ctool/docs/ctfetch.md

ctfetch

Fetch and decode entries from a Static CT log, outputting structured JSON.

Install

GOPRIVATE=git.ipng.ch go install git.ipng.ch/certificate-transparency/ctfetch/cmd/ctool@latest

Modes

ctool fetch operates in two modes depending on the arguments given.

Leaf-index mode

Fetch the entry at a specific leaf index:

ctool fetch [flags] <log-url> <leaf-index> [+sct] [+issuer] [+ctlog] [+all]

Examples:

ctool fetch https://halloumi2026h1.mon.ct.ipng.ch 629794635
ctool fetch https://halloumi2026h1.mon.ct.ipng.ch 629794635 +all

Tile-dump mode

Fetch all entries from a tile URL or local file. Automatically detects data tiles (log entries) and hash tiles (Merkle tree hashes).

ctool fetch [flags] <tile-url-or-file> [+sct] [+issuer] [+ctlog] [+all]

Examples:

ctool fetch https://halloumi2026h1.mon.ct.ipng.ch/tile/data/x002/x460/135
ctool fetch https://halloumi2026h1.mon.ct.ipng.ch/tile/data/x002/x460/135 +sct +ctlog
ctool fetch https://halloumi2026h1.mon.ct.ipng.ch/tile/0/x100/999
ctool fetch --monitoring-url https://halloumi2026h1.mon.ct.ipng.ch tile.bin +issuer

Output modifiers

Modifier	Description
+sct	Parse embedded Signed Certificate Timestamps from final (non-precert) certificates
+issuer	Fetch issuer certificate details from the log's /issuer/<fp> endpoint
+ctlog	Look up each SCT's log ID in the CT log list and include operator/state details
+all	Enable all of +sct, +issuer, and +ctlog

Flags

Flag	Default	Description
--logs-list-url	https://www.gstatic.com/ct/log_list/v3/all_logs_list.json	CT log list URL for +ctlog lookups
--monitoring-url	(none)	Log root URL for issuer lookups when input is a local file

Hash tiles vs data tiles

Data tiles (/tile/data/...) contain DER-encoded certificates and precertificates with metadata (leaf index, timestamp, chain fingerprints). Output modifiers +sct, +issuer, +ctlog, and +all only apply here.

Hash tiles (/tile/N/..., N ≥ 0) contain raw 32-byte SHA-256 hashes — the internal nodes of the Merkle tree used for inclusion and consistency proofs. ctfetch outputs only the list of hashes; using output modifiers with a hash tile is an error.

Notes

• With a tile URL, +issuer derives the log root by stripping the /tile/... path. With a local file, --monitoring-url must be provided.
• Partial tiles (.p/N suffix) are tried first; on 404 the full tile is fetched automatically.
• The CT log list and issuer certificates are cached in memory per invocation.