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…ocol#845) Add a Troubleshooting section to the publishing authentication guide covering the most common failure modes integrators hit during DNS- and HTTP-based publisher login. Patterned after modelcontextprotocol#1253: docs-only, no code changes, focused on the gaps that produce a generic "signature verification failed" error. Covers: - Comparing the CLI's "Expected proof record" output against what is actually published (the most frequent cause of false-fail loops). - DNS: verifying TXT propagation with dig, distinguishing missing / stale / misplaced records, and noting the registry's misplaced- selector probe (modelcontextprotocol#1126). - HTTP: verifying /.well-known/mcp-registry-auth with curl, plus the HTTPS-only / no-redirects / 4096-byte-cap / public-IP-only constraints that are enforced by the server fetcher. - Algorithm/key mismatch when --algorithm differs from the published k= field. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Reviewed against the current DNS/HTTP verifier and reconciled this with #1640 during rebase. The revised text links to the existing HTTP fetch requirements, corrects the claim that surrounding whitespace necessarily breaks HTTP verification, and explains that the verifier tries valid published keys rather than letting an old TXT key take precedence. It also explains the current key-fingerprint diagnostics and avoids advising removal of unrelated TXT records or keys still in use.
Auth tests, make validate, diff checks, and section/anchor checks passed. Documentation-only; no runtime behavior changes. #845 remains open because the requested interactive CLI/TUI work is not implemented here. Merge conditional on required CI passing on this head.
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Summary
Adds a Troubleshooting DNS and HTTP authentication section to the publishing authentication guide. Patterned after #1253 (my prior docs fix in the same file): docs-only, focused on the recurring failure modes that bottom out as a generic
signature verification failedorno MCP public key founderror.Motivated by #845 (improve CLI/TUI experience for DNS/HTTP auth) and the recurring confusion around DNS apex/selector placement called out in #1126. The full TUI work in #845 is a larger lift; this is the docs slice that lets people self-diagnose today using the tools they already have (
dig,curl).The new section covers, in order:
digbefore logging in — distinguishes missing / stale / misplaced records, and notes the existing misplaced-selector probe added for DNS authentication always fails: Ed25519 signature verification failed #1126 (so users know what error shape to expect)./.well-known/mcp-registry-authwithcurl -i— plus the four constraints baked into the server-side fetcher ininternal/api/handlers/v0/auth/http.go: HTTPS only, no redirects (the fetcher returnshttp.ErrUseLastResponsefromCheckRedirect),MaxKeyResponseSize = 4096byte cap, and thesafeDialContextblocklist of loopback / RFC1918 / link-local / CGNAT IPs.--algorithmmust match the publishedk=field.Nothing new in code; the existing apex/selector
<Warning>(already in the file) and the OpenSSL 3.x<Note>from #1253 are untouched.Test plan
git diff --statconfirms a single-file docs change (docs/modelcontextprotocol-io/authentication.mdx, +48/-0).internal/api/handlers/v0/auth/http.go:MaxKeyResponseSize = 4096,CheckRedirectreturningErrUseLastResponse,safeDialContextIP blocklist,https://URL construction,strings.TrimSpaceof the body.internal/api/handlers/v0/auth/dns.go(commonWrongSelectors = ["_mcp-auth", "_mcp-registry"],findMisplacedSelectorprobe).cmd/publisher/auth/common.goactually prints (PrintEd25519KeyInfo/printEcdsaKeyInfo).<CodeGroup>/ fenced blocks — relying on the existing patterns in this file for syntax validity, no new MDX components introduced.Continuing the publisher-devex thread from #1253. Happy to split or trim if maintainers prefer a smaller surface area.