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diff --git a/lib/crypto/doc/src/engine_keys.xml b/lib/crypto/doc/src/engine_keys.xml new file mode 100644 index 0000000000..64d1e6c2a3 --- /dev/null +++ b/lib/crypto/doc/src/engine_keys.xml @@ -0,0 +1,128 @@ +<?xml version="1.0" encoding="utf-8" ?> +<!DOCTYPE chapter SYSTEM "chapter.dtd"> + +<chapter> + <header> + <copyright> + <year>2017</year><year>2017</year> + <holder>Ericsson AB. All Rights Reserved.</holder> + </copyright> + <legalnotice> + The contents of this file are subject to the Erlang Public License, + Version 1.1, (the "License"); you may not use this file except in + compliance with the License. You should have received a copy of the + Erlang Public License along with this software. If not, it can be + retrieved online at http://www.erlang.org/. + + Software distributed under the License is distributed on an "AS IS" + basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See + the License for the specific language governing rights and limitations + under the License. + </legalnotice> + <title>Engine Stored Keys</title> + <prepared>Hans Nilsson</prepared> + <date>2017-11-10</date> + <file>engine_keys.xml</file> + </header> + <p> + <marker id="engine_key"></marker> + This chapter describes the support in the crypto application for using public and private keys stored in encryption engines. + </p> + + <section> + <title>Background</title> + <p> + <url href="https://www.openssl.org/">OpenSSL</url> exposes an Engine API, which makes + it possible to plug in alternative implementations for some of the cryptographic + operations implemented by OpenSSL. + See the chapter <seealso marker="crypto:engine_load#engine_load">Engine Load</seealso> + for details and how to load an Engine. + </p> + <p> + In addition to provide alternative cryptographic implementations, an engine could provide a storage for + private or public keys. Such a storage could be made safer than the normal file system. Such techniques are not + described in this User's Guide. Here we concentrate on how to use private or public keys stored in + such an engine. + </p> + <p> + The storage engine must call <c>ENGINE_set_load_privkey_function</c> and <c>ENGINE_set_load_pubkey_function</c>. + See the OpenSSL cryptolib's <url href="https://www.openssl.org/docs/manpages.html">manpages</url>. + </p> + <p> + OTP/Crypto requires that the user provides two or three items of information about the key. The application used + by the user is usually on a higher level, for example <seealso marker="ssl:ssl_app#application">SSL</seealso>. If using + the crypto application directly, it is required that: + </p> + <list> + <item>an Engine is loaded, see the chapter on <seealso marker="crypto:engine_load#engine_load">Engine Load</seealso> + or the <seealso marker="crypto:crypto#engine_load-3">Reference Manual</seealso> + </item> + <item>a reference to a key in the Engine is available. This should be an Erlang string or binary and depends + on the Engine loaded + </item> + <item>an Erlang map is constructed with the Engine reference, the key reference and possibly a key passphrase if + needed by the Engine. See the <seealso marker="crypto:crypto#engine_key_ref_type">Reference Manual</seealso> for + details of the map. + </item> + </list> + </section> + + <section> + <title>Use Cases</title> + <section> + <title>Sign with an engine stored private key</title> + <p> + This example shows how to construct a key reference that is used in a sign operation. + The actual key is stored in the engine that is loaded at prompt 1. + </p> + <code> +1> {ok, EngineRef} = crypto:engine_load(....). +... +{ok,#Ref<0.2399045421.3028942852.173962>} +2> PrivKey = #{engine => EngineRef, + key_id => "id of the private key in Engine"}. +... +3> Signature = crypto:sign(rsa, sha, <<"The message">>, PrivKey). +<<65,6,125,254,54,233,84,77,83,63,168,28,169,214,121,76, + 207,177,124,183,156,185,160,243,36,79,125,230,231,...>> + </code> + </section> + + <section> + <title>Verify with an engine stored public key</title> + <p> + Here the signature and message in the last example is verifyed using the public key. + The public key is stored in an engine, only to exemplify that it is possible. The public + key could of course be handled openly as usual. + </p> + <code> +4> PublicKey = #{engine => EngineRef, + key_id => "id of the public key in Engine"}. +... +5> crypto:verify(rsa, sha, <<"The message">>, Signature, PublicKey). +true +6> + </code> + </section> + + <section> + <title>Using a password protected private key</title> + <p> + The same example as the first sign example, except that a password protects the key down in the Engine. + </p> + <code> +6> PrivKeyPwd = #{engine => EngineRef, + key_id => "id of the pwd protected private key in Engine", + password => "password"}. +... +7> crypto:sign(rsa, sha, <<"The message">>, PrivKeyPwd). +<<140,80,168,101,234,211,146,183,231,190,160,82,85,163, + 175,106,77,241,141,120,72,149,181,181,194,154,175,76, + 223,...>> +8> + </code> + + </section> + + </section> +</chapter> |