Provided by: erlang-manpages_20.2.2+dfsg-1ubuntu2_all 
NAME
ssl - Interface Functions for Secure Socket Layer
DESCRIPTION
This module contains interface functions for the SSL/TLS protocol. For detailed information about the
supported standards see ssl(7).
DATA TYPES
The following data types are used in the functions for SSL:
boolean() =:
true | false
option() =:
socketoption() | ssl_option() | transport_option()
socketoption() =:
proplists:property()
The default socket options are [{mode,list},{packet, 0},{header, 0},{active, true}].
For valid options, see the inet(3erl) and gen_tcp(3erl) manual pages in Kernel.
ssl_option() =:
{verify, verify_type()}
| {verify_fun, {fun(), term()}}
| {fail_if_no_peer_cert, boolean()}
| {depth, integer()}
| {cert, public_key:der_encoded()}
| {certfile, path()}
| {key, {'RSAPrivateKey'| 'DSAPrivateKey' | 'ECPrivateKey' | 'PrivateKeyInfo',
public_key:der_encoded()} | #{algorithm := rsa | dss | ecdsa, engine := crypto:engine_ref(), key_id
:= crypto:key_id(), password => crypto:password()}
| {keyfile, path()}
| {password, string()}
| {cacerts, [public_key:der_encoded()]}
| {cacertfile, path()}
| {dh, public_key:der_encoded()}
| {dhfile, path()}
| {ciphers, ciphers()}
| {user_lookup_fun, {fun(), term()}}, {psk_identity, string()}, {srp_identity, {string(), string()}}
| {reuse_sessions, boolean()}
| {reuse_session, fun()} {next_protocols_advertised, [binary()]}
| {client_preferred_next_protocols, {client | server, [binary()]} | {client | server, [binary()],
binary()}}
| {log_alert, boolean()}
| {server_name_indication, hostname() | disable}
| {sni_hosts, [{hostname(), [ssl_option()]}]}
| {sni_fun, SNIfun::fun()}
transport_option() =:
{cb_info, {CallbackModule::atom(), DataTag::atom(), ClosedTag::atom(), ErrTag:atom()}}
Defaults to {gen_tcp, tcp, tcp_closed, tcp_error}. Can be used to customize the transport layer. The
callback module must implement a reliable transport protocol, behave as gen_tcp, and have functions
corresponding to inet:setopts/2, inet:getopts/2, inet:peername/1, inet:sockname/1, and inet:port/1.
The callback gen_tcp is treated specially and calls inet directly.
CallbackModule =:
atom()
DataTag =:
atom()
Used in socket data message.
ClosedTag =:
atom()
Used in socket close message.
verify_type() =:
verify_none | verify_peer
path() =:
string()
Represents a file path.
public_key:der_encoded() =:
binary()
ASN.1 DER-encoded entity as an Erlang binary.
host() =:
hostname() | ipaddress()
hostname() =:
string() - DNS hostname
ip_address() =:
{N1,N2,N3,N4} % IPv4 | {K1,K2,K3,K4,K5,K6,K7,K8} % IPv6
sslsocket() =:
opaque()
protocol() =:
sslv3 | tlsv1 | 'tlsv1.1' | 'tlsv1.2'
ciphers() =:
= [ciphersuite()] | string()
According to old API.
ciphersuite() =:
{key_exchange(), cipher(), MAC::hash()} | {key_exchange(), cipher(), MAC::hash(), PRF::hash()}
key_exchange()=:
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
cipher() =:
rc4_128 | des_cbc | '3des_ede_cbc' | aes_128_cbc | aes_256_cbc | aes_128_gcm | aes_256_gcm |
chacha20_poly1305
hash() =:
md5 | sha | sha224 | sha256 | sha348 | sha512
prf_random() =:
client_random | server_random
srp_param_type() =:
srp_1024 | srp_1536 | srp_2048 | srp_3072 | srp_4096 | srp_6144 | srp_8192
SNIfun::fun():
= fun(ServerName :: string()) -> [ssl_option()]
named_curve() =:
sect571r1 | sect571k1 | secp521r1 | brainpoolP512r1 | sect409k1 | sect409r1 | brainpoolP384r1 |
secp384r1 | sect283k1 | sect283r1 | brainpoolP256r1 | secp256k1 | secp256r1 | sect239k1 | sect233k1 |
sect233r1 | secp224k1 | secp224r1 | sect193r1 | sect193r2 | secp192k1 | secp192r1 | sect163k1 |
sect163r1 | sect163r2 | secp160k1 | secp160r1 | secp160r2
SSL OPTION DESCRIPTIONS - COMMON FOR SERVER AND CLIENT
The following options have the same meaning in the client and the server:
{protocol, tls | dtls}:
Choose TLS or DTLS protocol for the transport layer security. Defaults to tls Introduced in OTP 20,
DTLS support is considered experimental in this release. DTLS over other transports than UDP are not
yet supported.
{cert, public_key:der_encoded()}:
The DER-encoded users certificate. If this option is supplied, it overrides option certfile.
{certfile, path()}:
Path to a file containing the user certificate.
{key, {'RSAPrivateKey'| 'DSAPrivateKey' | 'ECPrivateKey' |'PrivateKeyInfo', public_key:der_encoded()} |
#{algorithm := rsa | dss | ecdsa, engine := crypto:engine_ref(), key_id := crypto:key_id(), password =>
crypto:password()}:
The DER-encoded user's private key or a map refering to a crypto engine and its key reference that
optionally can be password protected, seealso crypto:engine_load/4 and Crypto's Users Guide. If
this option is supplied, it overrides option keyfile.
{keyfile, path()}:
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 certfile.
{password, string()}:
String containing the user's password. Only used if the private keyfile is password-protected.
{ciphers, ciphers()}:
Supported cipher suites. The function cipher_suites/0 can be used to find all ciphers that are
supported by default. cipher_suites(all) can be called to find all available cipher suites. Pre-
Shared Key (RFC 4279 and RFC 5487), Secure Remote Password (RFC 5054), RC4 cipher suites, 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.
{eccs, [named_curve()]}:
Allows to specify the order of preference for named curves and to restrict their usage when using a
cipher suite supporting them.
{secure_renegotiate, boolean()}:
Specifies if to reject renegotiation attempt that does not live up to RFC 5746. By default
secure_renegotiate is set to false, that is, secure renegotiation is used if possible, but it falls
back to insecure renegotiation if the peer does not support RFC 5746.
{depth, integer()}:
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.
{verify_fun, {Verifyfun :: fun(), InitialUserState :: term()}}:
The verification fun is to be defined as follows:
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()}.
The verification fun is called during the X509-path validation when an error or an extension unknown
to the SSL 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 valid_peer or valid as
second argument to the verification fun. See the public_key User's Guide for definition of
#'OTPCertificate'{} and #'Extension'{}.
* If the verify callback fun returns {fail, Reason}, the verification process is immediately stopped,
an alert is sent to the peer, and the TLS/SSL handshake terminates.
* If the verify callback fun returns {valid, UserState}, the verification process continues.
* If the verify callback fun always returns {valid, UserState}, the TLS/SSL handshake does not
terminate regarding verification failures and the connection is established.
* If called with an extension unknown to the user application, return value {unknown, UserState} is
to be used.
Note that if the fun returns unknown for an extension marked as critical, validation will fail.
Default option verify_fun in verify_peer mode:
{fun(_,{bad_cert, _} = Reason, _) ->
{fail, Reason};
(_,{extension, _}, UserState) ->
{unknown, UserState};
(_, valid, UserState) ->
{valid, UserState};
(_, valid_peer, UserState) ->
{valid, UserState}
end, []}
Default option verify_fun in mode verify_none:
{fun(_,{bad_cert, _}, UserState) ->
{valid, UserState};
(_,{extension, #'Extension'{critical = true}}, UserState) ->
{valid, UserState};
(_,{extension, _}, UserState) ->
{unknown, UserState};
(_, valid, UserState) ->
{valid, UserState};
(_, valid_peer, UserState) ->
{valid, UserState}
end, []}
The possible path validation errors are given on form {bad_cert, Reason} where Reason is:
unknown_ca:
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 intermediate CA (trusted anchor does not
have to be self-signed according to X-509) by using option partial_chain.
selfsigned_peer:
The chain consisted only of one self-signed certificate.
PKIX X-509-path validation error:
For possible reasons, see public_key:pkix_path_validation/3
{crl_check, boolean() | peer | best_effort }:
Perform CRL (Certificate Revocation List) verification (public_key:pkix_crls_validate/3) on all the
certificates during the path validation (public_key:pkix_path_validation/3) of the certificate
chain. Defaults to false.
peer:
check is only performed on the peer certificate.
best_effort:
if certificate revocation status can not be determined it will be accepted as valid.
The CA certificates specified for the connection will be used to construct the certificate chain
validating the CRLs.
The CRLs will be fetched from a local or external cache. See ssl_crl_cache_api(3erl).
{crl_cache, {Module :: atom(), {DbHandle :: internal | term(), Args :: list()}}}:
Specify how to perform lookup and caching of certificate revocation lists. Module defaults to
ssl_crl_cache with DbHandle being internal and an empty argument list.
There are two implementations available:
ssl_crl_cache:
This module maintains a cache of CRLs. CRLs can be added to the cache using the function
ssl_crl_cache:insert/1, and optionally automatically fetched through HTTP if the following argument
is specified:
{http, timeout()}:
Enables fetching of CRLs specified as http URIs inX509 certificate extensions. Requires the OTP
inets application.
ssl_crl_hash_dir:
This module makes use of a directory where CRLs are stored in files named by the hash of the issuer
name.
The file names consist of eight hexadecimal digits followed by .rN, where N is an integer, e.g.
1a2b3c4d.r0. For the first version of the CRL, N starts at zero, and for each new version, N is
incremented by one. The OpenSSL utility c_rehash creates symlinks according to this pattern.
For a given hash value, this module finds all consecutive .r* files starting from zero, and those
files taken together make up the revocation list. CRL files whose nextUpdate fields are in the
past, or that are issued by a different CA that happens to have the same name hash, are excluded.
The following argument is required:
{dir, string()}:
Specifies the directory in which the CRLs can be found.
max_handshake_size:
Integer (24 bits unsigned). Used to limit the size of valid TLS handshake packets to avoid DoS
attacks. Defaults to 256*1024.
{partial_chain, fun(Chain::[DerCert]) -> {trusted_ca, DerCert} | unknown_ca }:
Claim an intermediate CA in the chain as trusted. TLS then performs public_key:pkix_path_validation/3
with the selected CA as trusted anchor and the rest of the chain.
{versions, [protocol()]}:
TLS protocol versions supported by started clients and servers. This option overrides the application
environment option protocol_version. If the environment option is not set, it defaults to all
versions, except SSL-3.0, supported by the SSL application. See also ssl(7).
{hibernate_after, integer()|undefined}:
When an integer-value is specified, ssl_connection goes into hibernation after the specified number
of milliseconds of inactivity, thus reducing its memory footprint. When undefined is specified (this
is the default), the process never goes into hibernation.
{user_lookup_fun, {Lookupfun :: fun(), UserState :: term()}}:
The lookup fun is to defined as follows:
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.
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, PSKIdentity is set to the hint presented by
the server or to undefined. When called by the server, PSKIdentity is the identity presented by the
client.
For Secure Remote Password (SRP), the fun is only used by the server to obtain parameters that it
uses to generate its session keys. DerivedKey is to be derived according to RFC 2945 and RFC 5054:
crypto:sha([Salt, crypto:sha([Username, <<$:>>, Password])])
{padding_check, boolean()}:
Affects TLS-1.0 connections only. If set to false, it disables the block cipher padding check to be
able to interoperate with legacy software.
Warning:
Using {padding_check, boolean()} makes TLS vulnerable to the Poodle attack.
{beast_mitigation, one_n_minus_one | zero_n | disabled}:
Affects SSL-3.0 and TLS-1.0 connections only. Used to change the BEAST mitigation strategy to
interoperate with legacy software. Defaults to one_n_minus_one.
one_n_minus_one - Perform 1/n-1 BEAST mitigation.
zero_n - Perform 0/n BEAST mitigation.
disabled - Disable BEAST mitigation.
Warning:
Using {beast_mitigation, disabled} makes SSL or TLS vulnerable to the BEAST attack.
SSL OPTION DESCRIPTIONS - CLIENT SIDE
The following options are client-specific or have a slightly different meaning in the client than in the
server:
{verify, verify_type()}:
In mode verify_none the default behavior is to allow all x509-path validation errors. See also option
verify_fun.
{reuse_sessions, boolean()}:
Specifies if the client is to try to reuse sessions when possible.
{cacerts, [public_key:der_encoded()]}:
The DER-encoded trusted certificates. If this option is supplied it overrides option cacertfile.
{cacertfile, path()}:
Path to a file containing PEM-encoded CA certificates. The CA certificates are used during server
authentication and when building the client certificate chain.
{alpn_advertised_protocols, [binary()]}:
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.
The list of protocols must not contain an empty binary.
The negotiated protocol can be retrieved using the negotiated_protocol/1 function.
{client_preferred_next_protocols, {Precedence :: server | client, ClientPrefs :: [binary()]}}
{client_preferred_next_protocols, {Precedence :: server | client, ClientPrefs :: [binary()], Default
:: binary()}}: Indicates that the client is to try to perform Next Protocol Negotiation.
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.
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.
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.
{psk_identity, string()}:
Specifies the identity the client presents to the server. The matching secret is found by calling
user_lookup_fun.
{srp_identity, {Username :: string(), Password :: string()} :
Specifies the username and password to use to authenticate to the server.
{server_name_indication, HostName :: hostname()}:
Specify the hostname to be used in TLS Server Name Indication extension. If not specified it will
default to the Host argument of connect/[3,4] unless it is of type inet:ipaddress().
The HostName will also be used in the hostname verification of the peer certificate using
public_key:pkix_verify_hostname/2.
{server_name_indication, disable}:
Prevents the Server Name Indication extension from being sent and disables the hostname verification
check public_key:pkix_verify_hostname/2
{fallback, boolean()}:
Send special cipher suite TLS_FALLBACK_SCSV to avoid undesired TLS version downgrade. Defaults to
false
Warning:
Note this option is not needed in normal TLS usage and should not be used to implement new clients. But
legacy clients that retries connections in the following manner
ssl:connect(Host, Port, [...{versions, ['tlsv2', 'tlsv1.1', 'tlsv1', 'sslv3']}])
ssl:connect(Host, Port, [...{versions, [tlsv1.1', 'tlsv1', 'sslv3']}, {fallback, true}])
ssl:connect(Host, Port, [...{versions, ['tlsv1', 'sslv3']}, {fallback, true}])
ssl:connect(Host, Port, [...{versions, ['sslv3']}, {fallback, true}])
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.
{signature_algs, [{hash(), ecdsa | rsa | dsa}]}:
In addition to the algorithms negotiated by the cipher suite used for key exchange, payload
encryption, message authentication and pseudo random calculation, the TLS signature algorithm
extension Section 7.4.1.4.1 in RFC 5246 may be used, from TLS 1.2, to negotiate which signature
algorithm to use during the TLS handshake. If no lower TLS versions than 1.2 are supported, the
client will send a TLS signature algorithm extension with the algorithms specified by this option.
Defaults to
[
%% SHA2
{sha512, ecdsa},
{sha512, rsa},
{sha384, ecdsa},
{sha384, rsa},
{sha256, ecdsa},
{sha256, rsa},
{sha224, ecdsa},
{sha224, rsa},
%% SHA
{sha, ecdsa},
{sha, rsa},
{sha, dsa},
]
The algorithms should be in the preferred order. Selected signature algorithm can restrict which hash
functions that may be selected. Default support for {md5, rsa} removed in ssl-8.0
SSL OPTION DESCRIPTIONS - SERVER SIDE
The following options are server-specific or have a slightly different meaning in the server than in the
client:
{cacerts, [public_key:der_encoded()]}:
The DER-encoded trusted certificates. If this option is supplied it overrides option cacertfile.
{cacertfile, path()}:
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.
{dh, public_key:der_encoded()}:
The DER-encoded Diffie-Hellman parameters. If specified, it overrides option dhfile.
{dhfile, path()}:
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.
{verify, verify_type()}:
A server only does x509-path validation in mode verify_peer, as it then sends a certificate request
to the client (this message is not sent if the verify option is verify_none). You can then also want
to specify option fail_if_no_peer_cert.
{fail_if_no_peer_cert, boolean()}:
Used together with {verify, verify_peer} by an SSL server. If set to true, the server fails if the
client does not have a certificate to send, that is, sends an empty certificate. If set to false, it
fails only if the client sends an invalid certificate (an empty certificate is considered valid).
Defaults to false.
{reuse_sessions, boolean()}:
Specifies if the server is to agree to reuse sessions when requested by the clients. See also option
reuse_session.
{reuse_session, fun(SuggestedSessionId, PeerCert, Compression, CipherSuite) -> boolean()}:
Enables the SSL server to have a local policy for deciding if a session is to be reused or not.
Meaningful only if reuse_sessions is set to true. SuggestedSessionId is a binary(), PeerCert is a
DER-encoded certificate, Compression is an enumeration integer, and CipherSuite is of type
ciphersuite().
{alpn_preferred_protocols, [binary()]}:
Indicates the server will try to perform Application-Layer Protocol Negotiation (ALPN).
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.
The negotiated protocol can be retrieved using the negotiated_protocol/1 function.
{next_protocols_advertised, Protocols :: [binary()]}:
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
negotiated_next_protocol/1 method.
{psk_identity, string()}:
Specifies the server identity hint, which the server presents to the client.
{log_alert, boolean()}:
If set to false, error reports are not displayed.
{honor_cipher_order, boolean()}:
If set to true, use the server preference for cipher selection. If set to false (the default), use
the client preference.
{sni_hosts, [{hostname(), [ssl_option()]}]}:
If the server receives a SNI (Server Name Indication) from the client matching a host listed in the
sni_hosts option, the specific options for that host will override previously specified options. The
option sni_fun, and sni_hosts are mutually exclusive.
{sni_fun, SNIfun::fun()}:
If the server receives a SNI (Server Name Indication) from the client, the given function will be
called to retrieve [ssl_option()] for the indicated server. These options will be merged into
predefined [ssl_option()]. The function should be defined as: fun(ServerName :: string()) ->
[ssl_option()] and can be specified as a fun or as named fun module:function/1 The option sni_fun,
and sni_hosts are mutually exclusive.
{client_renegotiation, boolean()}:
In protocols that support client-initiated renegotiation, the cost of resources of such an operation
is higher for the server than the client. This can act as a vector for denial of service attacks. The
SSL application already takes measures to counter-act such attempts, but client-initiated
renegotiation can be strictly disabled by setting this option to false. The default value is true.
Note that disabling renegotiation can result in long-lived connections becoming unusable due to
limits on the number of messages the underlying cipher suite can encipher.
{honor_cipher_order, boolean()}:
If true, use the server's preference for cipher selection. If false (the default), use the client's
preference.
{honor_ecc_order, boolean()}:
If true, use the server's preference for ECC curve selection. If false (the default), use the
client's preference.
{signature_algs, [{hash(), ecdsa | rsa | dsa}]}:
The algorithms specified by this option will be the ones accepted by the server in a signature
algorithm negotiation, introduced in TLS-1.2. The algorithms will also be offered to the client if a
client certificate is requested. For more details see the corresponding client option.
{v2_hello_compatible, boolean()}:
If true, the server accepts clients that send hello messages on SSL-2.0 format but offers supported
SSL/TLS versions. Defaults to false, that is the server will not interoperate with clients that
offers SSL-2.0.
GENERAL
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:
* {ssl, Socket, Data}
* {ssl_closed, Socket}
* {ssl_error, Socket, Reason}
A Timeout argument specifies a time-out in milliseconds. The default value for argument Timeout is
infinity.
EXPORTS
cipher_suites() ->
cipher_suites(Type) -> ciphers()
Types:
Type = erlang | openssl | all
Returns a list of supported cipher suites. cipher_suites() is equivalent to cipher_suites(erlang).
Type openssl is provided for backwards compatibility with the old SSL, which used OpenSSL.
cipher_suites(all) returns all available cipher suites. The cipher suites not present in
cipher_suites(erlang) but included in cipher_suites(all) are not used unless explicitly configured
by the user.
eccs() ->
eccs(protocol()) -> [named_curve()]
Returns a list of supported ECCs. eccs() is equivalent to calling eccs(Protocol) with all
supported protocols and then deduplicating the output.
clear_pem_cache() -> ok
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.
connect(Socket, SslOptions) ->
connect(Socket, SslOptions, Timeout) -> {ok, SslSocket} | {error, Reason}
Types:
Socket = socket()
SslOptions = [ssl_option()]
Timeout = integer() | infinity
SslSocket = sslsocket()
Reason = term()
Upgrades a gen_tcp, or equivalent, connected socket to an SSL socket, that is, performs the
client-side ssl handshake.
Note:
If the option verify is set to verify_peer the option server_name_indication shall also be
specified, if it is not no Server Name Indication extension will be sent, and
public_key:pkix_verify_hostname/2 will be called with the IP-address of the connection as
ReferenceID, which is proably not what you want.
connect(Host, Port, Options) ->
connect(Host, Port, Options, Timeout) -> {ok, SslSocket} | {error, Reason}
Types:
Host = host()
Port = integer()
Options = [option()]
Timeout = integer() | infinity
SslSocket = sslsocket()
Reason = term()
Opens an SSL connection to Host, Port.
When the option verify is set to verify_peer the check public_key:pkix_verify_hostname/2 will be
performed in addition to the usual x509-path validation checks. If the check fails the error
{bad_cert, hostname_check_failed} will be propagated to the path validation fun verify_fun, where
it is possible to do customized checks by using the full possibilitis of the
public_key:pkix_verify_hostname/2 API. When the option server_name_indication is provided, its
value (the DNS name) will be used as ReferenceID to public_key:pkix_verify_hostname/2. When no
server_name_indication option is given, the Host argument will be used as Server Name Indication
extension. The Host argument will also be used for the public_key:pkix_verify_hostname/2 check and
if the Host argument is an inet:ip_address() the ReferenceID used for the check will be {ip, Host}
otherwise dns_id will be assumed with a fallback to ip if that fails.
Note:
According to good practices certificates should not use IP-addresses as "server names". It would
be very surprising if this happen outside a closed network.
close(SslSocket) -> ok | {error, Reason}
Types:
SslSocket = sslsocket()
Reason = term()
Closes an SSL connection.
close(SslSocket, How) -> ok | {ok, port()} | {error, Reason}
Types:
SslSocket = sslsocket()
How = timeout() | {NewController::pid(), timeout()}
Reason = term()
Closes or downgrades an SSL connection. In the latter case the transport connection will be handed
over to the NewController process after receiving the TLS close alert from the peer. The returned
transport socket will have the following options set: [{active, false}, {packet, 0}, {mode,
binary}]
controlling_process(SslSocket, NewOwner) -> ok | {error, Reason}
Types:
SslSocket = sslsocket()
NewOwner = pid()
Reason = term()
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.
connection_information(SslSocket) -> {ok, Result} | {error, Reason}
Types:
Item = protocol | cipher_suite | sni_hostname | ecc | session_id | atom()
Meaningful atoms, not specified above, are the ssl option names.
Result = [{Item::atom(), Value::term()}]
Reason = term()
Returns the most relevant information about the connection, ssl options that are undefined will be
filtered out. Note that values that affect the security of the connection will only be returned if
explicitly requested by connection_information/2.
connection_information(SslSocket, Items) -> {ok, Result} | {error, Reason}
Types:
Items = [Item]
Item = protocol | cipher_suite | sni_hostname | ecc | session_id | client_random |
server_random | master_secret | atom()
Note that client_random, server_random and master_secret are values that affect the security
of connection. Meaningful atoms, not specified above, are the ssl option names.
Result = [{Item::atom(), Value::term()}]
Reason = term()
Returns the requested information items about the connection, if they are defined.
Note:
If only undefined options are requested the resulting list can be empty.
format_error(Reason) -> string()
Types:
Reason = term()
Presents the error returned by an SSL function as a printable string.
getopts(Socket, OptionNames) -> {ok, [socketoption()]} | {error, Reason}
Types:
Socket = sslsocket()
OptionNames = [atom()]
Gets the values of the specified socket options.
getstat(Socket) -> {ok, OptionValues} | {error, inet:posix()}
getstat(Socket, OptionNames) -> {ok, OptionValues} | {error, inet:posix()}
Types:
Socket = sslsocket()
OptionNames = [atom()]
OptionValues = [{inet:stat_option(), integer()}]
Gets one or more statistic options for the underlying TCP socket.
See inet:getstat/2 for statistic options description.
listen(Port, Options) -> {ok, ListenSocket} | {error, Reason}
Types:
Port = integer()
Options = options()
ListenSocket = sslsocket()
Creates an SSL listen socket.
negotiated_protocol(Socket) -> {ok, Protocol} | {error, protocol_not_negotiated}
Types:
Socket = sslsocket()
Protocol = binary()
Returns the protocol negotiated through ALPN or NPN extensions.
peercert(Socket) -> {ok, Cert} | {error, Reason}
Types:
Socket = sslsocket()
Cert = binary()
The peer certificate is returned as a DER-encoded binary. The certificate can be decoded with
public_key:pkix_decode_cert/2.
peername(Socket) -> {ok, {Address, Port}} | {error, Reason}
Types:
Socket = sslsocket()
Address = ipaddress()
Port = integer()
Returns the address and port number of the peer.
prf(Socket, Secret, Label, Seed, WantedLength) -> {ok, binary()} | {error, reason()}
Types:
Socket = sslsocket()
Secret = binary() | master_secret
Label = binary()
Seed = [binary() | prf_random()]
WantedLength = non_neg_integer()
Uses the Pseudo-Random Function (PRF) of a TLS session to generate extra key material. It either
takes user-generated values for Secret and Seed or atoms directing it to use a specific value from
the session security parameters.
Can only be used with TLS connections; {error, undefined} is returned for SSLv3 connections.
recv(Socket, Length) ->
recv(Socket, Length, Timeout) -> {ok, Data} | {error, Reason}
Types:
Socket = sslsocket()
Length = integer()
Timeout = integer()
Data = [char()] | binary()
Receives a packet from a socket in passive mode. A closed socket is indicated by return value
{error, closed}.
Argument Length is meaningful only when the socket is in mode raw and denotes the number of bytes
to read. If Length = 0, all available bytes are returned. If Length > 0, exactly Length bytes are
returned, or an error; possibly discarding less than Length bytes of data when the socket gets
closed from the other side.
Optional argument Timeout specifies a time-out in milliseconds. The default value is infinity.
renegotiate(Socket) -> ok | {error, Reason}
Types:
Socket = sslsocket()
Initiates a new handshake. A notable return value is {error, renegotiation_rejected} indicating
that the peer refused to go through with the renegotiation, but the connection is still active
using the previously negotiated session.
send(Socket, Data) -> ok | {error, Reason}
Types:
Socket = sslsocket()
Data = iodata()
Writes Data to Socket.
A notable return value is {error, closed} indicating that the socket is closed.
setopts(Socket, Options) -> ok | {error, Reason}
Types:
Socket = sslsocket()
Options = [socketoption]()
Sets options according to Options for socket Socket.
shutdown(Socket, How) -> ok | {error, Reason}
Types:
Socket = sslsocket()
How = read | write | read_write
Reason = reason()
Immediately closes a socket in one or two directions.
How == write means closing the socket for writing, reading from it is still possible.
To be able to handle that the peer has done a shutdown on the write side, option {exit_on_close,
false} is useful.
ssl_accept(Socket) ->
ssl_accept(Socket, Timeout) -> ok | {error, Reason}
Types:
Socket = sslsocket()
Timeout = integer()
Reason = term()
Performs the SSL/TLS server-side handshake.
Socket is a socket as returned by ssl:transport_accept/[1,2]
ssl_accept(Socket, SslOptions) ->
ssl_accept(Socket, SslOptions, Timeout) -> {ok, Socket} | ok | {error, Reason}
Types:
Socket = socket() | sslsocket()
SslOptions = [ssl_option()]
Timeout = integer()
Reason = term()
If Socket is a socket(): upgrades a gen_tcp, or equivalent, socket to an SSL socket, that is,
performs the SSL/TLS server-side handshake and returns the SSL socket.
Warning:
The listen socket is to be in mode {active, false} 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.
If Socket is an sslsocket(): provides extra SSL/TLS options to those specified in ssl:listen/2
and then performs the SSL/TLS handshake.
sockname(Socket) -> {ok, {Address, Port}} | {error, Reason}
Types:
Socket = sslsocket()
Address = ipaddress()
Port = integer()
Returns the local address and port number of socket Socket.
start() ->
start(Type) -> ok | {error, Reason}
Types:
Type = permanent | transient | temporary
Starts the SSL application. Default type is temporary.
stop() -> ok
Stops the SSL application.
transport_accept(ListenSocket) ->
transport_accept(ListenSocket, Timeout) -> {ok, NewSocket} | {error, Reason}
Types:
ListenSocket = NewSocket = sslsocket()
Timeout = integer()
Reason = reason()
Accepts an incoming connection request on a listen socket. ListenSocket must be a socket returned
from ssl:listen/2. The socket returned is to be passed to ssl:ssl_accept[2,3] to complete
handshaking, that is, establishing the SSL/TLS connection.
Warning:
The socket returned can only be used with ssl:ssl_accept[2,3]. No traffic can be sent or received
before that call.
The accepted socket inherits the options set for ListenSocket in ssl:listen/2.
The default value for Timeout is infinity. If Timeout is specified and no connection is accepted
within the given time, {error, timeout} is returned.
versions() -> [versions_info()]
Types:
versions_info() = {app_vsn, string()} | {supported | available, [protocol()]
Returns version information relevant for the SSL application.
app_vsn:
The application version of the SSL application.
supported:
TLS/SSL versions supported by default. Overridden by a version option on connect/[2,3,4],
listen/2, and ssl_accept/[1,2,3]. For the negotiated TLS/SSL version, see
ssl:connection_information/1 .
available:
All TLS/SSL versions supported by the SSL application. TLS 1.2 requires sufficient support
from the Crypto application.
SEE ALSO
inet(3erl) and gen_tcp(3erl)