new_ssl
Interface Functions for Secure Socket Layer
This module contains interface functions to the Secure Socket Layer.
NEW SSL
This manual page describes functions that are defined in the ssl module and represents the new ssl implementation that coexists with the old one, as the new implementation is not yet complete enough to replace the old one.
The new implementation can be accessed by providing the option {ssl_imp, new} to the ssl:connect and ssl:listen functions.
The new implementation is Erlang based and all logic is in Erlang and only payload encryption calculations are done in C via the crypto application. The main reason for making a new implementation is that the old solution was very crippled as the control of the ssl-socket was deep down in openssl making it hard if not impossible to support all inet options, ipv6 and upgrade of a tcp connection to a ssl connection. The alfa version has a few limitations that will be removed before the ssl-4.0 release. Main differences and limitations in the alfa are listed below.
- New ssl requires the crypto application.
- The option reuseaddr is supported and the default value is false as in gen_tcp. Old ssl is patched to accept that the option is set to true to provide a smoother migration between the versions. In old ssl the option is hard coded to true.
- ssl:version/0 is replaced by ssl:versions/0
- ssl:ciphers/0 is replaced by ssl:cipher_suites/0
- ssl:pid/1 is a meaningless function in new ssl and will be deprecated in ssl-4.0 until it is removed it will return a valid but meaningless pid.
- New API functions are ssl:shutdown/2, ssl:cipher_suites/[0,1] and ssl:versions/0
- Diffie-Hellman keyexchange is not supported yet.
- CRL and policy certificate extensions are not supported yet.
- Supported SSL/TLS-versions are SSL-3.0 and TLS-1.0
- For security reasons sslv2 is not supported.
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()} | {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()] | sting() (according to old API)
ciphersuite() =
{key_exchange(), cipher(), hash(), exportable()}
key_exchange() = rsa | dh_dss | dh_rsa | dh_anon | dhe_dss
| dhe_rsa | krb5 | KeyExchange_export
cipher() = rc4_128 | idea_cbc | des_cbc | '3des_ede_cbc'
des40_cbc | dh_dss | aes_128_cbc | aes_256_cbc |
rc2_cbc_40 | rc4_40
hash() = md5 | sha
exportable() = export | no_export | ignore
ssl_imp() = new | old - default is old.
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 isverify_peer
. See also the option verify_fun. Servers only do the path validation ifverify_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 isverify_none
) and you may then also want to specify the optionfail_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()} (Will be relevant later when an option is added for the user to be able to verify application specific extensions.) - {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.
- {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.
- {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().
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
.
Functions
cipher_suites() ->
cipher_suites(Type) -> ciphers()
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}
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}
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}
SslSocket = sslsocket()
Reason = term()
Close a ssl connection.
controlling_process(SslSocket, NewOwner) -> ok | {error, Reason}
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}
CipherSuite = ciphersuite()
ProtocolVersion = protocol()
Returns the negotiated protocol version and cipher suite.
getopts(Socket) ->
getopts(Socket, OptionNames) -> {ok, [socketoption()]} | {error, Reason}
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}
Port = integer()
Options = options()
ListenSocket = sslsocket()
Creates a ssl listen socket.
peercert(Socket) ->
peercert(Socket, Opts) -> {ok, Cert} | {error, Reason}
Socket = sslsocket()
Opts = [] | [otp] | [plain]
Cert = term()
Subject = term()
peercert(Cert)
is equivalent to peercert(Cert, [])
.
The form of the returned certificate depends on the options.
If the options list is empty the certificate is returned as a DER encoded binary.
The option otp
or plain
implies that the
certificate will be returned as a parsed ASN.1 structure in the
form of an Erlang term. For detail see the public_key application.
Currently only plain is officially supported see the public_key users
guide.
peername(Socket) -> {ok, {Address, Port}} | {error, Reason}
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}
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
.
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
.
shutdown(Socket, How) -> ok | {error, Reason}
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}
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}
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.
sockname(Socket) -> {ok, {Address, Port}} | {error, Reason}
Socket = sslsocket()
Address = ipaddress()
Port = integer()
Returns the local address and port number of the socket
Socket
.
start() ->
start(Type) -> ok | {error, Reason}
Type = permanent | transient | temporary
Starts the Ssl application. Default type is temporary. application(3)
stop() -> ok
Stops the Ssl application. application(3)
transport_accept(Socket) ->
transport_accept(Socket, Timeout) -> {ok, NewSocket} | {error, Reason}
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.
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.
versions() -> [{SslAppVer, SupportedSslVer, AvailableSslVsn}]
SslAppVer = string()
SupportedSslVer = [protocol()]
AvailableSslVsn = [protocol()]
Returns version information relevant for the ssl application.
SEE ALSO
inet(3) and gen_tcp(3)
- cipher_suites/0
- cipher_suites/1
- connect/2
- connect/3
- connect/3-1
- connect/4
- close/1
- controlling_process/2
- connection_info/1
- getopts/1
- getopts/2
- listen/2
- peercert/1
- peercert/2
- peername/1
- recv/2
- recv/3
- send/2
- setopts/2
- shutdown/2
- ssl_accept/1
- ssl_accept/2
- ssl_accept/2-1
- ssl_accept/3
- sockname/1
- start/0
- start/1
- stop/0
- transport_accept/1
- transport_accept/2
- versions/0