keys.go

// Copyright 2016, 2017 Thales e-Security, Inc
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

package crypto11

import (
	"crypto"
	"crypto/x509"
	"github.com/miekg/pkcs11"
	"github.com/pkg/errors"
)

const maxHandlePerFind = 20

// errNoCkaId is returned if a private key is found which has no CKA_ID attribute
var errNoCkaId = errors.New("private key has no CKA_ID")

// errNoPublicHalf is returned if a public half cannot be found to match a given private key
var errNoPublicHalf = errors.New("could not find public key to match private key")

func findKeysWithAttributes(session *pkcs11Session, template []*pkcs11.Attribute) (handles []pkcs11.ObjectHandle, err error) {
	if err = session.ctx.FindObjectsInit(session.handle, template); err != nil {
		return nil, err
	}
	defer func() {
		finalErr := session.ctx.FindObjectsFinal(session.handle)
		if err == nil {
			err = finalErr
		}
	}()

	newhandles, _, err := session.ctx.FindObjects(session.handle, maxHandlePerFind)
	if err != nil {
		return nil, err
	}

	for len(newhandles) > 0 {
		handles = append(handles, newhandles...)

		newhandles, _, err = session.ctx.FindObjects(session.handle, maxHandlePerFind)
		if err != nil {
			return nil, err
		}
	}

	return handles, nil
}

// Find key objects.  For asymmetric keys this only finds one half so
// callers will call it twice. Returns nil if the key does not exist on the token.
func findKeys(session *pkcs11Session, id []byte, label []byte, keyclass *uint, keytype *uint) (handles []pkcs11.ObjectHandle, err error) {
	var template []*pkcs11.Attribute

	if keyclass != nil {
		template = append(template, pkcs11.NewAttribute(pkcs11.CKA_CLASS, *keyclass))
	}
	if keytype != nil {
		template = append(template, pkcs11.NewAttribute(pkcs11.CKA_KEY_TYPE, *keytype))
	}
	if id != nil {
		template = append(template, pkcs11.NewAttribute(pkcs11.CKA_ID, id))
	}
	if label != nil {
		template = append(template, pkcs11.NewAttribute(pkcs11.CKA_LABEL, label))
	}

	if handles, err = findKeysWithAttributes(session, template); err != nil {
		return nil, err
	}

	return handles, nil
}

// Find a key object.  For asymmetric keys this only finds one half so
// callers will call it twice. Returns nil if the key does not exist on the token.
func findKey(session *pkcs11Session, id []byte, label []byte, keyclass *uint, keytype *uint) (obj *pkcs11.ObjectHandle, err error) {
	handles, err := findKeys(session, id, label, keyclass, keytype)
	if err != nil {
		return nil, err
	}

	if len(handles) == 0 {
		return nil, nil
	}
	return &handles[0], nil
}

// Takes a handles to the private half of a keypair, locates the public half with the matching CKA_ID and CKA_LABEL
// values and constructs a keypair object from them both.
func (c *Context) makeKeyPair(session *pkcs11Session, privHandle *pkcs11.ObjectHandle) (signer Signer, certificate *x509.Certificate, err error) {
	attributes := []*pkcs11.Attribute{
		pkcs11.NewAttribute(pkcs11.CKA_ID, nil),
		pkcs11.NewAttribute(pkcs11.CKA_LABEL, nil),
		pkcs11.NewAttribute(pkcs11.CKA_KEY_TYPE, 0),
	}
	if attributes, err = session.ctx.GetAttributeValue(session.handle, *privHandle, attributes); err != nil {
		return nil, nil, err
	}
	id := attributes[0].Value
	label := attributes[1].Value
	keyType := bytesToUlong(attributes[2].Value)

	// Ensure the private key actually has a non-empty CKA_ID to match on
	if id == nil || len(id) == 0 {
		return nil, nil, errNoCkaId
	}

	var pubHandle *pkcs11.ObjectHandle

	// Find the public half which has a matching CKA_ID
	pubHandle, err = findKey(session, id, label, uintPtr(pkcs11.CKO_PUBLIC_KEY), &keyType)
	if err != nil {
		p11Err, ok := err.(pkcs11.Error)

		if len(label) == 0 && ok && p11Err == pkcs11.CKR_TEMPLATE_INCONSISTENT {
			// This probably means we are using a token that doesn't like us passing empty attributes in a template.
			// For instance CloudHSM cannot search for a key with CKA_LABEL="". So if the private key doesn't have a
			// label, we need to pass nil into findKeys, then match against the first key without a label.

			pubHandles, err := findKeys(session, id, nil, uintPtr(pkcs11.CKO_PUBLIC_KEY), &keyType)
			if err != nil {
				return nil, nil, err
			}

			for _, handle := range pubHandles {
				template := []*pkcs11.Attribute{pkcs11.NewAttribute(pkcs11.CKA_LABEL, nil)}
				template, err = session.ctx.GetAttributeValue(session.handle, handle, template)
				if err != nil {
					return nil, nil, err
				}
				if len(template[0].Value) == 0 {
					pubHandle = &handle
					break
				}
			}
		} else {
			return nil, nil, err
		}
	}

	if pubHandle == nil {
		// Try harder to find a matching public key, based on CKA_ID alone
		pubHandle, err = findKey(session, id, nil, uintPtr(pkcs11.CKO_PUBLIC_KEY), &keyType)
	}

	resultPkcs11PrivateKey := pkcs11PrivateKey{
		pkcs11Object: pkcs11Object{
			handle:  *privHandle,
			context: c,
		},
	}

	var pub crypto.PublicKey
	certificate, _ = findCertificate(session, id, nil, nil)
	if certificate != nil && pubHandle == nil {
		pub = certificate.PublicKey
	}

	if pub == nil && pubHandle == nil {
		// We can't return a Signer if we don't have private and public key. Treat it as an error.
		return nil, nil, errNoPublicHalf
	}

	switch keyType {
	case pkcs11.CKK_DSA:
		result := &pkcs11PrivateKeyDSA{pkcs11PrivateKey: resultPkcs11PrivateKey}
		if pubHandle != nil {
			if pub, err = exportDSAPublicKey(session, *pubHandle); err != nil {
				return nil, nil, err
			}
			result.pkcs11PrivateKey.pubKeyHandle = *pubHandle
		}

		result.pkcs11PrivateKey.pubKey = pub
		return result, certificate, nil

	case pkcs11.CKK_RSA:
		result := &pkcs11PrivateKeyRSA{pkcs11PrivateKey: resultPkcs11PrivateKey}
		if pubHandle != nil {
			if pub, err = exportRSAPublicKey(session, *pubHandle); err != nil {
				return nil, nil, err
			}
			result.pkcs11PrivateKey.pubKeyHandle = *pubHandle
		}

		result.pkcs11PrivateKey.pubKey = pub
		return result, certificate, nil

	case pkcs11.CKK_ECDSA:
		result := &pkcs11PrivateKeyECDSA{pkcs11PrivateKey: resultPkcs11PrivateKey}
		if pubHandle != nil {
			if pub, err = exportECDSAPublicKey(session, *pubHandle); err != nil {
				return nil, nil, err
			}
			result.pkcs11PrivateKey.pubKeyHandle = *pubHandle
		}

		result.pkcs11PrivateKey.pubKey = pub
		return result, certificate, nil

	default:
		return nil, nil, errors.Errorf("unsupported key type: %X", keyType)
	}
}

// FindKeyPair retrieves a previously created asymmetric key pair, or nil if it cannot be found.
//
// At least one of id and label must be specified.
// Only private keys that have a non-empty CKA_ID will be found, as this is required to locate the matching public key.
// If the private key is found, but the public key with a corresponding CKA_ID is not, the key is not returned
// because we cannot implement crypto.Signer without the public key.
func (c *Context) FindKeyPair(id []byte, label []byte) (Signer, error) {
	if c.closed.Get() {
		return nil, errClosed
	}

	result, err := c.FindKeyPairs(id, label)
	if err != nil {
		return nil, err
	}

	if len(result) == 0 {
		return nil, nil
	}

	return result[0], nil
}

// FindKeyPairs retrieves all matching asymmetric key pairs, or a nil slice if none can be found.
//
// At least one of id and label must be specified.
// Only private keys that have a non-empty CKA_ID will be found, as this is required to locate the matching public key.
// If the private key is found, but the public key with a corresponding CKA_ID is not, the key is not returned
// because we cannot implement crypto.Signer without the public key.
func (c *Context) FindKeyPairs(id []byte, label []byte) (signer []Signer, err error) {
	if c.closed.Get() {
		return nil, errClosed
	}

	if id == nil && label == nil {
		return nil, errors.New("id and label cannot both be nil")
	}

	attributes := NewAttributeSet()

	if id != nil {
		err = attributes.Set(CkaId, id)
		if err != nil {
			return nil, err
		}
	}
	if label != nil {
		err = attributes.Set(CkaLabel, label)
		if err != nil {
			return nil, err
		}
	}

	return c.FindKeyPairsWithAttributes(attributes)
}

// FindKeyPairWithAttributes retrieves a previously created asymmetric key pair, or nil if it cannot be found.
// The given attributes are matched against the private half only. Then the public half with a matching CKA_ID
// and CKA_LABEL values is found.
//
// Only private keys that have a non-empty CKA_ID will be found, as this is required to locate the matching public key.
// If the private key is found, but the public key with a corresponding CKA_ID is not, the key is not returned
// because we cannot implement crypto.Signer without the public key.
func (c *Context) FindKeyPairWithAttributes(attributes AttributeSet) (Signer, error) {
	if c.closed.Get() {
		return nil, errClosed
	}

	result, err := c.FindKeyPairsWithAttributes(attributes)
	if err != nil {
		return nil, err
	}

	if len(result) == 0 {
		return nil, nil
	}

	return result[0], nil
}

// FindKeyPairsWithAttributes retrieves previously created asymmetric key pairs, or nil if none can be found.
// The given attributes are matched against the private half only. Then the public half with a matching CKA_ID
// and CKA_LABEL values is found.
//
// Only private keys that have a non-empty CKA_ID will be found, as this is required to locate the matching public key.
// If the private key is found, but the public key with a corresponding CKA_ID is not, the key is not returned
// because we cannot implement crypto.Signer without the public key.
func (c *Context) FindKeyPairsWithAttributes(attributes AttributeSet) (signer []Signer, err error) {
	if c.closed.Get() {
		return nil, errClosed
	}

	var keys []Signer

	if _, ok := attributes[CkaClass]; ok {
		return nil, errors.Errorf("keypair attribute set must not contain CkaClass")
	}

	err = c.withSession(func(session *pkcs11Session) error {
		// Add the private key class to the template to find the private half
		privAttributes := attributes.Copy()
		err = privAttributes.Set(CkaClass, pkcs11.CKO_PRIVATE_KEY)
		if err != nil {
			return err
		}

		privHandles, err := findKeysWithAttributes(session, privAttributes.ToSlice())
		if err != nil {
			return err
		}

		for _, privHandle := range privHandles {
			k, _, err := c.makeKeyPair(session, &privHandle)

			if err == errNoCkaId || err == errNoPublicHalf {
				continue
			}
			if err != nil {
				return err
			}

			keys = append(keys, k)
		}

		return nil
	})

	if err != nil {
		return nil, err
	}

	return keys, nil
}

// FindAllKeyPairs retrieves all existing asymmetric key pairs, or a nil slice if none can be found.
//
// If a private key is found, but the corresponding public key is not, the key is not returned because we cannot
// implement crypto.Signer without the public key.
func (c *Context) FindAllKeyPairs() ([]Signer, error) {
	if c.closed.Get() {
		return nil, errClosed
	}

	return c.FindKeyPairsWithAttributes(NewAttributeSet())
}

// Public returns the public half of a private key.
//
// This partially implements the go.crypto.Signer and go.crypto.Decrypter interfaces for
// pkcs11PrivateKey. (The remains of the implementation is in the
// key-specific types.)
func (k pkcs11PrivateKey) Public() crypto.PublicKey {
	return k.pubKey
}

// FindKey retrieves a previously created symmetric key, or nil if it cannot be found.
//
// Either (but not both) of id and label may be nil, in which case they are ignored.
func (c *Context) FindKey(id []byte, label []byte) (*SecretKey, error) {
	if c.closed.Get() {
		return nil, errClosed
	}

	result, err := c.FindKeys(id, label)
	if err != nil {
		return nil, err
	}

	if len(result) == 0 {
		return nil, nil
	}

	return result[0], nil
}

// FindKeys retrieves all matching symmetric keys, or a nil slice if none can be found.
//
// At least one of id and label must be specified.
func (c *Context) FindKeys(id []byte, label []byte) (key []*SecretKey, err error) {
	if c.closed.Get() {
		return nil, errClosed
	}

	if id == nil && label == nil {
		return nil, errors.New("id and label cannot both be nil")
	}

	attributes := NewAttributeSet()

	if id != nil {
		err = attributes.Set(CkaId, id)
		if err != nil {
			return nil, err
		}
	}
	if label != nil {
		err = attributes.Set(CkaLabel, label)
		if err != nil {
			return nil, err
		}
	}

	return c.FindKeysWithAttributes(attributes)
}

// FindKeyWithAttributes retrieves a previously created symmetric key, or nil if it cannot be found.
func (c *Context) FindKeyWithAttributes(attributes AttributeSet) (*SecretKey, error) {
	if c.closed.Get() {
		return nil, errClosed
	}

	result, err := c.FindKeysWithAttributes(attributes)
	if err != nil {
		return nil, err
	}

	if len(result) == 0 {
		return nil, nil
	}

	return result[0], nil
}

// FindKeysWithAttributes retrieves previously created symmetric keys, or a nil slice if none can be found.
func (c *Context) FindKeysWithAttributes(attributes AttributeSet) ([]*SecretKey, error) {
	if c.closed.Get() {
		return nil, errClosed
	}

	var keys []*SecretKey

	if _, ok := attributes[CkaClass]; ok {
		return nil, errors.Errorf("key attribute set must not contain CkaClass")
	}

	err := c.withSession(func(session *pkcs11Session) error {
		// Add the private key class to the template to find the private half
		privAttributes := attributes.Copy()
		err := privAttributes.Set(CkaClass, pkcs11.CKO_SECRET_KEY)
		if err != nil {
			return err
		}

		privHandles, err := findKeysWithAttributes(session, privAttributes.ToSlice())
		if err != nil {
			return err
		}

		for _, privHandle := range privHandles {
			attributes := []*pkcs11.Attribute{
				pkcs11.NewAttribute(pkcs11.CKA_KEY_TYPE, 0),
			}
			if attributes, err = session.ctx.GetAttributeValue(session.handle, privHandle, attributes); err != nil {
				return err
			}
			keyType := bytesToUlong(attributes[0].Value)

			if cipher, ok := Ciphers[int(keyType)]; ok {
				k := &SecretKey{pkcs11Object{privHandle, c}, cipher}
				keys = append(keys, k)
			} else {
				return errors.Errorf("unsupported key type: %X", keyType)
			}
		}

		return nil
	})

	if err != nil {
		return nil, err
	}
	return keys, nil
}

// FindAllKeyPairs retrieves all existing symmetric keys, or a nil slice if none can be found.
func (c *Context) FindAllKeys() ([]*SecretKey, error) {
	if c.closed.Get() {
		return nil, errClosed
	}

	return c.FindKeysWithAttributes(NewAttributeSet())
}

func uintPtr(i uint) *uint { return &i }

func (c *Context) getAttributes(handle pkcs11.ObjectHandle, attributes []AttributeType) (a AttributeSet, err error) {
	values := NewAttributeSet()

	err = c.withSession(func(session *pkcs11Session) error {
		var attrs []*pkcs11.Attribute
		for _, a := range attributes {
			attrs = append(attrs, pkcs11.NewAttribute(a, nil))
		}

		p11values, err := session.ctx.GetAttributeValue(session.handle, handle, attrs)
		if err != nil {
			return err
		}

		values.AddIfNotPresent(p11values)

		return nil
	})

	return values, err
}

// GetAttributes gets the values of the specified attributes on the given key or keypair.
// If the key is asymmetric, then the attributes are retrieved from the private half.
//
// If the object is not a crypto11 key or keypair then an error is returned.
func (c *Context) GetAttributes(key interface{}, attributes []AttributeType) (a AttributeSet, err error) {
	if c.closed.Get() {
		return nil, errClosed
	}

	var handle pkcs11.ObjectHandle

	switch k := (key).(type) {
	case *pkcs11PrivateKeyDSA:
		handle = k.handle
	case *pkcs11PrivateKeyRSA:
		handle = k.handle
	case *pkcs11PrivateKeyECDSA:
		handle = k.handle
	case *SecretKey:
		handle = k.handle
	default:
		return nil, errors.Errorf("not a PKCS#11 key")
	}

	return c.getAttributes(handle, attributes)
}

// GetAttribute gets the value of the specified attribute on the given key or keypair.
// If the key is asymmetric, then the attribute is retrieved from the private half.
//
// If the object is not a crypto11 key or keypair then an error is returned.
func (c *Context) GetAttribute(key interface{}, attribute AttributeType) (a *Attribute, err error) {
	if c.closed.Get() {
		return nil, errClosed
	}

	set, err := c.GetAttributes(key, []AttributeType{attribute})
	if err != nil {
		return nil, err
	}

	return set[attribute], nil
}

// GetPubAttributes gets the values of the specified attributes on the public half of the given keypair.
//
// If the object is not a crypto11 keypair then an error is returned.
func (c *Context) GetPubAttributes(key interface{}, attributes []AttributeType) (a AttributeSet, err error) {
	if c.closed.Get() {
		return nil, errClosed
	}

	var handle pkcs11.ObjectHandle

	switch k := (key).(type) {
	case *pkcs11PrivateKeyDSA:
		handle = k.pubKeyHandle
	case *pkcs11PrivateKeyRSA:
		handle = k.pubKeyHandle
	case *pkcs11PrivateKeyECDSA:
		handle = k.pubKeyHandle
	default:
		return nil, errors.Errorf("not an asymmetric PKCS#11 key")
	}

	return c.getAttributes(handle, attributes)
}

// GetPubAttribute gets the value of the specified attribute on the public half of the given key.
//
// If the object is not a crypto11 keypair then an error is returned.
func (c *Context) GetPubAttribute(key interface{}, attribute AttributeType) (a *Attribute, err error) {
	if c.closed.Get() {
		return nil, errClosed
	}

	set, err := c.GetPubAttributes(key, []AttributeType{attribute})
	if err != nil {
		return nil, err
	}

	return set[attribute], nil
}