+ "details": "### Summary\n\nTwo swallowed errors in `ClientAuthentication.provision()` cause mTLS client certificate authentication to silently fail open when a CA certificate file is missing, unreadable, or malformed. The server starts without error but accepts any client certificate signed by any system-trusted CA, completely bypassing the intended private CA trust boundary.\n\n### Details\n\nIn `modules/caddytls/connpolicy.go`, the `provision()` method has two `return nil` statements that should be `return err`:\n\n**Bug #1 — line 787:**\n```go\nders, err := convertPEMFilesToDER(fpath)\nif err != nil {\n return nil // BUG: should be \"return err\"\n}\n```\n\n**Bug #2 — line 800:**\n```go\nerr := caPool.Provision(ctx)\nif err != nil {\n return nil // BUG: should be \"return err\"\n}\n```\n\nCompare with line 811 which correctly returns the error:\n```go\ncaRaw, err := ctx.LoadModule(clientauth, \"CARaw\")\nif err != nil {\n return err // CORRECT\n}\n```\n\nWhen the error is swallowed on line 787, the chain is:\n\n1. `TrustedCACerts` remains empty (no DER data appended from the file)\n2. The `len(clientauth.TrustedCACerts) > 0` guard on line 794 is false — skipped\n3. `clientauth.CARaw` is nil — line 806 returns nil\n4. `clientauth.ca` remains nil — no CA pool was created\n5. `provision()` returns nil — caller thinks provisioning succeeded\n\nThen in `ConfigureTLSConfig()`:\n\n6. `Active()` returns true because `TrustedCACertPEMFiles` is non-empty\n7. Default mode is set to `RequireAndVerifyClientCert` (line 860)\n8. But `clientauth.ca` is nil, so `cfg.ClientCAs` is never set (line 867 skipped)\n9. Go's `crypto/tls` with `RequireAndVerifyClientCert` + nil `ClientCAs` verifies client certs against the **system root pool** instead of the intended CA\n\nThe fix is changing `return nil` to `return err` on lines 787 and 800.\n\n### PoC\n\n1. Configure Caddy with mTLS pointing to a nonexistent CA file:\n\n```\n{\n \"apps\": {\n \"http\": {\n \"servers\": {\n \"srv0\": {\n \"listen\": [\":443\"],\n \"tls_connection_policies\": [{\n \"client_authentication\": {\n \"trusted_ca_certs_pem_files\": [\"/nonexistent/ca.pem\"]\n }\n }]\n }\n }\n }\n }\n}\n```\n\n2. Start Caddy — it starts without any error or warning.\n\n3. Connect with any client certificate (even self-signed):\n```bash\nopenssl s_client -connect localhost:443 -cert client.pem -key client-key.pem\n```\n\n4. The TLS handshake succeeds despite the certificate not being signed by the intended CA.\n\nA full Go test that proves the bug end-to-end (including a successful TLS handshake with a random self-signed client cert) is here: https://gist.github.com/moscowchill/9566c79c76c0b64c57f8bd0716f97c48\n\nTest output:\n```\n=== RUN TestSwallowedErrorMTLSFailOpen\n BUG CONFIRMED: provision() swallowed the error from a nonexistent CA file.\n tls.Config has RequireAndVerifyClientCert but ClientCAs is nil.\n CRITICAL: TLS handshake succeeded with a self-signed client cert!\n The server accepted a client certificate NOT signed by the intended CA.\n--- PASS: TestSwallowedErrorMTLSFailOpen (0.03s)\n```\n\n### Impact\n\nAny deployment using `trusted_ca_cert_file` or `trusted_ca_certs_pem_files` for mTLS will silently degrade to accepting any system-trusted client certificate if the CA file becomes unavailable. This can happen due to a typo in the path, file rotation, corruption, or permission changes. The server gives no indication that mTLS is misconfigured.",
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