piv

package
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 Go to latest Published: Mar 16, 2023 License: Apache-2.0 Imports: 22 Imported by: 59

Documentation

Overview

Package piv implements management functionality for the YubiKey PIV applet.

Index

Constants

View Source 
const (
	FormfactorUSBAKeychain          = 0x1
	FormfactorUSBANano              = 0x2
	FormfactorUSBCKeychain          = 0x3
	FormfactorUSBCNano              = 0x4
	FormfactorUSBCLightningKeychain = 0x5

	FormfactorUSBAKeychainFIPS          = 0x81
	FormfactorUSBANanoFIPS              = 0x82
	FormfactorUSBCKeychainFIPS          = 0x83
	FormfactorUSBCNanoFIPS              = 0x84
	FormfactorUSBCLightningKeychainFIPS = 0x85
)

Formfactors recognized by this package. See the reference for more information: https://developers.yubico.com/yubikey-manager/Config_Reference.html#_form_factor

Variables

View Source 
var (
	SlotAuthentication     = Slot{0x9a, 0x5fc105}
	SlotSignature          = Slot{0x9c, 0x5fc10a}
	SlotCardAuthentication = Slot{0x9e, 0x5fc101}
	SlotKeyManagement      = Slot{0x9d, 0x5fc10b}
)

Slot combinations pre-defined by this package.

Object IDs are specified in NIST 800-73-4 section 4.3: https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-73-4.pdf#page=30

Key IDs are specified in NIST 800-73-4 section 5.1: https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-73-4.pdf#page=32

View Source 
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,
	}
)
View Source 
var ErrNotFound = errors.New("data object or application not found")

ErrNotFound is returned when the requested object on the smart card is not found.

Functions

func Cards 

func Cards() ([]string, error)

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".

Card names depend on the operating system and what port a card is plugged into. To uniquely identify a card, use its serial number.

See: https://ludovicrousseau.blogspot.com/2010/05/what-is-in-pcsc-reader-name.html

Types

type Algorithm 

type Algorithm int

Algorithm represents a specific algorithm and bit size supported by the PIV specification. 

const (
	AlgorithmEC256 Algorithm = iota + 1
	AlgorithmEC384
	AlgorithmEd25519
	AlgorithmRSA1024
	AlgorithmRSA2048
)

Algorithms supported by this package. Note that not all cards will support every algorithm.

AlgorithmEd25519 is currently only implemented by SoloKeys.

For algorithm discovery, see: https://github.com/ericchiang/piv-go/issues/1

type Attestation 

type Attestation struct {
	// Version of the YubiKey's firmware.
	Version Version
	// Serial is the YubiKey's serial number.
	Serial uint32
	// Formfactor indicates the physical type of the YubiKey.
	//
	// Formfactor may be empty Formfactor(0) for some YubiKeys.
	Formfactor Formfactor

	// PINPolicy set on the slot.
	PINPolicy PINPolicy
	// TouchPolicy set on the slot.
	TouchPolicy TouchPolicy

	// Slot is the inferred slot the attested key resides in based on the
	// common name in the attestation. If the slot cannot be determined,
	// this field will be an empty struct.
	Slot Slot
}

Attestation returns additional information about a key attested to be generated on a card. See https://developers.yubico.com/PIV/Introduction/PIV_attestation.html for more information.

func Verify 

func Verify(attestationCert, slotCert *x509.Certificate) (*Attestation, error)

Verify proves that a key was generated on a YubiKey. It ensures the slot and YubiKey certificate chains up to the Yubico CA, parsing additional information out of the slot certificate, such as the touch and PIN policies of a key.

type AuthErr added in v1.3.0 

type AuthErr struct {
	// Retries is the number of retries remaining if this error resulted from a retriable
	// authentication attempt.  If the authentication method is blocked or does not support
	// retries, this will be 0.
	Retries int
}

AuthErr is an error indicating an authentication error occurred (wrong PIN or blocked).

func (AuthErr) Error added in v1.3.0 

func (v AuthErr) Error() string

type ECDSAPrivateKey added in v1.6.0 

type ECDSAPrivateKey struct {
	// contains filtered or unexported fields
}

ECDSAPrivateKey is a crypto.PrivateKey implementation for ECDSA keys. It implements crypto.Signer and the method SharedKey performs Diffie-Hellman key agreements.

Keys returned by YubiKey.PrivateKey() may be type asserted to *ECDSAPrivateKey, if the slot contains an ECDSA key.

func (*ECDSAPrivateKey) Public added in v1.6.0 

func (k *ECDSAPrivateKey) Public() crypto.PublicKey

Public returns the public key associated with this private key.

func (*ECDSAPrivateKey) SharedKey added in v1.6.0 

func (k *ECDSAPrivateKey) SharedKey(peer *ecdsa.PublicKey) ([]byte, error)

SharedKey performs a Diffie-Hellman key agreement with the peer to produce a shared secret key.

Peer's public key must use the same algorithm as the key in this slot, or an error will be returned.

Length of the result depends on the types and sizes of the keys used for the operation. Callers should use a cryptographic key derivation function to extract the amount of bytes they need.

func (*ECDSAPrivateKey) Sign added in v1.6.0 

func (k *ECDSAPrivateKey) Sign(rand io.Reader, digest []byte, opts crypto.SignerOpts) ([]byte, error)

Sign implements crypto.Signer.

type Formfactor 

type Formfactor int

Formfactor enumerates the physical set of forms a key can take. USB-A vs. USB-C and Keychain vs. Nano (and FIPS variants for these).

func (Formfactor) String added in v1.9.0 

func (f Formfactor) String() string

String returns the human-readable description for the given form-factor value, or a fallback value for any other, unknown form-factor.

type Key 

type Key struct {
	// Algorithm to use when generating the key.
	Algorithm Algorithm
	// PINPolicy for the key.
	//
	// BUG(ericchiang): some older YubiKeys (third generation) will silently
	// drop this value. If PINPolicyNever or PINPolicyOnce is supplied but the
	// key still requires a PIN every time, you may be using a buggy key and
	// should supply PINPolicyAlways. See https://github.com/go-piv/piv-go/issues/60
	PINPolicy PINPolicy
	// TouchPolicy for the key.
	TouchPolicy TouchPolicy
}

Key is used for key generation and holds different options for the key.

While keys can have default PIN and touch policies, this package currently doesn't support this option, and all fields must be provided.

type KeyAuth 

type KeyAuth struct {
	// PIN, if provided, is a static PIN used to authenticate against the key.
	// If provided, PINPrompt is ignored.
	PIN string
	// PINPrompt can be used to interactively request the PIN from the user. The
	// method is only called when needed. For example, if a key specifies
	// PINPolicyOnce, PINPrompt will only be called once per YubiKey struct.
	PINPrompt func() (pin string, err error)

	// PINPolicy can be used to specify the PIN caching strategy for the slot. If
	// not provided, this will be inferred from the attestation certificate.
	//
	// This field is required on older (<4.3.0) YubiKeys when using PINPrompt,
	// as well as for keys imported to the card.
	PINPolicy PINPolicy
}

KeyAuth is used to authenticate against the YubiKey on each signing and decryption request.

type Metadata 

type Metadata struct {
	// ManagementKey is the management key stored directly on the YubiKey.
	ManagementKey *[24]byte
	// contains filtered or unexported fields
}

Metadata holds protected metadata. This is primarily used by YubiKey manager to implement PIN protect management keys, storing management keys on the card guarded by the PIN.

type PINPolicy 

type PINPolicy int

PINPolicy represents PIN requirements when signing or decrypting with an asymmetric key in a given slot. 

const (
	PINPolicyNever PINPolicy = iota + 1
	PINPolicyOnce
	PINPolicyAlways
)

PIN policies supported by this package.

BUG(ericchiang): Caching for PINPolicyOnce isn't supported on YubiKey versions older than 4.3.0 due to issues with verifying if a PIN is needed. If specified, a PIN will be required for every operation.

type Slot 

type Slot struct {
	// Key is a reference for a key type.
	//
	// See: https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-73-4.pdf#page=32
	Key uint32
	// Object is a reference for data object.
	//
	// See: https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-73-4.pdf#page=30
	Object uint32
}

Slot is a private key and certificate combination managed by the security key.

func RetiredKeyManagementSlot added in v1.7.0 

func RetiredKeyManagementSlot(key uint32) (Slot, bool)

RetiredKeyManagementSlot provides access to "retired" slots. Slots meant for old Key Management keys that have been rotated. YubiKeys 4 and later support values between 0x82 and 0x95 (inclusive). 

slot, ok := RetiredKeyManagementSlot(0x82)
if !ok {
    // unrecognized slot
}
pub, err := yk.GenerateKey(managementKey, slot, key)

https://developers.yubico.com/PIV/Introduction/Certificate_slots.html#_slot_82_95_retired_key_management

func (Slot) String added in v1.8.0 

func (s Slot) String() string

String returns the two-character hex representation of the slot

type TouchPolicy 

type TouchPolicy int

TouchPolicy represents proof-of-presence requirements when signing or decrypting with asymmetric key in a given slot. 

const (
	TouchPolicyNever TouchPolicy = iota + 1
	TouchPolicyAlways
	TouchPolicyCached
)

Touch policies supported by this package.

type Version 

type Version struct {
	Major int
	Minor int
	Patch int
}

Version encodes a major, minor, and patch version.

type YubiKey 

type YubiKey struct {
	// contains filtered or unexported fields
}

YubiKey is an exclusive open connection to a YubiKey smart card. While open, no other process can query the given card.

To release the connection, call the Close method.

func Open 

func Open(card string) (*YubiKey, error)

Open connects to a YubiKey smart card.

func (*YubiKey) Attest 

func (yk *YubiKey) Attest(slot Slot) (*x509.Certificate, error)

Attest generates a certificate for a key, signed by the YubiKey's attestation certificate. This can be used to prove a key was generate on a specific YubiKey.

This method is only supported for YubiKey versions >= 4.3.0. https://developers.yubico.com/PIV/Introduction/PIV_attestation.html

Certificates returned by this method MUST NOT be used for anything other than attestion or determining the slots public key. For example, the certificate is NOT suitable for TLS.

If the slot doesn't have a key, the returned error wraps ErrNotFound.

func (*YubiKey) AttestationCertificate 

func (yk *YubiKey) AttestationCertificate() (*x509.Certificate, error)

AttestationCertificate returns the YubiKey's attestation certificate, which is unique to the key and signed by Yubico.

func (*YubiKey) Certificate 

func (yk *YubiKey) Certificate(slot Slot) (*x509.Certificate, error)

Certificate returns the certifiate object stored in a given slot.

If a certificate hasn't been set in the provided slot, the returned error wraps ErrNotFound.

func (*YubiKey) Close 

func (yk *YubiKey) Close() error

Close releases the connection to the smart card.

func (*YubiKey) GenerateKey 

func (yk *YubiKey) GenerateKey(key [24]byte, slot Slot, opts Key) (crypto.PublicKey, error)

GenerateKey generates an asymmetric key on the card, returning the key's public key.

func (*YubiKey) Metadata 

func (yk *YubiKey) Metadata(pin string) (*Metadata, error)

Metadata returns protected data stored on the card. This can be used to retrieve PIN protected management keys.

func (*YubiKey) PrivateKey 

func (yk *YubiKey) PrivateKey(slot Slot, public crypto.PublicKey, auth KeyAuth) (crypto.PrivateKey, error)

PrivateKey is used to access signing and decryption options for the key stored in the slot. The returned key implements crypto.Signer and/or crypto.Decrypter depending on the key type.

If the public key hasn't been stored externally, it can be provided by fetching the slot's attestation certificate: 

cert, err := yk.Attest(slot)
if err != nil {
	// ...
}
priv, err := yk.PrivateKey(slot, cert.PublicKey, auth)

func (*YubiKey) Reset 

func (yk *YubiKey) Reset() error

Reset resets the YubiKey PIV applet to its factory settings, wiping all slots and resetting the PIN, PUK, and Management Key to their default values. This does NOT affect data on other applets, such as GPG or U2F.

func (*YubiKey) Retries 

func (yk *YubiKey) Retries() (int, error)

Retries returns the number of attempts remaining to enter the correct PIN.

func (*YubiKey) Serial 

func (yk *YubiKey) Serial() (uint32, error)

Serial returns the YubiKey's serial number.

func (*YubiKey) SetCertificate 

func (yk *YubiKey) SetCertificate(key [24]byte, slot Slot, cert *x509.Certificate) error

SetCertificate stores a certificate object in the provided slot. Setting a certificate isn't required to use the associated key for signing or decryption.

func (*YubiKey) SetManagementKey 

func (yk *YubiKey) SetManagementKey(oldKey, newKey [24]byte) error

SetManagementKey updates the management key to a new key. Management keys are triple-des keys, however padding isn't verified. To generate a new key, generate 24 random bytes. 

var newKey [24]byte
if _, err := io.ReadFull(rand.Reader, newKey[:]); err != nil {
	// ...
}
if err := yk.SetManagementKey(piv.DefaultManagementKey, newKey); err != nil {
	// ...
}

func (*YubiKey) SetMetadata 

func (yk *YubiKey) SetMetadata(key [24]byte, m *Metadata) error

SetMetadata sets PIN protected metadata on the key. This is primarily to store the management key on the smart card instead of managing the PIN and management key seperately.

func (*YubiKey) SetPIN 

func (yk *YubiKey) SetPIN(oldPIN, newPIN string) error

SetPIN updates the PIN to a new value. For compatibility, PINs should be 1-8 numeric characters.

To generate a new PIN, use the crypto/rand package. 

// Generate a 6 character PIN.
newPINInt, err := rand.Int(rand.Reader, bit.NewInt(1_000_000))
if err != nil {
	// ...
}
// Format with leading zeros.
newPIN := fmt.Sprintf("%06d", newPINInt)
if err := yk.SetPIN(piv.DefaultPIN, newPIN); err != nil {
	// ...
}

func (*YubiKey) SetPUK 

func (yk *YubiKey) SetPUK(oldPUK, newPUK string) error

SetPUK updates the PUK to a new value. For compatibility, PUKs should be 1-8 numeric characters.

To generate a new PUK, use the crypto/rand package. 

// Generate a 8 character PUK.
newPUKInt, err := rand.Int(rand.Reader, bit.NewInt(100_000_000))
if err != nil {
	// ...
}
// Format with leading zeros.
newPUK := fmt.Sprintf("%08d", newPUKInt)
if err := yk.SetPIN(piv.DefaultPUK, newPUK); err != nil {
	// ...
}

func (*YubiKey) SetPrivateKeyInsecure added in v1.7.0 

func (yk *YubiKey) SetPrivateKeyInsecure(key [24]byte, slot Slot, private crypto.PrivateKey, policy Key) error

SetPrivateKeyInsecure is an insecure method which imports a private key into the slot. Users should almost always use GeneratePrivateKey() instead.

Importing a private key breaks functionality provided by this package, including AttestationCertificate() and Attest(). There are no stability guarantees for other methods for imported private keys.

Keys generated outside of the YubiKey should not be considered hardware-backed, as there's no way to prove the key wasn't copied, exfiltrated, or replaced with malicious material before being imported.

func (*YubiKey) Unblock 

func (yk *YubiKey) Unblock(puk, newPIN string) error

Unblock unblocks the PIN, setting it to a new value.

func (*YubiKey) VerifyPIN added in v1.11.0 

func (yk *YubiKey) VerifyPIN(pin string) error

VerifyPIN attempts to authenticate against the card with the provided PIN.

PIN authentication for other operations are handled separately, and VerifyPIN does not need to be called before those methods.

After a specific number of authentication attemps with an invalid PIN, usually 3, the PIN will become block and refuse further attempts. At that point the PUK must be used to unblock the PIN.

Use DefaultPIN if the PIN hasn't been set.

func (*YubiKey) Version added in v1.6.0 

func (yk *YubiKey) Version() Version

Version returns the version as reported by the PIV applet. For newer YubiKeys (>=4.0.0) this corresponds to the version of the YubiKey itself.

Older YubiKeys return values that aren't directly related to the YubiKey version. For example, 3rd generation YubiKeys report 1.0.X.

Notes

Bugs

  • Caching for PINPolicyOnce isn't supported on YubiKey versions older than 4.3.0 due to issues with verifying if a PIN is needed. If specified, a PIN will be required for every operation.

  • some older YubiKeys (third generation) will silently drop this value. If PINPolicyNever or PINPolicyOnce is supplied but the key still requires a PIN every time, you may be using a buggy key and should supply PINPolicyAlways. See https://github.com/go-piv/piv-go/issues/60

Source Files

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