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Published: Nov 11, 2017 License: BSD-3-Clause Imports: 32 Imported by: 0



Package x509 parses X.509-encoded keys and certificates.

On UNIX systems the environment variables SSL_CERT_FILE and SSL_CERT_DIR can be used to override the system default locations for the SSL certificate file and SSL certificate files directory, respectively.




This section is empty.


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var ErrUnsupportedAlgorithm = errors.New("x509: cannot verify signature: algorithm unimplemented")

ErrUnsupportedAlgorithm results from attempting to perform an operation that involves algorithms that are not currently implemented.

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var IncorrectPasswordError = errors.New("x509: decryption password incorrect")

IncorrectPasswordError is returned when an incorrect password is detected.


func CreateCertificate

func CreateCertificate(rand io.Reader, template, parent *Certificate, pub, priv interface{}) (cert []byte, err error)

CreateCertificate creates a new certificate based on a template. The following members of template are used: AuthorityKeyId, BasicConstraintsValid, DNSNames, ExcludedDNSDomains, ExtKeyUsage, IsCA, KeyUsage, MaxPathLen, MaxPathLenZero, NotAfter, NotBefore, PermittedDNSDomains, PermittedDNSDomainsCritical, SerialNumber, SignatureAlgorithm, Subject, SubjectKeyId, and UnknownExtKeyUsage.

The certificate is signed by parent. If parent is equal to template then the certificate is self-signed. The parameter pub is the public key of the signee and priv is the private key of the signer.

The returned slice is the certificate in DER encoding.

All keys types that are implemented via crypto.Signer are supported (This includes *rsa.PublicKey and *ecdsa.PublicKey.)

The AuthorityKeyId will be taken from the SubjectKeyId of parent, if any, unless the resulting certificate is self-signed. Otherwise the value from template will be used.

func CreateCertificateRequest

func CreateCertificateRequest(rand io.Reader, template *CertificateRequest, priv interface{}) (csr []byte, err error)

CreateCertificateRequest creates a new certificate request based on a template. The following members of template are used: Attributes, DNSNames, EmailAddresses, ExtraExtensions, IPAddresses, URIs, SignatureAlgorithm, and Subject. The private key is the private key of the signer.

The returned slice is the certificate request in DER encoding.

All keys types that are implemented via crypto.Signer are supported (This includes *rsa.PublicKey and *ecdsa.PublicKey.)

func DecryptPEMBlock

func DecryptPEMBlock(b *pem.Block, password []byte) ([]byte, error)

DecryptPEMBlock takes a password encrypted PEM block and the password used to encrypt it and returns a slice of decrypted DER encoded bytes. It inspects the DEK-Info header to determine the algorithm used for decryption. If no DEK-Info header is present, an error is returned. If an incorrect password is detected an IncorrectPasswordError is returned. Because of deficiencies in the encrypted-PEM format, it's not always possible to detect an incorrect password. In these cases no error will be returned but the decrypted DER bytes will be random noise.

func EncryptPEMBlock

func EncryptPEMBlock(rand io.Reader, blockType string, data, password []byte, alg PEMCipher) (*pem.Block, error)

EncryptPEMBlock returns a PEM block of the specified type holding the given DER-encoded data encrypted with the specified algorithm and password.

func IsEncryptedPEMBlock

func IsEncryptedPEMBlock(b *pem.Block) bool

IsEncryptedPEMBlock returns if the PEM block is password encrypted.

func MarshalECPrivateKey

func MarshalECPrivateKey(key *ecdsa.PrivateKey) ([]byte, error)

MarshalECPrivateKey marshals an EC private key into ASN.1, DER format.

func MarshalPKCS1PrivateKey

func MarshalPKCS1PrivateKey(key *rsa.PrivateKey) []byte

MarshalPKCS1PrivateKey converts a private key to ASN.1 DER encoded form.

func MarshalPKCS8PrivateKey

func MarshalPKCS8PrivateKey(key interface{}) ([]byte, error)

MarshalPKCS8PrivateKey converts a private key to PKCS#8 encoded form. The following key types are supported: *rsa.PrivateKey, *ecdsa.PublicKey. Unsupported key types result in an error.

See RFC 5208.

func MarshalPKIXPublicKey

func MarshalPKIXPublicKey(pub interface{}) ([]byte, error)

MarshalPKIXPublicKey serialises a public key to DER-encoded PKIX format.

func ParseCRL

func ParseCRL(crlBytes []byte) (*pkix.CertificateList, error)

ParseCRL parses a CRL from the given bytes. It's often the case that PEM encoded CRLs will appear where they should be DER encoded, so this function will transparently handle PEM encoding as long as there isn't any leading garbage.

func ParseDERCRL

func ParseDERCRL(derBytes []byte) (*pkix.CertificateList, error)

ParseDERCRL parses a DER encoded CRL from the given bytes.

func ParseECPrivateKey

func ParseECPrivateKey(der []byte) (*ecdsa.PrivateKey, error)

ParseECPrivateKey parses an ASN.1 Elliptic Curve Private Key Structure.

func ParsePKCS1PrivateKey

func ParsePKCS1PrivateKey(der []byte) (*rsa.PrivateKey, error)

ParsePKCS1PrivateKey returns an RSA private key from its ASN.1 PKCS#1 DER encoded form.

func ParsePKCS8PrivateKey

func ParsePKCS8PrivateKey(der []byte) (key interface{}, err error)

ParsePKCS8PrivateKey parses an unencrypted, PKCS#8 private key. See RFC 5208.

func ParsePKIXPublicKey

func ParsePKIXPublicKey(derBytes []byte) (pub interface{}, err error)

ParsePKIXPublicKey parses a DER encoded public key. These values are typically found in PEM blocks with "BEGIN PUBLIC KEY".

Supported key types include RSA, DSA, and ECDSA. Unknown key types result in an error.

On success, pub will be of type *rsa.PublicKey, *dsa.PublicKey, or *ecdsa.PublicKey.

package main

import (

func main() {
	const pubPEM = `
-----END PUBLIC KEY-----`

	block, _ := pem.Decode([]byte(pubPEM))
	if block == nil {
		panic("failed to parse PEM block containing the public key")

	pub, err := x509.ParsePKIXPublicKey(block.Bytes)
	if err != nil {
		panic("failed to parse DER encoded public key: " + err.Error())

	switch pub := pub.(type) {
	case *rsa.PublicKey:
		fmt.Println("pub is of type RSA:", pub)
	case *dsa.PublicKey:
		fmt.Println("pub is of type DSA:", pub)
	case *ecdsa.PublicKey:
		fmt.Println("pub is of type ECDSA:", pub)
		panic("unknown type of public key")


type CertPool

type CertPool struct {
	// contains filtered or unexported fields

CertPool is a set of certificates.

func NewCertPool

func NewCertPool() *CertPool

NewCertPool returns a new, empty CertPool.

func SystemCertPool

func SystemCertPool() (*CertPool, error)

SystemCertPool returns a copy of the system cert pool.

Any mutations to the returned pool are not written to disk and do not affect any other pool.

func (*CertPool) AddCert

func (s *CertPool) AddCert(cert *Certificate)

AddCert adds a certificate to a pool.

func (*CertPool) AppendCertsFromPEM

func (s *CertPool) AppendCertsFromPEM(pemCerts []byte) (ok bool)

AppendCertsFromPEM attempts to parse a series of PEM encoded certificates. It appends any certificates found to s and reports whether any certificates were successfully parsed.

On many Linux systems, /etc/ssl/cert.pem will contain the system wide set of root CAs in a format suitable for this function.

func (*CertPool) Subjects

func (s *CertPool) Subjects() [][]byte

Subjects returns a list of the DER-encoded subjects of all of the certificates in the pool.

type Certificate

type Certificate struct {
	Raw                     []byte // Complete ASN.1 DER content (certificate, signature algorithm and signature).
	RawTBSCertificate       []byte // Certificate part of raw ASN.1 DER content.
	RawSubjectPublicKeyInfo []byte // DER encoded SubjectPublicKeyInfo.
	RawSubject              []byte // DER encoded Subject
	RawIssuer               []byte // DER encoded Issuer

	Signature          []byte
	SignatureAlgorithm SignatureAlgorithm

	PublicKeyAlgorithm PublicKeyAlgorithm
	PublicKey          interface{}

	Version             int
	SerialNumber        *big.Int
	Issuer              pkix.Name
	Subject             pkix.Name
	NotBefore, NotAfter time.Time // Validity bounds.
	KeyUsage            KeyUsage

	// Extensions contains raw X.509 extensions. When parsing certificates,
	// this can be used to extract non-critical extensions that are not
	// parsed by this package. When marshaling certificates, the Extensions
	// field is ignored, see ExtraExtensions.
	Extensions []pkix.Extension

	// ExtraExtensions contains extensions to be copied, raw, into any
	// marshaled certificates. Values override any extensions that would
	// otherwise be produced based on the other fields. The ExtraExtensions
	// field is not populated when parsing certificates, see Extensions.
	ExtraExtensions []pkix.Extension

	// UnhandledCriticalExtensions contains a list of extension IDs that
	// were not (fully) processed when parsing. Verify will fail if this
	// slice is non-empty, unless verification is delegated to an OS
	// library which understands all the critical extensions.
	// Users can access these extensions using Extensions and can remove
	// elements from this slice if they believe that they have been
	// handled.
	UnhandledCriticalExtensions []asn1.ObjectIdentifier

	ExtKeyUsage        []ExtKeyUsage           // Sequence of extended key usages.
	UnknownExtKeyUsage []asn1.ObjectIdentifier // Encountered extended key usages unknown to this package.

	// BasicConstraintsValid indicates whether IsCA, MaxPathLen,
	// and MaxPathLenZero are valid.
	BasicConstraintsValid bool
	IsCA                  bool

	// MaxPathLen and MaxPathLenZero indicate the presence and
	// value of the BasicConstraints' "pathLenConstraint".
	// When parsing a certificate, a positive non-zero MaxPathLen
	// means that the field was specified, -1 means it was unset,
	// and MaxPathLenZero being true mean that the field was
	// explicitly set to zero. The case of MaxPathLen==0 with MaxPathLenZero==false
	// should be treated equivalent to -1 (unset).
	// When generating a certificate, an unset pathLenConstraint
	// can be requested with either MaxPathLen == -1 or using the
	// zero value for both MaxPathLen and MaxPathLenZero.
	MaxPathLen int
	// MaxPathLenZero indicates that BasicConstraintsValid==true
	// and MaxPathLen==0 should be interpreted as an actual
	// maximum path length of zero. Otherwise, that combination is
	// interpreted as MaxPathLen not being set.
	MaxPathLenZero bool

	SubjectKeyId   []byte
	AuthorityKeyId []byte

	// RFC 5280, (Authority Information Access)
	OCSPServer            []string
	IssuingCertificateURL []string

	// Subject Alternate Name values
	DNSNames       []string
	EmailAddresses []string
	IPAddresses    []net.IP
	URIs           []*url.URL

	// Name constraints
	PermittedDNSDomainsCritical bool // if true then the name constraints are marked critical.
	PermittedDNSDomains         []string
	ExcludedDNSDomains          []string
	PermittedIPRanges           []*net.IPNet
	ExcludedIPRanges            []*net.IPNet
	PermittedEmailAddresses     []string
	ExcludedEmailAddresses      []string
	PermittedURIDomains         []string
	ExcludedURIDomains          []string

	// CRL Distribution Points
	CRLDistributionPoints []string

	PolicyIdentifiers []asn1.ObjectIdentifier

A Certificate represents an X.509 certificate.

func ParseCertificate

func ParseCertificate(asn1Data []byte) (*Certificate, error)

ParseCertificate parses a single certificate from the given ASN.1 DER data.

func ParseCertificates

func ParseCertificates(asn1Data []byte) ([]*Certificate, error)

ParseCertificates parses one or more certificates from the given ASN.1 DER data. The certificates must be concatenated with no intermediate padding.

func (*Certificate) CheckCRLSignature

func (c *Certificate) CheckCRLSignature(crl *pkix.CertificateList) error

CheckCRLSignature checks that the signature in crl is from c.

func (*Certificate) CheckSignature

func (c *Certificate) CheckSignature(algo SignatureAlgorithm, signed, signature []byte) error

CheckSignature verifies that signature is a valid signature over signed from c's public key.

func (*Certificate) CheckSignatureFrom

func (c *Certificate) CheckSignatureFrom(parent *Certificate) error

CheckSignatureFrom verifies that the signature on c is a valid signature from parent.

func (*Certificate) CreateCRL

func (c *Certificate) CreateCRL(rand io.Reader, priv interface{}, revokedCerts []pkix.RevokedCertificate, now, expiry time.Time) (crlBytes []byte, err error)

CreateCRL returns a DER encoded CRL, signed by this Certificate, that contains the given list of revoked certificates.

func (*Certificate) Equal

func (c *Certificate) Equal(other *Certificate) bool

func (*Certificate) Verify

func (c *Certificate) Verify(opts VerifyOptions) (chains [][]*Certificate, err error)

Verify attempts to verify c by building one or more chains from c to a certificate in opts.Roots, using certificates in opts.Intermediates if needed. If successful, it returns one or more chains where the first element of the chain is c and the last element is from opts.Roots.

If opts.Roots is nil and system roots are unavailable the returned error will be of type SystemRootsError.

WARNING: this doesn't do any revocation checking.

package main

import (

func main() {
	// Verifying with a custom list of root certificates.

	const rootPEM = `

	const certPEM = `

	// First, create the set of root certificates. For this example we only
	// have one. It's also possible to omit this in order to use the
	// default root set of the current operating system.
	roots := x509.NewCertPool()
	ok := roots.AppendCertsFromPEM([]byte(rootPEM))
	if !ok {
		panic("failed to parse root certificate")

	block, _ := pem.Decode([]byte(certPEM))
	if block == nil {
		panic("failed to parse certificate PEM")
	cert, err := x509.ParseCertificate(block.Bytes)
	if err != nil {
		panic("failed to parse certificate: " + err.Error())

	opts := x509.VerifyOptions{
		DNSName: "mail.google.com",
		Roots:   roots,

	if _, err := cert.Verify(opts); err != nil {
		panic("failed to verify certificate: " + err.Error())

func (*Certificate) VerifyHostname

func (c *Certificate) VerifyHostname(h string) error

VerifyHostname returns nil if c is a valid certificate for the named host. Otherwise it returns an error describing the mismatch.

type CertificateInvalidError

type CertificateInvalidError struct {
	Cert   *Certificate
	Reason InvalidReason
	Detail string

CertificateInvalidError results when an odd error occurs. Users of this library probably want to handle all these errors uniformly.

func (CertificateInvalidError) Error

func (e CertificateInvalidError) Error() string

type CertificateRequest

type CertificateRequest struct {
	Raw                      []byte // Complete ASN.1 DER content (CSR, signature algorithm and signature).
	RawTBSCertificateRequest []byte // Certificate request info part of raw ASN.1 DER content.
	RawSubjectPublicKeyInfo  []byte // DER encoded SubjectPublicKeyInfo.
	RawSubject               []byte // DER encoded Subject.

	Version            int
	Signature          []byte
	SignatureAlgorithm SignatureAlgorithm

	PublicKeyAlgorithm PublicKeyAlgorithm
	PublicKey          interface{}

	Subject pkix.Name

	// Attributes is the dried husk of a bug and shouldn't be used.
	Attributes []pkix.AttributeTypeAndValueSET

	// Extensions contains raw X.509 extensions. When parsing CSRs, this
	// can be used to extract extensions that are not parsed by this
	// package.
	Extensions []pkix.Extension

	// ExtraExtensions contains extensions to be copied, raw, into any
	// marshaled CSR. Values override any extensions that would otherwise
	// be produced based on the other fields but are overridden by any
	// extensions specified in Attributes.
	// The ExtraExtensions field is not populated when parsing CSRs, see
	// Extensions.
	ExtraExtensions []pkix.Extension

	// Subject Alternate Name values.
	DNSNames       []string
	EmailAddresses []string
	IPAddresses    []net.IP
	URIs           []*url.URL

CertificateRequest represents a PKCS #10, certificate signature request.

func ParseCertificateRequest

func ParseCertificateRequest(asn1Data []byte) (*CertificateRequest, error)

ParseCertificateRequest parses a single certificate request from the given ASN.1 DER data.

func (*CertificateRequest) CheckSignature

func (c *CertificateRequest) CheckSignature() error

CheckSignature reports whether the signature on c is valid.

type ConstraintViolationError

type ConstraintViolationError struct{}

ConstraintViolationError results when a requested usage is not permitted by a certificate. For example: checking a signature when the public key isn't a certificate signing key.

func (ConstraintViolationError) Error

type ExtKeyUsage

type ExtKeyUsage int

ExtKeyUsage represents an extended set of actions that are valid for a given key. Each of the ExtKeyUsage* constants define a unique action.

const (
	ExtKeyUsageAny ExtKeyUsage = iota

type HostnameError

type HostnameError struct {
	Certificate *Certificate
	Host        string

HostnameError results when the set of authorized names doesn't match the requested name.

func (HostnameError) Error

func (h HostnameError) Error() string

type InsecureAlgorithmError

type InsecureAlgorithmError SignatureAlgorithm

An InsecureAlgorithmError

func (InsecureAlgorithmError) Error

func (e InsecureAlgorithmError) Error() string

type InvalidReason

type InvalidReason int
const (
	// NotAuthorizedToSign results when a certificate is signed by another
	// which isn't marked as a CA certificate.
	NotAuthorizedToSign InvalidReason = iota
	// Expired results when a certificate has expired, based on the time
	// given in the VerifyOptions.
	// CANotAuthorizedForThisName results when an intermediate or root
	// certificate has a name constraint which doesn't permit a DNS or
	// other name (including IP address) in the leaf certificate.
	// TooManyIntermediates results when a path length constraint is
	// violated.
	// IncompatibleUsage results when the certificate's key usage indicates
	// that it may only be used for a different purpose.
	// NameMismatch results when the subject name of a parent certificate
	// does not match the issuer name in the child.
	// NameConstraintsWithoutSANs results when a leaf certificate doesn't
	// contain a Subject Alternative Name extension, but a CA certificate
	// contains name constraints.
	// UnconstrainedName results when a CA certificate contains permitted
	// name constraints, but leaf certificate contains a name of an
	// unsupported or unconstrained type.
	// TooManyConstraints results when the number of comparision operations
	// needed to check a certificate exceeds the limit set by
	// VerifyOptions.MaxConstraintComparisions. This limit exists to
	// prevent pathological certificates can consuming excessive amounts of
	// CPU time to verify.
	// CANotAuthorizedForExtKeyUsage results when an intermediate or root
	// certificate does not permit an extended key usage that is claimed by
	// the leaf certificate.

type KeyUsage

type KeyUsage int

KeyUsage represents the set of actions that are valid for a given key. It's a bitmap of the KeyUsage* constants.

const (
	KeyUsageDigitalSignature KeyUsage = 1 << iota

type PEMCipher

type PEMCipher int
const (
	PEMCipherDES PEMCipher

Possible values for the EncryptPEMBlock encryption algorithm.

type PublicKeyAlgorithm

type PublicKeyAlgorithm int
const (
	UnknownPublicKeyAlgorithm PublicKeyAlgorithm = iota

func (PublicKeyAlgorithm) String

func (algo PublicKeyAlgorithm) String() string

type SignatureAlgorithm

type SignatureAlgorithm int
const (
	UnknownSignatureAlgorithm SignatureAlgorithm = iota

func (SignatureAlgorithm) String

func (algo SignatureAlgorithm) String() string

type SystemRootsError

type SystemRootsError struct {
	Err error

SystemRootsError results when we fail to load the system root certificates.

func (SystemRootsError) Error

func (se SystemRootsError) Error() string

type UnhandledCriticalExtension

type UnhandledCriticalExtension struct{}

func (UnhandledCriticalExtension) Error

type UnknownAuthorityError

type UnknownAuthorityError struct {
	Cert *Certificate
	// contains filtered or unexported fields

UnknownAuthorityError results when the certificate issuer is unknown

func (UnknownAuthorityError) Error

func (e UnknownAuthorityError) Error() string

type VerifyOptions

type VerifyOptions struct {
	DNSName       string
	Intermediates *CertPool
	Roots         *CertPool // if nil, the system roots are used
	CurrentTime   time.Time // if zero, the current time is used
	// KeyUsage specifies which Extended Key Usage values are acceptable.
	// An empty list means ExtKeyUsageServerAuth. Key usage is considered a
	// constraint down the chain which mirrors Windows CryptoAPI behavior,
	// but not the spec. To accept any key usage, include ExtKeyUsageAny.
	KeyUsages []ExtKeyUsage
	// MaxConstraintComparisions is the maximum number of comparisons to
	// perform when checking a given certificate's name constraints. If
	// zero, a sensible default is used. This limit prevents pathalogical
	// certificates from consuming excessive amounts of CPU time when
	// validating.
	MaxConstraintComparisions int

VerifyOptions contains parameters for Certificate.Verify. It's a structure because other PKIX verification APIs have ended up needing many options.


Path Synopsis
Package pkix contains shared, low level structures used for ASN.1 parsing and serialization of X.509 certificates, CRL and OCSP.
Package pkix contains shared, low level structures used for ASN.1 parsing and serialization of X.509 certificates, CRL and OCSP.

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