.
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fetch-depth: 2
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# If this run was triggered by a pull request event, then checkout
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# the head of the pull request instead of the merge commit.
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- run: git checkout HEAD^2
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if: ${{ github.event_name == 'pull_request' }}
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# Ensure a compatible version of dotnet is installed.
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# The [Microsoft Security Code Analysis CLI](https://aka.ms/mscadocs) is built with dotnet v3.1.201.
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# A version greater than or equal to v3.1.201 of dotnet must be installed on the agent in order to run this action.
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# GitHub hosted runners already have a compatible version of dotnet installed and this step may be skipped.
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# For self-hosted runners, ensure dotnet version 3.1.201 or later is installed by including this action:
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# - name: Install .NET
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# uses: actions/setup-dotnet@v1
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# with:
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# dotnet-version: '3.1.x'
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# Run open source static analysis tools
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- name: Run OSSAR
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uses: github/ossar-action@v1
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id: ossar
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# Upload results to the Security tab
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- name: Upload OSSAR results
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uses: github/codeql-action/upload-sarif@v1
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with:
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sarif_file: ${{ steps.ossar.outputs.sarifFile }}
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14
README.md
14
README.md
@ -1,3 +1,7 @@
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# ExOTA-Milter - Exchange Online Tenant Authorisation Milter (Mail-Filter)
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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)**.
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@ -9,7 +13,7 @@ The **ExOTA-Milter** is kind of an authentication helper which plays an essentia
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So, the question is: *How can an Exchange-Online user/tenant be identified by a smarthost?*
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# Identification possibilities provided by Microsoft
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# Tenant identification options provided by Microsoft
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## Client-IP ranges specified by Microsoft
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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.
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```
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@ -37,10 +41,10 @@ Microsoft provides an ACL as [JSON file (ID: 10)](https://endpoints.office.com/e
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[...]
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```
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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!**
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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!**
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## x509 client certificate presented by Exchange-Online
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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!**
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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!**
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```
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Received: from DEU01-FR2-obe.outbound.protection.outlook.com (mail-fr2deu01lp2173.outbound.protection.outlook.com [104.47.11.173])
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(using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits))
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@ -48,7 +52,7 @@ Received: from DEU01-FR2-obe.outbound.protection.outlook.com (mail-fr2deu01lp217
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by some.secure.smarthost.example.com (Postfix) with ESMTPS id 4CjqCQ2WRCzGjg6
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for <blah.blubb@example.com>; Sat, 28 Nov 2020 12:34:26 +0100 (CET)
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```
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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.
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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.
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## DKIM - DomainKey Identified Message
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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.
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@ -118,4 +122,4 @@ The images are built on a weekly basis. The corresponding *Dockerfile* is locate
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Take a look [here](OCI/README.md)
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# How to test?
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First of all please take a look at how to set up the testing environment, which is described [here](tests/README.md)
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First of all please take a look at how to set up the testing environment, which is described [here](tests/README.md)
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