Fix circular SPF reference detection (A→B→A loops) #1398
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The existing self-reference checks only caught direct loops (A→A) but missed indirect circular references like A→B→A or longer chains. Added a -Visited parameter to track all domains in the resolution chain. Before recursing into an include or redirect, the function now checks if the target domain has already been visited in the current resolution path. - Direct self-references return specific messages (e.g., "Self-referencing SPF include") - Indirect circular references return "Circular SPF reference detected" Tested against oldmomutual.com which has a circular include with oldmissourimutual.com. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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Pull request overview
This PR fixes circular SPF reference detection by introducing a tracking mechanism for visited domains during SPF record resolution. Previously, only direct self-references (A→A) were detected, but indirect circular references (A→B→A) caused infinite loops and stack overflows.
Key changes:
- Added a
$Visitedparameter array to track all domains in the resolution chain - Updated circular reference detection logic for both redirect and include directives
- Distinguished between direct self-references and indirect circular references in error messages
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Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
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Accepted Copilot's suggestions, they make sense. |
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OK, cool. I didn't have a chance to test yet, so I just kicked off the Copilot review. |
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A little bump on this @SamErde. We're seeing this is production for quite a few tenants so would love to get the fix in place soon. |
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Description
The existing self-reference checks only caught direct loops (A→A) but missed indirect circular references like A→B→A or longer chains. This causes infinite loops which eventually result in a stack overflow.
Added a -Visited parameter to track all domains in the resolution chain. Before recursing into an include or redirect, the function now checks if the target domain has already been visited in the current resolution path.
Tested against oldmomutual.com which has a circular include with oldmissourimutual.com.
Contribution Checklist
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/powershell/tests/pester.ps1on your local system.