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%%% eturnal STUN/TURN server. |
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%%% |
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%%% Copyright (c) 2021 Holger Weiss <holger@zedat.fu-berlin.de>. |
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%%% Copyright (c) 2021 ProcessOne, SARL. |
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%%% All rights reserved. |
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%%% |
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%%% Licensed under the Apache License, Version 2.0 (the "License"); |
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%%% you may not use this file except in compliance with the License. |
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%%% You may obtain a copy of the License at |
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%%% |
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%%% http://www.apache.org/licenses/LICENSE-2.0 |
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%%% |
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%%% Unless required by applicable law or agreed to in writing, software |
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%%% distributed under the License is distributed on an "AS IS" BASIS, |
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%%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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%%% See the License for the specific language governing permissions and |
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%%% limitations under the License. |
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-module(eturnal_cert). |
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-export([create/1]). |
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-include_lib("public_key/include/public_key.hrl"). |
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-define(ETURNAL_KEY_SIZE, 4096). |
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% Currently not exported by calendar: |
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-type year() :: non_neg_integer(). |
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-type month() :: 1..12. |
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-type day() :: 1..31. |
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%% API. |
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-spec create(string() | binary()) -> binary(). |
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create(Domain) when is_binary(Domain) -> |
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create(binary_to_list(Domain)); |
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create(Domain) -> |
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Key = private_key(), |
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Crt = certificate(Domain, Key), |
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public_key:pem_encode([pem_entry(Key), pem_entry(Crt)]). |
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%% Internal functions. |
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-spec private_key() -> #'RSAPrivateKey'{}. |
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private_key() -> |
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public_key:generate_key({rsa, ?ETURNAL_KEY_SIZE, 65537}). |
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-spec certificate(string(), #'RSAPrivateKey'{}) -> public_key:der_encoded(). |
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certificate(Domain, Key) -> |
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TBS = #'OTPTBSCertificate'{ |
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serialNumber = serial_number(), |
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signature = signature(), |
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issuer = issuer(Domain), |
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validity = validity(), |
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subject = subject(Domain), |
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subjectPublicKeyInfo = subject_key_info(Key), |
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extensions = extensions(Domain)}, |
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public_key:pkix_sign(TBS, Key). |
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-spec serial_number() -> pos_integer(). |
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serial_number() -> |
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rand:uniform(1000000000). |
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-spec signature() -> #'SignatureAlgorithm'{}. |
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signature() -> |
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#'SignatureAlgorithm'{ |
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algorithm = ?'sha256WithRSAEncryption'}. |
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-spec issuer(string()) -> {rdnSequence, [[#'AttributeTypeAndValue'{}]]}. |
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issuer(Domain) -> % Self-signed. |
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subject(Domain). |
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-spec validity() -> #'Validity'{}. |
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validity() -> |
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#'Validity'{ |
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notBefore = format_date(calendar:universal_time()), |
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notAfter = format_date(2038, 1, 1)}. |
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-spec subject(string()) -> {rdnSequence, [[#'AttributeTypeAndValue'{}]]}. |
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subject(Domain) -> |
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{rdnSequence, |
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[[#'AttributeTypeAndValue'{ |
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type = ?'id-at-commonName', |
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value = {printableString, Domain}}]]}. |
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-spec subject_key_info(#'RSAPrivateKey'{}) -> #'OTPSubjectPublicKeyInfo'{}. |
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subject_key_info(#'RSAPrivateKey'{modulus = Modulus, publicExponent = Exp}) -> |
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#'OTPSubjectPublicKeyInfo'{ |
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algorithm = |
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#'PublicKeyAlgorithm'{ |
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algorithm = ?'rsaEncryption'}, |
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subjectPublicKey = |
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#'RSAPublicKey'{ |
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modulus = Modulus, |
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publicExponent = Exp}}. |
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-spec extensions(string()) -> [#'Extension'{}]. |
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extensions(Domain) -> |
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[#'Extension'{ |
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extnID = ?'id-ce-subjectAltName', |
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extnValue = [{dNSName, Domain}], |
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critical = false}, |
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#'Extension'{ |
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extnID = ?'id-ce-basicConstraints', |
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extnValue = #'BasicConstraints'{cA = true}, |
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critical = false}]. |
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-spec pem_entry(#'RSAPrivateKey'{} | public_key:der_encoded()) |
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-> public_key:pem_entry(). |
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pem_entry(#'RSAPrivateKey'{} = Key) -> |
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public_key:pem_entry_encode('RSAPrivateKey', Key); |
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pem_entry(Crt) when is_binary(Crt) -> |
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{'Certificate', Crt, not_encrypted}. |
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-spec format_date(year(), month(), day()) -> {utcTime, string()}. |
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format_date(Y, M, D) when Y >= 2000 -> |
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{utcTime, |
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lists:flatten( |
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io_lib:format("~2.10.0B~2.10.0B~2.10.0B~2.10.0B~2.10.0B~2.10.0BZ", |
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[Y - 2000, M, D, 0, 0, 0]))}. |
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-spec format_date(calendar:datetime()) -> {utcTime, string()}. |
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format_date({{Y, M, D}, {_, _, _}}) -> |
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format_date(Y, M, D). |