Refactor some utils.go; add another tool 'tiledump'

.gitignore

@@ -1 +1,2 @@
 /ctfetch
+/tiledump

README.md

@@ -1,20 +1,25 @@
 # ctfetch
 
-Fetch and dump leaf entries from Certificate Transparency logs.
+Tools for working with Certificate Transparency log tiles.
 
 ## Install
 
 ```bash
 go install ./cmd/ctfetch
+go install ./cmd/tiledump
 ```
 
-## Usage
+## Commands
+
+### ctfetch
+
+Fetch and dump leaf entries from CT logs.
 
 ```bash
 ctfetch [--dumpall] <log-url> <leaf-index>
 ```
 
-### Examples
+**Examples:**
 
 Dump a specific entry:
 ```bash
@@ -26,6 +31,25 @@ Dump all entries in the tile:
 ctfetch --dumpall https://halloumi2026h1.mon.ct.ipng.ch 629794635
 ```
 
-## Options
+**Options:**
-
 - `--dumpall`: Dump all entries in the tile instead of just the specified leaf
+
+### tiledump
+
+Read a CT log tile file or URL and dump all entries.
+
+```bash
+tiledump <tile-file-or-url>
+```
+
+**Examples:**
+
+From a file:
+```bash
+tiledump tile.data
+```
+
+From a URL:
+```bash
+tiledump https://halloumi2026h1.mon.ct.ipng.ch/tile/data/x002/x460/135
+```

cmd/ctfetch/main.go

@@ -4,17 +4,14 @@
 package main
 
 import (
-	"bytes"
-	"compress/gzip"
-	"encoding/json"
 	"flag"
 	"fmt"
-	"io"
-	"net/http"
 	"os"
 	"strconv"
 	"strings"
 
+	"ctfetch/internal/utils"
+
 	"filippo.io/sunlight"
 	"golang.org/x/mod/sumdb/tlog"
 )
@@ -66,7 +63,7 @@ func main() {
 	// Try partial tile first
 	partialURL := logURL + "/" + partialPath
 	fmt.Fprintf(os.Stderr, "Trying: %s\n", partialURL)
-	tileData, err = fetchURL(partialURL)
+	tileData, err = utils.FetchURL(partialURL)
 	if err == nil {
 		fetchedPath = partialPath
 		fmt.Fprintf(os.Stderr, "Successfully fetched partial tile\n")
@@ -74,7 +71,7 @@ func main() {
 		// Fall back to full tile
 		fullURL := logURL + "/" + fullPath
 		fmt.Fprintf(os.Stderr, "Partial tile failed, trying: %s\n", fullURL)
-		tileData, err = fetchURL(fullURL)
+		tileData, err = utils.FetchURL(fullURL)
 		if err != nil {
 			fatal("failed to fetch tile: %v", err)
 		}
@@ -83,7 +80,7 @@ func main() {
 	}
 
 	// Decompress if needed
-	tileData, err = decompress(tileData)
+	tileData, err = utils.Decompress(tileData)
 	if err != nil {
 		fatal("failed to decompress tile: %v", err)
 	}
@@ -93,105 +90,15 @@ func main() {
 
 	if *dumpAll {
 		// Dump all entries in the tile
-		dumpAllEntries(tileData)
+		if err := utils.DumpAllEntries(tileData); err != nil {
+			fatal("%v", err)
+		}
 	} else {
 		// Dump only the specific entry at the position
-		dumpEntryAtPosition(tileData, int(positionInTile), leafIndex)
+		if err := utils.DumpEntryAtPosition(tileData, int(positionInTile), leafIndex); err != nil {
+			fatal("%v", err)
 		}
 	}
-
-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) {

cmd/tiledump/main.go

@@ -0,0 +1,62 @@
+// Command tiledump reads a CT log tile file and dumps all entries.
+// (C) Copyright 2026 Pim van Pelt <pim@ipng.ch>
+package main
+
+import (
+	"fmt"
+	"os"
+	"strings"
+
+	"ctfetch/internal/utils"
+)
+
+func main() {
+	if len(os.Args) != 2 {
+		fmt.Fprintf(os.Stderr, "Usage: %s <tile-file-or-url>\n", os.Args[0])
+		fmt.Fprintf(os.Stderr, "Examples:\n")
+		fmt.Fprintf(os.Stderr, "  %s tile.data\n", os.Args[0])
+		fmt.Fprintf(os.Stderr, "  %s https://halloumi2026h1.mon.ct.ipng.ch/tile/data/x002/x460/135\n", os.Args[0])
+		os.Exit(1)
+	}
+
+	arg := os.Args[1]
+
+	var tileData []byte
+	var err error
+
+	// Check if argument is a URL
+	if strings.HasPrefix(arg, "http://") || strings.HasPrefix(arg, "https://") {
+		// Fetch from URL
+		fmt.Fprintf(os.Stderr, "Fetching: %s\n", arg)
+		tileData, err = utils.FetchURL(arg)
+		if err != nil {
+			fatal("failed to fetch URL: %v", err)
+		}
+		fmt.Fprintf(os.Stderr, "Fetched %d bytes\n", len(tileData))
+	} else {
+		// Read from file
+		tileData, err = os.ReadFile(arg)
+		if err != nil {
+			fatal("failed to read file: %v", err)
+		}
+		fmt.Fprintf(os.Stderr, "Read %d bytes from %s\n", len(tileData), arg)
+	}
+
+	// Decompress if needed
+	tileData, err = utils.Decompress(tileData)
+	if err != nil {
+		fatal("failed to decompress tile: %v", err)
+	}
+
+	fmt.Fprintf(os.Stderr, "Tile size: %d bytes\n\n", len(tileData))
+
+	// Dump all entries
+	if err := utils.DumpAllEntries(tileData); err != nil {
+		fatal("%v", err)
+	}
+}
+
+func fatal(format string, args ...any) {
+	fmt.Fprintf(os.Stderr, "Error: "+format+"\n", args...)
+	os.Exit(1)
+}

internal/utils/utils.go

@@ -0,0 +1,114 @@
+// Package utils provides shared functionality for dumping CT log tile entries.
+// (C) Copyright 2026 Pim van Pelt <pim@ipng.ch>
+package utils
+
+import (
+	"bytes"
+	"compress/gzip"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+
+	"filippo.io/sunlight"
+)
+
+const maxCompressRatio = 100
+
+// FetchURL fetches data from a URL.
+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)
+}
+
+// Decompress decompresses gzip-compressed data, or returns the data as-is if not compressed.
+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))
+}
+
+// DumpAllEntries reads and dumps all entries from tile data.
+func DumpAllEntries(tileData []byte) error {
+	entryNum := 0
+	for len(tileData) > 0 {
+		e, remaining, err := sunlight.ReadTileLeaf(tileData)
+		if err != nil {
+			return fmt.Errorf("failed to read entry %d: %w", entryNum, err)
+		}
+		tileData = remaining
+
+		dumpEntry(e, entryNum)
+		fmt.Println()
+		entryNum++
+	}
+
+	fmt.Printf("Total entries: %d\n", entryNum)
+	return nil
+}
+
+// DumpEntryAtPosition reads and dumps a specific entry at the given position.
+func DumpEntryAtPosition(tileData []byte, position int, expectedIndex int64) error {
+	entryNum := 0
+	for len(tileData) > 0 {
+		e, remaining, err := sunlight.ReadTileLeaf(tileData)
+		if err != nil {
+			return fmt.Errorf("failed to read entry %d: %w", 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 nil
+		}
+		entryNum++
+	}
+
+	return fmt.Errorf("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)
+		}
+	}
+}