fix: pin Azure instance identity roots on all platforms#25390
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fix: pin Azure instance identity roots on all platforms#25390jdomeracki-coder wants to merge 1 commit into
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Embed Azure root CAs on all platforms instead of falling back to x509.SystemCertPool() on non-darwin. This pins trust to the known Azure certificate chain by default, preventing any system-trusted CA from signing metadata documents accepted by Validate. Add --azure-instance-identity-root-ca-path flag (CODER_AZURE_INSTANCE_IDENTITY_ROOT_CA_PATH) so operators can override the embedded roots with a custom PEM file when Azure rotates CAs before a Coder binary update.
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Commit 132fa87 (#25312) changed non-darwin platforms to use
x509.SystemCertPool()for Azure instance identity verification. This broadened the trust boundary from 3 specific Azure root CAs to the entire OS trust store, allowing any system-trusted CA to potentially sign metadata documents accepted by the unauthenticated/api/v2/workspaceagents/azure-instance-identityendpoint.This PR re-embeds Azure root CAs on all platforms, making root-pinning the secure default. A new
--azure-instance-identity-root-ca-pathflag (CODER_AZURE_INSTANCE_IDENTITY_ROOT_CA_PATH) lets operators override the embedded roots with a custom PEM file when Azure rotates CAs before a Coder binary update.Security analysis
The previous code on non-darwin had
rootCertPool()returningx509.SystemCertPool(), which means any root CA in the host OS trust store (enterprise CAs, public WebPKI roots, etc.) could anchor a certificate chain accepted byValidate. The only other identity check is a CN regex (metadata.azure.*). Since the Azure auth endpoint is unauthenticated and returns agent session tokens, widening the trust store increases the attack surface for environments with enterprise or custom CAs.Note
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