<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE erlref SYSTEM "erlref.dtd">
<erlref>
<header>
<copyright>
<year>1999</year><year>2015</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
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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
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</legalnotice>
<title>ssl</title>
<prepared></prepared>
<docno></docno>
<date></date>
<rev></rev>
<file>ssl.xml</file>
</header>
<module>ssl</module>
<modulesummary>Interface Functions for Secure Socket Layer</modulesummary>
<description>
<p>This module contains interface functions for the SSL.</p>
</description>
<section>
<title>SSL</title>
<list type="bulleted">
<item><c>ssl</c> requires the <c>crypto</c> and <c>public_key</c>
applications.</item>
<item>Supported SSL/TLS-versions are SSL-3.0, TLS-1.0,
TLS-1.1, and TLS-1.2.</item>
<item>For security reasons SSL-2.0 is not supported.</item>
<item>For security reasons SSL-3.0 is no longer supported by default,
but can be configured.</item>
<item>Ephemeral Diffie-Hellman cipher suites are supported,
but not Diffie Hellman Certificates cipher suites.</item>
<item>Elliptic Curve cipher suites are supported if the <c>crypto</c>
application supports it and named curves are used.
</item>
<item>Export cipher suites are not supported as the
U.S. lifted its export restrictions in early 2000.</item>
<item>IDEA cipher suites are not supported as they have
become deprecated by the latest TLS specification so it is not
motivated to implement them.</item>
<item>CRL validation is supported.</item>
<item>Policy certificate extensions are not supported.</item>
<item>'Server Name Indication' extension client side
(RFC 6066, Section 3) is supported.</item>
</list>
</section>
<section>
<title>DATA TYPES</title>
<p>The following data types are used in the functions for <c>ssl</c>:</p>
<taglist>
<tag><c>boolean()</c></tag>
<item><p><c>= true | false</c></p></item>
<tag><c>option()</c></tag>
<item><p><c>= socketoption() | ssloption() | transportoption()</c></p>
</item>
<tag><c>socketoption()</c></tag>
<item><p><c>= proplists:property()</c></p>
<p>The default socket options are
<c>[{mode,list},{packet, 0},{header, 0},{active, true}]</c>.</p>
<p>For valid options, see the
<seealso marker="kernel:inet">inet(3)</seealso> and
<seealso marker="kernel:gen_tcp">gen_tcp(3)</seealso> manual pages
in <c>kernel</c>.</p></item>
<tag><c>ssloption()</c></tag>
<item><p><c>= {verify, verify_type()}</c></p>
<p><c>| {verify_fun, {fun(), term()}}</c></p>
<p><c>| {fail_if_no_peer_cert, boolean()} {depth, integer()}</c></p>
<p><c>| {cert, der_encoded()}</c></p>
<p><c>| {certfile, path()}</c></p>
<p><c>| {key, {'RSAPrivateKey'| 'DSAPrivateKey' | 'ECPrivateKey'
| 'PrivateKeyInfo', der_encoded()}}</c></p>
<p><c>| {keyfile, path()}</c></p>
<p><c>| {password, string()}</c></p>
<p><c>| {cacerts, [der_encoded()]}</c></p>
<p><c>| {cacertfile, path()}</c></p>
<p><c>| {dh, der_encoded()}</c></p>
<p><c>| {dhfile, path()}</c></p>
<p><c>| {ciphers, ciphers()}</c></p>
<p><c>| {user_lookup_fun, {fun(), term()}}, {psk_identity, string()},
{srp_identity, {string(), string()}}</c></p>
<p><c>| {ssl_imp, ssl_imp()}</c></p>
<p><c>| {reuse_sessions, boolean()}</c></p>
<p><c>| {reuse_session, fun()} {next_protocols_advertised, [binary()]}</c></p>
<p><c>| {client_preferred_next_protocols, {client | server,
[binary()]} | {client | server, [binary()], binary()}}</c></p>
<p><c>| {log_alert, boolean()}</c></p>
<p><c>| {server_name_indication, hostname() | disable}</c></p></item>
<tag><c>transportoption()</c></tag>
<item><p><c>= {cb_info, {CallbackModule::atom(), DataTag::atom(),
ClosedTag::atom(), ErrTag:atom()}}</c></p>
<p>Defaults to <c>{gen_tcp, tcp, tcp_closed, tcp_error}</c>. Can be used
to customize the transport layer. The callback module must implement a
reliable transport protocol, behave as <c>gen_tcp</c>, and have functions
corresponding to <c>inet:setopts/2</c>, <c>inet:getopts/2</c>,
<c>inet:peername/1</c>, <c>inet:sockname/1</c>, and <c>inet:port/1</c>.
The callback <c>gen_tcp</c> is treated specially and calls <c>inet</c>
directly.</p>
<taglist>
<tag><c>CallbackModule</c></tag>
<item><p><c>= atom()</c></p></item>
<tag><c>DataTag</c></tag>
<item><p><c>= atom()</c></p>
<p>Used in socket data message.</p></item>
<tag><c>ClosedTag</c></tag>
<item><p><c>= atom()</c></p>
<p>Used in socket close message.</p></item>
</taglist>
</item>
<tag><c>verify_type()</c></tag>
<item><p><c>= verify_none | verify_peer</c></p></item>
<tag><c>path()</c></tag>
<item><p><c>= string()</c></p>
<p>Represents a file path.</p></item>
<tag><c>der_encoded()</c></tag>
<item><p><c>= binary()</c></p>
<p>ASN.1 DER-encoded entity as an Erlang binary.</p></item>
<tag><c>host()</c></tag>
<item><p><c>= hostname() | ipaddress()</c></p></item>
<tag><c>hostname()</c></tag>
<item><p><c>= string()</c></p></item>
<tag><c>ip_address()</c></tag>
<item><p><c>= {N1,N2,N3,N4} % IPv4 | {K1,K2,K3,K4,K5,K6,K7,K8} % IPv6
</c></p></item>
<tag><c>sslsocket()</c></tag>
<item><p>Opaque to the user.</p></item>
<tag><c>protocol()</c></tag>
<item><p><c>= sslv3 | tlsv1 | 'tlsv1.1' | 'tlsv1.2'</c></p></item>
<tag><c>ciphers()</c></tag>
<item><p><c>= [ciphersuite()] | string()</c></p>
<p>According to old API.</p></item>
<tag><c>ciphersuite()</c></tag>
<item><p><c>= {key_exchange(), cipher(), hash()}</c></p></item>
<tag><c>key_exchange()</c></tag>
<item><p><c>= rsa | dhe_dss | dhe_rsa | dh_anon | psk | dhe_psk
| rsa_psk | srp_anon | srp_dss | srp_rsa | ecdh_anon | ecdh_ecdsa
| ecdhe_ecdsa | ecdh_rsa | ecdhe_rsa</c></p></item>
<tag><c>cipher()</c></tag>
<item><p><c>= rc4_128 | des_cbc | '3des_ede_cbc'
| aes_128_cbc | aes_256_cbc | aes_128_gcm | aes_256_gcm</c></p></item>
<tag><c>hash()</c></tag>
<item><p><c>= md5 | sha</c></p></item>
<tag><c>prf_random()</c></tag>
<item><p><c>= client_random | server_random</c></p></item>
<tag><c>srp_param_type()</c></tag>
<item><p><c>= srp_1024 | srp_1536 | srp_2048 | srp_3072
| srp_4096 | srp_6144 | srp_8192</c></p></item>
</taglist>
</section>
<section>
<title>SSL OPTION DESCRIPTIONS - COMMON for SERVER and CLIENT</title>
<p>The following options have the same meaning in the client and
the server:</p>
<taglist>
<tag><c>{cert, der_encoded()}</c></tag>
<item><p>The DER-encoded users certificate. If this option
is supplied, it overrides option <c>certfile</c>.</p></item>
<tag><c>{certfile, path()}</c></tag>
<item><p>Path to a file containing the user certificate.</p></item>
<tag><c>{key, {'RSAPrivateKey'| 'DSAPrivateKey' | 'ECPrivateKey'
|'PrivateKeyInfo', der_encoded()}}</c></tag>
<item><p>The DER-encoded user's private key. If this option
is supplied, it overrides option <c>keyfile</c>.</p></item>
<tag><c>{keyfile, path()}</c></tag>
<item><p>Path to the file containing the user's
private PEM-encoded key. As PEM-files can contain several
entries, this option defaults to the same file as given by
option <c>certfile</c>.</p></item>
<tag><c>{password, string()}</c></tag>
<item><p>String containing the user's password. Only used if the
private keyfile is password-protected.</p></item>
<tag><c>{cacerts, [der_encoded()]}</c></tag>
<item><p>The DER-encoded trusted certificates. If this option
is supplied it overrides option <c>cacertfile</c>.</p></item>
<tag><c>{ciphers, ciphers()}</c></tag>
<item><p>Supported cipher suites. The function
<c>cipher_suites/0</c> can be used to find all ciphers that are
supported by default. <c>cipher_suites(all)</c> can be called
to find all available cipher suites. Pre-Shared Key
(<url href="http://www.ietf.org/rfc/rfc4279.txt">RFC 4279</url> and
<url href="http://www.ietf.org/rfc/rfc5487.txt">RFC 5487</url>),
Secure Remote Password
(<url href="http://www.ietf.org/rfc/rfc5054.txt">RFC 5054</url>),
and anonymous cipher suites only work if explicitly enabled by
this option; they are supported/enabled by the peer also.
Anonymous cipher suites are supported for testing purposes
only and are not be used when security matters.</p></item>
<tag><c>{ssl_imp, new | old}</c></tag>
<item><p>Has no longer any meaning as the old implementation is
removed; it is ignored.</p></item>
<tag><c>{secure_renegotiate, boolean()}</c></tag>
<item><p>Specifies if to reject renegotiation attempt that does
not live up to
<url href="http://www.ietf.org/rfc/rfc5746.txt">RFC 5746</url>.
By default <c>secure_renegotiate</c> is set to <c>false</c>,
that is, secure renegotiation is used if possible,
but it fallback to unsecure renegotiation if the peer
does not support
<url href="http://www.ietf.org/rfc/rfc5746.txt">RFC 5746</url>.</p>
</item>
<tag><c>{depth, integer()}</c></tag>
<item><p>Maximum number of non-self-issued
intermediate certificates that can follow the peer certificate
in a valid certification path. So, if depth is 0 the PEER must
be signed by the trusted ROOT-CA directly; if 1 the path can
be PEER, CA, ROOT-CA; if 2 the path can be PEER, CA, CA,
ROOT-CA, and so on. The default value is 1.</p></item>
<tag><c>{verify_fun, {Verifyfun :: fun(), InitialUserState ::
term()}}</c></tag>
<item><p>The verification fun is to be defined as follows:</p>
<code>
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()}.
</code>
<p>The verification fun is called during the X509-path
validation when an error or an extension unknown to the <c>ssl</c>
application is encountered. It is also called
when a certificate is considered valid by the path validation
to allow access to each certificate in the path to the user
application. It differentiates between the peer
certificate and the CA certificates by using <c>valid_peer</c> or
<c>valid</c> as second argument to the verification fun. See the
<seealso marker="public_key:cert_records">public_key User's
Guide</seealso> for definition of <c>#'OTPCertificate'{}</c> and
<c>#'Extension'{}</c>.</p>
<list type="bulleted">
<item><p>If the verify callback fun returns <c>{fail, Reason}</c>,
the verification process is immediately stopped, an alert is
sent to the peer, and the TLS/SSL handshake terminates.</p></item>
<item><p>If the verify callback fun returns <c>{valid, UserState}</c>,
the verification process continues.</p></item>
<item><p>If the verify callback fun always returns
<c>{valid, UserState}</c>, the TLS/SSL handshake does not
terminate regarding verification failures and the connection is
established.</p></item>
<item><p>If called with an extension unknown to the user application,
return value <c>{unknown, UserState}</c> is to be used.</p></item>
</list>
<p>Default option <c>verify_fun</c> in <c>verify_peer mode</c>:</p>
<code>
{fun(_,{bad_cert, _} = Reason, _) ->
{fail, Reason};
(_,{extension, _}, UserState) ->
{unknown, UserState};
(_, valid, UserState) ->
{valid, UserState};
(_, valid_peer, UserState) ->
{valid, UserState}
end, []}
</code>
<p>Default option <c>verify_fun</c> in mode <c>verify_none</c>:</p>
<code>
{fun(_,{bad_cert, _}, UserState) ->
{valid, UserState};
(_,{extension, _}, UserState) ->
{unknown, UserState};
(_, valid, UserState) ->
{valid, UserState};
(_, valid_peer, UserState) ->
{valid, UserState}
end, []}
</code>
<p>The possible path validation errors are given on form
<c>{bad_cert, Reason}</c> where <c>Reason</c> is:</p>
<taglist>
<tag><c>unknown_ca</c></tag>
<item><p>No trusted CA was found in the trusted store. The trusted CA is
normally a so called ROOT CA, which is a self-signed certificate. Trust can
be claimed for an intermediat CA (trusted anchor does not have to be
self-signed according to X-509) by using option <c>partial_chain</c>.</p>
</item>
<tag><c>selfsigned_peer</c></tag>
<item><p>The chain consisted only of one self-signed certificate.</p></item>
<tag><c>PKIX X-509-path validation error</c></tag>
<item><p>For possible reasons, see <seealso
marker="public_key:public_key#pkix_path_validation-3">public_key:pkix_path_validation/3</seealso>
</p></item>
</taglist>
</item>
<tag>{crl_check, boolean() | peer | best_effort }</tag>
<item>
Perform CRL (Certificate Revocation List) verification
<seealso marker="public_key:public_key#pkix_crl_validate-3">
(public_key:pkix_crls_validate/3)</seealso> on all the certificates during the path validation
<seealso
marker="public_key:public_key#pkix_path_validation-3">(public_key:pkix_path_validation/3)
</seealso>
of the certificate chain. Defaults to false.
<p><c>peer</c> - check is only performed on
the peer certificate.</p>
<p><c>best_effort</c> - if certificate revocation status can not be determined
it will be accepted as valid.</p>
<p>The CA certificates specified for the connection will be used to
construct the certificate chain validating the CRLs.</p>
<p>The CRLs will be fetched from a local or external cache
<seealso marker="ssl:ssl_crl_cache_api">ssl_crl_cache_api(3)</seealso>.</p>
</item>
<tag>{crl_cache, {Module :: atom(), {DbHandle :: internal | term(), Args :: list()}}}</tag>
<item>
<p>Module defaults to ssl_crl_cache with <c> DbHandle </c> internal and an
empty argument list. The following arguments may be specified for the internal cache.</p>
<taglist>
<tag>{http, timeout()}</tag>
<item>
Enables fetching of CRLs specified as http URIs in<seealso
marker="public_key:cert_records"> X509 cerificate extensions.</seealso>
Requires the OTP inets application.
</item>
</taglist>
</item>
<tag><c>{partial_chain, fun(Chain::[DerCert]) -> {trusted_ca, DerCert} |
unknown_ca }</c></tag>
<item><p>Claim an intermediate CA in the chain as trusted. TLS then
performs <c>public_key:pkix_path_validation/3</c>
with the selected CA as trusted anchor and the rest of the chain.</p></item>
<tag><c>{versions, [protocol()]}</c></tag>
<item><p>TLS protocol versions supported by started clients and servers.
This option overrides the application environment option
<c>protocol_version</c>. If the environment option is not set, it defaults
to all versions, except SSL-3.0, supported by the <c>ssl</c> application.
See also <seealso marker="ssl:ssl_app">ssl(6).</seealso></p></item>
<tag><c>{hibernate_after, integer()|undefined}</c></tag>
<item><p>When an integer-value is specified, <c>ssl_connection</c>
goes into hibernation after the specified number of milliseconds
of inactivity, thus reducing its memory footprint. When
<c>undefined</c> is specified (this is the default), the process
never goes into hibernation.</p></item>
<tag><c>{user_lookup_fun, {Lookupfun :: fun(), UserState :: term()}}</c></tag>
<item><p>The lookup fun is to defined as follows:</p>
<code>
fun(psk, PSKIdentity ::string(), UserState :: term()) ->
{ok, SharedSecret :: binary()} | error;
fun(srp, Username :: string(), UserState :: term()) ->
{ok, {SRPParams :: srp_param_type(), Salt :: binary(), DerivedKey :: binary()}} | error.
</code>
<p>For Pre-Shared Key (PSK) cipher suites, the lookup fun is
called by the client and server to determine the shared
secret. When called by the client, <c>PSKIdentity</c> is set to the
hint presented by the server or to undefined. When called by the
server, <c>PSKIdentity</c> is the identity presented by the client.</p>
<p>For Secure Remote Password (SRP), the fun is only used by the server to
obtain parameters that it uses to generate its session keys.
<c>DerivedKey</c> is to be derived according to
<url href="http://tools.ietf.org/html/rfc2945#section-3"> RFC 2945</url> and
<url href="http://tools.ietf.org/html/rfc5054#section-2.4"> RFC 5054</url>:
<c>crypto:sha([Salt, crypto:sha([Username, <<$:>>, Password])])</c>
</p>
</item>
<tag><c>{padding_check, boolean()}</c></tag>
<item><p>Affects TLS-1.0 connections only.
If set to <c>false</c>, it disables the block cipher padding check
to be able to interoperate with legacy software.</p></item>
</taglist>
<warning><p>Using <c>{padding_check, boolean()}</c> makes TLS
vulnerable to the Poodle attack.</p></warning>
</section>
<section>
<title>SSL OPTION DESCRIPTIONS - CLIENT SIDE</title>
<p>The following options are client-specific or have a slightly different
meaning in the client than in the server:</p>
<taglist>
<tag><c>{verify, verify_type()}</c></tag>
<item><p>In mode <c>verify_none</c> the default behavior is to allow
all x509-path validation errors. See also option <c>verify_fun</c>.</p>
</item>
<tag><c>{reuse_sessions, boolean()}</c></tag>
<item><p>Specifies if the client is to try to reuse sessions
when possible.</p></item>
<tag><c>{cacertfile, path()}</c></tag>
<item><p>Path to a file containing PEM-encoded CA certificates. The CA
certificates are used during server authentication and when building the
client certificate chain.</p>
</item>
<tag>{alpn_advertised_protocols, [binary()]}</tag>
<item>
<p>The list of protocols supported by the client to be sent to the
server to be used for an Application-Layer Protocol Negotiation (ALPN).
If the server supports ALPN then it will choose a protocol from this
list; otherwise it will fail the connection with a "no_application_protocol"
alert. A server that does not support ALPN will ignore this value.</p>
<p>The list of protocols must not contain an empty binary.</p>
<p>The negotiated protocol can be retrieved using the <c>negotiated_protocol/1</c> function.</p>
</item>
<tag>{client_preferred_next_protocols, {Precedence :: server | client, ClientPrefs :: [binary()]}}</tag>
<tag>{client_preferred_next_protocols, {Precedence :: server | client, ClientPrefs :: [binary()], Default :: binary()}}</tag>
<item>
<p>Indicates that the client is to try to perform Next Protocol
Negotiation.</p>
<p>If precedence is server, the negotiated protocol is the
first protocol to be shown on the server advertised list, which is
also on the client preference list.</p>
<p>If precedence is client, the negotiated protocol is the
first protocol to be shown on the client preference list, which is
also on the server advertised list.</p>
<p>If the client does not support any of the server advertised
protocols or the server does not advertise any protocols, the
client falls back to the first protocol in its list or to the
default protocol (if a default is supplied). If the
server does not support Next Protocol Negotiation, the
connection terminates if no default protocol is supplied.</p>
</item>
<tag><c>{psk_identity, string()}</c></tag>
<item><p>Specifies the identity the client presents to the server.
The matching secret is found by calling <c>user_look_fun</c>.</p>
</item>
<tag><c>{srp_identity, {Username :: string(), Password :: string()}
</c></tag>
<item><p>Specifies the username and password to use to authenticate
to the server.</p></item>
<tag><c>{server_name_indication, hostname()}</c></tag>
<item></item>
<tag><c>{server_name_indication, disable}</c></tag>
<item>
<p>Can be specified when upgrading a TCP socket to a TLS
socket to use the TLS Server Name Indication extension.</p>
<p>When starting a TLS connection without upgrade, the Server Name
Indication extension is sent if possible. This option can also be
used to disable that behavior.</p>
</item>
<tag>{fallback, boolean()}</tag>
<item>
<p> Send special cipher suite TLS_FALLBACK_SCSV to avoid undesired TLS version downgrade.
Defaults to false</p>
<warning><p>Note this option is not needed in normal TLS usage and should not be used
to implement new clients. But legacy clients that that retries connections in the following manner</p>
<p><c> ssl:connect(Host, Port, [...{versions, ['tlsv2', 'tlsv1.1', 'tlsv1', 'sslv3']}])</c></p>
<p><c> ssl:connect(Host, Port, [...{versions, [tlsv1.1', 'tlsv1', 'sslv3']}, {fallback, true}])</c></p>
<p><c> ssl:connect(Host, Port, [...{versions, ['tlsv1', 'sslv3']}, {fallback, true}]) </c></p>
<p><c> ssl:connect(Host, Port, [...{versions, ['sslv3']}, {fallback, true}]) </c></p>
<p>may use it to avoid undesired TLS version downgrade. Note that TLS_FALLBACK_SCSV must also
be supported by the server for the prevention to work.
</p></warning>
</item>
</taglist>
</section>
<section>
<title>SSL OPTION DESCRIPTIONS - SERVER SIDE</title>
<p>The following options are server-specific or have a slightly different
meaning in the server than in the client:</p>
<taglist>
<tag><c>{cacertfile, path()}</c></tag>
<item><p>Path to a file containing PEM-encoded CA
certificates. The CA certificates are used to build the server
certificate chain and for client authentication. The CAs are
also used in the list of acceptable client CAs passed to the
client when a certificate is requested. Can be omitted if there
is no need to verify the client and if there are no
intermediate CAs for the server certificate.</p></item>
<tag><c>{dh, der_encoded()}</c></tag>
<item><p>The DER-encoded Diffie-Hellman parameters. If specified,
it overrides option <c>dhfile</c>.</p></item>
<tag><c>{dhfile, path()}</c></tag>
<item><p>Path to a file containing PEM-encoded Diffie Hellman parameters
to be used by the server if a cipher suite using Diffie Hellman key
exchange is negotiated. If not specified, default parameters are used.
</p></item>
<tag><c>{verify, verify_type()}</c></tag>
<item><p>A server only does x509-path validation in mode <c>verify_peer</c>,
as it then sends a certificate request to the client
(this message is not sent if the verify option is <c>verify_none</c>).
You can then also want to specify option <c>fail_if_no_peer_cert</c>.
</p></item>
<tag><c>{fail_if_no_peer_cert, boolean()}</c></tag>
<item><p>Used together with <c>{verify, verify_peer}</c> by an SSL server.
If set to <c>true</c>, the server fails if the client does not have
a certificate to send, that is, sends an empty certificate. If set to
<c>false</c>, it fails only if the client sends an invalid
certificate (an empty certificate is considered valid).</p>
</item>
<tag><c>{reuse_sessions, boolean()}</c></tag>
<item><p>Specifies if the server is to agree to reuse sessions
when requested by the clients. See also option <c>reuse_session</c>.
</p></item>
<tag><c>{reuse_session, fun(SuggestedSessionId,
PeerCert, Compression, CipherSuite) -> boolean()}</c></tag>
<item><p>Enables the SSL server to have a local policy
for deciding if a session is to be reused or not.
Meaningful only if <c>reuse_sessions</c> is set to <c>true</c>.
<c>SuggestedSessionId</c> is a <c>binary()</c>, <c>PeerCert</c> is
a DER-encoded certificate, <c>Compression</c> is an enumeration integer,
and <c>CipherSuite</c> is of type <c>ciphersuite()</c>.</p></item>
<tag>{alpn_preferred_protocols, [binary()]}</tag>
<item>
<p>Indicates the server will try to perform Application-Layer
Protocol Negotiation (ALPN).</p>
<p>The list of protocols is in order of preference. The protocol
negotiated will be the first in the list that matches one of the
protocols advertised by the client. If no protocol matches, the
server will fail the connection with a "no_application_protocol" alert.</p>
<p>The negotiated protocol can be retrieved using the <c>negotiated_protocol/1</c> function.</p>
</item>
<tag><c>{next_protocols_advertised, Protocols :: [binary()]}</c></tag>
<item><p>List of protocols to send to the client if the client indicates that
it supports the Next Protocol extension. The client can select a protocol
that is not on this list. The list of protocols must not contain an empty
binary. If the server negotiates a Next Protocol, it can be accessed
using the <c>negotiated_next_protocol/1</c> method.</p></item>
<tag><c>{psk_identity, string()}</c></tag>
<item><p>Specifies the server identity hint, which the server presents to
the client.</p></item>
<tag><c>{log_alert, boolean()}</c></tag>
<item><p>If set to <c>false</c>, error reports are not displayed.</p></item>
<tag><c>{honor_cipher_order, boolean()}</c></tag>
<item><p>If set to <c>true</c>, use the server preference for cipher
selection. If set to <c>false</c> (the default), use the client
preference.</p></item>
</taglist>
</section>
<section>
<title>General</title>
<p>When an SSL socket is in active mode (the default), data from the
socket is delivered to the owner of the socket in the form of
messages:</p>
<list type="bulleted">
<item><p><c>{ssl, Socket, Data}</c></p></item>
<item><p><c>{ssl_closed, Socket}</c></p></item>
<item><p><c>{ssl_error, Socket, Reason}</c></p></item>
</list>
<p>A <c>Timeout</c> argument specifies a time-out in milliseconds. The
default value for argument <c>Timeout</c> is <c>infinity</c>.</p>
</section>
<funcs>
<func>
<name>cipher_suites() -></name>
<name>cipher_suites(Type) -> ciphers()</name>
<fsummary>Returns a list of supported cipher suites.</fsummary>
<type>
<v>Type = erlang | openssl | all</v>
</type>
<desc><p>Returns a list of supported cipher suites.
<c>cipher_suites()</c> is equivalent to <c>cipher_suites(erlang).</c>
Type <c>openssl</c> is provided for backwards compatibility with the
old SSL, which used OpenSSL. <c>cipher_suites(all)</c> returns
all available cipher suites. The cipher suites not present
in <c>cipher_suites(erlang)</c> but included in
<c>cipher_suites(all)</c> are not used unless explicitly configured
by the user.</p>
</desc>
</func>
<func>
<name>clear_pem_cache() -> ok </name>
<fsummary> Clears the pem cache</fsummary>
<desc><p>PEM files, used by ssl API-functions, are cached. The
cache is regularly checked to see if any cache entries should be
invalidated, however this function provides a way to
unconditionally clear the whole cache.
</p>
</desc>
</func>
<func>
<name>connect(Socket, SslOptions) -> </name>
<name>connect(Socket, SslOptions, Timeout) -> {ok, SslSocket}
| {error, Reason}</name>
<fsummary>Upgrades a <c>gen_tcp</c>, or
equivalent, connected socket to an SSL socket.</fsummary>
<type>
<v>Socket = socket()</v>
<v>SslOptions = [ssloption()]</v>
<v>Timeout = integer() | infinity</v>
<v>SslSocket = sslsocket()</v>
<v>Reason = term()</v>
</type>
<desc><p>Upgrades a <c>gen_tcp</c>, or equivalent,
connected socket to an SSL socket, that is, performs the
client-side ssl handshake.</p>
</desc>
</func>
<func>
<name>connect(Host, Port, Options) -></name>
<name>connect(Host, Port, Options, Timeout) ->
{ok, SslSocket} | {error, Reason}</name>
<fsummary>Opens an SSL connection to <c>Host</c>, <c>Port</c>.</fsummary>
<type>
<v>Host = host()</v>
<v>Port = integer()</v>
<v>Options = [option()]</v>
<v>Timeout = integer() | infinity</v>
<v>SslSocket = sslsocket()</v>
<v>Reason = term()</v>
</type>
<desc><p>Opens an SSL connection to <c>Host</c>, <c>Port</c>.</p></desc>
</func>
<func>
<name>close(SslSocket) -> ok | {error, Reason}</name>
<fsummary>Closes an SSL connection.</fsummary>
<type>
<v>SslSocket = sslsocket()</v>
<v>Reason = term()</v>
</type>
<desc><p>Closes an SSL connection.</p>
</desc>
</func>
<func>
<name>connection_info(SslSocket) ->
{ok, {ProtocolVersion, CipherSuite}} | {error, Reason}</name>
<fsummary>Returns the Negotiated Protocol version and cipher suite.
</fsummary>
<type>
<v>CipherSuite = ciphersuite()</v>
<v>ProtocolVersion = protocol()</v>
</type>
<desc><p>Returns the Negotiated Protocol version and cipher suite.</p>
</desc>
</func>
<func>
<name>controlling_process(SslSocket, NewOwner) ->
ok | {error, Reason}</name>
<fsummary>Assigns a new controlling process to the
SSL socket.</fsummary>
<type>
<v>SslSocket = sslsocket()</v>
<v>NewOwner = pid()</v>
<v>Reason = term()</v>
</type>
<desc><p>Assigns a new controlling process to the SSL socket. A
controlling process is the owner of an SSL socket, and receives
all messages from the socket.</p>
</desc>
</func>
<func>
<name>format_error(Reason) -> string()</name>
<fsummary>Returns an error string.</fsummary>
<type>
<v>Reason = term()</v>
</type>
<desc>
<p>Presents the error returned by an SSL function as a printable string.</p>
</desc>
</func>
<func>
<name>getopts(Socket, OptionNames) ->
{ok, [socketoption()]} | {error, Reason}</name>
<fsummary>Gets the values of the specified options.</fsummary>
<type>
<v>Socket = sslsocket()</v>
<v>OptionNames = [atom()]</v>
</type>
<desc>
<p>Gets the values of the specified socket options.
</p>
</desc>
</func>
<func>
<name>listen(Port, Options) ->
{ok, ListenSocket} | {error, Reason}</name>
<fsummary>Creates an SSL listen socket.</fsummary>
<type>
<v>Port = integer()</v>
<v>Options = options()</v>
<v>ListenSocket = sslsocket()</v>
</type>
<desc>
<p>Creates an SSL listen socket.</p>
</desc>
</func>
<func>
<name>negotiated_next_protocol(Socket) -> {ok, Protocol} | {error, next_protocol_not_negotiated}</name>
<fsummary>Returns the Next Protocol negotiated.</fsummary>
<type>
<v>Socket = sslsocket()</v>
<v>Protocol = binary()</v>
</type>
<desc>
<p>Returns the Next Protocol negotiated.</p>
</desc>
</func>
<func>
<name>peercert(Socket) -> {ok, Cert} | {error, Reason}</name>
<fsummary>Returns the peer certificate.</fsummary>
<type>
<v>Socket = sslsocket()</v>
<v>Cert = binary()</v>
</type>
<desc>
<p>The peer certificate is returned as a DER-encoded binary.
The certificate can be decoded with
<c>public_key:pkix_decode_cert/2</c>.</p>
</desc>
</func>
<func>
<name>peername(Socket) -> {ok, {Address, Port}} |
{error, Reason}</name>
<fsummary>Returns the peer address and port.</fsummary>
<type>
<v>Socket = sslsocket()</v>
<v>Address = ipaddress()</v>
<v>Port = integer()</v>
</type>
<desc>
<p>Returns the address and port number of the peer.</p>
</desc>
</func>
<func>
<name>prf(Socket, Secret, Label, Seed, WantedLength) -> {ok, binary()} | {error, reason()}</name>
<fsummary>Uses a session Pseudo-Random Function to generate key material.</fsummary>
<type>
<v>Socket = sslsocket()</v>
<v>Secret = binary() | master_secret</v>
<v>Label = binary()</v>
<v>Seed = [binary() | prf_random()]</v>
<v>WantedLength = non_neg_integer()</v>
</type>
<desc>
<p>Uses the Pseudo-Random Function (PRF) of a TLS session to generate
extra key material. It either takes user-generated values for
<c>Secret</c> and <c>Seed</c> or atoms directing it to use a specific
value from the session security parameters.</p>
<p>Can only be used with TLS connections; <c>{error, undefined}</c>
is returned for SSLv3 connections.</p>
</desc>
</func>
<func>
<name>recv(Socket, Length) -> </name>
<name>recv(Socket, Length, Timeout) -> {ok, Data} | {error,
Reason}</name>
<fsummary>Receives data on a socket.</fsummary>
<type>
<v>Socket = sslsocket()</v>
<v>Length = integer()</v>
<v>Timeout = integer()</v>
<v>Data = [char()] | binary()</v>
</type>
<desc>
<p>Receives a packet from a socket in passive
mode. A closed socket is indicated by return value
<c>{error, closed}</c>.</p>
<p>Argument <c>Length</c> is meaningful only when
the socket is in mode <c>raw</c> and denotes the number of
bytes to read. If <c>Length</c> = 0, all available bytes are
returned. If <c>Length</c> > 0, exactly <c>Length</c>
bytes are returned, or an error; possibly discarding less
than <c>Length</c> bytes of data when the socket gets closed
from the other side.</p>
<p>Optional argument <c>Timeout</c> specifies a time-out in
milliseconds. The default value is <c>infinity</c>.</p>
</desc>
</func>
<func>
<name>renegotiate(Socket) -> ok | {error, Reason}</name>
<fsummary>Initiates a new handshake.</fsummary>
<type>
<v>Socket = sslsocket()</v>
</type>
<desc><p>Initiates a new handshake. A notable return value is
<c>{error, renegotiation_rejected}</c> indicating that the peer
refused to go through with the renegotiation, but the connection
is still active using the previously negotiated session.</p>
</desc>
</func>
<func>
<name>send(Socket, Data) -> ok | {error, Reason}</name>
<fsummary>Writes data to a socket.</fsummary>
<type>
<v>Socket = sslsocket()</v>
<v>Data = iodata()</v>
</type>
<desc>
<p>Writes <c>Data</c> to <c>Socket</c>.</p>
<p>A notable return value is <c>{error, closed}</c> indicating that
the socket is closed.</p>
</desc>
</func>
<func>
<name>setopts(Socket, Options) -> ok | {error, Reason}</name>
<fsummary>Sets socket options.</fsummary>
<type>
<v>Socket = sslsocket()</v>
<v>Options = [socketoption]()</v>
</type>
<desc>
<p>Sets options according to <c>Options</c> for socket
<c>Socket</c>.</p>
</desc>
</func>
<func>
<name>shutdown(Socket, How) -> ok | {error, Reason}</name>
<fsummary>Immediately closes a socket.</fsummary>
<type>
<v>Socket = sslsocket()</v>
<v>How = read | write | read_write</v>
<v>Reason = reason()</v>
</type>
<desc>
<p>Immediately closes a socket in one or two directions.</p>
<p><c>How == write</c> means closing the socket for writing,
reading from it is still possible.</p>
<p>To be able to handle that the peer has done a shutdown on
the write side, option <c>{exit_on_close, false}</c>
is useful.</p>
</desc>
</func>
<func>
<name>ssl_accept(Socket) -> </name>
<name>ssl_accept(Socket, Timeout) -> ok | {error, Reason}</name>
<fsummary>Performs server-side SSL/TLS handshake.</fsummary>
<type>
<v>Socket = sslsocket()</v>
<v>Timeout = integer()</v>
<v>Reason = term()</v>
</type>
<desc>
<p>Performs the SSL/TLS server-side handshake.</p>
<p><c>Socket</c> is a socket as returned by
<seealso marker="#transport_accept-2">ssl:transport_accept/[1,2]</seealso>
</p>
</desc>
</func>
<func>
<name>ssl_accept(Socket, SslOptions) -> </name>
<name>ssl_accept(Socket, SslOptions, Timeout) -> {ok, Socket} | ok | {error, Reason}</name>
<fsummary>Performs server-side SSL/TLS handshake.</fsummary>
<type>
<v>Socket = socket() | sslsocket() </v>
<v>SslOptions = ssloptions()</v>
<v>Timeout = integer()</v>
<v>Reason = term()</v>
</type>
<desc>
<p>If <c>Socket</c> is a <c>socket()</c>: upgrades a <c>gen_tcp</c>,
or equivalent, socket to an SSL socket, that is, performs
the SSL/TLS server-side handshake and returns the SSL socket.</p>
<warning><p>The listen socket is to be in mode <c>{active, false}</c>
before telling the client that the server is ready to upgrade
by calling this function, else the upgrade succeeds or does not
succeed depending on timing.</p></warning>
<p>If <c>Socket</c> is an <c>sslsocket()</c>: provides extra SSL/TLS
options to those specified in
<seealso marker="#listen-2">ssl:listen/2 </seealso> and then performs
the SSL/TLS handshake.
</p>
</desc>
</func>
<func>
<name>sockname(Socket) -> {ok, {Address, Port}} |
{error, Reason}</name>
<fsummary>Returns the local address and port.</fsummary>
<type>
<v>Socket = sslsocket()</v>
<v>Address = ipaddress()</v>
<v>Port = integer()</v>
</type>
<desc>
<p>Returns the local address and port number of socket
<c>Socket</c>.</p>
</desc>
</func>
<func>
<name>start() -> </name>
<name>start(Type) -> ok | {error, Reason}</name>
<fsummary>Starts the <c>ssl</c>application.</fsummary>
<type>
<v>Type = permanent | transient | temporary</v>
</type>
<desc>
<p>Starts the <c>ssl</c> application. Default type
is <c>temporary</c>.</p>
</desc>
</func>
<func>
<name>stop() -> ok </name>
<fsummary>Stops the <c>ssl</c> application.</fsummary>
<desc>
<p>Stops the <c>ssl</c> application.</p>
</desc>
</func>
<func>
<name>transport_accept(ListenSocket) -></name>
<name>transport_accept(ListenSocket, Timeout) ->
{ok, NewSocket} | {error, Reason}</name>
<fsummary>Accepts an incoming connection and
prepares for <c>ssl_accept</c>.</fsummary>
<type>
<v>ListenSocket = NewSocket = sslsocket()</v>
<v>Timeout = integer()</v>
<v>Reason = reason()</v>
</type>
<desc>
<p>Accepts an incoming connection request on a listen socket.
<c>ListenSocket</c> must be a socket returned from
<seealso marker="#listen-2"> ssl:listen/2</seealso>.
The socket returned is to be passed to
<seealso marker="#ssl_accept-2"> ssl:ssl_accept[2,3]</seealso>
to complete handshaking, that is,
establishing the SSL/TLS connection.</p>
<warning>
<p>The socket returned can only be used with
<seealso marker="#ssl_accept-2"> ssl:ssl_accept[2,3]</seealso>.
No traffic can be sent or received before that call.</p>
</warning>
<p>The accepted socket inherits the options set for
<c>ListenSocket</c> in
<seealso marker="#listen-2"> ssl:listen/2</seealso>.</p>
<p>The default
value for <c>Timeout</c> is <c>infinity</c>. If
<c>Timeout</c> is specified and no connection is accepted
within the given time, <c>{error, timeout}</c> is
returned.</p>
</desc>
</func>
<func>
<name>versions() -> [versions_info()]</name>
<fsummary>Returns version information relevant for the
<c>ssl</c> application.</fsummary>
<type>
<v>versions_info() = {app_vsn, string()} | {supported | available, [protocol()] </v>
</type>
<desc>
<p>Returns version information relevant for the <c>ssl</c>
application.</p>
<taglist>
<tag>app_vsn</tag>
<item>The application version of the <c>ssl</c> application.</item>
<tag>supported</tag>
<item>TLS/SSL versions supported by default.
Overridden by a version option on
<seealso marker="#connect-2"> connect/[2,3,4]</seealso>,
<seealso marker="#listen-2"> listen/2</seealso>, and <seealso
marker="#ssl_accept-2">ssl_accept/[1,2,3]</seealso>.
For the negotiated TLS/SSL version, see <seealso
marker="#connection_info-1">ssl:connection_info/1
</seealso>.</item>
<tag>available</tag>
<item>All TLS/SSL versions supported by the <c>ssl</c> application.
TLS 1.2 requires sufficient support from the <c>crypto</c>
application.</item>
</taglist>
</desc>
</func>
<func>
<name>negotiated_protocol(Socket) -> {ok, Protocol} | {error, protocol_not_negotiated}</name>
<fsummary>Returns the protocol negotiated through ALPN or NPN extensions.</fsummary>
<type>
<v>Socket = sslsocket()</v>
<v>Protocol = binary()</v>
</type>
<desc>
<p>
Returns the protocol negotiated through ALPN or NPN extensions.
</p>
</desc>
</func>
</funcs>
<section>
<title>SEE ALSO</title>
<p><seealso marker="kernel:inet">inet(3)</seealso> and
<seealso marker="kernel:gen_tcp">gen_tcp(3)</seealso>
</p>
</section>
</erlref>