feat: implement ecdsa keyfile signing support

internal/assuan/assuan.go

@@ -95,8 +95,8 @@ func New(rw io.ReadWriter, log *zap.Logger, ks ...KeyService) *Assuan {
 					}
 					keyFound, keygrip, err = haveKey(ks, keygrips)
 					if err != nil {
-						_, _ = io.WriteString(rw, "ERR 1 couldn't check for keygrip\n")
-						return fmt.Errorf("couldn't check for keygrip: %v", err)
+						_, _ = io.WriteString(rw, "ERR 1 couldn't match keygrip\n")
+						return fmt.Errorf("couldn't match keygrip: %v", err)
 					}
 					if keyFound {
 						_, err = io.WriteString(rw,
@@ -108,6 +108,38 @@ func New(rw io.ReadWriter, log *zap.Logger, ks ...KeyService) *Assuan {
 				case scd:
 					// ignore scdaemon requests
 					_, err = io.WriteString(rw, "ERR 100696144 No such device <SCD>\n")
+				case readkey:
+					// READKEY argument is a keygrip
+					// return information about the given key
+					keygrips, err = hexDecode(assuan.data...)
+					if err != nil {
+						return fmt.Errorf("couldn't decode keygrips: %v", err)
+					}
+					var signer crypto.Signer
+					for _, k := range ks {
+						signer, err = k.GetSigner(keygrips[0])
+						if err == nil {
+							break
+						}
+					}
+					if signer == nil {
+						_, _ = io.WriteString(rw, "ERR 1 couldn't match keygrip\n")
+						return fmt.Errorf("couldn't match keygrip: %v", err)
+					}
+					readKeyData, err := readKeyData(signer.Public())
+					if err != nil {
+						_, _ = io.WriteString(rw, "ERR 1 couldn't get key data\n")
+						return fmt.Errorf("couldn't get key data: %v", err)
+					}
+					_, err = io.WriteString(rw, readKeyData)
+				case setkeydesc:
+					// ignore this event since we don't currently use the client's
+					// description in the prompt
+					_, err = io.WriteString(rw, "OK\n")
+				case passwd:
+					// ignore this event since we assume that if the key is decrypted the
+					// user has permissions
+					_, err = io.WriteString(rw, "OK\n")
 				default:
 					return fmt.Errorf("unknown event: %v", e)
 				}

internal/assuan/assuan_test.go

@@ -468,3 +468,89 @@ func TestSignRSAKeyfile(t *testing.T) {
 		})
 	}
 }
+
+func TestReadKey(t *testing.T) {
+	var testCases = map[string]struct {
+		keyPath string
+		input   []string
+		expect  []string
+	}{
+		"rsa": {
+			keyPath: "testdata/private-subkeys",
+			input: []string{
+				"RESET\n",
+				"READKEY EA8E47C68880D1620FF10CC7CB91E5605758CC8D\n",
+				"SETKEYDESC Please+enter+the+passphrase+to+unlock+the+OpenPGP+secret+key:%0A%22foo@example.com%22%0A3072-bit+RSA+key,+ID+AD024955495A860B,%0Acreated+2021-08-07.%0A\n",
+				"PASSWD  --verify B242AADA8260B77F0F5069F127D6B7E4F44B5FAA\n",
+			},
+			expect: []string{
+				"OK Pleased to meet you, process 123456789\n",
+				"OK\n",
+				"\x44\x20\x28\x31\x30\x3a\x70\x75\x62\x6c\x69\x63\x2d\x6b\x65\x79\x28\x33\x3a\x72\x73\x61\x28\x31\x3a\x6e\x33\x38\x35\x3a\x00\xbe\xe3\x07\x13\x3c\xae\xd7\x10\xe4\xdd\x84\x20\xc3\x96\xba\xdc\xe0\x09\x6d\xce\xbf\xc2\x55\xe3\x24\x4b\x96\x76\xf5\xd9\xcf\x02\x58\xbf\x69\x16\xcf\x2a\xa4\xdc\x8c\x82\x57\xb0\x5a\x16\x74\xf6\xd5\x21\xee\xdc\xce\x89\x64\xcd\x66\xf5\xee\x89\x09\xa6\x44\xce\x9d\x03\xc0\x44\x4d\x90\xdf\x60\x07\xc6\xf8\x2f\x98\x07\x9b\x95\xb3\xe5\x16\xb8\x1d\x59\xd1\x19\x97\x4c\x36\xbd\xce\xc7\xe1\x17\x7d\x6a\xdc\xa0\x16\x93\x2c\x91\x70\x7c\xf2\x1b\xd9\x5b\x4a\xd5\x46\x65\x9e\x09\xcc\x38\xbe\x86\xbd\xdd\xbf\x91\x7c\x04\x6c\xba\x38\xaf\xe6\xb4\xbb\x38\xa0\x3b\x3b\x07\x60\x2e\xbb\x6d\x45\x31\x1b\x0e\x37\x85\xdb\xa0\x93\xa5\x5c\xf6\xde\x69\x9e\x66\x3e\xa2\x3c\xf9\x59\x4b\x18\xc5\x5b\xdb\x4d\xa8\xcb\x80\xe6\xf9\x52\x1e\x2c\xb8\xab\xac\x7b\x14\xe9\xa8\x6a\x6d\xc6\x51\xb1\x74\x02\xa5\x13\x58\x66\x25\x32\x35\x3b\xed\xe3\x63\xb2\x7a\x8f\x93\x9b\x2c\x04\xdd\xf6\x56\xa9\xb2\x40\x34\xa9\x9b\xe6\xe1\x33\x5b\xe2\xa8\x12\x18\x48\x4e\xa6\xb7\xdd\xbf\xf0\xd2\x70\x18\x7b\x9d\xd3\xec\x55\x5f\xb7\xe8\x07\x1a\x90\x1e\xe4\x68\xa9\x67\x5c\xda\xe9\xea\x29\x19\xeb\x4c\x1c\x6a\x44\x06\x39\xea\xa2\xda\x29\x49\xdf\xd1\x00\x86\x5a\xe2\xe2\xe0\xa4\xa6\x2f\x74\x57\xbc\x78\x75\xa9\xd6\x81\xb1\x11\xbd\xca\x08\x17\x56\x9f\x42\xfe\x3f\x1a\xd1\x7e\xb2\x90\x27\x8a\x31\x8c\x88\x32\x3a\x28\x90\x10\xaf\x4d\xf8\x51\x94\x6f\x29\x21\xa4\x74\xfb\x65\x24\xcc\x5f\x48\x68\xdd\xff\x41\xb2\xe4\xa7\xbf\x25\x32\x35\xbe\x8d\xd8\x9f\x95\xd3\x7d\xe8\xf2\x4b\x78\xa1\x93\x29\xa5\x8b\xfa\x8d\x83\x6e\xbf\x9c\x5b\x1e\x38\xe3\x47\x60\xc6\xde\x4a\xd0\x78\x80\x6f\x20\xbf\xfd\x63\x12\x6f\xdd\xa3\x81\xf5\xf9\x29\x28\x31\x3a\x65\x33\x3a\x01\x00\x01\x29\x29\x29\x0a",
+				"OK\n",
+				"OK\n",
+			},
+		},
+		"ecdsa": {
+			keyPath: "testdata/private-subkeys",
+			input: []string{
+				"RESET\n",
+				"READKEY 586A6F8E9CD839FD26D868D084DDFEBB0CCC7EF0\n",
+				"SETKEYDESC Please+enter+the+passphrase+to+unlock+the+OpenPGP+secret+key:%0A%22foo@example.com%22%0A3072-bit+RSA+key,+ID+AD024955495A860B,%0Acreated+2021-08-07.%0A\n",
+				"PASSWD  --verify B242AADA8260B77F0F5069F127D6B7E4F44B5FAA\n",
+			},
+			expect: []string{
+				"OK Pleased to meet you, process 123456789\n",
+				"OK\n",
+				"\x44\x20\x28\x31\x30\x3a\x70\x75\x62\x6c\x69\x63\x2d\x6b\x65\x79\x28\x33\x3a\x65\x63\x63\x28\x35\x3a\x63\x75\x72\x76\x65\x31\x30\x3a\x4e\x49\x53\x54\x20\x50\x2d\x32\x35\x36\x29\x28\x31\x3a\x71\x36\x35\x3a\x04\xbf\x06\xac\x95\x31\xae\x04\x93\x98\x21\x03\x83\x35\x9d\x4e\x58\x92\xa2\xe9\x24\x2f\x76\x54\x67\x45\xf0\x35\x28\xf4\x47\x14\x59\x26\x0c\xf9\x1b\x24\x10\x6b\x07\xe3\x33\x05\x4c\xcb\x96\xe2\xdd\x96\xd4\x0f\x3e\x4b\xd7\x67\x44\xdb\x82\x42\x24\xe6\x8b\x7f\xa6\x29\x29\x29\x0a",
+				"OK\n",
+				"OK\n",
+			},
+		},
+	}
+	for name, tc := range testCases {
+		t.Run(name, func(tt *testing.T) {
+			ctrl := gomock.NewController(tt)
+			defer ctrl.Finish()
+			// no securityKeys available
+			mockPES := mock.NewMockPINEntryService(ctrl)
+			log, err := zap.NewDevelopment()
+			if err != nil {
+				tt.Fatal(err)
+			}
+			keyfileService, err := gpg.New(log, mockPES, tc.keyPath)
+			if err != nil {
+				tt.Fatal(err)
+			}
+			// mockConn is a pair of buffers that the assuan statemachine reads/write
+			// to/from.
+			mockConn := MockConn{}
+			a := assuan.New(&mockConn, log, keyfileService)
+			// write all the lines into the statemachine
+			for _, in := range tc.input {
+				if _, err := mockConn.ReadBuf.WriteString(in); err != nil {
+					tt.Fatal(err)
+				}
+			}
+			// start the state machine
+			if err := a.Run(); err != nil {
+				tt.Fatal(err)
+			}
+			// check the responses
+			for _, expected := range tc.expect {
+				//spew.Dump(mockConn.WriteBuf.String())
+				line, err := mockConn.WriteBuf.ReadString(byte('\n'))
+				if err != nil && err != io.EOF {
+					tt.Fatal(err)
+				}
+				if line != expected {
+					fmt.Println("got")
+					spew.Dump(line)
+					fmt.Println("expected")
+					spew.Dump(expected)
+					tt.Fatalf("error")
+				}
+			}
+		})
+	}
+}

internal/assuan/fsm.go

@@ -29,6 +29,8 @@ const (
 	setkey
 	pkdecrypt
 	scd
+	readkey
+	passwd
 )
 
 //go:generate enumer -type=State -text -transform upper
@@ -102,6 +104,18 @@ var assuanTransitions = []fsm.Transition{
 		Src:   fsm.State(connected),
 		Event: fsm.Event(scd),
 		Dst:   fsm.State(connected),
+	}, {
+		Src:   fsm.State(connected),
+		Event: fsm.Event(readkey),
+		Dst:   fsm.State(connected),
+	}, {
+		Src:   fsm.State(connected),
+		Event: fsm.Event(setkeydesc),
+		Dst:   fsm.State(connected),
+	}, {
+		Src:   fsm.State(connected),
+		Event: fsm.Event(passwd),
+		Dst:   fsm.State(connected),
 	},
 	// signing transitions
 	{

internal/assuan/readkey.go

@@ -0,0 +1,39 @@
+package assuan
+
+import (
+	"crypto"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rsa"
+	"fmt"
+	"math/big"
+)
+
+// readKeyData returns information about the given key in a libgcrypt-specific
+// format
+func readKeyData(pub crypto.PublicKey) (string, error) {
+	switch k := pub.(type) {
+	case *rsa.PublicKey:
+		n := k.N.Bytes()
+		nLen := len(n)           // need the actual byte length before munging
+		n = percentEncodeSExp(n) // ugh
+		ei := new(big.Int)
+		ei.SetInt64(int64(k.E))
+		e := ei.Bytes()
+		// prefix the key with a null byte for compatibility
+		return fmt.Sprintf("D (10:public-key(3:rsa(1:n%d:\x00%s)(1:e%d:%s)))\n",
+			nLen+1, n, len(e), e), nil
+	case *ecdsa.PublicKey:
+		switch k.Curve {
+		case elliptic.P256():
+			q := elliptic.Marshal(k.Curve, k.X, k.Y)
+			return fmt.Sprintf(
+				"D (10:public-key(3:ecc(5:curve10:NIST P-256)(1:q%d:%s)))\n",
+				len(q), q), nil
+		default:
+			return "", fmt.Errorf("unsupported curve: %T", k.Curve)
+		}
+	default:
+		return "", nil
+	}
+}