Initial checkin

.gitignore

@@ -0,0 +1 @@
+ctfetch

LICENSE

@@ -0,0 +1,202 @@
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+   Copyright 2026, IPng Networks GmbH, Pim van Pelt <pim@ipng.ch>
+
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+   limitations under the License.

README.md

@@ -0,0 +1,31 @@
+# ctfetch
+
+Fetch and dump leaf entries from Certificate Transparency logs.
+
+## Install
+
+```bash
+go install
+```
+
+## Usage
+
+```bash
+ctfetch [--dumpall] <log-url> <leaf-index>
+```
+
+### Examples
+
+Dump a specific entry:
+```bash
+ctfetch https://halloumi2026h1.mon.ct.ipng.ch 629794635
+```
+
+Dump all entries in the tile:
+```bash
+ctfetch --dumpall https://halloumi2026h1.mon.ct.ipng.ch 629794635
+```
+
+## Options
+
+- `--dumpall`: Dump all entries in the tile instead of just the specified leaf

go.mod

@@ -0,0 +1,15 @@
+module ctfetch
+
+go 1.24.6
+
+require (
+	filippo.io/sunlight v0.6.3
+	golang.org/x/mod v0.32.0
+)
+
+require (
+	filippo.io/torchwood v0.5.1-0.20250713221105-b067ac9d4cf6 // indirect
+	github.com/google/certificate-transparency-go v1.3.2 // indirect
+	golang.org/x/crypto v0.39.0 // indirect
+	golang.org/x/sync v0.15.0 // indirect
+)

go.sum

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+filippo.io/sunlight v0.6.3 h1:bxN0JLUoW2rV8jNluRWKpj+9ZpWutBfoiWgM6FGlTMw=
+filippo.io/sunlight v0.6.3/go.mod h1:1wUWZmC0tYtzP0PC2rsegshLsLYZ6sgFSe4Utj33Tyg=
+filippo.io/torchwood v0.5.1-0.20250713221105-b067ac9d4cf6 h1:feb1i6byodl8n5WEJJ1fafcP3eVBiiVloh3mYvnRmJY=
+filippo.io/torchwood v0.5.1-0.20250713221105-b067ac9d4cf6/go.mod h1:Z+iz3Syg0RCaVkL9nBjG2STp/9HpuFl1+SbaNSZ/Ez8=
+github.com/google/certificate-transparency-go v1.3.2 h1:9ahSNZF2o7SYMaKaXhAumVEzXB2QaayzII9C8rv7v+A=
+github.com/google/certificate-transparency-go v1.3.2/go.mod h1:H5FpMUaGa5Ab2+KCYsxg6sELw3Flkl7pGZzWdBoYLXs=
+golang.org/x/crypto v0.39.0 h1:SHs+kF4LP+f+p14esP5jAoDpHU8Gu/v9lFRK6IT5imM=
+golang.org/x/crypto v0.39.0/go.mod h1:L+Xg3Wf6HoL4Bn4238Z6ft6KfEpN0tJGo53AAPC632U=
+golang.org/x/mod v0.32.0 h1:9F4d3PHLljb6x//jOyokMv3eX+YDeepZSEo3mFJy93c=
+golang.org/x/mod v0.32.0/go.mod h1:SgipZ/3h2Ci89DlEtEXWUk/HteuRin+HHhN+WbNhguU=
+golang.org/x/sync v0.15.0 h1:KWH3jNZsfyT6xfAfKiz6MRNmd46ByHDYaZ7KSkCtdW8=
+golang.org/x/sync v0.15.0/go.mod h1:1dzgHSNfp02xaA81J2MS99Qcpr2w7fw1gpm99rleRqA=

main.go

@@ -0,0 +1,200 @@
+// Command ctfetch fetches and dumps a specific leaf entry from a given Static CT log.
+// It can also dump the whole contents of the tile, if the -dumpall flag is specified.
+// (C) Copyright 2026 Pim van Pelt <pim@ipng.ch>
+package main
+
+import (
+	"bytes"
+	"compress/gzip"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"strconv"
+	"strings"
+
+	"filippo.io/sunlight"
+	"golang.org/x/mod/sumdb/tlog"
+)
+
+func main() {
+	dumpAll := flag.Bool("dumpall", false, "dump all entries in the tile")
+	flag.Usage = func() {
+		fmt.Fprintf(os.Stderr, "Usage: %s [--dumpall] <log-url> <leaf-index>\n", os.Args[0])
+		fmt.Fprintf(os.Stderr, "Example: %s https://halloumi2026h1.mon.ct.ipng.ch 457683896\n", os.Args[0])
+		fmt.Fprintf(os.Stderr, "\nFlags:\n")
+		flag.PrintDefaults()
+	}
+	flag.Parse()
+
+	if flag.NArg() != 2 {
+		flag.Usage()
+		os.Exit(1)
+	}
+
+	logURL := strings.TrimSuffix(flag.Arg(0), "/")
+	leafIndex, err := strconv.ParseInt(flag.Arg(1), 10, 64)
+	if err != nil {
+		fatal("invalid leaf index: %v", err)
+	}
+
+	// Convert leaf index to tile coordinates
+	tile := tlog.TileForIndex(sunlight.TileHeight, tlog.StoredHashIndex(0, leafIndex))
+	tile.L = -1 // Data tiles are at level -1
+
+	// Get the tile path (both partial and full versions)
+	partialPath := sunlight.TilePath(tile)
+
+	// For full tile path, we need to remove the .p/W suffix if present
+	fullTile := tile
+	fullTile.W = sunlight.TileWidth
+	fullPath := sunlight.TilePath(fullTile)
+
+	positionInTile := leafIndex % sunlight.TileWidth
+
+	fmt.Fprintf(os.Stderr, "Leaf Index: %d\n", leafIndex)
+	fmt.Fprintf(os.Stderr, "Position in tile: %d\n", positionInTile)
+	fmt.Fprintf(os.Stderr, "Partial tile path: %s\n", partialPath)
+	fmt.Fprintf(os.Stderr, "Full tile path: %s\n", fullPath)
+
+	// Try to fetch the tile (partial first, then full)
+	var tileData []byte
+	var fetchedPath string
+
+	// Try partial tile first
+	partialURL := logURL + "/" + partialPath
+	fmt.Fprintf(os.Stderr, "Trying: %s\n", partialURL)
+	tileData, err = fetchURL(partialURL)
+	if err == nil {
+		fetchedPath = partialPath
+		fmt.Fprintf(os.Stderr, "Successfully fetched partial tile\n")
+	} else {
+		// Fall back to full tile
+		fullURL := logURL + "/" + fullPath
+		fmt.Fprintf(os.Stderr, "Partial tile failed, trying: %s\n", fullURL)
+		tileData, err = fetchURL(fullURL)
+		if err != nil {
+			fatal("failed to fetch tile: %v", err)
+		}
+		fetchedPath = fullPath
+		fmt.Fprintf(os.Stderr, "Successfully fetched full tile\n")
+	}
+
+	// Decompress if needed
+	tileData, err = decompress(tileData)
+	if err != nil {
+		fatal("failed to decompress tile: %v", err)
+	}
+
+	fmt.Fprintf(os.Stderr, "Tile size: %d bytes\n", len(tileData))
+	fmt.Fprintf(os.Stderr, "Fetched path: %s\n\n", fetchedPath)
+
+	if *dumpAll {
+		// Dump all entries in the tile
+		dumpAllEntries(tileData)
+	} else {
+		// Dump only the specific entry at the position
+		dumpEntryAtPosition(tileData, int(positionInTile), leafIndex)
+	}
+}
+
+func fetchURL(url string) ([]byte, error) {
+	resp, err := http.Get(url)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("HTTP %d", resp.StatusCode)
+	}
+
+	return io.ReadAll(resp.Body)
+}
+
+func dumpAllEntries(tileData []byte) {
+	entryNum := 0
+	for len(tileData) > 0 {
+		e, remaining, err := sunlight.ReadTileLeaf(tileData)
+		if err != nil {
+			fatal("failed to read entry %d: %v", entryNum, err)
+		}
+		tileData = remaining
+
+		dumpEntry(e, entryNum)
+		fmt.Println()
+		entryNum++
+	}
+
+	fmt.Printf("Total entries: %d\n", entryNum)
+}
+
+func dumpEntryAtPosition(tileData []byte, position int, expectedIndex int64) {
+	entryNum := 0
+	for len(tileData) > 0 {
+		e, remaining, err := sunlight.ReadTileLeaf(tileData)
+		if err != nil {
+			fatal("failed to read entry %d: %v", entryNum, err)
+		}
+		tileData = remaining
+
+		if entryNum == position {
+			if e.LeafIndex != expectedIndex {
+				fmt.Fprintf(os.Stderr, "WARNING: Expected leaf index %d but found %d at position %d\n",
+					expectedIndex, e.LeafIndex, position)
+			}
+			dumpEntry(e, entryNum)
+			return
+		}
+		entryNum++
+	}
+
+	fatal("position %d not found in tile (only %d entries)", position, entryNum)
+}
+
+func dumpEntry(e *sunlight.LogEntry, entryNum int) {
+	fmt.Printf("=== Entry %d ===\n", entryNum)
+	fmt.Printf("Leaf Index: %d\n", e.LeafIndex)
+	fmt.Printf("Timestamp: %d\n", e.Timestamp)
+	fmt.Printf("Is Precert: %v\n", e.IsPrecert)
+
+	if e.IsPrecert {
+		fmt.Printf("Issuer Key Hash: %x\n", e.IssuerKeyHash)
+	}
+
+	fmt.Printf("Certificate: %d bytes\n", len(e.Certificate))
+	if e.PreCertificate != nil {
+		fmt.Printf("PreCertificate: %d bytes\n", len(e.PreCertificate))
+	}
+
+	fmt.Printf("Chain Fingerprints: %d entries\n", len(e.ChainFingerprints))
+	for i, fp := range e.ChainFingerprints {
+		fmt.Printf("  [%d]: %x\n", i, fp)
+	}
+
+	// Try to extract parsed certificate info
+	if trimmed, err := e.TrimmedEntry(); err == nil {
+		if data, err := json.MarshalIndent(trimmed, "  ", "  "); err == nil {
+			fmt.Printf("Parsed Certificate Info:\n  %s\n", data)
+		}
+	}
+}
+
+const maxCompressRatio = 100
+
+func decompress(data []byte) ([]byte, error) {
+	r, err := gzip.NewReader(bytes.NewReader(data))
+	if err != nil {
+		// Not gzipped, return as-is
+		return data, nil
+	}
+	maxSize := int64(len(data)) * maxCompressRatio
+	return io.ReadAll(io.LimitReader(r, maxSize))
+}
+
+func fatal(format string, args ...any) {
+	fmt.Fprintf(os.Stderr, "Error: "+format+"\n", args...)
+	os.Exit(1)
+}