From 1456db6e3da92e2187334d5d0fd713b6c95ed94e Mon Sep 17 00:00:00 2001
From: sudoforge <9c001b67637a@sudoforge.com>
Date: Fri, 12 May 2023 22:51:04 -0700
Subject: [PATCH] feat: add support for gopass as a credential store

This change adds support for `gopass` as a credential store, based on
the `pass` implementation.

Closes: #138
Closes: #166
Signed-off-by: sudoforge <9c001b67637a@sudoforge.com>
---
 .github/workflows/build.yml |   6 +
 Dockerfile                  |  16 ++-
 Makefile                    |   5 +-
 README.md                   |  25 +++--
 gopass/cmd/main.go          |  10 ++
 gopass/gopass.go            | 218 ++++++++++++++++++++++++++++++++++++
 gopass/gopass_test.go       |  82 ++++++++++++++
 7 files changed, 350 insertions(+), 12 deletions(-)
 create mode 100644 gopass/cmd/main.go
 create mode 100644 gopass/gopass.go
 create mode 100644 gopass/gopass_test.go

diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 201281b7..7fda5158 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -63,6 +63,12 @@ jobs:
         run: |
           sudo apt-get update
           sudo apt-get install -y dbus-x11 gnome-keyring libsecret-1-dev pass
+      -
+        name: Install gopass
+        env:
+          GOPASS_VERSION: v1.15.5
+        run: go install github.com/gopasspw/gopass@${{ env.GOPASS_VERSION }}
+
       -
         name: GPG conf
         if: ${{ matrix.os == 'ubuntu-20.04' }}
diff --git a/Dockerfile b/Dockerfile
index 41432719..9c597a3d 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -5,6 +5,7 @@ ARG XX_VERSION=1.2.1
 ARG OSXCROSS_VERSION=11.3-r7-debian
 ARG GOLANGCI_LINT_VERSION=v1.51.1
 ARG DEBIAN_FRONTEND=noninteractive
+ARG GOPASS_VERSION=v1.15.5
 
 ARG PACKAGE=github.com/docker/docker-credential-helpers
 
@@ -68,7 +69,12 @@ RUN xx-apt-get install -y binutils gcc libc6-dev libgcc-10-dev libsecret-1-dev p
 
 FROM base AS test
 ARG DEBIAN_FRONTEND
+ARG GOPASS_VERSION
 RUN xx-apt-get install -y dbus-x11 gnome-keyring gpg-agent gpgconf libsecret-1-dev pass
+RUN --mount=type=bind,target=. \
+    --mount=type=cache,target=/root/.cache \
+    --mount=type=cache,target=/go/pkg/mod \
+    go install github.com/gopasspw/gopass@${GOPASS_VERSION}
 RUN --mount=type=bind,target=. \
     --mount=type=cache,target=/root/.cache \
     --mount=type=cache,target=/go/pkg/mod <<EOT
@@ -106,7 +112,8 @@ RUN --mount=type=bind,target=. \
     --mount=type=bind,source=/tmp/.revision,target=/tmp/.revision,from=version <<EOT
   set -ex
   xx-go --wrap
-  make build-pass build-secretservice PACKAGE=$PACKAGE VERSION=$(cat /tmp/.version) REVISION=$(cat /tmp/.revision) DESTDIR=/out
+  make build-gopass build-pass build-secretservice PACKAGE=$PACKAGE VERSION=$(cat /tmp/.version) REVISION=$(cat /tmp/.revision) DESTDIR=/out
+  xx-verify /out/docker-credential-gopass
   xx-verify /out/docker-credential-pass
   xx-verify /out/docker-credential-secretservice
 EOT
@@ -122,7 +129,8 @@ RUN --mount=type=bind,target=. \
   set -ex
   xx-go --wrap
   go install std
-  make build-osxkeychain build-pass PACKAGE=$PACKAGE VERSION=$(cat /tmp/.version) REVISION=$(cat /tmp/.revision) DESTDIR=/out
+  make build-gopass build-osxkeychain build-pass PACKAGE=$PACKAGE VERSION=$(cat /tmp/.version) REVISION=$(cat /tmp/.revision) DESTDIR=/out
+  xx-verify /out/docker-credential-gopass
   xx-verify /out/docker-credential-osxkeychain
   xx-verify /out/docker-credential-pass
 EOT
@@ -136,7 +144,9 @@ RUN --mount=type=bind,target=. \
     --mount=type=bind,source=/tmp/.revision,target=/tmp/.revision,from=version <<EOT
   set -ex
   xx-go --wrap
-  make build-wincred PACKAGE=$PACKAGE VERSION=$(cat /tmp/.version) REVISION=$(cat /tmp/.revision) DESTDIR=/out
+  make build-gopass build-wincred PACKAGE=$PACKAGE VERSION=$(cat /tmp/.version) REVISION=$(cat /tmp/.revision) DESTDIR=/out
+  mv /out/docker-credential-gopass /out/docker-credential-gopass.exe
+  xx-verify /out/docker-credential-gopass.exe
   mv /out/docker-credential-wincred /out/docker-credential-wincred.exe
   xx-verify /out/docker-credential-wincred.exe
 EOT
diff --git a/Makefile b/Makefile
index ceb860f2..a5d42908 100644
--- a/Makefile
+++ b/Makefile
@@ -16,11 +16,12 @@ clean:
 	rm -rf bin
 
 .PHONY: build-%
-build-%: # build, can be one of build-osxkeychain build-pass build-secretservice build-wincred
+build-%: # build, can be one of build-gopass build-osxkeychain build-pass build-secretservice build-wincred
 	go build -trimpath -ldflags="$(GO_LDFLAGS) -X ${GO_PKG}/credentials.Name=docker-credential-$*" -o "$(DESTDIR)/docker-credential-$*" ./$*/cmd/
 
 # aliases for build-* targets
-.PHONY: osxkeychain secretservice pass wincred
+.PHONY: gopass osxkeychain secretservice pass wincred
+gopass: build-gopass
 osxkeychain: build-osxkeychain
 secretservice: build-secretservice
 pass: build-pass
diff --git a/README.md b/README.md
index 300705c0..cc46960f 100644
--- a/README.md
+++ b/README.md
@@ -77,15 +77,26 @@ You can see examples of each function in the [client](https://godoc.org/github.c
 
 ### Available programs
 
-1. osxkeychain: Provides a helper to use the OS X keychain as credentials store.
-2. secretservice: Provides a helper to use the D-Bus secret service as credentials store.
-3. wincred: Provides a helper to use Windows credentials manager as store.
-4. pass: Provides a helper to use `pass` as credentials store.
+- gopass: Provides a helper to use `gopass` as credentials store.
+- osxkeychain: Provides a helper to use the OS X keychain as credentials store.
+- pass: Provides a helper to use `pass` as credentials store.
+- secretservice: Provides a helper to use the D-Bus secret service as credentials store.
+- wincred: Provides a helper to use Windows credentials manager as store.
 
-#### Note
+#### Note regarding `gopass`
 
-`pass` needs to be configured for `docker-credential-pass` to work properly.
-It must be initialized with a `gpg2` key ID. Make sure your GPG key exists is in `gpg2` keyring as `pass` uses `gpg2` instead of the regular `gpg`.
+`gopass` requires manual intervention in order for `docker-credential-gopass` to
+work properly: a password store must be initialized. Please ensure to review the
+upstream [quick start guide][gopass-quick-start] for more information.
+
+[gopass-quick-start]: https://github.com/gopasspw/gopass#quick-start-guide
+
+#### Note regarding `pass`
+
+`pass` requires manual interview in order for `docker-credential-pass` to
+work properly. It must be initialized with a `gpg2` key ID. Make sure your GPG
+key exists is in `gpg2` keyring as `pass` uses `gpg2` instead of the regular
+`gpg`.
 
 ## Development
 
diff --git a/gopass/cmd/main.go b/gopass/cmd/main.go
new file mode 100644
index 00000000..3a4a165e
--- /dev/null
+++ b/gopass/cmd/main.go
@@ -0,0 +1,10 @@
+package main
+
+import (
+	"github.com/docker/docker-credential-helpers/credentials"
+	"github.com/docker/docker-credential-helpers/gopass"
+)
+
+func main() {
+	credentials.Serve(gopass.Gopass{})
+}
diff --git a/gopass/gopass.go b/gopass/gopass.go
new file mode 100644
index 00000000..2b069288
--- /dev/null
+++ b/gopass/gopass.go
@@ -0,0 +1,218 @@
+// Package gopass implements a `gopass` based credential helper. Passwords are
+// stored as arguments to gopass of the form:
+//
+// "$GOPASS_FOLDER/base64-url(serverURL)/username"
+//
+// We base64-url encode the serverURL, because under the hood gopass uses files
+// and folders, so /s will get translated into additional folders.
+package gopass
+
+import (
+	"bytes"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io/fs"
+	"os"
+	"os/exec"
+	"path"
+	"strings"
+	"sync"
+
+	"github.com/docker/docker-credential-helpers/credentials"
+)
+
+// GOPASS_FOLDER contains the directory where credentials are stored
+const GOPASS_FOLDER = "docker-credential-helpers" //nolint:revive
+
+// Gopass handles secrets using gopass as a store.
+type Gopass struct{}
+
+// Ideally these would be stored as members of Gopass, but since all of Gopass's
+// methods have value receivers, not pointer receivers, and changing that is
+// backwards incompatible, we assume that all Gopass instances share the same
+// configuration
+
+// initializationMutex is held while initializing so that only one 'gopass'
+// round-tripping is done to check that gopass is functioning.
+var initializationMutex sync.Mutex
+var gopassInitialized bool
+
+// CheckInitialized checks whether the password helper can be used. It
+// internally caches and so may be safely called multiple times with no impact
+// on performance, though the first call may take longer.
+func (g Gopass) CheckInitialized() bool {
+	return g.checkInitialized() == nil
+}
+
+func (g Gopass) checkInitialized() error {
+	initializationMutex.Lock()
+	defer initializationMutex.Unlock()
+	if gopassInitialized {
+		return nil
+	}
+
+	// We just run a `gopass ls`, if it fails then gopass is not initialized.
+	_, err := g.runGopassHelper("", "ls", "--flat")
+	if err != nil {
+		return fmt.Errorf("gopass is not initialized: %v", err)
+	}
+	gopassInitialized = true
+	return nil
+}
+
+func (g Gopass) runGopass(stdinContent string, args ...string) (string, error) {
+	if err := g.checkInitialized(); err != nil {
+		return "", err
+	}
+	return g.runGopassHelper(stdinContent, args...)
+}
+
+func (g Gopass) runGopassHelper(stdinContent string, args ...string) (string, error) {
+	var stdout, stderr bytes.Buffer
+	cmd := exec.Command("gopass", args...)
+	cmd.Stdin = strings.NewReader(stdinContent)
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+
+	err := cmd.Run()
+	if err != nil {
+		return "", fmt.Errorf("%s: %s", err, stderr.String())
+	}
+
+	// trim newlines; gopass includes a newline at the end of `show` output
+	return strings.TrimRight(stdout.String(), "\n\r"), nil
+}
+
+// Add adds new credentials to the keychain.
+func (g Gopass) Add(creds *credentials.Credentials) error {
+	if creds == nil {
+		return errors.New("missing credentials")
+	}
+
+	encoded := base64.URLEncoding.EncodeToString([]byte(creds.ServerURL))
+
+	_, err := g.runGopass(creds.Secret, "insert", "-f", path.Join(GOPASS_FOLDER, encoded, creds.Username))
+	return err
+}
+
+// Delete removes credentials from the store.
+func (g Gopass) Delete(serverURL string) error {
+	if serverURL == "" {
+		return errors.New("missing server url")
+	}
+
+	encoded := base64.URLEncoding.EncodeToString([]byte(serverURL))
+	_, err := g.runGopass("", "rm", "-rf", path.Join(GOPASS_FOLDER, encoded))
+	return err
+}
+
+func (g Gopass) getGopassDir() (string, error) {
+	gopassDir, err := g.runGopass("", "config", "mounts.path")
+
+	if err != nil {
+		return "", fmt.Errorf("error getting gopass dir: %v", err)
+	}
+
+	return gopassDir, nil
+}
+
+// listGopassDir lists all the contents of a directory in the password store.
+// Gopass uses fancy unicode to emit stuff to stdout, so rather than try
+// and parse this, let's just look at the directory structure instead.
+func (g Gopass) listGopassDir(args ...string) ([]os.FileInfo, error) {
+	gopassDir, err := g.getGopassDir()
+	if err != nil {
+		return nil, err
+	}
+
+	p := path.Join(append([]string{gopassDir, GOPASS_FOLDER}, args...)...)
+
+	entries, err := os.ReadDir(p)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return []os.FileInfo{}, nil
+		}
+		return nil, err
+	}
+
+	infos := make([]fs.FileInfo, 0, len(entries))
+	for _, entry := range entries {
+		info, err := entry.Info()
+		if err != nil {
+			return nil, err
+		}
+		infos = append(infos, info)
+	}
+	return infos, nil
+}
+
+// Get returns the username and secret to use for a given registry server URL.
+func (g Gopass) Get(serverURL string) (string, string, error) {
+	if serverURL == "" {
+		return "", "", errors.New("missing server url")
+	}
+
+	gopassDir, err := g.getGopassDir()
+	if err != nil {
+		return "", "", err
+	}
+
+	encoded := base64.URLEncoding.EncodeToString([]byte(serverURL))
+
+	if _, err := os.Stat(path.Join(gopassDir, GOPASS_FOLDER, encoded)); err != nil {
+		if os.IsNotExist(err) {
+			return "", "", credentials.NewErrCredentialsNotFound()
+		}
+
+		return "", "", err
+	}
+
+	usernames, err := g.listGopassDir(encoded)
+	if err != nil {
+		return "", "", err
+	}
+
+	if len(usernames) < 1 {
+		return "", "", fmt.Errorf("no usernames for %s", serverURL)
+	}
+
+	actual := strings.TrimSuffix(usernames[0].Name(), ".gpg")
+	secret, err := g.runGopass("", "show", "-o", path.Join(GOPASS_FOLDER, encoded, actual))
+
+	return actual, secret, err
+}
+
+// List returns the stored URLs and corresponding usernames for a given credentials label
+func (g Gopass) List() (map[string]string, error) {
+	servers, err := g.listGopassDir()
+	if err != nil {
+		return nil, err
+	}
+
+	resp := map[string]string{}
+
+	for _, server := range servers {
+		if !server.IsDir() {
+			continue
+		}
+
+		serverURL, err := base64.URLEncoding.DecodeString(server.Name())
+		if err != nil {
+			return nil, err
+		}
+
+		usernames, err := g.listGopassDir(server.Name())
+		if err != nil {
+			return nil, err
+		}
+
+		if len(usernames) < 1 {
+			return nil, fmt.Errorf("no usernames for %s", serverURL)
+		}
+
+		resp[string(serverURL)] = strings.TrimSuffix(usernames[0].Name(), ".gpg")
+	}
+
+	return resp, nil
+}
diff --git a/gopass/gopass_test.go b/gopass/gopass_test.go
new file mode 100644
index 00000000..77cc5f57
--- /dev/null
+++ b/gopass/gopass_test.go
@@ -0,0 +1,82 @@
+package gopass
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/docker/docker-credential-helpers/credentials"
+)
+
+func TestGopassHelper(t *testing.T) {
+	helper := Gopass{}
+
+	creds := &credentials.Credentials{
+		ServerURL: "https://foobar.docker.io:2376/v1",
+		Username:  "maryhadalittlelamb",
+		Secret:    "andbingowasitsname-o",
+	}
+
+	_ = helper.CheckInitialized()
+
+	helper.Add(creds)
+
+	creds.ServerURL = "https://foobar.docker.io:9999/v2"
+	helper.Add(creds)
+
+	credsList, err := helper.List()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for server, username := range credsList {
+		if !(strings.Contains(server, "2376") ||
+			strings.Contains(server, "9999")) {
+			t.Fatalf("invalid url: %s", creds.ServerURL)
+		}
+
+		if username != "maryhadalittlelamb" {
+			t.Fatalf("invalid username: %v", username)
+		}
+
+		u, s, err := helper.Get(server)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if u != username {
+			t.Fatalf("invalid username %s", u)
+		}
+
+		if s != "andbingowasitsname-o" {
+			t.Fatalf("invalid secret: %s", s)
+		}
+
+		err = helper.Delete(server)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		_, _, err = helper.Get(server)
+		if !credentials.IsErrCredentialsNotFound(err) {
+			t.Fatalf("expected credentials not found, actual: %v", err)
+		}
+	}
+
+	credsList, err = helper.List()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(credsList) != 0 {
+		t.Fatal("didn't delete all creds?")
+	}
+}
+
+func TestMissingCred(t *testing.T) {
+	helper := Gopass{}
+
+	_, _, err := helper.Get("garbage")
+	if !credentials.IsErrCredentialsNotFound(err) {
+		t.Fatalf("expected credentials not found, actual: %v", err)
+	}
+}