ssl

MODULE

ssl

MODULE SUMMARY

Interface Functions for Secure Socket Layer

DESCRIPTION

This module contains interface functions to the Secure Socket Layer. New implementations will use this module, and not the old ssl_socket module, which is obsolete.

Common data types

The following datatypes are used in the functions below:

• options() = [option()]
  


• option() = socketoption() | ssloption()
  


• socketoption() = binary | {packet, size()} | {nodelay, boolean()} | {active, boolean()} | {backlog, integer()} | {ip, ipaddress()}
  


• ssloption() = {verify, code()} | {depth, depth()} | {certfile, path()} | {keyfile, path()} | {password, string()} | {cacertfile, path()} | {ciphers, string()} | {cachetimeout, integer()}
  


• size() = 0 | 1 | 2 | 4
  


• reason() = atom() | {atom(), string()}
  


• bytes() = [byte()]
  


• string() = [byte()]
  


• byte() = 0 | 1 | 2 | ... | 255
  


• code() = 0 | 1 | 2
  


• depth() = byte()
  


• address() = hostname() | ipstring() | ipaddress()
  


• ipaddress() = ipstring() | iptuple()
  


• hostname() = string()
  


• ipstring() = string()
  


• iptuple() = {byte(), byte(), byte(), byte()}
  


• sslsocket()
  


• 
  



The socket options {backlog, integer()} and {ip, ipaddress} are for listen/2 only.

The following socket options are set by default: {packet, 0}, {nodelay, false}, {active, true}, {backlog, 5}, and {ip, {0,0,0,0}}.

The ssl options are for setting specific SSL parameters as follows:

• {verify, code()} Specifies type of verification: 0 = do not verify peer; 1 = verify peer, verify client once, 2 = verify peer, verify client once, fail if no peer certificate. The default value is 0.
  


• {depth, depth()} Specifies verification depth, i.e. how far in a chain of certificates the verification process shall proceed before the verification is considered successful. The default value is 1.
  


• {certfile, path()} Path to a file containing a chain of PEM encoded certificates.
  


• {keyfile, path()} Path to file containing user's private PEM encoded key.
  


• {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.
  


• {ciphers, string()} String of ciphers as a colon separated list of ciphers.
  


• {cachetimeout, integer()} Session cache timeout in seconds.
  



The type sslsocket() is opaque to the user.

The owner of a socket is the one that created it by a call to accept/1, connect/3/4/, or listen/2.

When a 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.

Functions listed below may return the value {error, closed}, which only indicates that the SSL socket is considered closed for the operation in question. It is for instance possible to have {error, closed} returned from an call to send/2, and a subsequent call to recv/3 returning {ok, Data}.

Hence a return value of {error, closed} must not be interpreted as if the socket was completely closed. On the contrary, in order to free all resources occupied by an SSL socket, close/1 must be called, or else the process owning the socket has to terminate.

For each SSL socket there is an Erlang process representing the socket. When a socket is opened, that process links to the calling client process. Implementations that want to detect abnormal exits from the socket process by receiving {'EXIT', Pid, Reason} messages, should use the function pid/1 to retreive the process identifier from the socket, in order to be able to match exit messages properly.

EXPORTS

accept(ListenSocket) -> {ok, Socket} | {error, Reason}
accept(ListenSocket, Timeout) -> {ok, Socket} | {error, Reason}

Types:
ListenSocket = Socket = sslsocket()
Timeout = integer()

Accepts an incoming connection request on a listen socket. ListenSocket must be a socket returned from listen/2.

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.

close(Socket) -> ok | {error, Reason}

Types:
Socket = sslsocket()

Closes a socket returned by accept/1/2, connect/3/4, or listen/2

connect(Address, Port, Options) -> {ok, Socket} | {error, Reason}
connect(Address, Port, Options, Timeout) -> {ok, Socket} | {error, Reason}

Types:
Address = address()
Port = integer()
Options = [connect_option()]
connect_option() = binary | {packet, size()} | {nodelay, boolean()} | {active, boolean()} | {verify, code()} | {depth, depth()} | {certfile, path()} | {keyfile, path()} | {password, string()} | {cacertfile, path()} | {ciphers, string()} | {cachetimeout, integer()}
Timeout = integer()
Socket = sslsocket()

Connects to Port at Address. If the optional Timeout argument is specified, and a connection could not be established within the given time, {error, timeout} is returned. The default value for Timeout is infinity.

controlling_process(Socket, NewOwner) -> ok | {error, Reason}

Types:
Socket = sslsocket()
NewOwner = pid()

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

format_error(ErrorCode) -> string()

Types:
ErrorCode = term()

Returns a diagnostic string describing an error.

listen(Port, Options) -> {ok, ListenSocket} | {error, Reason}

Types:
Port = integer()
Options = [listen_option()]
listen_option() = binary | {packet, size()} | {active, boolean()} | {backlog, integer()} | {ip, ipaddress()} | {verify, code()} | {depth, depth()} | {certfile, path()} | {keyfile, path()} | {password, string()} | {cacertfile, path()} | {ciphers, string()} | {cachetimeout, integer()}
ListenSocket = sslsocket()

Sets up a socket to listen on port Port at the local host. If Port is zero, listen/2 picks an available port number (use port/1 to retreive it).

The listen queue size defaults to 5. If a different value is wanted, the option {backlog, Size} should be added to the list of options.

The returned ListenSocket can only be used in calls to accept/1/2.

peername(Socket) -> {ok, {Address, Port}} | {error, Reason}

Types:
Socket = sslsocket()
Address = ipaddress()
Port = integer()

Returns the address and port number of the peer.

pid(Socket) -> pid()

Types:
Socket = sslsocket()

Returns the pid of the socket process. The returned pid should only be used for receiving exit messages.

port(Socket) -> {ok, Port}

Types:
Socket = sslsocket()
Port = integer()

Returns the local port number of socket Socket.

recv(Socket, Length) -> {ok, Data} | {error, Reason}
recv(Socket, Length, Timeout) -> {ok, Data} | {error, Reason}

Types:
Socket = sslsocket()
Length = integer() >= 0
Timeout = integer()
Data = bytes() | binary()

Receives data on socket Socket when the socket is in passive mode, i.e. when the option {active, false} has been specified.

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

A positive value of the Length argument is only valid when the socket is in raw mode (option {packet, 0} is set, and the option binary is not set); otherwise it should be set to 0, whence all available bytes are returned.

If the optional Timeout parameter is specified, and no data was available within the given time, {error, timeout} is returned. The default value for Timeout is infinity.

send(Socket, Data) -> ok | {error, Reason}

Types:
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}

Types:
Socket = sslsocket()
Options = options()

Sets options according to Options for the socket Socket.

Only the following option can be set: {nodelay, boolean()}.

sockname(Socket) -> {ok, {Address, Port}} | {error, Reason}

Types:
Socket = sslsocket()
Address = ipaddress()
Port = integer()

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

ERRORS

The possible error reasons and the corresponding diagnostic strings returned by format_error/1 are either the same as those defined in the inet(3) reference manual, or as follows:

closed

Connection closed for the operation in question.


ebadsocket

Connection not found (internal error).


ebadstate

Connection not in connect state (internal error).


ebrokertype

Wrong broker type (internal error).


ecacertfile

Own CA certificate file is invalid.


ecertfile

Own certificate file is invalid.


echaintoolong

The chain of certificates provided by peer is too long.


ecipher

Own list of specified ciphers is invalid.


ekeyfile

Own private key file is invalid.


ekeymismatch

Own private key does not match own certificate.


enoissuercert

Cannot find certificate of issuer of certificate provided by peer.


enoservercert

Attempt to do accept without having set own certificate.


enotlistener

Attempt to accept on a non-listening socket.


enoproxysocket

No proxy socket found (internal error).


eoptions

Invalid list of options.


epeercert

Certificate provided by peer is in error.


epeercertexpired

Certificate provided by peer has expired.


epeercertinvalid

Certificate provided by peer is invalid.


eselfsignedcert

Certificate provided by peer is self signed.


esslaccept

Server SSL handshake procedure between client and server failed.


esslconnect

Client SSL handshake procedure between client and server failed.


esslerrssl

SSL protocol failure. Typically because of a fatal alert from peer.


ewantconnect

Protocol wants to connect, which is not supported in this version of the SSL application.


ex509lookup

Protocol wants X.509 lookup, which is not supported in this version of the SSL application.


{badcall, Call}

Call not recognized for current mode (active or passive) and state of socket.


{badcast, Cast}

Call not recognized for current mode (active or passive) and state of socket.


{badinfo, Info}

Call not recognized for current mode (active or passive) and state of socket.

SEE ALSO

gen_tcp(3), inet(3)

AUTHORS

Peter Högfeldt - support@erlang.ericsson.se