public_key(3erl)

💖 NAME 💖

public_key(3erl) — the Erlang module definition for the API module for public-key infrastructure. This is part 1 of 3, bestie, and we are keeping every single detail. No cap.

✨ DESCRIPTION ✨

Okay so this module provides functions to handle public-key infrastructure. For the full tea, see public_key(7). Periodt.

🎀 COMMON RECORDS AND ASN.1 TYPES 🎀

📝 Note 📝

All records used in this Reference Manual are generated from ASN.1 specifications and are documented in the User's Guide. See Public-key Records.

Use the following include directive to get access to the records and constant macros described here and in the User's Guide:

-include_lib("public_key/include/public_key.hrl").

🌈 DATA TYPES 🌈

Okay bestie, data-type era. Here is every definition, exactly as it is. 🫶

🦋 oid() = tuple() 🦋

Object identifier, a tuple of integers as generated by the ASN.1 compiler.

💅 key_oid_name() 💅

key_oid_name() =
    rsaEncryption | 'id-RSASSA-PSS' | 'id-ecPublicKey' |
    'id-Ed25519' | 'id-Ed448' | 'id-dsa'

Macro names for key object identifiers used by prefixing with ?.

der_encoded() = binary()

der_encoded() = binary()

pki_asn1_type()

pki_asn1_type() =
    'Certificate' | 'RSAPrivateKey' | 'RSAPublicKey' |
    'SubjectPublicKeyInfo' | 'DSAPrivateKey' | 'DHParameter' |
    'PrivateKeyInfo' | 'CertificationRequest' | 'ContentInfo' |
    'CertificateList' | 'ECPrivateKey' | 'OneAsymmetricKey' |
    'EcpkParameters'

asn1_type() = atom()

ASN.1 type present in the Public Key applications ASN.1 specifications.

pem_entry()

pem_entry() =
    {pki_asn1_type(),
     der_or_encrypted_der(),
     not_encrypted | cipher_info()}

der_or_encrypted_der() = binary()

der_or_encrypted_der() = binary()

cipher_info() = {cipher(), cipher_info_params()}

cipher_info() = {cipher(), cipher_info_params()}

cipher() = string()

cipher() = string()

salt() = binary()

salt() = binary()

cipher_info_params()

cipher_info_params() =
    salt() |
    {#'PBEParameter'{}, digest_type()} |
    #'PBES2-params'{}

Cipher = "RC2-CBC" | "DES-CBC" | "DES-EDE3-CBC"

Salt could be generated with crypto:strong_rand_bytes(8).

public_key()

public_key() =
    rsa_public_key() |
    rsa_pss_public_key() |
    dsa_public_key() |
    ec_public_key() |
    ed_public_key()

rsa_public_key() = #'RSAPublicKey'{}

rsa_public_key() = #'RSAPublicKey'{}

dss_public_key() = integer()

dss_public_key() = integer()

rsa_pss_public_key()

rsa_pss_public_key() =
    {rsa_pss_public_key(), #'RSASSA-PSS-params'{}}

dsa_public_key() = {dss_public_key(), #'Dss-Parms'{}}

dsa_public_key() = {dss_public_key(), #'Dss-Parms'{}}

ec_public_key() = {#'ECPoint'{}, ecpk_parameters_api()}

ec_public_key() = {#'ECPoint'{}, ecpk_parameters_api()}

public_key_params()

public_key_params() =
    'NULL' |
    #'RSASSA-PSS-params'{} |
    {namedCurve, oid()} |
    #'ECParameters'{} |
    #'Dss-Parms'{}

ecpk_parameters()

ecpk_parameters() =
    {ecParameters, #'ECParameters'{}} |
    {namedCurve, Oid :: tuple()}

ecpk_parameters_api()

ecpk_parameters_api() =
    ecpk_parameters() |
    #'ECParameters'{} |
    {namedCurve, Name :: crypto:ec_named_curve()}

public_key_info()

public_key_info() =
    {key_oid_name(),
     rsa_public_key() | #'ECPoint'{} | dss_public_key(),
     public_key_params()}

ed_public_key() = {#'ECPoint'{}, ed_params()}

ed_public_key() = {#'ECPoint'{}, ed_params()}

ed_params() = {namedCurve, ed_oid_name()}

ed_params() = {namedCurve, ed_oid_name()}

private_key()

private_key() =
    rsa_private_key() |
    rsa_pss_private_key() |
    dsa_private_key() |
    ec_private_key() |
    ed_private_key()

rsa_private_key() = #'RSAPrivateKey'{}

rsa_private_key() = #'RSAPrivateKey'{}

rsa_pss_private_key()

rsa_pss_private_key() =
    {#'RSAPrivateKey'{}, #'RSASSA-PSS-params'{}}

dsa_private_key() = #'DSAPrivateKey'{}

dsa_private_key() = #'DSAPrivateKey'{}

ec_private_key() = #'ECPrivateKey'{}

ec_private_key() = #'ECPrivateKey'{}

ed_private_key() = #'ECPrivateKey'{parameters = ed_params()}

ed_private_key() = #'ECPrivateKey'{parameters = ed_params()}

ed_oid_name() = 'id-Ed25519' | 'id-Ed448'

ed_oid_name() = 'id-Ed25519' | 'id-Ed448'

Macro names for object identifiers for EDDSA curves used by prefixing with ?.

key_params()

key_params() =
    #'DHParameter'{} |
    {namedCurve, oid()} |
    #'ECParameters'{} |
    {rsa, Size :: integer(), PubExp :: integer()}

digest_type()

digest_type() =
    none | sha1 |
    crypto:rsa_digest_type() |
    crypto:dss_digest_type() |
    crypto:ecdsa_digest_type()

issuer_name() = {rdnSequence, [[#'AttributeTypeAndValue'{}]]}

issuer_name() = {rdnSequence, [[#'AttributeTypeAndValue'{}]]}

referenceIDs() = [referenceID()]

referenceIDs() = [referenceID()]

referenceID()

referenceID() =
    {uri_id | dns_id | ip | srv_id | atom() | oid(), string()} |
    {ip, inet:ip_address() | string()}

cert_id() = {SerialNr :: integer(), issuer_name()}

cert_id() = {SerialNr :: integer(), issuer_name()}

cert() = der_cert() | otp_cert()

cert() = der_cert() | otp_cert()

otp_cert() = #'OTPCertificate'{}

otp_cert() = #'OTPCertificate'{}

der_cert() = der_encoded()

der_cert() = der_encoded()

combined_cert()

combined_cert() =
    #cert{der = public_key:der_encoded(),
          otp = #'OTPCertificate'{}}

bad_cert_reason()

bad_cert_reason() =
    cert_expired | invalid_issuer | invalid_signature |
    name_not_permitted | missing_basic_constraint |
    invalid_key_usage |
    {key_usage_mismatch, term()} |
    {revoked, crl_reason()} |
    atom()

crl_reason()

crl_reason() =
    unspecified | keyCompromise | cACompromise |
    affiliationChanged | superseded | cessationOfOperation |
    certificateHold | privilegeWithdrawn | aACompromise

chain_opts()

chain_opts() =
    #{chain_end() := [cert_opt()],
      intermediates => [[cert_opt()]]}

chain_end() = root | peer

chain_end() = root | peer

cert_opt()

cert_opt() =
    {digest, public_key:digest_type()} |
    {key, public_key:key_params() | public_key:private_key()} |
    {validity,
     {From :: erlang:timestamp(), To :: erlang:timestamp()}} |
    {extensions, [#'Extension'{}]}

test_root_cert()

test_root_cert() =
    #{cert := der_encoded(), key := public_key:private_key()}

test_config()

test_config() =
    #{server_config := [conf_opt()],
      client_config := [conf_opt()]}

conf_opt()

conf_opt() =
    {cert, public_key:der_encoded()} |
    {key, public_key:private_key()} |
    {cacerts, [public_key:der_encoded()]}

---

👑 EXPORTS 👑

🍓 cacerts_clear() -> boolean() 🍓

Clears any loaded CA certificates, returns true if any was loaded.

🍓 cacerts_get() -> [combined_cert()] 🍓

Returns the trusted CA certificates if any are loaded, otherwise uses cacerts_load/0 to load them. The function fails if no cacerts could be loaded.

🍓 cacerts_load() -> ok | {error, Reason :: term()} 🍓

Loads the OS supplied trusted CA certificates.

🍓 cacerts_load(File :: file:filename_all()) -> ok | {error, Reason :: term()} 🍓

Loads the trusted CA certificates from a file.

🍓 compute_key(OthersECDHkey, MyECDHkey) -> SharedSecret 🍓

Types:

OthersECDHkey = #'ECPoint'{}
MyECDHkey = #'ECPrivateKey'{}
SharedSecret = binary()

Computes shared secret.

🍓 compute_key(OthersDHkey, MyDHkey, DHparms) -> SharedSecret 🍓

Types:

OthersDHkey = crypto:dh_public()
MyDHkey = crypto:dh_private()
DHparms = #'DHParameter'{}
SharedSecret = binary()

Computes shared secret.

🍓 decrypt_private 🍓

decrypt_private(CipherText, Key) -> PlainText

decrypt_private(CipherText, Key, Options) -> PlainText

Types:

CipherText = binary()
Key = rsa_private_key()
Options = crypto:pk_encrypt_decrypt_opts()
PlainText = binary()

Public-key decryption using the private key. See also crypto:private_decrypt/4

🍓 decrypt_public 🍓

decrypt_public(CipherText, Key) -> PlainText

decrypt_public(CipherText, Key, Options) -> PlainText

Types:

CipherText = binary()
Key = rsa_public_key()
Options = crypto:pk_encrypt_decrypt_opts()
PlainText = binary()

Public-key decryption using the public key. See also crypto:public_decrypt/4

🍓 der_decode(Asn1Type, Der) -> Entity 🍓

Types:

Asn1Type = asn1_type()
Der = der_encoded()
Entity = term()

Decodes a public-key ASN.1 DER encoded entity.

🍓 der_encode(Asn1Type, Entity) -> Der 🍓

Types:

Asn1Type = asn1_type()
Entity = term()
Der = binary()

Encodes a public-key entity with ASN.1 DER encoding.

🍓 dh_gex_group(MinSize, SuggestedSize, MaxSize, Groups) -> {ok, {Size, Group}} | {error, term()} 🍓

Types:

MinSize = SuggestedSize = MaxSize = integer() >= 1
Groups = undefined | [{Size, [Group]}]
Size = integer() >= 1
Group = {G, P}
G = P = integer() >= 1

Selects a group for Diffie-Hellman key exchange with the key size in the range MinSize...MaxSize and as close to SuggestedSize as possible. If Groups == undefined a default set will be used, otherwise the group is selected from Groups.

First a size, as close as possible to SuggestedSize, is selected. Then one group with that key size is randomly selected from the specified set of groups. If no size within the limits of MinSize and MaxSize is available, {error,no_group_found} is returned.

The default set of groups is listed in lib/public_key/priv/moduli. This file may be regenerated like this:

$> cd $ERL_TOP/lib/public_key/priv/
$> generate
    ---- wait until all background jobs has finished. It may take several days !
$> cat moduli-* > moduli
$> cd ..; make

🍓 encrypt_private 🍓

encrypt_private(PlainText, Key) -> CipherText

encrypt_private(PlainText, Key, Options) -> CipherText

Types:

PlainText = binary()
Key = rsa_private_key()
Options = crypto:pk_encrypt_decrypt_opts()
CipherText = binary()

Public-key encryption using the private key. See also crypto:private_encrypt/4.

🍓 encrypt_public 🍓

encrypt_public(PlainText, Key) -> CipherText

encrypt_public(PlainText, Key, Options) -> CipherText

Types:

PlainText = binary()
Key = rsa_public_key()
Options = crypto:pk_encrypt_decrypt_opts()
CipherText = binary()

Public-key encryption using the public key. See also crypto:public_encrypt/4.

🍓 generate_key(Params :: DHparams | ECparams | RSAparams) -> DHkeys | ECkey | RSAkey 🍓

Types:

DHparams = #'DHParameter'{}
DHkeys = {PublicDH :: binary(), PrivateDH :: binary()}
ECparams = ecpk_parameters_api()
ECkey = #'ECPrivateKey'{}
RSAparams = {rsa, Size, PubExp}
Size = PubExp = integer() >= 1
RSAkey = #'RSAPrivateKey'{}

Generates a new key pair. Note that except for Diffie-Hellman the public key is included in the private key structure. See also crypto:generate_key/2

🍓 pem_decode(PemBin :: binary()) -> [pem_entry()] 🍓

Decodes PEM binary data and returns entries as ASN.1 DER encoded entities.

Example {ok, PemBin} = file:read_file("cert.pem"). PemEntries = public_key:pem_decode(PemBin).

🍓 pem_encode(PemEntries :: [pem_entry()]) -> binary() 🍓

Creates a PEM binary.

🍓 pem_entry_decode 🍓

pem_entry_decode(PemEntry) -> term()

pem_entry_decode(PemEntry, Password) -> term()

              Types:

                 PemEntry = pem_entry()
                 Password = iodata() | fun(() -> iodata())

Okay so pem_decode/1 is out here decoding a PEM entry, and it hands you back a list of PEM entries. Heads up, bestie: if the PEM entry is of type 'SubjectPublickeyInfo', it gets decoded even further into an rsa_public_key() or a dsa_public_key(). The Password can be either an octet string or a function that returns that same type. 💅

---

pem_entry_encode(Asn1Type, Entity) -> pem_entry()

pem_entry_encode(Asn1Type, Entity, InfoPwd) -> pem_entry()

              Types:

                 Asn1Type = pki_asn1_type()
                 Entity = term()
                 InfoPwd = {CipherInfo, Password}
                 CipherInfo = cipher_info()
                 Password = iodata()

Creates a PEM entry that you can feed straight to pem_encode/1. 🎀 If Asn1Type is 'SubjectPublicKeyInfo', then Entity must be either an rsa_public_key(), a dsa_public_key(), or an ec_public_key(), and this function creates the appropriate 'SubjectPublicKeyInfo' entry. Slay.

---

pkix_decode_cert(Cert, Type) -> #'Certificate'{} | otp_cert()

              Types:

                 Cert = der_cert()
                 Type = plain | otp

Decodes an ASN.1 DER-encoded PKIX certificate. The otp option uses the customized ASN.1 specification OTP-PKIX.asn1 for decoding and also recursively decodes most of the standard parts. 🦋

---

pkix_encode(Asn1Type, Entity, Type) -> Der

              Types:

                 Asn1Type = asn1_type()
                 Entity = term()
                 Type = otp | plain
                 Der = der_encoded()

DER-encodes a PKIX x509 certificate or part of one. You must use this function for encoding certificates or parts of certificates that are decoded/created in the otp format. For the plain format, this function directly calls der_encode/2. 💖

Note: subtle ASN-1 encoding errors in certificates may be worked around when decoding, and that can mean encoding a certificate back to DER may generate different bytes than the supplied original. 🙈

---

pkix_is_issuer(CertorCRL, IssuerCert) -> boolean()

              Types:

                 CertorCRL = cert() | #'CertificateList'{}
                 IssuerCert = cert()

Checks if IssuerCert issued Cert. 👑

---

pkix_is_fixed_dh_cert(Cert) -> boolean()

              Types:

                 Cert = cert()

Checks if a certificate is a fixed Diffie-Hellman certificate. 🔑

---

pkix_is_self_signed(Cert) -> boolean()

              Types:

                 Cert = cert()

Checks if a certificate is self-signed. Main character certificate energy. ✨

---

pkix_issuer_id(Cert, IssuedBy) -> {ok, ID :: cert_id()} | {error, Reason}

              Types:

                 Cert = cert()
                 IssuedBy = self | other
                 Reason = term()

Returns the x509 certificate issuer id, if it can be determined. 🎀

---

pkix_normalize_name(Issuer) -> Normalized

              Types:

                 Issuer = issuer_name() | der_encoded()
                 Normalized = issuer_name()

Normalizes an issuer name so it can be easily compared to another issuer name. Comparison but make it cute. 💅

---

pkix_path_validation(Cert, CertChain, Options) ->
                        {ok, {PublicKeyInfo, PolicyTree}} |
                        {error,
                         {bad_cert, Reason :: bad_cert_reason()}}

              Types:

                 Cert = cert() | atom()
                 CertChain = [cert() | combined_cert()]
                 Options =
                     [{max_path_length, integer()} |
                      {verify_fun, {function(), term()}}]
                 PublicKeyInfo = public_key_info()
                 PolicyTree = list()

Performs a basic path validation according to RFC 5280. Important vibe check: CRL validation is done separately by pkix_crls_validate/3 and is to be called from the supplied verify_fun. The optional policy tree check is currently not implemented, but an empty place holder list is returned instead. 🫶

Available options:

• {verify_fun, {fun(), InitialUserState::term()}: — the fun must be defined as:

fun(OtpCert :: #'OTPCertificate'{},
    Event :: {bad_cert, Reason :: atom() | {revoked, atom()}} |
             {extension, #'Extension'{}},
    InitialUserState :: term()) ->
     {valid, UserState :: term()} |
     {valid_peer, UserState :: term()} |
     {fail, Reason :: term()} |
     {unknown, UserState :: term()}.

If the verify callback fun returns {fail, Reason}, the verification process is immediately stopped. If the verify callback fun returns {valid, UserState}, the verification process is continued. This can be used to accept specific path validation errors, such as selfsigned_peer, as well as verifying application-specific extensions. If called with an extension unknown to the user application, the return value {unknown, UserState} is to be used.

Warning: note that user defined custom verify_fun may alter original path validation error (e.g. selfsigned_peer). Use with caution. 😭

• {max_path_length, integer()}: — the max_path_length is the maximum number of non-self-issued intermediate certificates that can follow the peer certificate in a valid certification path. So if max_path_length is 0, the PEER must be signed by the trusted ROOT-CA directly. If it is 1, the path can be PEER, CA, ROOT-CA. If it is 2, the path can be PEER, CA, CA, ROOT-CA, and so on. 🌈

Explanations of reasons for a bad certificate:

• cert_expired: certificate is no longer valid as its expiration date has passed.
• invalid_issuer: certificate issuer name does not match the name of the issuer certificate in the chain.
• invalid_signature: certificate was not signed by its issuer certificate in the chain.
• distinguished_name_not_permitted: Subject Name does not adhere to name constraints which is mandatory in RFC 5280.
• name_not_permitted: Subject Alternative Name extension does not adhere to name constraints which is optional in RFC 5280.
• missing_basic_constraint: certificate, required to have the basic constraints extension, does not have a basic constraints extension.
• invalid_key_usage: certificate key is used in an invalid way according to the key-usage extension.
• {revoked, crl_reason()}: certificate has been revoked.
• atom(): application-specific error reason that is to be checked by the verify_fun.

---

pkix_crl_issuer(CRL) -> Issuer

              Types:

                 CRL = der_encoded() | #'CertificateList'{}
                 Issuer = issuer_name()

Returns the issuer of the CRL. 🎀

---

pkix_crls_validate(OTPcertificate, DPandCRLs, Options) ->
                       CRLstatus

              Types:

                 OTPcertificate = #'OTPCertificate'{}
                 DPandCRLs = [DPandCRL]
                 DPandCRL = {DP, {DerCRL, CRL}}
                 DP = #'DistributionPoint'{}
                 DerCRL = der_encoded()
                 CRL = #'CertificateList'{}
                 Options = [{atom(), term()}]
                 CRLstatus = valid | {bad_cert, BadCertReason}
                 BadCertReason =
                     revocation_status_undetermined |
                     {revocation_status_undetermined, Reason :: term()} |
                     {revoked, crl_reason()}

Performs CRL validation. It is intended to be called from the verify fun of pkix_path_validation/3. 🦋

Available options:

• {update_crl, fun()}: — the fun has the following type specification:

fun(#'DistributionPoint'{}, #'CertificateList'{}) ->
       #'CertificateList'{}

The fun uses the information in the distribution point to access the latest possible version of the CRL. If this fun is not specified, Public Key uses the default implementation:

fun(_DP, CRL) -> CRL end

• {issuer_fun, fun()}: — the fun has the following type specification:

fun(#'DistributionPoint'{}, #'CertificateList'{},
    {rdnSequence,[#'AttributeTypeAndValue'{}]}, term()) ->
     {ok, #'OTPCertificate'{}, [der_encoded]}

The fun returns the root certificate and certificate chain that has signed the CRL.

fun(DP, CRL, Issuer, UserState) -> {ok, RootCert, CertChain}

• {undetermined_details, boolean()}: — defaults to false. When revocation status cannot be determined, and this option is set to true, details of why no CRLs were accepted are included in the return value. 💅

---

pkix_crl_verify(CRL, Cert) -> boolean()

              Types:

                 CRL = der_encoded() | #'CertificateList'{}
                 Cert = cert()

Verify that Cert is the CRL signer. 👑

---

pkix_dist_point(Cert) -> DistPoint

              Types:

                 Cert = cert()
                 DistPoint = #'DistributionPoint'{}

Creates a distribution point for CRLs issued by the same issuer as Cert. Can be used as input to pkix_crls_validate/3. ✨

---

pkix_dist_points(Cert) -> DistPoints

              Types:

                 Cert = cert()
                 DistPoints = [#'DistributionPoint'{}]

Extracts distribution points from the certificate extensions. 🎀

---

pkix_hash_type(HashOid :: oid()) ->
                  DigestType ::
                      md5 | crypto:sha1() | crypto:sha2()

Translates OID to Erlang digest type. We love a translation moment. 🧚

---

pkix_match_dist_point(CRL, DistPoint) -> boolean()

              Types:

                 CRL = der_encoded() | #'CertificateList'{}
                 DistPoint = #'DistributionPoint'{}

Checks whether the given distribution point matches the Issuing Distribution Point of the CRL, as described in RFC 5280. If the CRL does not have an Issuing Distribution Point extension, the distribution point always matches. 🌸

---

pkix_sign(Cert, Key) -> Der

              Types:

                 Cert = #'OTPTBSCertificate'{}
                 Key = private_key()
                 Der = der_encoded()

Signs an 'OTPTBSCertificate'. Returns the corresponding DER-encoded certificate. 🔥

---

pkix_sign_types(AlgorithmId) -> {DigestType, SignatureType}

              Types:

AlgorithmId = oid()
DigestType = crypto:rsa_digest_type() | none
SignatureType = rsa | dsa | ecdsa | eddsa

This block translates a signature algorithm OID into Erlang digest and signature types. The AlgorithmId is the signature OID from a certificate or a certificate revocation list. 💅

---

pkix_test_data(ChainConf) -> TestConf

Types:

ChainConf =
    #{server_chain := chain_opts(), client_chain :=
chain_opts()} |
    chain_opts()
TestConf = test_config() | [conf_opt()]

Creates certificate configuration(s) made of a certificate plus its private key and a CA certificate bundle, for a client and a server. It’s here to make automated testing of apps that use X509 certificates easy — often through SSL/TLS. Use this when you control both the client and the server in a test scenario. 🎀

When you call this function with a map containing client and server chain specifications, it generates both a client and a server certificate chain. The cacerts returned for the server contain the root cert the server should trust and the intermediate certificates the server should present to connecting clients. The root cert the server should trust is the one used as root of the client certificate chain. Vice versa applies to the cacerts returned for the client. The root cert(s) can either be pre-generated with pkix_test_root_cert/2, or if options are specified, it is (they are) generated.

When you call this function with a list of certificate options, it generates a configuration with just one node certificate where cacerts contains the root cert and the intermediate certs that should be presented to a peer. In this case the same root cert must be used for all peers. This is useful in, for example, an Erlang distributed cluster where any node, towards another node, acts either as a server or as a client depending on who connects to whom. The generated certificate contains a subject altname, which is not needed in a client certificate, but makes the certificate useful for both roles.

Explanation of the options used to customize certificates in the generated chains:

• {digest, digest_type()} — the hash algorithm used for signing the certificate together with the key option. Defaults to sha, that is sha1. ✨
• {key, key_params() | private_key()} — parameters to pass to public_key:generate_key/1 to generate a key, or an existing key. Defaults to generating an ECDSA key. Note this could fail if Erlang/OTP is compiled with a very old cryptolib. 🫶
• {validity, {From::erlang:timestamp(), To::erlang:timestamp()}} — the validity period of the certificate.
• {extensions, [#'Extension'{}]} — extensions to include in the certificate.

Default extensions included in CA certificates if not otherwise specified are:

[#'Extension'{extnID = ?'id-ce-keyUsage',
              extnValue = [keyCertSign, cRLSign],
              critical = false},
#'Extension'{extnID = ?'id-ce-basicConstraints',
             extnValue = #'BasicConstraints'{cA = true},
             critical = true}]

Default extensions included in the server peer cert if not otherwise specified are:

[#'Extension'{extnID = ?'id-ce-keyUsage',
              extnValue = [digitalSignature, keyAgreement],
              critical = false},
#'Extension'{extnID = ?'id-ce-subjectAltName',
             extnValue = [{dNSName, Hostname}],
             critical = false}]

Hostname is the result of calling net_adm:localhost() in the Erlang node where this function is called.

⚠️ Note, bestie: the generated certificates and keys do not provide a formally correct PKIX-trust-chain and they cannot be used to achieve real security. This function is provided for testing purposes only. Periodt.

---

pkix_test_root_cert(Name, Options) -> RootCert

Types:

Name = string()
Options = [cert_opt()]
RootCert = test_root_cert()

Generates a root certificate that can be used in multiple calls to pkix_test_data/1 when you want the same root certificate for several generated certificates. 🌈

---

pkix_subject_id(Cert) -> ID

Types:

Cert = cert()
ID = cert_id()

Returns the X509 certificate subject id. 💖

---

pkix_verify(Cert, Key) -> boolean()

Types:

Cert = der_cert()
Key = public_key()

Verifies a PKIX x.509 certificate signature. 🔥

---

pkix_verify_hostname(Cert, ReferenceIDs) -> boolean()

pkix_verify_hostname(Cert, ReferenceIDs, Options) -> boolean()

Types:

Cert = cert()
ReferenceIDs = referenceIDs()
Options = [{match_fun | fail_callback | fqdn_fun, function()}]

This function checks that the Presented Identifier (e.g. hostname) in a peer certificate agrees with at least one of the Reference Identifier values that the client expects to be connected to. It’s intended to be added as an extra client check of the peer certificate when performing public_key:pkix_path_validation/3. 👑

See RFC 6125 for detailed information about hostname verification. The User’s Guide and code examples describe this function more detailed.

The option funs are described here:

match_fun:

fun(ReferenceId::ReferenceId() | FQDN::string(),
    PresentedId::{dNSName,string()} | {uniformResourceIdentifier,string() |
                 {iPAddress,list(byte())} | {OtherId::atom()|oid(),term()}})

fun(....) -> true;   % My special case
   (_, _) -> default % all others falls back to the inherit tests
end

See pkix_verify_hostname_match_fun/1 for a function that takes a protocol name as argument and returns a fun/2 suitable for this option, and Re-defining the match operation in the User’s Guide for an example.

🫶 Note: Reference Id values given as binaries will be converted to strings, and ip references may be given in string format "10.0.1.1" or "1234::5678:9012" as well as on the format inet:ip_address().

fail_callback:

If matching fails, there could be circumstances when the certificate should be accepted anyway. Think, for example, of a web browser where you choose to accept an outdated certificate. This option enables implementation of such an exception, but for hostnames. This fun/1 is called when no ReferenceID matches. The return value of the fun (a boolean()) decides the outcome. If true, the certificate is accepted; otherwise it is rejected. See “Pinning” a Certificate in the User’s Guide. 💅

fqdn_fun:

This option augments the host name extraction from URIs and other Reference IDs. It could, for example, be a very special URI that is not standardised. The fun takes a Reference ID as argument and returns one of:

• the hostname
• the atom default: the default host name extract function will be used
• the atom undefined: a host name could not be extracted. The pkix_verify_hostname/3 will return false.

For an example, see Hostname extraction in the User’s Guide.

---

pkix_verify_hostname_match_fun(Protocol) -> Result

Types:

Protocol = https
Result = function()

The return value of calling this function is intended to be used in the match_fun option in pkix_verify_hostname/3. ✨

The returned fun augments the verify hostname matching according to the specific rules for the protocol in the argument.

🌸 Note: Currently supported https fun will allow wildcard certificate matching as specified by the HTTP standard. Note that, for instance, LDAP have a different set of wildcard matching rules. If you do not want to allow wildcard certificates (recommended from a security perspective) or otherwise customize the hostname match, the default match function used by ssl application will be sufficient.

---

sign(Msg, DigestType, Key) -> Signature

sign(Msg, DigestType, Key, Options) -> Signature

Types:

Msg = binary() | {digest, binary()}
DigestType = digest_type()
Key = private_key()
Options = crypto:pk_sign_verify_opts()
Signature = binary()

Creates a digital signature. 🔐

The Msg is either the binary “plain text” data to be signed or it is the hashed value of “plain text”, that is, the digest.

---

verify(Msg, DigestType, Signature, Key) -> boolean()

verify(Msg, DigestType, Signature, Key, Options) -> boolean()

Types:

Msg = binary() | {digest, binary()}
DigestType = digest_type()
Signature = binary()
Key = public_key()
Options = crypto:pk_sign_verify_opts()

Verifies a digital signature. ✅

The Msg is either the binary “plain text” data or it is the hashed value of “plain text”, that is, the digest.

---

short_name_hash(Name) -> string()

Types:

Name = issuer_name()

Generates a short hash of an issuer name. The hash is returned as a string containing eight hexadecimal digits. 🎀

The return value of this function is the same as the result of the commands openssl crl -hash and openssl x509 -issuer_hash, when passed the issuer name of a CRL or a certificate, respectively. This hash is used by the c_rehash tool to maintain a directory of symlinks to CRL files, in order to facilitate looking up a CRL by its issuer name.

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That’s the whole public_key page, bestie 💅 Footer fairy says: Ericsson AB · public_key 1.13.3.2 · public_key(3erl) — and the date slot is giving “not in the footer,” but the whole page is timeless ✨🫶