ssl
Interface Functions for Secure Socket Layer
This module contains interface functions to the Secure Socket Layer.
General
There is a new implementation of ssl available in this module but until it is 100 % complete, so that it can replace the old implementation in all aspects it will be described here new ssl API
The reader is advised to also read the ssl(6)
manual page
describing the SSL application.
Warning!
It is strongly advised to seed the random generator after
the ssl application has been started (see seed/1
below), and before any connections are established. Although
the port program interfacing to the ssl libraries does a
"random" seeding of its own in order to make everything work
properly, that seeding is by no means random for the world
since it has a constant value which is known to everyone
reading the source code of the port program.
Common data types
The following datatypes are used in the functions below:
-
options() = [option()]
-
option() = socketoption() | ssloption()
-
socketoption() = {mode, list} | {mode, binary} | binary | {packet, packettype()} | {header, integer()} | {nodelay, boolean()} | {active, activetype()} | {backlog, integer()} | {ip, ipaddress()} | {port, integer()}
-
ssloption() = {verify, code()} | {depth, depth()} | {certfile, path()} | {keyfile, path()} | {password, string()} | {cacertfile, path()} | {ciphers, string()}
-
packettype()
(see inet(3)) -
activetype()
(see inet(3)) -
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()
-
protocol() = sslv2 | sslv3 | tlsv1
-
The socket option {backlog, integer()}
is for
listen/2
only, and the option {port, integer()}
is for connect/3/4
only.
The following socket options are set by default: {mode, list}
, {packet, 0}
, {header, 0}
, {nodelay, false}
, {active, true}
, {backlog, 5}
,
{ip, {0,0,0,0}}
, and {port, 0}
.
Note that the options {mode, binary}
and binary
are equivalent. Similarly {mode, list}
and the absence of
option binary
are equivalent.
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, 2 = verify peer, fail if no peer certificate. The default value is 0. -
{depth, depth()}
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. 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 (trusted certificates used for verifying a peer certificate). -
{ciphers, string()}
String of ciphers as a colon separated list of ciphers. The functionciphers/0
can be used to find all available ciphers.
The type sslsocket()
is opaque to the user.
The owner of a socket is the one that created it by a call to
transport_accept/[1,2]
, 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 retrieve the process identifier from the socket, in order to
be able to match exit messages properly.
Functions
ciphers() -> {ok, string()} | {error, enotstarted}
Returns a string consisting of colon separated cipher designations that are supported by the current SSL library implementation.
The SSL application has to be started to return the string of ciphers.
close(Socket) -> ok | {error, Reason}
Socket = sslsocket()
Closes a socket returned by transport_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}
Address = address()
Port = integer()
Options = [connect_option()]
connect_option() = {mode, list} | {mode, binary} | binary | {packet, packettype()} | {header, integer()} | {nodelay, boolean()} | {active, activetype()} | {ip, ipaddress()} | {port, integer()} | {verify, code()} | {depth, depth()} | {certfile, path()} | {keyfile, path()} | {password, string()} | {cacertfile, path()} | {ciphers, string()}
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
.
The ip
and port
options are for binding to a
particular local address and port, respectively.
connection_info(Socket) -> {ok, {Protocol, Cipher}} | {error, Reason}
Socket = sslsocket()
Protocol = protocol()
Cipher = string()
Gets the chosen protocol version and cipher for an established connection (accepted och connected).
controlling_process(Socket, NewOwner) -> ok | {error, Reason}
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()
ErrorCode = term()
Returns a diagnostic string describing an error.
getopts(Socket, OptionsTags) -> {ok, Options} | {error, Reason}
Socket = sslsocket()
OptionTags = [optiontag()]()
Returns the options the tags of which are OptionTags
for
for the socket Socket
.
listen(Port, Options) -> {ok, ListenSocket} | {error, Reason}
Port = integer()
Options = [listen_option()]
listen_option() = {mode, list} | {mode, binary} | binary | {packet, packettype()} | {header, integer()} | {active, activetype()} | {backlog, integer()} | {ip, ipaddress()} | {verify, code()} | {depth, depth()} | {certfile, path()} | {keyfile, path()} | {password, string()} | {cacertfile, path()} | {ciphers, string()}
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 retrieve 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.
An empty Options
list is considered an error, and
{error, enooptions}
is returned.
The returned ListenSocket
can only be used in calls to
transport_accept/[1,2]
.
peercert(Socket) -> {ok, Cert} | {error, Reason}
Socket = sslsocket()
Cert = binary()()
Subject = term()()
Returns the DER encoded peer certificate, the certificate can be decoded with
public_key:pkix_decode_cert/2
.
peername(Socket) -> {ok, {Address, Port}} | {error, Reason}
Socket = sslsocket()
Address = ipaddress()
Port = integer()
Returns the address and port number of the peer.
pid(Socket) -> pid()
Socket = sslsocket()
Returns the pid of the socket process. The returned pid should only be used for receiving exit messages.
recv(Socket, Length) -> {ok, Data} | {error, Reason}
recv(Socket, Length, Timeout) -> {ok, Data} | {error, Reason}
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
.
seed(Data) -> ok | {error, Reason}
Data = iolist() | binary()
Seeds the ssl random generator.
It is strongly advised to seed the random generator after the ssl application has been started, and before any connections are established. Although the port program interfacing to the OpenSSL libraries does a "random" seeding of its own in order to make everything work properly, that seeding is by no means random for the world since it has a constant value which is known to everyone reading the source code of the seeding.
A notable return value is {error, edata}}
indicating that
Data
was not a binary nor an iolist.
send(Socket, Data) -> ok | {error, Reason}
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}
Socket = sslsocket()
Options = [socketoption]()
Sets options according to Options
for the socket
Socket
.
ssl_accept(Socket) -> ok | {error, Reason}
ssl_accept(Socket, Timeout) -> ok | {error, Reason}
Socket = sslsocket()
Timeout = integer()
Reason = atom()
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.
Note that the ssl connection is not complete until ssl_accept
has returned true
, and if an error is returned, the socket
is unavailable and for instance close/1
will crash.
sockname(Socket) -> {ok, {Address, Port}} | {error, Reason}
Socket = sslsocket()
Address = ipaddress()
Port = integer()
Returns the local address and port number of the socket
Socket
.
transport_accept(Socket) -> {ok, NewSocket} | {error, Reason}
transport_accept(Socket, Timeout) -> {ok, NewSocket} | {error, Reason}
Socket = NewSocket = sslsocket()
Timeout = integer()
Reason = atom()
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.
Warning!
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.
version() -> {ok, {SSLVsn, CompVsn, LibVsn}}
SSLVsn = CompVsn = LibVsn = string()()
Returns the SSL application version (SSLVsn
), the library
version used when compiling the SSL application port program
(CompVsn
), and the actual library version used when
dynamically linking in runtime (LibVsn
).
If the SSL application has not been started, CompVsn
and
LibVsn
are empty strings.
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).
enooptions
-
The list of options is empty.
enotstarted
-
The SSL application has not been started.
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) public_key(3)