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Add basic support for 5.7.0+ yubikeys that default to AES192 management keys #148

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Add basic support for 5.7.0+ yubikeys that default to AES192 management keys #148

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106 changes: 67 additions & 39 deletions piv/piv.go
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,8 @@ package piv

import (
"bytes"
"crypto/aes"
"crypto/cipher"
"crypto/des"
"crypto/rand"
"encoding/asn1"
Expand All @@ -26,23 +28,6 @@ import (
"math/big"
)

var (
// DefaultPIN for the PIV applet. The PIN is used to change the Management Key,
// and slots can optionally require it to perform signing operations.
DefaultPIN = "123456"
// DefaultPUK for the PIV applet. The PUK is only used to reset the PIN when
// the card's PIN retries have been exhausted.
DefaultPUK = "12345678"
// DefaultManagementKey for the PIV applet. The Management Key is a Triple-DES
// key required for slot actions such as generating keys, setting certificates,
// and signing.
DefaultManagementKey = [24]byte{
0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
}
)

// Cards lists all smart cards available via PC/SC interface. Card names are
// strings describing the key, such as "Yubico Yubikey NEO OTP+U2F+CCID 00 00".
//
Expand All @@ -59,6 +44,7 @@ const (
// https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-78-4.pdf#page=17
algTag = 0x80
alg3DES = 0x03
algAES192 = 0x0a
algRSA1024 = 0x06
algRSA2048 = 0x07
algECCP256 = 0x11
Expand Down Expand Up @@ -96,6 +82,24 @@ const (
insGetMetadata = 0xf7
)

var (
// DefaultPIN for the PIV applet. The PIN is used to change the Management Key,
// and slots can optionally require it to perform signing operations.
DefaultPIN = "123456"
// DefaultPUK for the PIV applet. The PUK is only used to reset the PIN when
// the card's PIN retries have been exhausted.
DefaultPUK = "12345678"
// DefaultManagementKey for the PIV applet. The Management Key is a Triple-DES
// key required for slot actions such as generating keys, setting certificates,
// and signing.
DefaultManagementKey = [24]byte{
0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
}
DefaultManagementKeyType byte = alg3DES
)

// YubiKey is an exclusive open connection to a YubiKey smart card. While open,
// no other process can query the given card.
//
Expand Down Expand Up @@ -176,6 +180,12 @@ func (c *client) Open(card string) (*YubiKey, error) {
return nil, fmt.Errorf("getting yubikey version: %w", err)
}
yk.version = v

// If yubikey is 5.7.0 or newer, management key default is AES192
if int(v.major) >= 5 && int(v.minor) >= 7 {
DefaultManagementKeyType = algAES192
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can this be on the client rather than global to the package?

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I tested with v4.3.7, v5.4.3, and v5.7.1 yubikeys. It has been possible for users to change the type of management key since 5.4, but the default has remained 3DES. I decided in lieu of this minimal fix, I would take things a step further and just implement dynamic support for all the supported management key types. Closing this PR in favor of : #149

}

if c.Rand != nil {
yk.rand = c.Rand
} else {
Expand Down Expand Up @@ -368,10 +378,18 @@ func ykAuthenticate(tx *scTx, key [24]byte, rand io.Reader) error {
// https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-73-4.pdf#page=92
// https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=918402#page=114

var challengeLength byte
switch DefaultManagementKeyType {
case algAES192:
challengeLength = 16
default:
challengeLength = 8
}

// request a witness
cmd := apdu{
instruction: insAuthenticate,
param1: alg3DES,
param1: DefaultManagementKeyType,
param2: keyCardManagement,
data: []byte{
0x7c, // Dynamic Authentication Template tag
Expand All @@ -389,45 +407,55 @@ func ykAuthenticate(tx *scTx, key [24]byte, rand io.Reader) error {
}
if !bytes.Equal(resp[:4], []byte{
0x7c,
0x0a,
0x80, // 'Witness'
0x08, // Tag length
challengeLength + 2,
0x80, // 'Witness'
challengeLength, // Tag length
}) {
return fmt.Errorf("invalid authentication object header: %x", resp[:4])
}

cardChallenge := resp[4 : 4+8]
cardResponse := make([]byte, 8)

block, err := des.NewTripleDESCipher(key[:])
if err != nil {
return fmt.Errorf("creating triple des block cipher: %v", err)
var block cipher.Block
switch DefaultManagementKeyType {
case algAES192:
block, err = aes.NewCipher(key[:])
if err != nil {
return fmt.Errorf("creating aes block cipher: %v", err)
}
default:
block, err = des.NewTripleDESCipher(key[:])
if err != nil {
return fmt.Errorf("creating des block cipher: %v", err)
}
}

cardChallenge := resp[4 : 4+challengeLength]
cardResponse := make([]byte, challengeLength)

block.Decrypt(cardResponse, cardChallenge)

challenge := make([]byte, 8)
challenge := make([]byte, challengeLength)
if _, err := io.ReadFull(rand, challenge); err != nil {
return fmt.Errorf("reading rand data: %v", err)
}
response := make([]byte, 8)
response := make([]byte, challengeLength)
block.Encrypt(response, challenge)

data := []byte{
0x7c, // Dynamic Authentication Template tag
20, // 2+8+2+8
0x80, // 'Witness'
0x08, // Tag length
(challengeLength + 2) * 2,
0x80, // 'Witness'
challengeLength, // Tag length
}
data = append(data, cardResponse...)
data = append(data,
0x81, // 'Challenge'
0x08, // Tag length
0x81, // 'Challenge'
challengeLength, // Tag length
)
data = append(data, challenge...)

cmd = apdu{
instruction: insAuthenticate,
param1: alg3DES,
param1: DefaultManagementKeyType,
param2: keyCardManagement,
data: data,
}
Expand All @@ -440,13 +468,13 @@ func ykAuthenticate(tx *scTx, key [24]byte, rand io.Reader) error {
}
if !bytes.Equal(resp[:4], []byte{
0x7c,
0x0a,
challengeLength + 2,
0x82, // 'Response'
0x08,
challengeLength,
}) {
return fmt.Errorf("response invalid authentication object header: %x", resp[:4])
}
if !bytes.Equal(resp[4:4+8], response) {
if !bytes.Equal(resp[4:4+challengeLength], response) {
return fmt.Errorf("challenge failed")
}

Expand Down Expand Up @@ -482,7 +510,7 @@ func ykSetManagementKey(tx *scTx, key [24]byte, touch bool) error {
param1: 0xff,
param2: 0xff,
data: append([]byte{
alg3DES, keyCardManagement, 24,
DefaultManagementKeyType, keyCardManagement, 24,
}, key[:]...),
}
if touch {
Expand Down
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