From 1ddaf9ef90c2287a9704efd7fd4f501828181acd Mon Sep 17 00:00:00 2001
From: Matthias Glastra <matglas.git@gmail.com>
Date: Tue, 24 Sep 2024 21:22:39 +0200
Subject: [PATCH] chore: Add additional git attestor output.

When the git binary is used to for status we also include
the path to the binary and the hash of the binary files.

Also by default the git tool used to generate the attestation
data is added as contextual information.

Signed-off-by: Matthias Glastra <matglas.git@gmail.com>
---
 attestation/git/git.go     | 17 +++++++++++++++++
 attestation/git/git_bin.go | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/attestation/git/git.go b/attestation/git/git.go
index 1e2b5b2a..4ded0b93 100644
--- a/attestation/git/git.go
+++ b/attestation/git/git.go
@@ -79,6 +79,9 @@ type Tag struct {
 }
 
 type Attestor struct {
+	GitTool        string               `json:"gittool"`
+	GitBinPath     string               `json:"gitbinpath,omitempty"`
+	GitBinHash     string               `json:"gitbinhash,omitempty"`
 	CommitHash     string               `json:"commithash"`
 	Author         string               `json:"author"`
 	AuthorEmail    string               `json:"authoremail"`
@@ -222,11 +225,25 @@ func (a *Attestor) Attest(ctx *attestation.AttestationContext) error {
 	a.TreeHash = commit.TreeHash.String()
 
 	if GitExists() {
+		a.GitTool = "go-git+git-bin"
+		
+		a.GitBinPath, err = GitGetBinPath()
+		if err != nil {
+			return err
+		}
+		
+		a.GitBinHash, err = GitGetBinHash(ctx)
+		if err != nil {
+			return err
+		}
+
 		a.Status, err = GitGetStatus(ctx.WorkingDir())
 		if err != nil {
 			return err
 		}
 	} else {
+		a.GitTool = "go-git"
+
 		a.Status, err = GoGitGetStatus(repo)
 		if err != nil {
 			return err
diff --git a/attestation/git/git_bin.go b/attestation/git/git_bin.go
index 21432ce7..22853a1a 100644
--- a/attestation/git/git_bin.go
+++ b/attestation/git/git_bin.go
@@ -15,10 +15,13 @@
 package git
 
 import (
+	"fmt"
 	"os/exec"
 	"strings"
 
 	"github.com/go-git/go-git/v5"
+	"github.com/in-toto/go-witness/attestation"
+	"github.com/in-toto/go-witness/cryptoutil"
 )
 
 // GitExists checks if the git binary is available.
@@ -33,6 +36,40 @@ func GitExists() bool {
 	}
 }
 
+// GitGetBinPath retrieves the path to the git binary that is used by the attestor.
+func GitGetBinPath() (string, error) {
+	path, err := exec.LookPath("git")
+	if err != nil {
+		return "", err
+	} else {
+		return path, nil
+	}
+}
+
+// GitGetBinHash retrieves a sha256 hash of the git binary that is located on the system.
+// The path is determined based on exec.LookPath().
+func GitGetBinHash(ctx *attestation.AttestationContext) (string, error) {
+	path, err := exec.LookPath("git")
+	if err != nil {
+		return "", err
+	}
+
+	gitBinDigest, err := cryptoutil.CalculateDigestSetFromFile(path, ctx.Hashes())
+	fmt.Printf("%s", gitBinDigest)
+	if err != nil {
+		return "", err
+	}
+
+	digestMap, err := gitBinDigest.ToNameMap()
+	if err != nil {
+		return "", err
+	}
+
+	return fmt.Sprintf("sha256:%s", digestMap["sha256"]), nil
+}
+
+// GitGetStatus retrieves the status of staging and worktree
+// from the git status --porcelain output
 func GitGetStatus(workDir string) (map[string]Status, error) {
 
 	// Execute the git status --porcelain command