tests: Add new source for testing checksum

Created a new test program which will damage an ISO image
file to ensure that checksum validation is working properly.

Signed-off-by: Mark D Horn <[email protected]>

Makefile

@@ -414,6 +414,11 @@ PHONY += dev-check-all
 dev-check-all: check-for-root-user build lint functional-check check
 	@echo "Running dev tests have passed"
 
+PHONY += damage
+damage:
+	@echo "Building damage_file"
+	go build tests/damage_file.go
+
 all: build
 
 PHONY += all

tests/damage_file.go

@@ -0,0 +1,99 @@
+// Copyright © 2020 Intel Corporation
+//
+// SPDX-License-Identifier: GPL-3.0-only
+
+// Test program to inject random bytes into image files
+// to help validate ISO checksums are working.
+
+// Build: go build damage_file.go
+// Usage: damage_file my.iso
+
+package main
+
+import (
+	"crypto/rand"
+	"flag"
+	"fmt"
+	"os"
+	"path"
+)
+
+func main() {
+	prog := path.Base(os.Args[0])
+
+	var damageFile string
+	var offset, count int64
+
+	fs := flag.NewFlagSet(prog, flag.ExitOnError)
+
+	fs.StringVar(&damageFile, "file", "", "File to be damaged")
+	fs.Int64Var(&offset, "offset", -4194304, "Byte offset where to start damage")
+	fs.Int64Var(&count, "count", 1024, "Number of bytes to damage")
+
+	var Usage = func() {
+		fmt.Fprintf(fs.Output(), "Usage of %s:\n", prog)
+		fs.PrintDefaults()
+	}
+
+	if err := fs.Parse(os.Args[1:]); err != nil {
+		fmt.Printf("Error: Failed to parse: %+v\n", os.Args[1:])
+		os.Exit(1)
+	}
+
+	if len(damageFile) < 1 {
+		Usage()
+		os.Exit(1)
+	}
+
+	srcFile, err := os.OpenFile(damageFile, os.O_RDWR, 0)
+	if err != nil {
+		if os.IsNotExist(err) {
+			fmt.Printf("No such file: %s\n", damageFile)
+		}
+		fmt.Printf("Failed to open '%s': %s\n", damageFile, err)
+		os.Exit(1)
+	}
+	defer srcFile.Close()
+
+	// 0 means relative to the origin of the file,
+	// 1 means relative to the current offset, and
+	// 2 means relative to the end.
+	whence := 0
+	if offset < 0 {
+		whence = 2
+	}
+
+	// Save the EOF
+	saveEOF, err := srcFile.Seek(0, 2)
+	if err != nil {
+		fmt.Printf("Failed to seek '%s': %s\n", damageFile, err)
+		os.Exit(1)
+	}
+
+	newPosition, err := srcFile.Seek(offset, whence)
+	if err != nil {
+		fmt.Printf("Failed to seek '%s': %s\n", damageFile, err)
+		os.Exit(1)
+	}
+
+	fmt.Printf("Injecting %d zero bytes at position %d for %s\n", count, newPosition, damageFile)
+
+	damage := make([]byte, count)
+	if _, err := rand.Read(damage); err != nil {
+		fmt.Printf("Failed to generate random data: %s\n", err)
+		os.Exit(1)
+	}
+
+	if cnt, err := srcFile.Write(damage); err != nil {
+		fmt.Printf("Failed to write into '%s' (%d): %s\n", damageFile, cnt, err)
+		os.Exit(1)
+	} else {
+		fmt.Printf(" Injected %d zero bytes at position %d for %s\n", cnt, newPosition, damageFile)
+	}
+
+	// Seek to the end of the file
+	if _, err := srcFile.Seek(saveEOF, 2); err != nil {
+		fmt.Printf("Failed to seek to end-of-file '%s': %s\n", damageFile, err)
+		os.Exit(1)
+	}
+}