| ssl(3erl) | Erlang Module Definition | ssl(3erl) |
ssl - Interface Functions for Secure Socket Layer
This module contains interface functions for the SSL/TLS/DTLS protocol. For detailed information about the supported standards see ssl(7).
The following data types are used in the functions for SSL/TLS/DTLS:
The default socket options are [{mode,list},{packet, 0},{header, 0},{active, true}].
For valid options, see the inet(3erl), gen_tcp(3erl) and gen_udp(3erl) manual pages in Kernel. Note that stream oriented options such as packet are only relevant for SSL/TLS and not DTLS
| {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}
| {customize_hostname_check, list()}
| {sni_hosts, [{hostname(), [ssl_option()]}]}
| {sni_fun, SNIfun::fun()}
Defaults to {gen_tcp, tcp, tcp_closed, tcp_error} for TLS and {gen_udp, udp, udp_closed, udp_error} for DTLS. Can be used to customize the transport layer. For TLS 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. For DTLS this feature must be considered exprimental.
Used in socket data message.
Used in socket close message.
Represents a file path.
ASN.1 DER-encoded entity as an Erlang binary.
Tuples and string formats accepted by versions before ssl-8.2.4 will be converted for backwards compatibility
The following options have the same meaning in the client and the server:
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'{}.
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:
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).
There are two implementations available:
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:
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])])
one_n_minus_one - Perform 1/n-1 BEAST mitigation.
zero_n - Perform 0/n BEAST mitigation.
disabled - Disable BEAST mitigation.
The following options are client-specific or have a slightly different meaning in the client than in the server:
The list of protocols must not contain an empty binary.
The negotiated protocol can be retrieved using the negotiated_protocol/1 function.
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.
The HostName will also be used in the hostname verification of the peer certificate using public_key:pkix_verify_hostname/2.
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.
[
%% 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
The following options are server-specific or have a slightly different meaning in the server than in the client:
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.
When an TLS/DTLS socket is in active mode (the default), data from the socket is delivered to the owner of the socket in the form of messages:
A Timeout argument specifies a time-out in milliseconds. The default value for argument Timeout is infinity.
append_cipher_suites(Deferred, Suites) -> ciphers()
Types:
Make Deferred suites become the least preferred suites, that is put them at the end of the cipher suite list Suites after removing them from Suites if present. Deferred may be a list of cipher suits or a list of filters in which case the filters are use on Suites to extract the Deferred cipher list.
cipher_suites() ->
cipher_suites(Type) -> old_ciphers()
Types:
Deprecated in OTP 21, use cipher_suites/2 instead.
cipher_suites(Supported, Version) -> ciphers()
Types:
Returns all default or all supported (except anonymous), or all anonymous cipher suites for a TLS version
eccs() ->
eccs(protocol_version()) -> [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} | {ok,
SslSocket, Ext} | {error, Reason}
Types:
Upgrades a gen_tcp, or equivalent, connected socket to an TLS socket, that is, performs the client-side TLS handshake.
If the option {handshake, hello} is used the handshake is paused after receiving the server hello message and the success response is {ok, SslSocket, Ext} instead of {ok, SslSocket}. Thereafter the handshake is continued or canceled by calling handshake_continue/3 or handshake_cancel/1.
connect(Host, Port, Options) ->
connect(Host, Port, Options, Timeout) -> {ok, SslSocket}| {ok,
SslSocket, Ext} | {error, Reason}
Types:
Opens an TLS/DTLS 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 possibilities of the public_key:pkix_verify_hostname/3 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.
If the option {handshake, hello} is used the handshake is paused after receiving the server hello message and the success response is {ok, SslSocket, Ext} instead of {ok, SslSocket}. Thereafter the handshake is continued or canceled by calling handshake_continue/3 or handshake_cancel/1.
close(SslSocket) -> ok | {error, Reason}
Types:
Closes an TLS/DTLS connection.
close(SslSocket, How) -> ok | {ok, port()} | {error,
Reason}
Types:
Closes or downgrades an TLS 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:
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:
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:
Returns the requested information items about the connection, if they are defined.
filter_cipher_suites(Suites, Filters) -> ciphers()
Types:
Removes cipher suites if any of the filter functions returns false for any part of the cipher suite. This function also calls default filter functions to make sure the cipher suites are supported by crypto. If no filter function is supplied for some part the default behaviour is fun(Algorithm) -> true.
format_error(Reason) -> string()
Types:
Presents the error returned by an SSL function as a printable string.
getopts(SslSocket, OptionNames) -> {ok, [socketoption()]} |
{error, Reason}
Types:
Gets the values of the specified socket options.
getstat(SslSocket) -> {ok, OptionValues} | {error,
inet:posix()}
getstat(SslSocket, OptionNames) -> {ok, OptionValues} | {error,
inet:posix()}
Types:
Gets one or more statistic options for the underlying TCP socket.
See inet:getstat/2 for statistic options description.
handshake(HsSocket) ->
handshake(HsSocket, Timeout) -> {ok, SslSocket} | {error, Reason}
Types:
Performs the SSL/TLS/DTLS server-side handshake.
Returns a new TLS/DTLS socket if the handshake is successful.
handshake(Socket, SslOptions) ->
handshake(Socket, SslOptions, Timeout) -> {ok, SslSocket} | {ok,
SslSocket, Ext} | {error, Reason}
Types:
If Socket is a ordinary socket(): upgrades a gen_tcp, or equivalent, socket to an SSL socket, that is, performs the SSL/TLS server-side handshake and returns a TLS socket.
If Socket is an sslsocket(): provides extra SSL/TLS/DTLS options to those specified in listen/2 and then performs the SSL/TLS/DTLS handshake. Returns a new TLS/DTLS socket if the handshake is successful.
If option {handshake, hello} is specified the handshake is paused after receiving the client hello message and the success response is {ok, SslSocket, Ext} instead of {ok, SslSocket}. Thereafter the handshake is continued or canceled by calling handshake_continue/3 or handshake_cancel/1.
handshake_cancel(SslSocket) -> ok
Types:
Cancel the handshake with a fatal USER_CANCELED alert.
handshake_continue(HsSocket, SSLOptions) -> {ok, SslSocket}
| {error, Reason}
handshake_continue(HsSocket, SSLOptions, Timeout) -> {ok, SslSocket} |
{error, Reason}
Types:
Continue the SSL/TLS handshake possiby with new, additional or changed options.
listen(Port, Options) -> {ok, ListenSocket} | {error,
Reason}
Types:
Creates an SSL listen socket.
negotiated_protocol(SslSocket) -> {ok, Protocol} | {error,
protocol_not_negotiated}
Types:
Returns the protocol negotiated through ALPN or NPN extensions.
peercert(SslSocket) -> {ok, Cert} | {error, Reason}
Types:
The peer certificate is returned as a DER-encoded binary. The certificate can be decoded with public_key:pkix_decode_cert/2
peername(SslSocket) -> {ok, {Address, Port}} | {error,
Reason}
Types:
Returns the address and port number of the peer.
prepend_cipher_suites(Preferred, Suites) -> ciphers()
Types:
Make Preferred suites become the most preferred suites that is put them at the head of the cipher suite list Suites after removing them from Suites if present. Preferred may be a list of cipher suits or a list of filters in which case the filters are use on Suites to extract the preferred cipher list.
prf(Socket, Secret, Label, Seed, WantedLength) -> {ok,
binary()} | {error, reason()}
Types:
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/DTLS connections; {error, undefined} is returned for SSLv3 connections.
recv(SslSocket, Length) ->
recv(SslSocket, Length, Timeout) -> {ok, Data} | {error, Reason}
Types:
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(SslSocket) -> ok | {error, Reason}
Types:
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(SslSocket, Data) -> ok | {error, Reason}
Types:
Writes Data to Socket.
A notable return value is {error, closed} indicating that the socket is closed.
setopts(SslSocket, Options) -> ok | {error, Reason}
Types:
Sets options according to Options for socket Socket.
shutdown(SslSocket, How) -> ok | {error, Reason}
Types:
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(SslSocket) ->
ssl_accept(SslSocket, Timeout) -> ok | {error, Reason}
Types:
Deprecated in OTP 21, use handshake/[1,2] instead.
ssl_accept(Socket, SslOptions) ->
ssl_accept(Socket, SslOptions, Timeout) -> {ok, Socket} | ok | {error,
Reason}
Types:
Deprecated in OTP 21, use handshake/[2,3] instead.
sockname(SslSocket) -> {ok, {Address, Port}} | {error,
Reason}
Types:
Returns the local address and port number of socket Socket.
start() ->
start(Type) -> ok | {error, Reason}
Types:
Starts the SSL application. Default type is temporary.
stop() -> ok
Stops the SSL application.
suite_to_str(CipherSuite) -> String
Types:
Returns the string representation of a cipher suite.
transport_accept(ListenSocket) ->
transport_accept(ListenSocket, Timeout) -> {ok, SslSocket} | {error,
Reason}
Types:
Accepts an incoming connection request on a listen socket. ListenSocket must be a socket returned from listen/2. The socket returned is to be passed to handshake/[2,3] to complete handshaking, that is, establishing the SSL/TLS/DTLS connection.
The accepted socket inherits the options set for ListenSocket in 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:
Returns version information relevant for the SSL application.
| ssl 9.1.2 | Ericsson AB |