Add rhash for hashing remote files.

This was originally rsha256, but it's been updated to support multiple
algorithms.

README.md

@@ -6,6 +6,7 @@ of these in superfluous repositories of their own, I'm putting them here.
 
 Contents:
 
+    ahash/          Provides hashes from string algorithm specifiers.
     assert/         Error handling, assertion-style.
     cmd/
         atping/     Automated TCP ping, meant for putting in cronjobs.
@@ -32,6 +33,7 @@ Contents:
         readchain/  Print the common name for the certificates
                     in a bundle.
         renfnv/     Rename a file to base32-encoded 64-bit FNV-1a hash.
+        rhash/      Compute the digest of remote files.
         showimp     Display the external imports in a package.
         ski         Display the SKI for PEM-encoded TLS material.
         stealchain/ Dump the verified chain from a TLS

cmd/rhash/README

@@ -0,0 +1,22 @@
+rhash: remote hashing tool
+
+Usage: rhash [-a algo] [-h] [-l set] urls...
+Compute the hash over each URL.
+
+Flags:
+	-a algo		Specify the hash algorithm to use; the default is sha256.
+	-h		Print this help message.
+	-l set		List the hash functions under set. Set can be one of all,
+			secure to list only cryptographic hash functions, or
+			insecure to list only non-cryptographic hash functions.
+	
+Examples:
+	Compute the SHA256 digest of the LICENSE in this repository:
+
+	$ rhash https://raw.githubusercontent.com/kisom/goutils/7391da8567952f69990194ead2842d21df217c89/LICENSE
+	LICENSE: sha256=620bfadeb698df6c6db73908689a29371a9d4cff32b08c48a5c4307946093980
+
+	Compute the SHA-1 digest of the LICENSE in this repository:
+
+	$ rhash -a sha1 https://raw.githubusercontent.com/kisom/goutils/7391da8567952f69990194ead2842d21df217c89/LICENSE
+	LICENSE: sha1=83c6e2e410715058ed6e7c1572176122c024e367

cmd/rhash/main.go

@@ -0,0 +1,106 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+	"os"
+	"path/filepath"
+
+	"github.com/kisom/goutils/ahash"
+	"github.com/kisom/goutils/die"
+	"github.com/kisom/goutils/lib"
+)
+
+func fetch(remote string) ([]byte, error) {
+	resp, err := http.Get(remote)
+	if err != nil {
+		return nil, err
+	}
+
+	defer resp.Body.Close()
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+	return body, nil
+}
+
+func usage(w io.Writer) {
+	fmt.Fprintf(w, `Usage: %s [-a algo] [-h] [-l set] urls...
+Compute the hash over each URL.
+
+Flags:
+	-a algo		Specify the hash algorithm to use; the default is sha256.
+	-h		Print this help message.
+	-l set		List the hash functions under set. Set can be one of all,
+			secure to list only cryptographic hash functions, or
+			insecure to list only non-cryptographic hash functions.
+	
+`, lib.ProgName())
+}
+
+func init() {
+	flag.Usage = func() { usage(os.Stderr) }
+}
+
+func main() {
+	var algo, list string
+	var help bool
+	flag.StringVar(&algo, "a", "sha256", "hash algorithm to use")
+	flag.BoolVar(&help, "h", false, "print a help message")
+	flag.StringVar(&list, "l", "", "list known hash algorithms (one of all, secure, insecure)")
+	flag.Parse()
+	
+	if help {
+		usage(os.Stdout)
+	}
+
+	if list != "" {
+		var hashes []string
+		switch list {
+		case "all":
+			hashes = ahash.HashList()
+		case "secure":
+			hashes = ahash.SecureHashList()
+		case "insecure":
+			hashes = ahash.InsecureHashList()
+		default:
+			die.With("list option must be one of all, secure, or insecure.")
+		}
+
+		for _, algo := range hashes {
+			fmt.Printf("- %s\n", algo)
+		}
+		os.Exit(1)
+	}
+
+	for _, remote := range flag.Args() {
+		u, err := url.Parse(remote)
+		if err != nil {
+			lib.Warn(err, "parsing %s", remote)
+			continue
+		}
+
+		name := filepath.Base(u.Path)
+		if name == "" {
+			lib.Warnx("source URL doesn't appear to name a file")
+			continue
+		}
+
+		body, err := fetch(remote)
+		if err != nil {
+			lib.Warn(err, "fetching %s", remote)
+			continue
+		}
+
+		sum, err := ahash.Sum(algo, body)
+		if err != nil {
+			lib.Err(lib.ExitFailure, err, "while hashing data")
+		}
+		fmt.Printf("%s: %s=%x\n", name, algo, sum)
+	}
+}

cmd/rsha256/main.go

@@ -1,54 +0,0 @@
-package main
-
-import (
-	"crypto/sha256"
-	"flag"
-	"fmt"
-	"io/ioutil"
-	"net/http"
-	"net/url"
-	"path/filepath"
-
-	"github.com/kisom/goutils/lib"
-)
-
-func fetch(remote string) ([]byte, error) {
-	resp, err := http.Get(remote)
-	if err != nil {
-		return nil, err
-	}
-
-	defer resp.Body.Close()
-	body, err := ioutil.ReadAll(resp.Body)
-	if err != nil {
-		return nil, err
-	}
-	return body, nil
-}
-
-func main() {
-	flag.Parse()
-
-	for _, remote := range flag.Args() {
-		u, err := url.Parse(remote)
-		if err != nil {
-			lib.Warn(err, "parsing %s", remote)
-			continue
-		}
-
-		name := filepath.Base(u.Path)
-		if name == "" {
-			lib.Warnx("source URL doesn't appear to name a file")
-			continue
-		}
-
-		body, err := fetch(remote)
-		if err != nil {
-			lib.Warn(err, "fetching %s", remote)
-			continue
-		}
-
-		h := sha256.Sum256(body)
-		fmt.Printf("%s: sha256=%x\n", name, h)
-	}
-}