ErrUnsupportedAlgorithm results from attempting to perform an operation that involves algorithms that are not currently implemented.
var ErrUnsupportedAlgorithm = errors.New("x509: cannot verify signature: algorithm unimplemented")
IncorrectPasswordError is returned when an incorrect password is detected.
var IncorrectPasswordError = errors.New("x509: decryption password incorrect")
func CreateCertificate(rand io.Reader, template, parent *Certificate, pub, priv interface{}) ([]byte, error)
CreateCertificate creates a new X.509 v3 certificate based on a template. The following members of template are currently used:
- AuthorityKeyId - BasicConstraintsValid - CRLDistributionPoints - DNSNames - EmailAddresses - ExcludedDNSDomains - ExcludedEmailAddresses - ExcludedIPRanges - ExcludedURIDomains - ExtKeyUsage - ExtraExtensions - IPAddresses - IsCA - IssuingCertificateURL - KeyUsage - MaxPathLen - MaxPathLenZero - NotAfter - NotBefore - OCSPServer - PermittedDNSDomains - PermittedDNSDomainsCritical - PermittedEmailAddresses - PermittedIPRanges - PermittedURIDomains - PolicyIdentifiers - SerialNumber - SignatureAlgorithm - Subject - SubjectKeyId - URIs - 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 certificate to be generated and priv is the private key of the signer.
The returned slice is the certificate in DER encoding.
The currently supported key types are *rsa.PublicKey, *ecdsa.PublicKey and ed25519.PublicKey. pub must be a supported key type, and priv must be a crypto.Signer with a supported public key.
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.
If SubjectKeyId from template is empty and the template is a CA, SubjectKeyId will be generated from the hash of the public key.
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:
- SignatureAlgorithm - Subject - DNSNames - EmailAddresses - IPAddresses - URIs - ExtraExtensions - Attributes (deprecated)
priv is the private key to sign the CSR with, and the corresponding public key will be included in the CSR. It must implement crypto.Signer and its Public() method must return a *rsa.PublicKey or a *ecdsa.PublicKey or a ed25519.PublicKey. (A *rsa.PrivateKey, *ecdsa.PrivateKey or ed25519.PrivateKey satisfies this.)
The returned slice is the certificate request in DER encoding.
func CreateRevocationList(rand io.Reader, template *RevocationList, issuer *Certificate, priv crypto.Signer) ([]byte, error)
CreateRevocationList creates a new X.509 v2 Certificate Revocation List, according to RFC 5280, based on template.
The CRL is signed by priv which should be the private key associated with the public key in the issuer certificate.
The issuer may not be nil, and the crlSign bit must be set in KeyUsage in order to use it as a CRL issuer.
The issuer distinguished name CRL field and authority key identifier extension are populated using the issuer certificate. issuer must have SubjectKeyId set.
func DecryptPEMBlock(b *pem.Block, password []byte) ([]byte, error)
DecryptPEMBlock takes a PEM block encrypted according to RFC 1423 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 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.
Deprecated: Legacy PEM encryption as specified in RFC 1423 is insecure by design. Since it does not authenticate the ciphertext, it is vulnerable to padding oracle attacks that can let an attacker recover the plaintext.
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 according to RFC 1423.
Deprecated: Legacy PEM encryption as specified in RFC 1423 is insecure by design. Since it does not authenticate the ciphertext, it is vulnerable to padding oracle attacks that can let an attacker recover the plaintext.
func IsEncryptedPEMBlock(b *pem.Block) bool
IsEncryptedPEMBlock returns whether the PEM block is password encrypted according to RFC 1423.
Deprecated: Legacy PEM encryption as specified in RFC 1423 is insecure by design. Since it does not authenticate the ciphertext, it is vulnerable to padding oracle attacks that can let an attacker recover the plaintext.
func MarshalECPrivateKey(key *ecdsa.PrivateKey) ([]byte, error)
MarshalECPrivateKey converts an EC private key to SEC 1, ASN.1 DER form.
This kind of key is commonly encoded in PEM blocks of type "EC PRIVATE KEY". For a more flexible key format which is not EC specific, use MarshalPKCS8PrivateKey.
func MarshalPKCS1PrivateKey(key *rsa.PrivateKey) []byte
MarshalPKCS1PrivateKey converts an RSA private key to PKCS #1, ASN.1 DER form.
This kind of key is commonly encoded in PEM blocks of type "RSA PRIVATE KEY". For a more flexible key format which is not RSA specific, use MarshalPKCS8PrivateKey.
func MarshalPKCS1PublicKey(key *rsa.PublicKey) []byte
MarshalPKCS1PublicKey converts an RSA public key to PKCS #1, ASN.1 DER form.
This kind of key is commonly encoded in PEM blocks of type "RSA PUBLIC KEY".
func MarshalPKCS8PrivateKey(key interface{}) ([]byte, error)
MarshalPKCS8PrivateKey converts a private key to PKCS #8, ASN.1 DER form.
The following key types are currently supported: *rsa.PrivateKey, *ecdsa.PrivateKey and ed25519.PrivateKey. Unsupported key types result in an error.
This kind of key is commonly encoded in PEM blocks of type "PRIVATE KEY".
func MarshalPKIXPublicKey(pub interface{}) ([]byte, error)
MarshalPKIXPublicKey converts a public key to PKIX, ASN.1 DER form. The encoded public key is a SubjectPublicKeyInfo structure (see RFC 5280, Section 4.1).
The following key types are currently supported: *rsa.PublicKey, *ecdsa.PublicKey and ed25519.PublicKey. Unsupported key types result in an error.
This kind of key is commonly encoded in PEM blocks of type "PUBLIC KEY".
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(derBytes []byte) (*pkix.CertificateList, error)
ParseDERCRL parses a DER encoded CRL from the given bytes.
func ParseECPrivateKey(der []byte) (*ecdsa.PrivateKey, error)
ParseECPrivateKey parses an EC private key in SEC 1, ASN.1 DER form.
This kind of key is commonly encoded in PEM blocks of type "EC PRIVATE KEY".
func ParsePKCS1PrivateKey(der []byte) (*rsa.PrivateKey, error)
ParsePKCS1PrivateKey parses an RSA private key in PKCS #1, ASN.1 DER form.
This kind of key is commonly encoded in PEM blocks of type "RSA PRIVATE KEY".
func ParsePKCS1PublicKey(der []byte) (*rsa.PublicKey, error)
ParsePKCS1PublicKey parses an RSA public key in PKCS #1, ASN.1 DER form.
This kind of key is commonly encoded in PEM blocks of type "RSA PUBLIC KEY".
func ParsePKCS8PrivateKey(der []byte) (key interface{}, err error)
ParsePKCS8PrivateKey parses an unencrypted private key in PKCS #8, ASN.1 DER form.
It returns a *rsa.PrivateKey, a *ecdsa.PrivateKey, or a ed25519.PrivateKey. More types might be supported in the future.
This kind of key is commonly encoded in PEM blocks of type "PRIVATE KEY".
func ParsePKIXPublicKey(derBytes []byte) (pub interface{}, err error)
ParsePKIXPublicKey parses a public key in PKIX, ASN.1 DER form. The encoded public key is a SubjectPublicKeyInfo structure (see RFC 5280, Section 4.1).
It returns a *rsa.PublicKey, *dsa.PublicKey, *ecdsa.PublicKey, or ed25519.PublicKey. More types might be supported in the future.
This kind of key is commonly encoded in PEM blocks of type "PUBLIC KEY".
CertPool is a set of certificates.
type CertPool struct {
// contains filtered or unexported fields
}
func NewCertPool() *CertPool
NewCertPool returns a new, empty CertPool.
func SystemCertPool() (*CertPool, error)
SystemCertPool returns a copy of the system cert pool.
On Unix systems other than macOS 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. The latter can be a colon-separated list.
Any mutations to the returned pool are not written to disk and do not affect any other pool returned by SystemCertPool.
New changes in the system cert pool might not be reflected in subsequent calls.
func (s *CertPool) AddCert(cert *Certificate)
AddCert adds a certificate to a pool.
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 (s *CertPool) Subjects() [][]byte
Subjects returns a list of the DER-encoded subjects of all of the certificates in the pool.
A Certificate represents an X.509 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 // Go 1.2
// 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 // Go 1.2
// 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 // Go 1.5
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 // Go 1.4
SubjectKeyId []byte
AuthorityKeyId []byte
// RFC 5280, 4.2.2.1 (Authority Information Access)
OCSPServer []string // Go 1.2
IssuingCertificateURL []string // Go 1.2
// Subject Alternate Name values. (Note that these values may not be valid
// if invalid values were contained within a parsed certificate. For
// example, an element of DNSNames may not be a valid DNS domain name.)
DNSNames []string
EmailAddresses []string
IPAddresses []net.IP // Go 1.1
URIs []*url.URL // Go 1.10
// Name constraints
PermittedDNSDomainsCritical bool // if true then the name constraints are marked critical.
PermittedDNSDomains []string
ExcludedDNSDomains []string // Go 1.9
PermittedIPRanges []*net.IPNet // Go 1.10
ExcludedIPRanges []*net.IPNet // Go 1.10
PermittedEmailAddresses []string // Go 1.10
ExcludedEmailAddresses []string // Go 1.10
PermittedURIDomains []string // Go 1.10
ExcludedURIDomains []string // Go 1.10
// CRL Distribution Points
CRLDistributionPoints []string // Go 1.2
PolicyIdentifiers []asn1.ObjectIdentifier
}
func ParseCertificate(der []byte) (*Certificate, error)
ParseCertificate parses a single certificate from the given ASN.1 DER data.
func ParseCertificates(der []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 (c *Certificate) CheckCRLSignature(crl *pkix.CertificateList) error
CheckCRLSignature checks that the signature in crl is from c.
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 (c *Certificate) CheckSignatureFrom(parent *Certificate) error
CheckSignatureFrom verifies that the signature on c is a valid signature from parent.
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.
Note: this method does not generate an RFC 5280 conformant X.509 v2 CRL. To generate a standards compliant CRL, use CreateRevocationList instead.
func (c *Certificate) Equal(other *Certificate) bool
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, the platform verifier might be used, and verification details might differ from what is described below. If system roots are unavailable the returned error will be of type SystemRootsError.
Name constraints in the intermediates will be applied to all names claimed in the chain, not just opts.DNSName. Thus it is invalid for a leaf to claim example.com if an intermediate doesn't permit it, even if example.com is not the name being validated. Note that DirectoryName constraints are not supported.
Name constraint validation follows the rules from RFC 5280, with the addition that DNS name constraints may use the leading period format defined for emails and URIs. When a constraint has a leading period it indicates that at least one additional label must be prepended to the constrained name to be considered valid.
Extended Key Usage values are enforced nested down a chain, so an intermediate or root that enumerates EKUs prevents a leaf from asserting an EKU not in that list. (While this is not specified, it is common practice in order to limit the types of certificates a CA can issue.)
WARNING: this function doesn't do any revocation checking.
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.
IP addresses can be optionally enclosed in square brackets and are checked against the IPAddresses field. Other names are checked case insensitively against the DNSNames field. If the names are valid hostnames, the certificate fields can have a wildcard as the left-most label.
Note that the legacy Common Name field is ignored.
CertificateInvalidError results when an odd error occurs. Users of this library probably want to handle all these errors uniformly.
type CertificateInvalidError struct {
Cert *Certificate
Reason InvalidReason
Detail string // Go 1.10
}
func (e CertificateInvalidError) Error() string
CertificateRequest represents a PKCS #10, certificate signature request.
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 contains the CSR attributes that can parse as
// pkix.AttributeTypeAndValueSET.
//
// Deprecated: Use Extensions and ExtraExtensions instead for parsing and
// generating the requestedExtensions attribute.
Attributes []pkix.AttributeTypeAndValueSET
// Extensions contains all requested extensions, in raw form. 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 CSR
// marshaled by CreateCertificateRequest. 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 by ParseCertificateRequest,
// see Extensions instead.
ExtraExtensions []pkix.Extension
// Subject Alternate Name values.
DNSNames []string
EmailAddresses []string
IPAddresses []net.IP
URIs []*url.URL // Go 1.10
}
func ParseCertificateRequest(asn1Data []byte) (*CertificateRequest, error)
ParseCertificateRequest parses a single certificate request from the given ASN.1 DER data.
func (c *CertificateRequest) CheckSignature() error
CheckSignature reports whether the signature on c is valid.
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.
type ConstraintViolationError struct{}
func (ConstraintViolationError) Error() string
ExtKeyUsage represents an extended set of actions that are valid for a given key. Each of the ExtKeyUsage* constants define a unique action.
type ExtKeyUsage int
const ( ExtKeyUsageAny ExtKeyUsage = iota ExtKeyUsageServerAuth ExtKeyUsageClientAuth ExtKeyUsageCodeSigning ExtKeyUsageEmailProtection ExtKeyUsageIPSECEndSystem ExtKeyUsageIPSECTunnel ExtKeyUsageIPSECUser ExtKeyUsageTimeStamping ExtKeyUsageOCSPSigning ExtKeyUsageMicrosoftServerGatedCrypto ExtKeyUsageNetscapeServerGatedCrypto ExtKeyUsageMicrosoftCommercialCodeSigning ExtKeyUsageMicrosoftKernelCodeSigning )
HostnameError results when the set of authorized names doesn't match the requested name.
type HostnameError struct {
Certificate *Certificate
Host string
}
func (h HostnameError) Error() string
An InsecureAlgorithmError
type InsecureAlgorithmError SignatureAlgorithm
func (e InsecureAlgorithmError) Error() string
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. Expired // 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. CANotAuthorizedForThisName // TooManyIntermediates results when a path length constraint is // violated. TooManyIntermediates // IncompatibleUsage results when the certificate's key usage indicates // that it may only be used for a different purpose. IncompatibleUsage // NameMismatch results when the subject name of a parent certificate // does not match the issuer name in the child. NameMismatch // NameConstraintsWithoutSANs is a legacy error and is no longer returned. NameConstraintsWithoutSANs // UnconstrainedName results when a CA certificate contains permitted // name constraints, but leaf certificate contains a name of an // unsupported or unconstrained type. UnconstrainedName // TooManyConstraints results when the number of comparison 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. TooManyConstraints // CANotAuthorizedForExtKeyUsage results when an intermediate or root // certificate does not permit a requested extended key usage. CANotAuthorizedForExtKeyUsage )
KeyUsage represents the set of actions that are valid for a given key. It's a bitmap of the KeyUsage* constants.
type KeyUsage int
const ( KeyUsageDigitalSignature KeyUsage = 1 << iota KeyUsageContentCommitment KeyUsageKeyEncipherment KeyUsageDataEncipherment KeyUsageKeyAgreement KeyUsageCertSign KeyUsageCRLSign KeyUsageEncipherOnly KeyUsageDecipherOnly )
type PEMCipher int
Possible values for the EncryptPEMBlock encryption algorithm.
const ( PEMCipherDES PEMCipher PEMCipher3DES PEMCipherAES128 PEMCipherAES192 PEMCipherAES256 )
type PublicKeyAlgorithm int
const ( UnknownPublicKeyAlgorithm PublicKeyAlgorithm = iota RSA DSA // Unsupported. ECDSA Ed25519 )
func (algo PublicKeyAlgorithm) String() string
RevocationList contains the fields used to create an X.509 v2 Certificate Revocation list with CreateRevocationList.
type RevocationList struct {
// SignatureAlgorithm is used to determine the signature algorithm to be
// used when signing the CRL. If 0 the default algorithm for the signing
// key will be used.
SignatureAlgorithm SignatureAlgorithm
// RevokedCertificates is used to populate the revokedCertificates
// sequence in the CRL, it may be empty. RevokedCertificates may be nil,
// in which case an empty CRL will be created.
RevokedCertificates []pkix.RevokedCertificate
// Number is used to populate the X.509 v2 cRLNumber extension in the CRL,
// which should be a monotonically increasing sequence number for a given
// CRL scope and CRL issuer.
Number *big.Int
// ThisUpdate is used to populate the thisUpdate field in the CRL, which
// indicates the issuance date of the CRL.
ThisUpdate time.Time
// NextUpdate is used to populate the nextUpdate field in the CRL, which
// indicates the date by which the next CRL will be issued. NextUpdate
// must be greater than ThisUpdate.
NextUpdate time.Time
// ExtraExtensions contains any additional extensions to add directly to
// the CRL.
ExtraExtensions []pkix.Extension
}
type SignatureAlgorithm int
const ( UnknownSignatureAlgorithm SignatureAlgorithm = iota MD2WithRSA // Unsupported. MD5WithRSA // Only supported for signing, not verification. SHA1WithRSA SHA256WithRSA SHA384WithRSA SHA512WithRSA DSAWithSHA1 // Unsupported. DSAWithSHA256 // Unsupported. ECDSAWithSHA1 ECDSAWithSHA256 ECDSAWithSHA384 ECDSAWithSHA512 SHA256WithRSAPSS SHA384WithRSAPSS SHA512WithRSAPSS PureEd25519 )
func (algo SignatureAlgorithm) String() string
SystemRootsError results when we fail to load the system root certificates.
type SystemRootsError struct {
Err error // Go 1.7
}
func (se SystemRootsError) Error() string
func (se SystemRootsError) Unwrap() error
type UnhandledCriticalExtension struct{}
func (h UnhandledCriticalExtension) Error() string
UnknownAuthorityError results when the certificate issuer is unknown
type UnknownAuthorityError struct {
Cert *Certificate // Go 1.8
// contains filtered or unexported fields
}
func (e UnknownAuthorityError) Error() string
VerifyOptions contains parameters for Certificate.Verify.
type VerifyOptions struct {
// DNSName, if set, is checked against the leaf certificate with
// Certificate.VerifyHostname or the platform verifier.
DNSName string
// Intermediates is an optional pool of certificates that are not trust
// anchors, but can be used to form a chain from the leaf certificate to a
// root certificate.
Intermediates *CertPool
// Roots is the set of trusted root certificates the leaf certificate needs
// to chain up to. If nil, the system roots or the platform verifier are used.
Roots *CertPool
// CurrentTime is used to check the validity of all certificates in the
// chain. If zero, the current time is used.
CurrentTime time.Time
// KeyUsages specifies which Extended Key Usage values are acceptable. A
// chain is accepted if it allows any of the listed values. An empty list
// means ExtKeyUsageServerAuth. To accept any key usage, include ExtKeyUsageAny.
KeyUsages []ExtKeyUsage // Go 1.1
// 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 pathological
// certificates from consuming excessive amounts of CPU time when
// validating. It does not apply to the platform verifier.
MaxConstraintComparisions int // Go 1.10
}