From fc20a808ece9a082e043e13e3cfa69c571721d76 Mon Sep 17 00:00:00 2001
From: Paolo Calao <paolo.calao@gmail.com>
Date: Thu, 2 Dec 2021 11:00:45 +0100
Subject: [PATCH] Add generic function to verify checksum

---
 indexes/download/download.go | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/indexes/download/download.go b/indexes/download/download.go
index 3811911a..707b6889 100644
--- a/indexes/download/download.go
+++ b/indexes/download/download.go
@@ -22,6 +22,7 @@ import (
 	"bytes"
 	"crypto"
 	"encoding/hex"
+	"errors"
 	"fmt"
 	"hash"
 	"io"
@@ -153,10 +154,10 @@ func Download(d *downloader.Downloader) error {
 	return nil
 }
 
-// VerifyFileChecksum is taken and adapted from https://github.com/arduino/arduino-cli/blob/59b6277a4d6731a1c1579d43aef6df2a46a771d5/arduino/resources/checksums.go
-func VerifyFileChecksum(checksum string, filePath *paths.Path) error {
+// VerifyChecksum is taken and adapted from https://github.com/arduino/arduino-cli/blob/59b6277a4d6731a1c1579d43aef6df2a46a771d5/arduino/resources/checksums.go
+func VerifyChecksum(checksum string, file io.Reader) error {
 	if checksum == "" {
-		return fmt.Errorf("missing checksum for: %s", filePath)
+		return errors.New("missing checksum")
 	}
 	split := strings.SplitN(checksum, ":", 2)
 	if len(split) != 2 {
@@ -180,21 +181,29 @@ func VerifyFileChecksum(checksum string, filePath *paths.Path) error {
 		return fmt.Errorf("unsupported hash algorithm: %s", split[0])
 	}
 
-	file, err := filePath.Open()
-	if err != nil {
-		return fmt.Errorf("opening file: %s", err)
-	}
-	defer file.Close()
 	if _, err := io.Copy(algo, file); err != nil {
 		return fmt.Errorf("computing hash: %s", err)
 	}
-	if bytes.Compare(algo.Sum(nil), digest) != 0 {
+	if !bytes.Equal(algo.Sum(nil), digest) {
 		return fmt.Errorf("archive hash differs from hash in index")
 	}
 
 	return nil
 }
 
+// VerifyFileChecksum checks if the passed checksum matches the passed file checksum
+func VerifyFileChecksum(checksum string, filePath *paths.Path) error {
+	file, err := filePath.Open()
+	if err != nil {
+		return fmt.Errorf("opening file: %s", err)
+	}
+	defer file.Close()
+	if err = VerifyChecksum(checksum, file); err != nil {
+		return fmt.Errorf("verifying checksum of file %s: %w", filePath, err)
+	}
+	return nil
+}
+
 // VerifyFileSize is taken and adapted from https://github.com/arduino/arduino-cli/blob/59b6277a4d6731a1c1579d43aef6df2a46a771d5/arduino/resources/checksums.go
 func VerifyFileSize(size int64, filePath *paths.Path) error {
 	info, err := filePath.Stat()