19992010 Ericsson AB. All Rights Reserved. The contents of this file are subject to the Erlang Public License, Version 1.1, (the "License"); you may not use this file except in compliance with the License. You should have received a copy of the Erlang Public License along with this software. If not, it can be retrieved online at http://www.erlang.org/. Software distributed under the License is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for the specific language governing rights and limitations under the License. ssl ssl.xml
ssl Interface Functions for Secure Socket Layer

This module contains interface functions to the Secure Socket Layer.

SSL ssl requires the crypto an public_key applications. Supported SSL/TLS-versions are SSL-3.0 and TLS-1.0 For security reasons sslv2 is not supported. Ephemeral Diffie-Hellman cipher suites are supported but not Diffie Hellman Certificates cipher suites. Export cipher suites are not supported as the U.S. lifted its export restrictions in early 2000. CRL and policy certificate extensions are not supported yet.
COMMON DATA TYPES

The following data types are used in the functions below:

boolean() = true | false

property() = atom()

option() = socketoption() | ssloption() | transportoption()

socketoption() = [{property(), term()}] - defaults to [{mode,list},{packet, 0},{header, 0},{active, true}].

For valid options see inet(3) and gen_tcp(3) .

ssloption() = {verify, verify_type()} | {fail_if_no_peer_cert, boolean()} {depth, integer()} | {certfile, path()} | {keyfile, path()} | {password, string()} | {cacertfile, path()} | {dhfile, path()} | {ciphers, ciphers()} | {ssl_imp, ssl_imp()} | {reuse_sessions, boolean()} | {reuse_session, fun()}

transportoption() = {CallbackModule, DataTag, ClosedTag} - defaults to {gen_tcp, tcp, tcp_closed}. Ssl may be run over any reliable transport protocol that has an equivalent API to gen_tcp's.

      CallbackModule = atom()

      DataTag = atom() - tag used in socket data message.

      ClosedTag = atom() - tag used in socket close message.

verify_type() = verify_none | verify_peer

path() = string() - representing a file path.

host() = hostname() | ipaddress()

hostname() = string()

ip_address() = {N1,N2,N3,N4} % IPv4 | {K1,K2,K3,K4,K5,K6,K7,K8} % IPv6

sslsocket() - opaque to the user.

protocol() = sslv3 | tlsv1

ciphers() = [ciphersuite()] | string() (according to old API)

ciphersuite() = {key_exchange(), cipher(), hash()}

key_exchange() = rsa | dhe_dss | dhe_rsa

cipher() = rc4_128 | des_cbc | '3des_ede_cbc' | aes_128_cbc | aes_256_cbc

hash() = md5 | sha

ssl_imp() = new | old - default is new.

SSL OPTION DESCRIPTIONS {verify, verify_type()} If verify_none is specified x509-certificate path validation errors at the client side will not automatically cause the connection to fail, as it will if the verify type is verify_peer. See also the option verify_fun. Servers only do the path validation if verify_peer is set to true, as it then will send a certificate request to the client (this message is not sent if the verify option is verify_none) and you may then also want to specify the option fail_if_no_peer_cert. {fail_if_no_peer_cert, boolean()} Used together with {verify, verify_peer} by a ssl server. If set to true, the server will fail if the client does not have a certificate to send, e.i sends a empty certificate, if set to false it will only fail if the client sends a invalid certificate (an empty certificate is considered valid). {verify_fun, fun(ErrorList) -> boolean()} Used by the ssl client to determine if x509-certificate path validations errors are acceptable or if the connection should fail. Defaults to: fun(ErrorList) -> case lists:foldl(fun({bad_cert,unknown_ca}, Acc) -> Acc; (Other, Acc) -> [Other | Acc] end, [], ErrorList) of [] -> true; [_|_] -> false end end I.e. by default if the only error found was that the CA-certificate holder was unknown this will be accepted. Possible errors in the error list are: {bad_cert, cert_expired}, {bad_cert, invalid_issuer}, {bad_cert, invalid_signature}, {bad_cert, name_not_permitted}, {bad_cert, unknown_ca}, {bad_cert, cert_expired}, {bad_cert, invalid_issuer}, {bad_cert, invalid_signature}, {bad_cert, name_not_permitted}, {bad_cert, cert_revoked} (not implemented yet), {bad_cert, unknown_critical_extension} or {bad_cert, term()} {validate_extensions_fun, fun()} This options makes it possible to supply a fun to validate possible application specific certificate extensions during the certificat path validation. This option will be better documented onec the public_key API is more mature. {depth, integer()} Specifies the maximum verification depth, i.e. how far in a chain of certificates the verification process can proceed before the verification is considered to fail. Peer certificate = 0, CA certificate = 1, higher level CA certificate = 2, etc. The value 2 thus means that a chain can at most contain peer cert, CA cert, next CA cert, and an additional CA cert. The default value is 1. {certfile, path()} Path to a file containing the user's certificate. Optional for clients but note that some servers requires that the client can certify itself. {keyfile, path()} Path to file containing user's private PEM encoded key. As PEM-files may contain several entries this option defaults to the same file as given by certfile option. {password, string()} String containing the user's password. Only used if the private keyfile is password protected. {cacertfile, path()} Path to file containing PEM encoded CA certificates (trusted certificates used for verifying a peer certificate). May be omitted if you do not want to verify the peer. {dhfile, path()} Path to file containing PEM encoded Diffie Hellman parameters, for the server to use if a cipher suite using Diffie Hellman key exchange is negotiated. If not specified hardcode parameters will be used. {ciphers, ciphers()} The function ciphers_suites/0 can be used to find all available ciphers. {ssl_imp, ssl_imp()} Specify which ssl implementation you want to use. Defaults to new. {reuse_sessions, boolean()} Specifies if ssl sessions should be reused when possible. {reuse_session, fun(SuggestedSessionId, PeerCert, Compression, CipherSuite) -> boolean()} Enables the ssl server to have a local policy for deciding if a session should be reused or not, only meaning full if reuse_sessions is set to true. SuggestedSessionId is a binary(), PeerCert is a DER encoded certificate, Compression is an enumeration integer and CipherSuite of type ciphersuite(). {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 e.i. secure renegotiation will be used if possible but it will fallback to unsecure renegotiation if the peer does not support RFC 5746.
General

When a 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 timeout in milliseconds. The default value for a Timeout argument is infinity.

cipher_suites() -> cipher_suites(Type) -> ciphers() Returns a list of supported cipher suites Type = erlang | openssl

Returns a list of supported cipher suites. cipher_suites() is equivalent to cipher_suites(erlang). Type openssl is provided for backwards compatibility with old ssl that used openssl.

connect(Socket, SslOptions) -> connect(Socket, SslOptions, Timeout) -> {ok, SslSocket} | {error, Reason} Upgrades a gen_tcp, or equivalent, connected socket to a ssl socket. Socket = socket() SslOptions = [ssloption()] Timeout = integer() | infinity SslSocket = sslsocket() Reason = term()

Upgrades a gen_tcp, or equivalent, connected socket to a ssl socket e.i performs the client-side ssl handshake.

 connect(Host, Port, Options) -> connect(Host, Port, Options, Timeout) -> {ok, SslSocket} | {error, Reason} Opens an ssl connection to Host, Port. Host = host() Port = integer() Options = [option()] Timeout = integer() | infinity SslSocket = sslsocket() Reason = term()

Opens an ssl connection to Host, Port.

 close(SslSocket) -> ok | {error, Reason} Close a ssl connection SslSocket = sslsocket() Reason = term()

Close a ssl connection.

 controlling_process(SslSocket, NewOwner) -> ok | {error, Reason} Assigns a new controlling process to the ssl-socket. SslSocket = sslsocket() NewOwner = pid() Reason = term()

Assigns a new controlling process to the ssl-socket. A controlling process is the owner of a ssl-socket, and receives all messages from the socket.

 connection_info(SslSocket) -> {ok, {ProtocolVersion, CipherSuite}} | {error, Reason} Returns the negotiated protocol version and cipher suite. CipherSuite = ciphersuite() ProtocolVersion = protocol()

Returns the negotiated protocol version and cipher suite.

 format_error(Reason) -> string() Return an error string. Reason = term()

Presents the error returned by an ssl function as a printable string.

 getopts(Socket) -> getopts(Socket, OptionNames) -> {ok, [socketoption()]} | {error, Reason} Get the value of the specified options. Socket = sslsocket() OptionNames = [property()]

Get the value of the specified socket options, if no options are specified all options are returned.

listen(Port, Options) -> {ok, ListenSocket} | {error, Reason} Creates a ssl listen socket. Port = integer() Options = options() ListenSocket = sslsocket()

Creates a ssl listen socket.

 peercert(Socket) -> {ok, Cert} | {error, Reason} Return the peer certificate. 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} Return peer address and port. Socket = sslsocket() Address = ipaddress() Port = integer()

Returns the address and port number of the peer.

 recv(Socket, Length) -> recv(Socket, Length, Timeout) -> {ok, Data} | {error, Reason} Receive data on a socket. Socket = sslsocket() Length = integer() Timeout = integer() Data = [char()] | binary()

This function receives a packet from a socket in passive mode. A closed socket is indicated by a return value {error, closed}.

The Length argument is only meaningful when the socket is in raw mode 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.

The optional Timeout parameter specifies a timeout in milliseconds. The default value is infinity.

 renegotiate(Socket) -> ok | {error, Reason} Initiates a new handshake. 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} Write data to a socket. Socket = sslsocket() Data = iolist() | binary()

Writes Data to Socket.

A notable return value is {error, closed} indicating that the socket is closed.

 setopts(Socket, Options) -> ok | {error, Reason} Set socket options. Socket = sslsocket() Options = [socketoption]()

Sets options according to Options for the socket Socket.

shutdown(Socket, How) -> ok | {error, Reason} Immediately close a socket Socket = sslsocket() How = read | write | read_write Reason = reason()

Immediately close 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, the {exit_on_close, false} option is useful.

 ssl_accept(ListenSocket) -> ssl_accept(ListenSocket, Timeout) -> ok | {error, Reason} Perform server-side SSL handshake ListenSocket = sslsocket() Timeout = integer() Reason = term()

The ssl_accept function establish the SSL connection on the server side. It should be called directly after transport_accept, in the spawned server-loop.

 ssl_accept(ListenSocket, SslOptions) -> ssl_accept(ListenSocket, SslOptions, Timeout) -> {ok, Socket} | {error, Reason} Perform server-side SSL handshake ListenSocket = socket() SslOptions = ssloptions() Timeout = integer() Reason = term()

Upgrades a gen_tcp, or equivalent, socket to a ssl socket e.i performs the ssl server-side handshake.

Note that the listen socket should be in {active, false} mode before telling the client that the server is ready to upgrade and calling this function, otherwise the upgrade may or may not succeed depending on timing.

 sockname(Socket) -> {ok, {Address, Port}} | {error, Reason} Return the local address and port. Socket = sslsocket() Address = ipaddress() Port = integer()

Returns the local address and port number of the socket Socket.

 start() -> start(Type) -> ok | {error, Reason} Starts the Ssl application. Type = permanent | transient | temporary

Starts the Ssl application. Default type is temporary. application(3)

 stop() -> ok Stops the Ssl application.

Stops the Ssl application. application(3)

 transport_accept(Socket) -> transport_accept(Socket, Timeout) -> {ok, NewSocket} | {error, Reason} Accept an incoming connection and prepare for ssl_accept Socket = NewSocket = sslsocket() Timeout = integer() Reason = reason()

Accepts an incoming connection request on a listen socket. ListenSocket must be a socket returned from listen/2. The socket returned should be passed to ssl_accept to complete ssl handshaking and establishing the connection.

The socket returned can only be used with ssl_accept, no traffic can be sent or received before that call.

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() -> [{SslAppVer, SupportedSslVer, AvailableSslVsn}] Returns version information relevant for the ssl application. SslAppVer = string() SupportedSslVer = [protocol()] AvailableSslVsn = [protocol()]

Returns version information relevant for the ssl application.
SEE ALSO

inet(3) and gen_tcp(3)