# Class X509Certificate

Encapsulates an X509 certificate and provides read-only access to its information.

    const { X509Certificate } = await import('node:crypto');

    const x509 = new X509Certificate('{... pem encoded cert ...}');

    console.log(x509.subject);

#### Since

v15.6.0

#### Hierarchy

- X509Certificate

#####
Index

### Constructors

constructor

### Properties

ca
fingerprint
fingerprint256
fingerprint512
infoAccess
issuer
issuerCertificate?
keyUsage
publicKey
raw
serialNumber
subject
subjectAltName
validFrom
validTo

### Methods

checkEmail
checkHost
checkIP
checkIssued
checkPrivateKey
toJSON
toLegacyObject
toString
verify

## Constructors

### constructor

- new X509Certificate(buffer): X509Certificate

- #### Parameters

  - ##### buffer: BinaryLike

  #### Returns X509Certificate

## Properties

### `Readonly` ca

ca: boolean

Will be `true` if this is a Certificate Authority (CA) certificate.

#### Since

v15.6.0

### `Readonly` fingerprint

fingerprint: string

The SHA-1 fingerprint of this certificate.

Because SHA-1 is cryptographically broken and because the security of SHA-1 is significantly worse than that of algorithms that are commonly used to sign certificates, consider using `x509.fingerprint256` instead.

#### Since

v15.6.0

### `Readonly` fingerprint256

fingerprint256: string

The SHA-256 fingerprint of this certificate.

#### Since

v15.6.0

### `Readonly` fingerprint512

fingerprint512: string

The SHA-512 fingerprint of this certificate.

Because computing the SHA-256 fingerprint is usually faster and because it is only half the size of the SHA-512 fingerprint, `x509.fingerprint256` may be a better choice. While SHA-512 presumably provides a higher level of security in general, the security of SHA-256 matches that of most algorithms that are commonly used to sign certificates.

#### Since

v17.2.0, v16.14.0

### `Readonly` infoAccess

infoAccess: undefined | string

A textual representation of the certificate's authority information access extension.

This is a line feed separated list of access descriptions. Each line begins with the access method and the kind of the access location, followed by a colon and the value associated with the access location.

After the prefix denoting the access method and the kind of the access location, the remainder of each line might be enclosed in quotes to indicate that the value is a JSON string literal. For backward compatibility, Node.js only uses JSON string literals within this property when necessary to avoid ambiguity. Third-party code should be prepared to handle both possible entry formats.

#### Since

v15.6.0

### `Readonly` issuer

issuer: string

The issuer identification included in this certificate.

#### Since

v15.6.0

### `Optional` `Readonly` issuerCertificate

issuerCertificate?: X509Certificate

The issuer certificate or `undefined` if the issuer certificate is not available.

#### Since

v15.9.0

### `Readonly` keyUsage

keyUsage: string[]

An array detailing the key usages for this certificate.

#### Since

v15.6.0

### `Readonly` publicKey

publicKey: KeyObject

The public key `KeyObject` for this certificate.

#### Since

v15.6.0

### `Readonly` raw

raw: Buffer

A `Buffer` containing the DER encoding of this certificate.

#### Since

v15.6.0

### `Readonly` serialNumber

serialNumber: string

The serial number of this certificate.

Serial numbers are assigned by certificate authorities and do not uniquely identify certificates. Consider using `x509.fingerprint256` as a unique identifier instead.

#### Since

v15.6.0

### `Readonly` subject

subject: string

The complete subject of this certificate.

#### Since

v15.6.0

### `Readonly` subjectAltName

subjectAltName: undefined | string

The subject alternative name specified for this certificate.

This is a comma-separated list of subject alternative names. Each entry begins with a string identifying the kind of the subject alternative name followed by a colon and the value associated with the entry.

Earlier versions of Node.js incorrectly assumed that it is safe to split this property at the two-character sequence `', '` (see CVE-2021-44532). However, both malicious and legitimate certificates can contain subject alternative names that include this sequence when represented as a string.

After the prefix denoting the type of the entry, the remainder of each entry might be enclosed in quotes to indicate that the value is a JSON string literal. For backward compatibility, Node.js only uses JSON string literals within this property when necessary to avoid ambiguity. Third-party code should be prepared to handle both possible entry formats.

#### Since

v15.6.0

### `Readonly` validFrom

validFrom: string

The date/time from which this certificate is considered valid.

#### Since

v15.6.0

### `Readonly` validTo

validTo: string

The date/time until which this certificate is considered valid.

#### Since

v15.6.0

## Methods

### checkEmail

- checkEmail(email, options?): undefined | string

- Checks whether the certificate matches the given email address.

  If the `'subject'` option is undefined or set to `'default'`, the certificate subject is only considered if the subject alternative name extension either does not exist or does not contain any email addresses.

  If the `'subject'` option is set to `'always'` and if the subject alternative name extension either does not exist or does not contain a matching email address, the certificate subject is considered.

  If the `'subject'` option is set to `'never'`, the certificate subject is never considered, even if the certificate contains no subject alternative names.

  #### Parameters

  - ##### email: string

  - ##### `Optional` options: Pick<X509CheckOptions, "subject">

  #### Returns undefined | string

  Returns `email` if the certificate matches, `undefined` if it does not.

  #### Since

  v15.6.0

### checkHost

- checkHost(name, options?): undefined | string

- Checks whether the certificate matches the given host name.

  If the certificate matches the given host name, the matching subject name is returned. The returned name might be an exact match (e.g., `foo.example.com`) or it might contain wildcards (e.g., `*.example.com`). Because host name comparisons are case-insensitive, the returned subject name might also differ from the given `name` in capitalization.

  If the `'subject'` option is undefined or set to `'default'`, the certificate subject is only considered if the subject alternative name extension either does not exist or does not contain any DNS names. This behavior is consistent with RFC 2818 ("HTTP Over TLS").

  If the `'subject'` option is set to `'always'` and if the subject alternative name extension either does not exist or does not contain a matching DNS name, the certificate subject is considered.

  If the `'subject'` option is set to `'never'`, the certificate subject is never considered, even if the certificate contains no subject alternative names.

  #### Parameters

  - ##### name: string

  - ##### `Optional` options: X509CheckOptions

  #### Returns undefined | string

  Returns a subject name that matches `name`, or `undefined` if no subject name matches `name`.

  #### Since

  v15.6.0

### checkIP

- checkIP(ip): undefined | string

- Checks whether the certificate matches the given IP address (IPv4 or IPv6).

  Only RFC 5280 `iPAddress` subject alternative names are considered, and they must match the given `ip` address exactly. Other subject alternative names as well as the subject field of the certificate are ignored.

  #### Parameters

  - ##### ip: string

  #### Returns undefined | string

  Returns `ip` if the certificate matches, `undefined` if it does not.

  #### Since

  v15.6.0

### checkIssued

- checkIssued(otherCert): boolean

- Checks whether this certificate was issued by the given `otherCert`.

  #### Parameters

  - ##### otherCert: X509Certificate

  #### Returns boolean

  #### Since

  v15.6.0

### checkPrivateKey

- checkPrivateKey(privateKey): boolean

- Checks whether the public key for this certificate is consistent with the given private key.

  #### Parameters

  - ##### privateKey: KeyObject

    A private key.

  #### Returns boolean

  #### Since

  v15.6.0

### toJSON

- toJSON(): string

- There is no standard JSON encoding for X509 certificates. The`toJSON()` method returns a string containing the PEM encoded certificate.

  #### Returns string

  #### Since

  v15.6.0

### toLegacyObject

- toLegacyObject(): PeerCertificate

- Returns information about this certificate using the legacy `certificate object` encoding.

  #### Returns PeerCertificate

  #### Since

  v15.6.0

### toString

- toString(): string

- Returns the PEM-encoded certificate.

  #### Returns string

  #### Since

  v15.6.0

### verify

- verify(publicKey): boolean

- Verifies that this certificate was signed by the given public key. Does not perform any other validation checks on the certificate.

  #### Parameters

  - ##### publicKey: KeyObject

    A public key.

  #### Returns boolean

  #### Since

  v15.6.0

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