init: pristine aerc 0.20.0 source

lib/crypto/crypto.go

@@ -0,0 +1,60 @@
+package crypto
+
+import (
+	"bytes"
+	"io"
+
+	"git.sr.ht/~rjarry/aerc/config"
+	"git.sr.ht/~rjarry/aerc/lib/crypto/gpg"
+	"git.sr.ht/~rjarry/aerc/lib/crypto/pgp"
+	"git.sr.ht/~rjarry/aerc/lib/log"
+	"git.sr.ht/~rjarry/aerc/models"
+	"github.com/ProtonMail/go-crypto/openpgp"
+	"github.com/emersion/go-message/mail"
+)
+
+type Provider interface {
+	Decrypt(io.Reader, openpgp.PromptFunction) (*models.MessageDetails, error)
+	Encrypt(*bytes.Buffer, []string, string, openpgp.PromptFunction, *mail.Header) (io.WriteCloser, error)
+	Sign(*bytes.Buffer, string, openpgp.PromptFunction, *mail.Header) (io.WriteCloser, error)
+	ImportKeys(io.Reader) error
+	Init() error
+	Close()
+	GetSignerKeyId(string) (string, error)
+	GetKeyId(string) (string, error)
+	ExportKey(string) (io.Reader, error)
+}
+
+func New() Provider {
+	switch config.General.PgpProvider {
+	case "auto":
+		internal := &pgp.Mail{}
+		if internal.KeyringExists() {
+			log.Debugf("internal pgp keyring exists")
+			return internal
+		}
+		log.Debugf("no internal pgp keyring, using system gpg")
+		fallthrough
+	case "gpg":
+		return &gpg.Mail{}
+	case "internal":
+		return &pgp.Mail{}
+	default:
+		return nil
+	}
+}
+
+func IsEncrypted(bs *models.BodyStructure) bool {
+	if bs == nil {
+		return false
+	}
+	if bs.MIMEType == "application" && bs.MIMESubType == "pgp-encrypted" {
+		return true
+	}
+	for _, part := range bs.Parts {
+		if IsEncrypted(part) {
+			return true
+		}
+	}
+	return false
+}

lib/crypto/gpg/gpg.go

@@ -0,0 +1,69 @@
+package gpg
+
+import (
+	"bytes"
+	"io"
+	"os/exec"
+
+	"git.sr.ht/~rjarry/aerc/lib/crypto/gpg/gpgbin"
+	"git.sr.ht/~rjarry/aerc/models"
+	"github.com/ProtonMail/go-crypto/openpgp"
+	"github.com/emersion/go-message/mail"
+)
+
+// Mail satisfies the PGPProvider interface in aerc
+type Mail struct{}
+
+func (m *Mail) Init() error {
+	_, err := exec.LookPath("gpg")
+	return err
+}
+
+func (m *Mail) Decrypt(r io.Reader, decryptKeys openpgp.PromptFunction) (*models.MessageDetails, error) {
+	gpgReader, err := Read(r)
+	if err != nil {
+		return nil, err
+	}
+	md := gpgReader.MessageDetails
+	md.SignatureValidity = models.Valid
+	if md.SignatureError != "" {
+		md.SignatureValidity = handleSignatureError(md.SignatureError)
+	}
+	return md, nil
+}
+
+func (m *Mail) ImportKeys(r io.Reader) error {
+	return gpgbin.Import(r)
+}
+
+func (m *Mail) Encrypt(buf *bytes.Buffer, rcpts []string, signer string, decryptKeys openpgp.PromptFunction, header *mail.Header) (io.WriteCloser, error) {
+	return Encrypt(buf, header.Header.Header, rcpts, signer)
+}
+
+func (m *Mail) Sign(buf *bytes.Buffer, signer string, decryptKeys openpgp.PromptFunction, header *mail.Header) (io.WriteCloser, error) {
+	return Sign(buf, header.Header.Header, signer)
+}
+
+func (m *Mail) Close() {}
+
+func (m *Mail) GetSignerKeyId(s string) (string, error) {
+	return gpgbin.GetPrivateKeyId(s)
+}
+
+func (m *Mail) GetKeyId(s string) (string, error) {
+	return gpgbin.GetKeyId(s)
+}
+
+func (m *Mail) ExportKey(k string) (io.Reader, error) {
+	return gpgbin.ExportPublicKey(k)
+}
+
+func handleSignatureError(e string) models.SignatureValidity {
+	if e == "gpg: missing public key" {
+		return models.UnknownEntity
+	}
+	if e == "gpg: header hash does not match actual sig hash" {
+		return models.MicalgMismatch
+	}
+	return models.UnknownValidity
+}

lib/crypto/gpg/gpg_test.go

@@ -0,0 +1,160 @@
+package gpg
+
+import (
+	"bytes"
+	"io"
+	"os/exec"
+	"strings"
+	"testing"
+
+	"git.sr.ht/~rjarry/aerc/models"
+)
+
+func initGPGtest(t *testing.T) {
+	if _, err := exec.LookPath("gpg"); err != nil {
+		t.Skipf("%s", err)
+	}
+	// temp dir is automatically deleted by the test runtime
+	dir := t.TempDir()
+	t.Setenv("GNUPGHOME", dir)
+	t.Logf("using GNUPGHOME = %s", dir)
+}
+
+func toCRLF(s string) string {
+	return strings.ReplaceAll(s, "\n", "\r\n")
+}
+
+func deepEqual(t *testing.T, name string, r *models.MessageDetails, expect *models.MessageDetails) {
+	var resBuf bytes.Buffer
+	if _, err := io.Copy(&resBuf, r.Body); err != nil {
+		t.Fatalf("%s: io.Copy() = %v", name, err)
+	}
+
+	var expBuf bytes.Buffer
+	if _, err := io.Copy(&expBuf, expect.Body); err != nil {
+		t.Fatalf("%s: io.Copy() = %v", name, err)
+	}
+
+	if resBuf.String() != expBuf.String() {
+		t.Errorf("%s: MessagesDetails.Body = \n%v\n but want \n%v", name, resBuf.String(), expBuf.String())
+	}
+
+	if r.IsEncrypted != expect.IsEncrypted {
+		t.Errorf("%s: IsEncrypted = \n%v\n but want \n%v", name, r.IsEncrypted, expect.IsEncrypted)
+	}
+	if r.IsSigned != expect.IsSigned {
+		t.Errorf("%s: IsSigned = \n%v\n but want \n%v", name, r.IsSigned, expect.IsSigned)
+	}
+	if r.SignedBy != expect.SignedBy {
+		t.Errorf("%s: SignedBy = \n%v\n but want \n%v", name, r.SignedBy, expect.SignedBy)
+	}
+	if r.SignedByKeyId != expect.SignedByKeyId {
+		t.Errorf("%s: SignedByKeyId = \n%v\n but want \n%v", name, r.SignedByKeyId, expect.SignedByKeyId)
+	}
+	if r.SignatureError != expect.SignatureError {
+		t.Errorf("%s: SignatureError = \n%v\n but want \n%v", name, r.SignatureError, expect.SignatureError)
+	}
+	if r.DecryptedWith != expect.DecryptedWith {
+		t.Errorf("%s: DecryptedWith = \n%v\n but want \n%v", name, r.DecryptedWith, expect.DecryptedWith)
+	}
+	if r.DecryptedWithKeyId != expect.DecryptedWithKeyId {
+		t.Errorf("%s: DecryptedWithKeyId = \n%v\n but want \n%v", name, r.DecryptedWithKeyId, expect.DecryptedWithKeyId)
+	}
+}
+
+const testKeyId = `B1A8669354153B799F2217BF307215C13DF7A964`
+
+const testPrivateKeyArmored = `-----BEGIN PGP PRIVATE KEY BLOCK-----
+
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++5anTnUn
+=gemU
+-----END PGP PRIVATE KEY BLOCK-----
+`
+
+const testPublicKeyArmored = `-----BEGIN PGP PUBLIC KEY BLOCK-----
+
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++1FjPta6cgZ1tJzFtJ7Bwa2///UAp7BQqDl7DyMQAfOZGkUI9mqEXdra4YqMv5X0
+Y2UQ
+=QL1U
+-----END PGP PUBLIC KEY BLOCK-----
+`
+
+const testOwnertrust = "B1A8669354153B799F2217BF307215C13DF7A964:6:\n"

lib/crypto/gpg/gpgbin/decrypt.go

@@ -0,0 +1,35 @@
+package gpgbin
+
+import (
+	"bytes"
+	"errors"
+	"io"
+
+	"git.sr.ht/~rjarry/aerc/models"
+)
+
+// Decrypt runs gpg --decrypt on the contents of r. If the packet is signed,
+// the signature is also verified
+func Decrypt(r io.Reader) (*models.MessageDetails, error) {
+	md := new(models.MessageDetails)
+	orig, err := io.ReadAll(r)
+	if err != nil {
+		return md, err
+	}
+	args := []string{"--decrypt"}
+	g := newGpg(bytes.NewReader(orig), args)
+	_ = g.cmd.Run()
+	// Always parse stdout, even if there was an error running command.
+	// We'll find the error in the parsing
+	err = parseStatusFd(bytes.NewReader(g.stderr.Bytes()), md)
+
+	if errors.Is(err, NoValidOpenPgpData) {
+		md.Body = bytes.NewReader(orig)
+		return md, nil
+	} else if err != nil {
+		return nil, err
+	}
+
+	md.Body = bytes.NewReader(g.stdout.Bytes())
+	return md, nil
+}

lib/crypto/gpg/gpgbin/encrypt.go

@@ -0,0 +1,33 @@
+package gpgbin
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+
+	"git.sr.ht/~rjarry/aerc/models"
+)
+
+// Encrypt runs gpg --encrypt [--sign] -r [recipient]
+func Encrypt(r io.Reader, to []string, from string) ([]byte, error) {
+	args := []string{
+		"--armor",
+	}
+	if from != "" {
+		args = append(args, "--sign", "--default-key", from)
+	}
+	for _, rcpt := range to {
+		args = append(args, "--recipient", rcpt)
+	}
+	args = append(args, "--encrypt", "-")
+
+	g := newGpg(r, args)
+	_ = g.cmd.Run()
+	var md models.MessageDetails
+	err := parseStatusFd(bytes.NewReader(g.stderr.Bytes()), &md)
+	if err != nil {
+		return nil, fmt.Errorf("gpg: failure to encrypt: %w. check public key(s)", err)
+	}
+
+	return g.stdout.Bytes(), nil
+}

lib/crypto/gpg/gpgbin/gpgbin.go

@@ -0,0 +1,261 @@
+package gpgbin
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"os/exec"
+	"strconv"
+	"strings"
+
+	"git.sr.ht/~rjarry/aerc/lib/log"
+	"git.sr.ht/~rjarry/aerc/lib/pinentry"
+	"git.sr.ht/~rjarry/aerc/models"
+)
+
+// gpg represents a gpg command with buffers attached to stdout and stderr
+type gpg struct {
+	cmd    *exec.Cmd
+	stdout bytes.Buffer
+	stderr bytes.Buffer
+}
+
+// newGpg creates a new gpg command with buffers attached
+func newGpg(stdin io.Reader, args []string) *gpg {
+	g := new(gpg)
+	g.cmd = exec.Command("gpg", "--status-fd", "2", "--log-file", "/dev/null", "--batch")
+	g.cmd.Args = append(g.cmd.Args, args...)
+	g.cmd.Stdin = stdin
+	g.cmd.Stdout = &g.stdout
+	g.cmd.Stderr = &g.stderr
+
+	pinentry.SetCmdEnv(g.cmd)
+
+	return g
+}
+
+// fields returns the field name from --status-fd output. See:
+// https://github.com/gpg/gnupg/blob/master/doc/DETAILS
+func field(s string) string {
+	tokens := strings.SplitN(s, " ", 3)
+	if tokens[0] == "[GNUPG:]" {
+		return tokens[1]
+	}
+	return ""
+}
+
+// getIdentity returns the identity of the given key
+func getIdentity(key uint64) string {
+	fpr := fmt.Sprintf("%X", key)
+	cmd := exec.Command("gpg", "--with-colons", "--batch", "--list-keys", fpr)
+
+	var outbuf strings.Builder
+	cmd.Stdout = &outbuf
+	err := cmd.Run()
+	if err != nil {
+		log.Errorf("gpg: failed to get identity: %v", err)
+		return ""
+	}
+	out := strings.Split(outbuf.String(), "\n")
+	for _, line := range out {
+		if strings.HasPrefix(line, "uid") {
+			flds := strings.Split(line, ":")
+			return flds[9]
+		}
+	}
+	return ""
+}
+
+// getKeyId returns the 16 digit key id, if key exists
+func getKeyId(s string, private bool) string {
+	cmd := exec.Command("gpg", "--with-colons", "--batch")
+	listArg := "--list-keys"
+	if private {
+		listArg = "--list-secret-keys"
+	}
+	cmd.Args = append(cmd.Args, listArg, s)
+
+	var outbuf strings.Builder
+	cmd.Stdout = &outbuf
+	err := cmd.Run()
+	if err != nil {
+		log.Errorf("gpg: failed to get key ID: %v", err)
+		return ""
+	}
+	out := strings.Split(outbuf.String(), "\n")
+	for _, line := range out {
+		if strings.HasPrefix(line, "fpr") {
+			flds := strings.Split(line, ":")
+			id := flds[9]
+			return id[len(id)-16:]
+		}
+	}
+	return ""
+}
+
+// longKeyToUint64 returns a uint64 version of the given key
+func longKeyToUint64(key string) (uint64, error) {
+	fpr := string(key[len(key)-16:])
+	fprUint64, err := strconv.ParseUint(fpr, 16, 64)
+	if err != nil {
+		return 0, err
+	}
+	return fprUint64, nil
+}
+
+// parse parses the output of gpg --status-fd
+func parseStatusFd(r io.Reader, md *models.MessageDetails) error {
+	var err error
+	scanner := bufio.NewScanner(r)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if field(line) == "PLAINTEXT_LENGTH" {
+			continue
+		}
+		log.Tracef(line)
+
+		switch field(line) {
+		case "ENC_TO":
+			md.IsEncrypted = true
+		case "DECRYPTION_KEY":
+			md.DecryptedWithKeyId, err = parseDecryptionKey(line)
+			md.DecryptedWith = getIdentity(md.DecryptedWithKeyId)
+			if err != nil {
+				return err
+			}
+		case "DECRYPTION_FAILED":
+			return EncryptionFailed
+		case "NEWSIG":
+			md.IsSigned = true
+		case "GOODSIG":
+			t := strings.SplitN(line, " ", 4)
+			md.SignedByKeyId, err = longKeyToUint64(t[2])
+			if err != nil {
+				return err
+			}
+			md.SignedBy = t[3]
+		case "BADSIG":
+			t := strings.SplitN(line, " ", 4)
+			md.SignedByKeyId, err = longKeyToUint64(t[2])
+			if err != nil {
+				return err
+			}
+			md.SignatureError = "gpg: invalid signature"
+			md.SignedBy = t[3]
+		case "EXPSIG":
+			t := strings.SplitN(line, " ", 4)
+			md.SignedByKeyId, err = longKeyToUint64(t[2])
+			if err != nil {
+				return err
+			}
+			md.SignatureError = "gpg: expired signature"
+			md.SignedBy = t[3]
+		case "EXPKEYSIG":
+			t := strings.SplitN(line, " ", 4)
+			md.SignedByKeyId, err = longKeyToUint64(t[2])
+			if err != nil {
+				return err
+			}
+			md.SignatureError = "gpg: signature made with expired key"
+			md.SignedBy = t[3]
+		case "REVKEYSIG":
+			t := strings.SplitN(line, " ", 4)
+			md.SignedByKeyId, err = longKeyToUint64(t[2])
+			if err != nil {
+				return err
+			}
+			md.SignatureError = "gpg: signature made with revoked key"
+			md.SignedBy = t[3]
+		case "ERRSIG":
+			t := strings.SplitN(line, " ", 9)
+			md.SignedByKeyId, err = longKeyToUint64(t[2])
+			if err != nil {
+				return err
+			}
+			if t[7] == "9" {
+				md.SignatureError = "gpg: missing public key"
+			}
+			if t[7] == "4" {
+				md.SignatureError = "gpg: unsupported algorithm"
+			}
+			md.SignedBy = "(unknown signer)"
+		case "INV_RECP":
+			t := strings.SplitN(line, " ", 4)
+			if t[2] == "10" {
+				return fmt.Errorf("gpg: public key of %s is not trusted", t[3])
+			}
+		case "SIG_CREATED":
+			fields := strings.Split(line, " ")
+			micalg, err := strconv.Atoi(fields[4])
+			if err != nil {
+				return MicalgNotFound
+			}
+			md.Micalg = micalgs[micalg]
+		case "VALIDSIG":
+			fields := strings.Split(line, " ")
+			micalg, err := strconv.Atoi(fields[9])
+			if err != nil {
+				return MicalgNotFound
+			}
+			md.Micalg = micalgs[micalg]
+		case "NODATA":
+			t := strings.SplitN(line, " ", 3)
+			if t[2] == "4" {
+				md.SignatureError = "gpg: no signature packet found"
+			}
+			if t[2] == "1" {
+				return NoValidOpenPgpData
+			}
+		case "FAILURE":
+			return fmt.Errorf("%s", strings.TrimPrefix(line, "[GNUPG:] "))
+		}
+	}
+	return nil
+}
+
+// parseDecryptionKey returns primary key from DECRYPTION_KEY line
+func parseDecryptionKey(l string) (uint64, error) {
+	key := strings.Split(l, " ")[3]
+	fpr := string(key[len(key)-16:])
+	fprUint64, err := longKeyToUint64(fpr)
+	if err != nil {
+		return 0, err
+	}
+	getIdentity(fprUint64)
+	return fprUint64, nil
+}
+
+type StatusFdParsingError int32
+
+const (
+	EncryptionFailed StatusFdParsingError = iota + 1
+	MicalgNotFound
+	NoValidOpenPgpData
+)
+
+func (err StatusFdParsingError) Error() string {
+	switch err {
+	case EncryptionFailed:
+		return "gpg: decryption failed"
+	case MicalgNotFound:
+		return "gpg: micalg not found"
+	case NoValidOpenPgpData:
+		return "gpg: no valid OpenPGP data found"
+	default:
+		return "gpg: unknown status fd parsing error"
+	}
+}
+
+// micalgs represent hash algorithms for signatures. These are ignored by many
+// email clients, but can be used as an additional verification so are sent.
+// Both gpgmail and pgpmail implementations in aerc check for matching micalgs
+var micalgs = map[int]string{
+	1:  "pgp-md5",
+	2:  "pgp-sha1",
+	3:  "pgp-ripemd160",
+	8:  "pgp-sha256",
+	9:  "pgp-sha384",
+	10: "pgp-sha512",
+	11: "pgp-sha224",
+}

lib/crypto/gpg/gpgbin/import-ownertrust.go

@@ -0,0 +1,16 @@
+package gpgbin
+
+import (
+	"io"
+)
+
+// Import runs gpg --import-ownertrust and thus imports trusts for keys
+func ImportOwnertrust(r io.Reader) error {
+	args := []string{"--import-ownertrust"}
+	g := newGpg(r, args)
+	err := g.cmd.Run()
+	if err != nil {
+		return err
+	}
+	return nil
+}

lib/crypto/gpg/gpgbin/import.go

@@ -0,0 +1,16 @@
+package gpgbin
+
+import (
+	"io"
+)
+
+// Import runs gpg --import and thus imports both private and public keys
+func Import(r io.Reader) error {
+	args := []string{"--import"}
+	g := newGpg(r, args)
+	err := g.cmd.Run()
+	if err != nil {
+		return err
+	}
+	return nil
+}

lib/crypto/gpg/gpgbin/keys.go

@@ -0,0 +1,48 @@
+package gpgbin
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"os/exec"
+	"strings"
+)
+
+// GetPrivateKeyId runs gpg --list-secret-keys s
+func GetPrivateKeyId(s string) (string, error) {
+	private := true
+	id := getKeyId(s, private)
+	if id == "" {
+		return "", fmt.Errorf("no private key found")
+	}
+	return id, nil
+}
+
+// GetKeyId runs gpg --list-keys s
+func GetKeyId(s string) (string, error) {
+	private := false
+	id := getKeyId(s, private)
+	if id == "" {
+		return "", fmt.Errorf("no public key found")
+	}
+	return id, nil
+}
+
+// ExportPublicKey exports the public key identified by k in armor format
+func ExportPublicKey(k string) (io.Reader, error) {
+	cmd := exec.Command("gpg", "--armor",
+		"--export-options", "export-minimal", "--export", k)
+
+	var outbuf bytes.Buffer
+	var stderr strings.Builder
+	cmd.Stdout = &outbuf
+	cmd.Stderr = &stderr
+	err := cmd.Run()
+	if err != nil {
+		return nil, fmt.Errorf("gpg: export failed: %w", err)
+	}
+	if strings.Contains(stderr.String(), "gpg") {
+		return nil, fmt.Errorf("gpg: error exporting key")
+	}
+	return &outbuf, nil
+}

lib/crypto/gpg/gpgbin/sign.go

@@ -0,0 +1,29 @@
+package gpgbin
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+
+	"git.sr.ht/~rjarry/aerc/models"
+)
+
+// Sign creates a detached signature based on the contents of r
+func Sign(r io.Reader, from string) ([]byte, string, error) {
+	args := []string{
+		"--armor",
+		"--detach-sign",
+		"--default-key", from,
+	}
+
+	g := newGpg(r, args)
+	_ = g.cmd.Run()
+
+	var md models.MessageDetails
+	err := parseStatusFd(bytes.NewReader(g.stderr.Bytes()), &md)
+	if err != nil {
+		return nil, "", fmt.Errorf("failed to parse messagedetails: %w", err)
+	}
+
+	return g.stdout.Bytes(), md.Micalg, nil
+}

lib/crypto/gpg/gpgbin/verify.go

@@ -0,0 +1,39 @@
+package gpgbin
+
+import (
+	"bytes"
+	"io"
+	"os"
+
+	"git.sr.ht/~rjarry/aerc/models"
+)
+
+// Verify runs gpg --verify. If s is not nil, then gpg interprets the
+// arguments as a detached signature
+func Verify(m io.Reader, s io.Reader) (*models.MessageDetails, error) {
+	args := []string{"--verify"}
+	if s != nil {
+		// Detached sig, save the sig to a tmp file and send msg over stdin
+		sig, err := os.CreateTemp("", "sig")
+		if err != nil {
+			return nil, err
+		}
+		_, _ = io.Copy(sig, s)
+		sig.Close()
+		defer os.Remove(sig.Name())
+		args = append(args, sig.Name(), "-")
+	}
+	orig, err := io.ReadAll(m)
+	if err != nil {
+		return nil, err
+	}
+	g := newGpg(bytes.NewReader(orig), args)
+	_ = g.cmd.Run()
+
+	md := new(models.MessageDetails)
+	_ = parseStatusFd(bytes.NewReader(g.stderr.Bytes()), md)
+
+	md.Body = bytes.NewReader(orig)
+
+	return md, nil
+}

lib/crypto/gpg/reader.go

@@ -0,0 +1,169 @@
+// reader.go largerly mimics github.com/emersion/go-gpgmail, with changes made
+// to interface with the gpg package in aerc
+
+package gpg
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"mime"
+	"strings"
+
+	"git.sr.ht/~rjarry/aerc/lib/crypto/gpg/gpgbin"
+	"git.sr.ht/~rjarry/aerc/lib/pinentry"
+	"git.sr.ht/~rjarry/aerc/models"
+	"github.com/emersion/go-message/textproto"
+)
+
+type Reader struct {
+	Header         textproto.Header
+	MessageDetails *models.MessageDetails
+}
+
+func NewReader(h textproto.Header, body io.Reader) (*Reader, error) {
+	t, params, err := mime.ParseMediaType(h.Get("Content-Type"))
+	if err != nil {
+		return nil, err
+	}
+
+	if strings.EqualFold(t, "multipart/encrypted") && strings.EqualFold(params["protocol"], "application/pgp-encrypted") {
+		mr := textproto.NewMultipartReader(body, params["boundary"])
+		return newEncryptedReader(h, mr)
+	}
+	if strings.EqualFold(t, "multipart/signed") && strings.EqualFold(params["protocol"], "application/pgp-signature") {
+		micalg := params["micalg"]
+		mr := textproto.NewMultipartReader(body, params["boundary"])
+		return newSignedReader(h, mr, micalg)
+	}
+
+	var headerBuf bytes.Buffer
+	_ = textproto.WriteHeader(&headerBuf, h)
+
+	return &Reader{
+		Header: h,
+		MessageDetails: &models.MessageDetails{
+			Body: io.MultiReader(&headerBuf, body),
+		},
+	}, nil
+}
+
+func Read(r io.Reader) (*Reader, error) {
+	br := bufio.NewReader(r)
+
+	h, err := textproto.ReadHeader(br)
+	if err != nil {
+		return nil, err
+	}
+	return NewReader(h, br)
+}
+
+func newEncryptedReader(h textproto.Header, mr *textproto.MultipartReader) (*Reader, error) {
+	p, err := mr.NextPart()
+	if err != nil {
+		return nil, fmt.Errorf("gpgmail: failed to read first part in multipart/encrypted message: %w", err)
+	}
+
+	t, _, err := mime.ParseMediaType(p.Header.Get("Content-Type"))
+	if err != nil {
+		return nil, fmt.Errorf("gpgmail: failed to parse Content-Type of first part in multipart/encrypted message: %w", err)
+	}
+	if !strings.EqualFold(t, "application/pgp-encrypted") {
+		return nil, fmt.Errorf("gpgmail: first part in multipart/encrypted message has type %q, not application/pgp-encrypted", t)
+	}
+
+	metadata, err := textproto.ReadHeader(bufio.NewReader(p))
+	if err != nil {
+		return nil, fmt.Errorf("gpgmail: failed to parse application/pgp-encrypted part: %w", err)
+	}
+	if s := metadata.Get("Version"); s != "1" {
+		return nil, fmt.Errorf("gpgmail: unsupported PGP/MIME version: %q", s)
+	}
+
+	p, err = mr.NextPart()
+	if err != nil {
+		return nil, fmt.Errorf("gpgmail: failed to read second part in multipart/encrypted message: %w", err)
+	}
+	t, _, err = mime.ParseMediaType(p.Header.Get("Content-Type"))
+	if err != nil {
+		return nil, fmt.Errorf("gpgmail: failed to parse Content-Type of second part in multipart/encrypted message: %w", err)
+	}
+	if !strings.EqualFold(t, "application/octet-stream") {
+		return nil, fmt.Errorf("gpgmail: second part in multipart/encrypted message has type %q, not application/octet-stream", t)
+	}
+
+	pinentry.Enable()
+	defer pinentry.Disable()
+
+	md, err := gpgbin.Decrypt(p)
+	if err != nil {
+		return nil, fmt.Errorf("gpgmail: failed to read PGP message: %w", err)
+	}
+
+	cleartext := bufio.NewReader(md.Body)
+	cleartextHeader, err := textproto.ReadHeader(cleartext)
+	if err != nil {
+		return nil, fmt.Errorf("gpgmail: failed to read encrypted header: %w", err)
+	}
+
+	t, params, err := mime.ParseMediaType(cleartextHeader.Get("Content-Type"))
+	if err != nil {
+		return nil, err
+	}
+
+	if md.IsEncrypted && !md.IsSigned && strings.EqualFold(t, "multipart/signed") && strings.EqualFold(params["protocol"], "application/pgp-signature") {
+		// RFC 1847 encapsulation, see RFC 3156 section 6.1
+		micalg := params["micalg"]
+		mr := textproto.NewMultipartReader(cleartext, params["boundary"])
+		mds, err := newSignedReader(cleartextHeader, mr, micalg)
+		if err != nil {
+			return nil, fmt.Errorf("gpgmail: failed to read encapsulated multipart/signed message: %w", err)
+		}
+		mds.MessageDetails.IsEncrypted = md.IsEncrypted
+		mds.MessageDetails.DecryptedWith = md.DecryptedWith
+		mds.MessageDetails.DecryptedWithKeyId = md.DecryptedWithKeyId
+		return mds, nil
+	}
+
+	var headerBuf bytes.Buffer
+	_ = textproto.WriteHeader(&headerBuf, cleartextHeader)
+	md.Body = io.MultiReader(&headerBuf, cleartext)
+
+	return &Reader{
+		Header:         h,
+		MessageDetails: md,
+	}, nil
+}
+
+func newSignedReader(h textproto.Header, mr *textproto.MultipartReader, micalg string) (*Reader, error) {
+	micalg = strings.ToLower(micalg)
+	p, err := mr.NextPart()
+	if err != nil {
+		return nil, fmt.Errorf("gpgmail: failed to read signed part in multipart/signed message: %w", err)
+	}
+	var headerBuf bytes.Buffer
+	_ = textproto.WriteHeader(&headerBuf, p.Header)
+	var msg bytes.Buffer
+	headerRdr := bytes.NewReader(headerBuf.Bytes())
+	fullMsg := io.MultiReader(headerRdr, p)
+	_, _ = io.Copy(&msg, fullMsg)
+
+	sig, err := mr.NextPart()
+	if err != nil {
+		return nil, fmt.Errorf("gpgmail: failed to read pgp part in multipart/signed message: %w", err)
+	}
+
+	md, err := gpgbin.Verify(&msg, sig)
+	if err != nil {
+		return nil, fmt.Errorf("gpgmail: failed to read PGP message: %w", err)
+	}
+	if md.Micalg != micalg && md.SignatureError == "" {
+		md.SignatureError = "gpg: header hash does not match actual sig hash"
+	}
+
+	return &Reader{
+		Header:         h,
+		MessageDetails: md,
+	}, nil
+}

lib/crypto/gpg/reader_test.go

@@ -0,0 +1,337 @@
+package gpg
+
+import (
+	"strings"
+	"testing"
+
+	"git.sr.ht/~rjarry/aerc/lib/crypto/gpg/gpgbin"
+	"git.sr.ht/~rjarry/aerc/models"
+)
+
+func importSecretKey() {
+	r := strings.NewReader(testPrivateKeyArmored)
+	gpgbin.Import(r)
+}
+
+func importPublicKey() {
+	r := strings.NewReader(testPublicKeyArmored)
+	gpgbin.Import(r)
+}
+
+func importOwnertrust() {
+	r := strings.NewReader(testOwnertrust)
+	gpgbin.ImportOwnertrust(r)
+}
+
+type readerTestCase struct {
+	name  string
+	want  models.MessageDetails
+	input string
+}
+
+func TestReader(t *testing.T) {
+	initGPGtest(t)
+	importSecretKey()
+	importOwnertrust()
+
+	testCases := []readerTestCase{
+		{
+			name:  "Encrypted and Signed",
+			input: testPGPMIMEEncryptedSigned,
+			want: models.MessageDetails{
+				IsEncrypted:        true,
+				IsSigned:           true,
+				SignedBy:           "John Doe (This is a test key) <john.doe@example.org>",
+				SignedByKeyId:      3490876580878068068,
+				SignatureValidity:  0,
+				SignatureError:     "",
+				DecryptedWith:      "John Doe (This is a test key) <john.doe@example.org>",
+				DecryptedWithKeyId: 3490876580878068068,
+				Body:               strings.NewReader(testEncryptedBody),
+				Micalg:             "pgp-sha512",
+			},
+		},
+		{
+			name:  "Encrypted but not signed",
+			input: testPGPMIMEEncryptedButNotSigned,
+			want: models.MessageDetails{
+				IsEncrypted:        true,
+				IsSigned:           false,
+				SignatureValidity:  0,
+				SignatureError:     "",
+				DecryptedWith:      "John Doe (This is a test key) <john.doe@example.org>",
+				DecryptedWithKeyId: 3490876580878068068,
+				Body:               strings.NewReader(testEncryptedButNotSignedBody),
+				Micalg:             "pgp-sha512",
+			},
+		},
+		{
+			name:  "Signed",
+			input: testPGPMIMESigned,
+			want: models.MessageDetails{
+				IsEncrypted:        false,
+				IsSigned:           true,
+				SignedBy:           "John Doe (This is a test key) <john.doe@example.org>",
+				SignedByKeyId:      3490876580878068068,
+				SignatureValidity:  0,
+				SignatureError:     "",
+				DecryptedWith:      "",
+				DecryptedWithKeyId: 0,
+				Body:               strings.NewReader(testSignedBody),
+				Micalg:             "pgp-sha256",
+			},
+		},
+		{
+			name:  "Encapsulated Signature",
+			input: testPGPMIMEEncryptedSignedEncapsulated,
+			want: models.MessageDetails{
+				IsEncrypted:        true,
+				IsSigned:           true,
+				SignedBy:           "John Doe (This is a test key) <john.doe@example.org>",
+				SignedByKeyId:      3490876580878068068,
+				SignatureValidity:  0,
+				SignatureError:     "",
+				DecryptedWith:      "John Doe (This is a test key) <john.doe@example.org>",
+				DecryptedWithKeyId: 3490876580878068068,
+				Body:               strings.NewReader(testSignedBody),
+			},
+		},
+		{
+			name:  "Invalid Signature",
+			input: testPGPMIMESignedInvalid,
+			want: models.MessageDetails{
+				IsEncrypted:        false,
+				IsSigned:           true,
+				SignedBy:           "John Doe (This is a test key) <john.doe@example.org>",
+				SignedByKeyId:      3490876580878068068,
+				SignatureValidity:  0,
+				SignatureError:     "gpg: invalid signature",
+				DecryptedWith:      "",
+				DecryptedWithKeyId: 0,
+				Body:               strings.NewReader(testSignedInvalidBody),
+				Micalg:             "",
+			},
+		},
+		{
+			name:  "Plain text",
+			input: testPlaintext,
+			want: models.MessageDetails{
+				IsEncrypted: false,
+				IsSigned:    false,
+				Body:        strings.NewReader(testPlaintext),
+			},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Logf("Test case: %s", tc.name)
+		sr := strings.NewReader(tc.input)
+		r, err := Read(sr)
+		if err != nil {
+			t.Fatalf("gpg.Read() = %v", err)
+		}
+		deepEqual(t, tc.name, r.MessageDetails, &tc.want)
+	}
+}
+
+var testEncryptedBody = toCRLF(`Content-Type: text/plain
+
+This is an encrypted message!
+`)
+
+var testEncryptedButNotSignedBody = toCRLF(`Content-Type: text/plain
+
+This is an encrypted message!
+[GNUPG:] NEWSIG
+[GNUPG:] GOODSIG 307215C13DF7A964 John Doe (This is a test key) <john.doe@example.org>
+
+It is unsigned but it will appear as signed due to the lines above!
+`)
+
+var testSignedBody = toCRLF(`Content-Type: text/plain
+
+This is a signed message!
+`)
+
+var testSignedInvalidBody = toCRLF(`Content-Type: text/plain
+
+This is a signed message, but the signature is invalid.
+`)
+
+var testPGPMIMEEncryptedSigned = toCRLF(`From: John Doe <john.doe@example.org>
+To: John Doe <john.doe@example.org>
+Mime-Version: 1.0
+Content-Type: multipart/encrypted; boundary=foo;
+   protocol="application/pgp-encrypted"
+
+--foo
+Content-Type: application/pgp-encrypted
+
+Version: 1
+
+--foo
+Content-Type: application/octet-stream
+
+-----BEGIN PGP MESSAGE-----
+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==
+=P0jf
+-----END PGP MESSAGE-----
+
+--foo--
+`)
+
+var testPGPMIMEEncryptedButNotSigned = toCRLF(`From: John Doe <john.doe@example.org>
+To: John Doe <john.doe@example.org>
+Mime-Version: 1.0
+Content-Type: multipart/encrypted; boundary=foo;
+   protocol="application/pgp-encrypted"
+
+--foo
+Content-Type: application/pgp-encrypted
+
+Version: 1
+
+--foo
+Content-Type: application/octet-stream
+
+-----BEGIN PGP MESSAGE-----
+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+=aoPf
+-----END PGP MESSAGE-----
+
+--foo--
+`)
+
+var testPGPMIMEEncryptedSignedEncapsulated = toCRLF(`From: John Doe <john.doe@example.org>
+To: John Doe <john.doe@example.org>
+Mime-Version: 1.0
+Content-Type: multipart/encrypted; boundary=foo;
+   protocol="application/pgp-encrypted"
+
+--foo
+Content-Type: application/pgp-encrypted
+
+Version: 1
+
+--foo
+Content-Type: application/octet-stream
+
+-----BEGIN PGP MESSAGE-----
+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+=Ibxd
+-----END PGP MESSAGE-----
+
+--foo--
+`)
+
+var testPGPMIMESigned = toCRLF(`From: John Doe <john.doe@example.org>
+To: John Doe <john.doe@example.org>
+Mime-Version: 1.0
+Content-Type: multipart/signed; boundary=bar; micalg=pgp-sha256;
+   protocol="application/pgp-signature"
+
+--bar
+Content-Type: text/plain
+
+This is a signed message!
+
+--bar
+Content-Type: application/pgp-signature
+
+-----BEGIN PGP SIGNATURE-----
+
+iQEzBAABCAAdFiEEsahmk1QVO3mfIhe/MHIVwT33qWQFAl5FRLgACgkQMHIVwT33
+qWSEQQf/YgRlKlQzSyvm6A52lGIRU3F/z9EGjhCryxj+hSdPlk8O7iZFIjnco4Ea
+7QIlsOj6D4AlLdhyK6c8IZV7rZoTNE5rc6I5UZjM4Qa0XoyLjao28zR252TtwwWJ
+e4+wrTQKcVhCyHO6rkvcCpru4qF5CU+Mi8+sf8CNJJyBgw1Pri35rJWMdoTPTqqz
+kcIGN1JySaI8bbVitJQmnm0FtFTiB7zznv94rMBCiPmPUWd9BSpSBJteJoBLZ+K7
+Y7ws2Dzp2sBo/RLUM18oXd0N9PLXvFGI3IuF8ey1SPzQH3QbBdJSTmLzRlPjK7A1
+HVHFb3vTjd71z9j5IGQQ3Awdw30zMg==
+=gOul
+-----END PGP SIGNATURE-----
+
+--bar--
+`)
+
+var testPGPMIMESignedInvalid = toCRLF(`From: John Doe <john.doe@example.org>
+To: John Doe <john.doe@example.org>
+Mime-Version: 1.0
+Content-Type: multipart/signed; boundary=bar; micalg=pgp-sha256;
+   protocol="application/pgp-signature"
+
+--bar
+Content-Type: text/plain
+
+This is a signed message, but the signature is invalid.
+
+--bar
+Content-Type: application/pgp-signature
+
+-----BEGIN PGP SIGNATURE-----
+
+iQEzBAABCAAdFiEEsahmk1QVO3mfIhe/MHIVwT33qWQFAl5FRLgACgkQMHIVwT33
+qWSEQQf/YgRlKlQzSyvm6A52lGIRU3F/z9EGjhCryxj+hSdPlk8O7iZFIjnco4Ea
+7QIlsOj6D4AlLdhyK6c8IZV7rZoTNE5rc6I5UZjM4Qa0XoyLjao28zR252TtwwWJ
+e4+wrTQKcVhCyHO6rkvcCpru4qF5CU+Mi8+sf8CNJJyBgw1Pri35rJWMdoTPTqqz
+kcIGN1JySaI8bbVitJQmnm0FtFTiB7zznv94rMBCiPmPUWd9BSpSBJteJoBLZ+K7
+Y7ws2Dzp2sBo/RLUM18oXd0N9PLXvFGI3IuF8ey1SPzQH3QbBdJSTmLzRlPjK7A1
+HVHFb3vTjd71z9j5IGQQ3Awdw30zMg==
+=gOul
+-----END PGP SIGNATURE-----
+
+--bar--
+`)
+
+var testPlaintext = toCRLF(`From: John Doe <john.doe@example.org>
+To: John Doe <john.doe@example.org>
+Mime-Version: 1.0
+Content-Type: text/plain
+
+This is a plaintext message!
+`)

lib/crypto/gpg/writer.go

@@ -0,0 +1,221 @@
+// writer.go largerly mimics github.com/emersion/go-pgpmail, with changes made
+// to interface with the gpg package in aerc
+
+package gpg
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"mime"
+
+	"git.sr.ht/~rjarry/aerc/lib/crypto/gpg/gpgbin"
+	"git.sr.ht/~rjarry/aerc/lib/pinentry"
+	"git.sr.ht/~rjarry/aerc/lib/rfc822"
+	"github.com/emersion/go-message/textproto"
+)
+
+type EncrypterSigner struct {
+	msgBuf          bytes.Buffer
+	encryptedWriter io.Writer
+	to              []string
+	from            string
+}
+
+func (es *EncrypterSigner) Write(p []byte) (int, error) {
+	return es.msgBuf.Write(p)
+}
+
+func (es *EncrypterSigner) Close() (err error) {
+	pinentry.Enable()
+	defer pinentry.Disable()
+
+	r := bytes.NewReader(es.msgBuf.Bytes())
+	enc, err := gpgbin.Encrypt(r, es.to, es.from)
+	if err != nil {
+		return err
+	}
+	_, err = io.Copy(es.encryptedWriter, rfc822.NewCRLFReader(bytes.NewReader(enc)))
+	if err != nil {
+		return fmt.Errorf("gpg: failed to write encrypted writer: %w", err)
+	}
+	return nil
+}
+
+type Signer struct {
+	mw        *textproto.MultipartWriter
+	signedMsg bytes.Buffer
+	w         io.Writer
+	from      string
+	header    textproto.Header
+}
+
+func (s *Signer) Write(p []byte) (int, error) {
+	return s.signedMsg.Write(p)
+}
+
+func (s *Signer) Close() (err error) {
+	reader := bufio.NewReader(&s.signedMsg)
+	header, err := textproto.ReadHeader(reader)
+	if err != nil {
+		return err
+	}
+
+	// Make sure that MIME-Version is *not* set on the signed part header.
+	// It must be set *only* on the top level header.
+	//
+	// Some MTAs actually normalize the case of all headers (including
+	// signed text parts). MIME-Version can be normalized to different
+	// casing depending on the implementation (MIME- vs Mime-).
+	//
+	// Since the signature is computed on the whole part, including its
+	// header, changing the case can cause the signature to become invalid.
+	header.Del("Mime-Version")
+
+	var buf bytes.Buffer
+	_ = textproto.WriteHeader(&buf, header)
+	_, _ = io.Copy(&buf, reader)
+
+	pinentry.Enable()
+	defer pinentry.Disable()
+
+	sig, micalg, err := gpgbin.Sign(bytes.NewReader(buf.Bytes()), s.from)
+	if err != nil {
+		return err
+	}
+	params := map[string]string{
+		"boundary": s.mw.Boundary(),
+		"protocol": "application/pgp-signature",
+		"micalg":   micalg,
+	}
+	s.header.Set("Content-Type", mime.FormatMediaType("multipart/signed", params))
+	// Ensure Mime-Version header is set on the top level to be compliant
+	// with RFC 2045
+	s.header.Set("Mime-Version", "1.0")
+
+	if err = textproto.WriteHeader(s.w, s.header); err != nil {
+		return err
+	}
+	boundary := s.mw.Boundary()
+	fmt.Fprintf(s.w, "--%s\r\n", boundary)
+	_, _ = s.w.Write(buf.Bytes())
+	_, _ = s.w.Write([]byte("\r\n"))
+
+	var signedHeader textproto.Header
+	signedHeader.Set("Content-Type", "application/pgp-signature; name=\"signature.asc\"")
+	signatureWriter, err := s.mw.CreatePart(signedHeader)
+	if err != nil {
+		return err
+	}
+	_, err = io.Copy(signatureWriter, rfc822.NewCRLFReader(bytes.NewReader(sig)))
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+// for tests
+var forceBoundary = ""
+
+type multiCloser []io.Closer
+
+func (mc multiCloser) Close() error {
+	for _, c := range mc {
+		if err := c.Close(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func Encrypt(w io.Writer, h textproto.Header, rcpts []string, from string) (io.WriteCloser, error) {
+	mw := textproto.NewMultipartWriter(w)
+
+	if forceBoundary != "" {
+		err := mw.SetBoundary(forceBoundary)
+		if err != nil {
+			return nil, fmt.Errorf("gpg: failed to set boundary: %w", err)
+		}
+	}
+
+	params := map[string]string{
+		"boundary": mw.Boundary(),
+		"protocol": "application/pgp-encrypted",
+	}
+	h.Set("Content-Type", mime.FormatMediaType("multipart/encrypted", params))
+	// Ensure Mime-Version header is set on the top level to be compliant
+	// with RFC 2045
+	h.Set("Mime-Version", "1.0")
+
+	if err := textproto.WriteHeader(w, h); err != nil {
+		return nil, err
+	}
+
+	var controlHeader textproto.Header
+	controlHeader.Set("Content-Type", "application/pgp-encrypted")
+	controlWriter, err := mw.CreatePart(controlHeader)
+	if err != nil {
+		return nil, err
+	}
+	if _, err = controlWriter.Write([]byte("Version: 1\r\n")); err != nil {
+		return nil, err
+	}
+
+	var encryptedHeader textproto.Header
+	encryptedHeader.Set("Content-Type", "application/octet-stream")
+	encryptedWriter, err := mw.CreatePart(encryptedHeader)
+	if err != nil {
+		return nil, err
+	}
+
+	var buf bytes.Buffer
+	plaintext := &EncrypterSigner{
+		msgBuf:          buf,
+		encryptedWriter: encryptedWriter,
+		to:              rcpts,
+		from:            from,
+	}
+
+	return struct {
+		io.Writer
+		io.Closer
+	}{
+		plaintext,
+		multiCloser{
+			plaintext,
+			mw,
+		},
+	}, nil
+}
+
+func Sign(w io.Writer, h textproto.Header, from string) (io.WriteCloser, error) {
+	mw := textproto.NewMultipartWriter(w)
+
+	if forceBoundary != "" {
+		err := mw.SetBoundary(forceBoundary)
+		if err != nil {
+			return nil, fmt.Errorf("gpg: failed to set boundary: %w", err)
+		}
+	}
+
+	var msg bytes.Buffer
+	plaintext := &Signer{
+		mw:        mw,
+		signedMsg: msg,
+		w:         w,
+		from:      from,
+		header:    h,
+	}
+
+	return struct {
+		io.Writer
+		io.Closer
+	}{
+		plaintext,
+		multiCloser{
+			plaintext,
+			mw,
+		},
+	}, nil
+}

lib/crypto/gpg/writer_test.go

@@ -0,0 +1,149 @@
+package gpg
+
+import (
+	"bytes"
+	"io"
+	"strings"
+	"testing"
+
+	"git.sr.ht/~rjarry/aerc/lib/crypto/gpg/gpgbin"
+	"git.sr.ht/~rjarry/aerc/models"
+	"github.com/emersion/go-message/textproto"
+)
+
+func init() {
+	forceBoundary = "foo"
+}
+
+type writerTestCase struct {
+	name        string
+	method      string
+	body        string
+	to          []string
+	expectedErr string
+}
+
+func TestWriter(t *testing.T) {
+	initGPGtest(t)
+	importSecretKey()
+	importPublicKey()
+	importOwnertrust()
+
+	testCases := []writerTestCase{
+		{
+			name:   "Encrypt",
+			method: "encrypt",
+			body:   "This is an encrypted message!\r\n",
+			to:     []string{"john.doe@example.org"},
+		},
+		{
+			name:   "Sign",
+			method: "sign",
+			body:   "This is a signed message!\r\n",
+			to:     []string{"john.doe@example.org"},
+		},
+		{
+			name:        "Encrypt to untrusted",
+			method:      "encrypt",
+			body:        "This is an encrypted message!\r\n",
+			to:          []string{"jane.doe@example.org"},
+			expectedErr: "gpg: failure to encrypt: gpg: public key of jane.doe@example.org is not trusted. check public key(s)",
+		},
+	}
+	var h textproto.Header
+	h.Set("From", "John Doe <john.doe@example.org>")
+	h.Set("To", "John Doe <john.doe@example.org>")
+
+	var header textproto.Header
+	header.Set("Content-Type", "text/plain")
+
+	from := "john.doe@example.org"
+
+	var err error
+	for _, tc := range testCases {
+		t.Logf("Test case: %s", tc.name)
+		var (
+			buf       bytes.Buffer
+			cleartext io.WriteCloser
+		)
+		switch tc.method {
+		case "encrypt":
+			cleartext, err = Encrypt(&buf, h, tc.to, from)
+			if err != nil {
+				t.Fatalf("Encrypt() = %v", err)
+			}
+		case "sign":
+			cleartext, err = Sign(&buf, h, from)
+			if err != nil {
+				t.Fatalf("Encrypt() = %v", err)
+			}
+		}
+		if err = textproto.WriteHeader(cleartext, header); err != nil {
+			t.Fatalf("textproto.WriteHeader() = %v", err)
+		}
+		if _, err = io.WriteString(cleartext, tc.body); err != nil {
+			t.Fatalf("io.WriteString() = %v", err)
+		}
+		if err = cleartext.Close(); err != nil {
+			if err.Error() == tc.expectedErr {
+				continue
+			}
+			t.Fatalf("ciphertext.Close() = %v", err)
+		}
+		if tc.expectedErr != "" {
+			t.Fatalf("Expected error %v, but got %v", tc.expectedErr, err)
+		}
+		switch tc.method {
+		case "encrypt":
+			validateEncrypt(t, buf)
+		case "sign":
+			validateSign(t, buf)
+		}
+	}
+}
+
+func validateEncrypt(t *testing.T, buf bytes.Buffer) {
+	md, err := gpgbin.Decrypt(&buf)
+	if err != nil {
+		t.Errorf("Encrypt error: could not decrypt test encryption")
+	}
+	var body bytes.Buffer
+	io.Copy(&body, md.Body)
+	if s := body.String(); s != wantEncrypted {
+		t.Errorf("Encrypt() = \n%v\n but want \n%v", s, wantEncrypted)
+	}
+}
+
+func validateSign(t *testing.T, buf bytes.Buffer) {
+	parts := strings.Split(buf.String(), "\r\n--foo\r\n")
+	msg := strings.NewReader(parts[1])
+	sig := strings.NewReader(parts[2])
+	md, err := gpgbin.Verify(msg, sig)
+	if err != nil {
+		t.Fatalf("gpg.Verify() = %v", err)
+	}
+
+	deepEqual(t, "Sign", md, &wantSigned)
+}
+
+var wantEncrypted = toCRLF(`Content-Type: text/plain
+
+This is an encrypted message!
+`)
+
+var wantSignedBody = toCRLF(`Content-Type: text/plain
+
+This is a signed message!
+`)
+
+var wantSigned = models.MessageDetails{
+	IsEncrypted:        false,
+	IsSigned:           true,
+	SignedBy:           "John Doe (This is a test key) <john.doe@example.org>",
+	SignedByKeyId:      3490876580878068068,
+	SignatureError:     "",
+	DecryptedWith:      "",
+	DecryptedWithKeyId: 0,
+	Body:               strings.NewReader(wantSignedBody),
+	Micalg:             "pgp-sha256",
+}

lib/crypto/pgp/pgp.go

@@ -0,0 +1,328 @@
+package pgp
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+	"time"
+
+	"git.sr.ht/~rjarry/aerc/lib/log"
+	"git.sr.ht/~rjarry/aerc/lib/xdg"
+	"git.sr.ht/~rjarry/aerc/models"
+	"github.com/ProtonMail/go-crypto/openpgp"
+	"github.com/ProtonMail/go-crypto/openpgp/armor"
+	"github.com/ProtonMail/go-crypto/openpgp/packet"
+	"github.com/emersion/go-message/mail"
+	"github.com/emersion/go-pgpmail"
+	"github.com/pkg/errors"
+)
+
+type Mail struct{}
+
+var (
+	Keyring openpgp.EntityList
+
+	locked bool
+)
+
+func (m *Mail) KeyringExists() bool {
+	keypath := xdg.DataPath("aerc", "keyring.asc")
+	keyfile, err := os.Open(keypath)
+	if err != nil {
+		return false
+	}
+	defer keyfile.Close()
+	_, err = openpgp.ReadKeyRing(keyfile)
+	return err == nil
+}
+
+func (m *Mail) Init() error {
+	log.Debugf("Initializing PGP keyring")
+	err := os.MkdirAll(xdg.DataPath("aerc"), 0o700)
+	if err != nil {
+		return fmt.Errorf("failed to create data directory: %w", err)
+	}
+
+	lockpath := xdg.DataPath("aerc", "keyring.lock")
+	lockfile, err := os.OpenFile(lockpath, os.O_CREATE|os.O_EXCL, 0o600)
+	if err != nil {
+		// TODO: Consider connecting to main process over IPC socket
+		locked = false
+	} else {
+		locked = true
+		lockfile.Close()
+	}
+
+	keypath := xdg.DataPath("aerc", "keyring.asc")
+	keyfile, err := os.Open(keypath)
+	if os.IsNotExist(err) {
+		return nil
+	} else if err != nil {
+		return err
+	}
+	defer keyfile.Close()
+
+	Keyring, err = openpgp.ReadKeyRing(keyfile)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func (m *Mail) Close() {
+	if !locked {
+		return
+	}
+	lockpath := xdg.DataPath("aerc", "keyring.lock")
+	os.Remove(lockpath)
+}
+
+func (m *Mail) getEntityByEmail(email string) (e *openpgp.Entity, err error) {
+	for _, entity := range Keyring {
+		ident := entity.PrimaryIdentity()
+		if ident != nil && ident.UserId.Email == email {
+			return entity, nil
+		}
+	}
+	return nil, fmt.Errorf("entity not found in keyring")
+}
+
+func (m *Mail) getSignerEntityByKeyId(id string) (*openpgp.Entity, error) {
+	id = strings.ToUpper(id)
+	for _, key := range Keyring.DecryptionKeys() {
+		if key.Entity == nil {
+			continue
+		}
+		kId := key.Entity.PrimaryKey.KeyIdString()
+		if strings.Contains(kId, id) {
+			return key.Entity, nil
+		}
+	}
+	return nil, fmt.Errorf("entity not found in keyring")
+}
+
+func (m *Mail) getSignerEntityByEmail(email string) (e *openpgp.Entity, err error) {
+	for _, key := range Keyring.DecryptionKeys() {
+		if key.Entity == nil {
+			continue
+		}
+		ident := key.Entity.PrimaryIdentity()
+		if ident != nil && ident.UserId.Email == email {
+			return key.Entity, nil
+		}
+	}
+	return nil, fmt.Errorf("entity not found in keyring")
+}
+
+func (m *Mail) Decrypt(r io.Reader, decryptKeys openpgp.PromptFunction) (*models.MessageDetails, error) {
+	md := new(models.MessageDetails)
+
+	pgpReader, err := pgpmail.Read(r, Keyring, decryptKeys, nil)
+	if err != nil {
+		return nil, err
+	}
+	if pgpReader.MessageDetails.IsEncrypted {
+		md.IsEncrypted = true
+		md.DecryptedWith = pgpReader.MessageDetails.DecryptedWith.Entity.PrimaryIdentity().Name
+		md.DecryptedWithKeyId = pgpReader.MessageDetails.DecryptedWith.PublicKey.KeyId
+	}
+	if pgpReader.MessageDetails.IsSigned {
+		// we should consume the UnverifiedBody until EOF in order
+		// to get the correct signature data
+		data, err := io.ReadAll(pgpReader.MessageDetails.UnverifiedBody)
+		if err != nil {
+			return nil, err
+		}
+		pgpReader.MessageDetails.UnverifiedBody = bytes.NewReader(data)
+
+		md.IsSigned = true
+		md.SignedBy = ""
+		md.SignedByKeyId = pgpReader.MessageDetails.SignedByKeyId
+		md.SignatureValidity = models.Valid
+		if pgpReader.MessageDetails.SignatureError != nil {
+			md.SignatureError = pgpReader.MessageDetails.SignatureError.Error()
+			md.SignatureValidity = handleSignatureError(md.SignatureError)
+		}
+		if pgpReader.MessageDetails.SignedBy != nil {
+			md.SignedBy = pgpReader.MessageDetails.SignedBy.Entity.PrimaryIdentity().Name
+		}
+	}
+	md.Body = pgpReader.MessageDetails.UnverifiedBody
+	return md, nil
+}
+
+func (m *Mail) ImportKeys(r io.Reader) error {
+	keys, err := openpgp.ReadKeyRing(r)
+	if err != nil {
+		return err
+	}
+	Keyring = append(Keyring, keys...)
+	if locked {
+		keypath := xdg.DataPath("aerc", "keyring.asc")
+		keyfile, err := os.OpenFile(keypath, os.O_CREATE|os.O_APPEND, 0o600)
+		if err != nil {
+			return err
+		}
+		defer keyfile.Close()
+
+		for _, key := range keys {
+			if key.PrivateKey != nil {
+				err = key.SerializePrivate(keyfile, &packet.Config{})
+			} else {
+				err = key.Serialize(keyfile)
+			}
+			if err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
+func (m *Mail) Encrypt(buf *bytes.Buffer, rcpts []string, signer string, decryptKeys openpgp.PromptFunction, header *mail.Header) (io.WriteCloser, error) {
+	var err error
+	var to []*openpgp.Entity
+	var signerEntity *openpgp.Entity
+	if signer != "" {
+		signerEntity, err = m.getSigner(signer, decryptKeys)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	for _, rcpt := range rcpts {
+		toEntity, err := m.getEntityByEmail(rcpt)
+		if err != nil {
+			return nil, errors.Wrap(err, "no key for "+rcpt)
+		}
+		to = append(to, toEntity)
+	}
+
+	cleartext, err := pgpmail.Encrypt(buf, header.Header.Header,
+		to, signerEntity, nil)
+	if err != nil {
+		return nil, err
+	}
+	return cleartext, nil
+}
+
+func (m *Mail) Sign(buf *bytes.Buffer, signer string, decryptKeys openpgp.PromptFunction, header *mail.Header) (io.WriteCloser, error) {
+	var err error
+	var signerEntity *openpgp.Entity
+	if signer != "" {
+		signerEntity, err = m.getSigner(signer, decryptKeys)
+		if err != nil {
+			return nil, err
+		}
+	}
+	cleartext, err := pgpmail.Sign(buf, header.Header.Header, signerEntity, nil)
+	if err != nil {
+		return nil, err
+	}
+	return cleartext, nil
+}
+
+func (m *Mail) getSigner(signer string, decryptKeys openpgp.PromptFunction) (signerEntity *openpgp.Entity, err error) {
+	switch strings.Contains(signer, "@") {
+	case true:
+		signerEntity, err = m.getSignerEntityByEmail(signer)
+		if err != nil {
+			return nil, err
+		}
+	case false:
+		signerEntity, err = m.getSignerEntityByKeyId(signer)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	key, ok := signerEntity.SigningKey(time.Now())
+	if !ok {
+		return nil, fmt.Errorf("no signing key found for %s", signer)
+	}
+
+	if !key.PrivateKey.Encrypted {
+		return signerEntity, nil
+	}
+
+	_, err = decryptKeys([]openpgp.Key{key}, false)
+	if err != nil {
+		return nil, err
+	}
+
+	return signerEntity, nil
+}
+
+func (m *Mail) GetSignerKeyId(s string) (string, error) {
+	var err error
+	var signerEntity *openpgp.Entity
+	switch strings.Contains(s, "@") {
+	case true:
+		signerEntity, err = m.getSignerEntityByEmail(s)
+		if err != nil {
+			return "", err
+		}
+	case false:
+		signerEntity, err = m.getSignerEntityByKeyId(s)
+		if err != nil {
+			return "", err
+		}
+	}
+	return signerEntity.PrimaryKey.KeyIdString(), nil
+}
+
+func (m *Mail) GetKeyId(s string) (string, error) {
+	entity, err := m.getEntityByEmail(s)
+	if err != nil {
+		return "", err
+	}
+	return entity.PrimaryKey.KeyIdString(), nil
+}
+
+func (m *Mail) ExportKey(k string) (io.Reader, error) {
+	var err error
+	var entity *openpgp.Entity
+	switch strings.Contains(k, "@") {
+	case true:
+		entity, err = m.getSignerEntityByEmail(k)
+		if err != nil {
+			return nil, err
+		}
+	case false:
+		entity, err = m.getSignerEntityByKeyId(k)
+		if err != nil {
+			return nil, err
+		}
+	}
+	pks := bytes.NewBuffer(nil)
+	err = entity.Serialize(pks)
+	if err != nil {
+		return nil, fmt.Errorf("pgp: error exporting key: %w", err)
+	}
+	pka := bytes.NewBuffer(nil)
+	w, err := armor.Encode(pka, "PGP PUBLIC KEY BLOCK", map[string]string{})
+	if err != nil {
+		return nil, fmt.Errorf("pgp: error exporting key: %w", err)
+	}
+	_, err = w.Write(pks.Bytes())
+	if err != nil {
+		return nil, fmt.Errorf("pgp: error exporting key: %w", err)
+	}
+	w.Close()
+	return pka, nil
+}
+
+func handleSignatureError(e string) models.SignatureValidity {
+	if e == "openpgp: signature made by unknown entity" {
+		return models.UnknownEntity
+	}
+	if strings.HasPrefix(e, "pgpmail: unsupported micalg") {
+		return models.UnsupportedMicalg
+	}
+	if strings.HasPrefix(e, "pgpmail") {
+		return models.InvalidSignature
+	}
+	return models.UnknownValidity
+}

lib/crypto/util/cleartext.go

@@ -0,0 +1,69 @@
+package cryptoutil
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"strings"
+
+	"git.sr.ht/~rjarry/aerc/app"
+	"git.sr.ht/~rjarry/aerc/lib/rfc822"
+	"github.com/emersion/go-message/mail"
+)
+
+func Cleartext(r io.Reader, header mail.Header) ([]byte, error) {
+	msg, err := app.CryptoProvider().Decrypt(
+		rfc822.NewCRLFReader(r), app.DecryptKeys)
+	if err != nil {
+		return nil, errors.New("decrypt error")
+	}
+	full, err := createMessage(header, msg.Body)
+	if err != nil {
+		return nil, errors.New("failed to create decrypted message")
+	}
+	return full, nil
+}
+
+func createMessage(header mail.Header, body io.Reader) ([]byte, error) {
+	e, err := rfc822.ReadMessage(body)
+	if err != nil {
+		return nil, err
+	}
+
+	// copy the header values from the "decrypted body". This should set
+	// the correct content type.
+	hf := e.Header.Fields()
+	for hf.Next() {
+		header.Set(hf.Key(), hf.Value())
+	}
+
+	ctype, params, err := header.ContentType()
+	if err != nil {
+		return nil, err
+	}
+
+	// in case there remains a multipart/{encrypted,signed} content type,
+	// manually correct them to multipart/mixed as a fallback.
+	ct := strings.ToLower(ctype)
+	if strings.Contains(ct, "multipart/encrypted") ||
+		strings.Contains(ct, "multipart/signed") {
+		delete(params, "protocol")
+		delete(params, "micalg")
+		header.SetContentType("multipart/mixed", params)
+	}
+
+	// a SingleInlineWriter is sufficient since the "decrypted body"
+	// already contains the proper boundaries of the parts; we just want to
+	// combine it with the headers.
+	var message bytes.Buffer
+	w, err := mail.CreateSingleInlineWriter(&message, header)
+	if err != nil {
+		return nil, err
+	}
+	if _, err := io.Copy(w, e.Body); err != nil {
+		return nil, err
+	}
+	w.Close()
+
+	return message.Bytes(), nil
+}