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(6).
DATA TYPES
The following data types are used in the functions for SSL/TLS/DTLS:
boolean() =
true | false
option() =
socketoption() | ssl_option() | transport_option()
socketoption() =
proplists:property()
The default socket options are
[{mode,list},{packet, 0},{header, 0},{active, true}]
.
For valid options, see the inet(3), gen_tcp(3) and gen_udp(3) manual pages in Kernel. Note that stream oriented options such as packet are only relevant for SSL/TLS and not DTLS
ssl_option() =
{verify, verify_type()}
| {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()}
transport_option() =
{cb_info, {CallbackModule::atom(), DataTag::atom(),
ClosedTag::atom(), ErrTag:atom()}}
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.
CallbackModule =
atom()
DataTag =
atom()
Used in socket data message.
ClosedTag =
atom()
Used in socket close message.
verify_type() =
verify_none | verify_peer
path() =
string()
Represents a file path.
public_key:der_encoded() =
binary()
ASN.1 DER-encoded entity as an Erlang binary.
host() =
hostname() | ipaddress()
hostname() =
string() - DNS hostname
ip_address() =
{N1,N2,N3,N4} % IPv4 | {K1,K2,K3,K4,K5,K6,K7,K8} % IPv6
sslsocket() =
opaque()
protocol_version() =
ssl_tls_protocol() | dtls_protocol()
sslv3 | tlsv1 | 'tlsv1.1' | 'tlsv1.2'
dtls_protocol() =
'dtlsv1' | 'dtlsv1.2'
ciphers() =
= [ciphersuite()]
Tuples and string formats accepted by versions before ssl-8.2.4 will be converted for backwards compatibility
ciphersuite() =
#{key_exchange := key_exchange(),
cipher := cipher(),
mac := MAC::hash() | aead,
prf := PRF::hash() | default_prf}
key_exchange()=
rsa | dhe_dss | dhe_rsa | dh_anon | psk | dhe_psk
| rsa_psk | srp_anon | srp_dss | srp_rsa | ecdh_anon | ecdh_ecdsa
| ecdhe_ecdsa | ecdh_rsa | ecdhe_rsa
cipher() =
rc4_128 | des_cbc | '3des_ede_cbc'
| aes_128_cbc | aes_256_cbc | aes_128_gcm | aes_256_gcm | chacha20_poly1305
hash() =
md5 | sha | sha224 | sha256 | sha348 | sha512
prf_random() =
client_random | server_random
cipher_filters() =
[{key_exchange | cipher | mac | prf, algo_filter()}])
algo_filter() =
fun(key_exchange() | cipher() | hash() | aead | default_prf) -> true | false
srp_param_type() =
srp_1024 | srp_1536 | srp_2048 | srp_3072
| srp_4096 | srp_6144 | srp_8192
SNIfun::fun()
= fun(ServerName :: string()) -> [ssl_option()]
named_curve() =
sect571r1 | sect571k1 | secp521r1 | brainpoolP512r1
| sect409k1 | sect409r1 | brainpoolP384r1 | secp384r1
| sect283k1 | sect283r1 | brainpoolP256r1 | secp256k1 | secp256r1
| sect239k1 | sect233k1 | sect233r1 | secp224k1 | secp224r1
| sect193r1 | sect193r2 | secp192k1 | secp192r1 | sect163k1
| sect163r1 | sect163r2 | secp160k1 | secp160r1 | secp160r2
hello_extensions() =
#{renegotiation_info =>
signature_algs => [{hash(), ecsda| rsa| dsa}] | undefined
alpn => binary() | undefined,
next_protocol_negotiation,
srp => string() | undefined,
ec_point_formats ,
elliptic_curves = [oid] | undefined
sni = string()}
}
TLS/DTLS OPTION DESCRIPTIONS - COMMON for SERVER and CLIENT
The following options have the same meaning in the client and the server:
{protocol, tls | dtls}
Choose TLS or DTLS protocol for the transport layer security.
Defaults to tls
Introduced in OTP 20, DTLS support is considered
experimental in this release. Other transports than UDP are not yet supported.
{handshake, hello | full}
Defaults to full
. If hello is specified the handshake will
pause after the hello message and give the user a possibility make decisions
based on hello extensions before continuing or aborting the handshake by calling
handshake_continue/3 or
handshake_cancel/1
{cert, public_key:der_encoded()}
The DER-encoded users certificate. If this option
is supplied, it overrides option certfile
.
{certfile, path()}
Path to a file containing the user certificate.
{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()}
The DER-encoded user's private key or a map refering to a crypto
engine and its key reference that optionally can be password protected,
seealso crypto:engine_load/4
and Crypto's Users Guide. If this option
is supplied, it overrides option keyfile
.
{keyfile, path()}
Path to the file containing the user's
private PEM-encoded key. As PEM-files can contain several
entries, this option defaults to the same file as given by
option certfile
.
{password, string()}
String containing the user's password. Only used if the private keyfile is password-protected.
{ciphers, ciphers()}
Supported cipher suites. The function
cipher_suites/0
can be used to find all ciphers that are
supported by default. cipher_suites(all)
can be called
to find all available cipher suites. Pre-Shared Key
(
{eccs, [named_curve()]}
Allows to specify the order of preference for named curves and to restrict their usage when using a cipher suite supporting them.
{secure_renegotiate, boolean()}
Specifies if to reject renegotiation attempt that does
not live up to
secure_renegotiate
is set to true
,
that is, secure renegotiation is enforced. If set to false
secure renegotiation
will still be used if possible,
but it falls back to insecure renegotiation if the peer
does not support
{depth, integer()}
Maximum number of non-self-issued intermediate certificates that can follow the peer certificate in a valid certification path. So, if depth is 0 the PEER must be signed by the trusted ROOT-CA directly; if 1 the path can be PEER, CA, ROOT-CA; if 2 the path can be PEER, CA, CA, ROOT-CA, and so on. The default value is 1.
{verify_fun, {Verifyfun :: fun(), InitialUserState ::
term()}}
The verification fun is to be defined as follows:
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'{}
.
If the verify callback fun returns
{fail, Reason}
, the verification process is immediately stopped, an alert is sent to the peer, and the TLS/DTLS handshake terminates.If the verify callback fun returns
{valid, UserState}
, the verification process continues.If the verify callback fun always returns
{valid, UserState}
, the TLS/DTLS handshake does not terminate regarding verification failures and the connection is established.If called with an extension unknown to the user application, return value
{unknown, UserState}
is to be used.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:
unknown_ca
No trusted CA was found in the trusted store. The trusted CA is
normally a so called ROOT CA, which is a self-signed certificate. Trust can
be claimed for an intermediate CA (trusted anchor does not have to be
self-signed according to X-509) by using option partial_chain
.
selfsigned_peer
The chain consisted only of one self-signed certificate.
PKIX X-509-path validation error
For possible reasons, see public_key:pkix_path_validation/3
{crl_check, boolean() | peer | best_effort }
Perform CRL (Certificate Revocation List) verification
(public_key:pkix_crls_validate/3) on all the certificates during the path validation
(public_key:pkix_path_validation/3)
of the certificate chain. Defaults to false
.
peer
best_effort
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(3).
{crl_cache, {Module :: atom(), {DbHandle :: internal | term(), Args :: list()}}}
Specify how to perform lookup and caching of certificate revocation lists.
Module
defaults to ssl_crl_cache
with DbHandle
being internal
and an
empty argument list.
There are two implementations available:
ssl_crl_cache
This module maintains a cache of CRLs. CRLs can be added to the cache using the function ssl_crl_cache:insert/1, and optionally automatically fetched through HTTP if the following argument is specified:
{http, timeout()}
Enables fetching of CRLs specified as http URIs inX509 certificate extensions. Requires the OTP inets application.
ssl_crl_hash_dir
This module makes use of a directory where CRLs are stored in files named by the hash of the issuer name.
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:
{dir, string()}
Specifies the directory in which the CRLs can be found.
max_handshake_size
Integer (24 bits unsigned). Used to limit the size of valid TLS handshake packets to avoid DoS attacks. Defaults to 256*1024.
{partial_chain, fun(Chain::[DerCert]) -> {trusted_ca, DerCert} |
unknown_ca }
Claim an intermediate CA in the chain as trusted. TLS then performs public_key:pkix_path_validation/3 with the selected CA as trusted anchor and the rest of the chain.
{versions, [protocol_version()]}
TLS protocol versions supported by started clients and servers.
This option overrides the application environment option
protocol_version
and dtls_protocol_version
. If the environment option is not set, it defaults
to all versions, except SSL-3.0, supported by the SSL application.
See also ssl(6).
{hibernate_after, integer()|undefined}
When an integer-value is specified, TLS/DTLS-connection
goes into hibernation after the specified number of milliseconds
of inactivity, thus reducing its memory footprint. When
undefined
is specified (this is the default), the process
never goes into hibernation.
{user_lookup_fun, {Lookupfun :: fun(), UserState :: term()}}
The lookup fun is to defined as follows:
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
crypto:sha([Salt, crypto:sha([Username, <<$:>>, Password])])
{padding_check, boolean()}
Affects TLS-1.0 connections only.
If set to false
, it disables the block cipher padding check
to be able to interoperate with legacy software.
Warning!
Using {padding_check, boolean()}
makes TLS
vulnerable to the Poodle attack.
{beast_mitigation, one_n_minus_one | zero_n | disabled}
Affects SSL-3.0 and TLS-1.0 connections only. Used to change the BEAST
mitigation strategy to interoperate with legacy software.
Defaults to one_n_minus_one
.
one_n_minus_one
- Perform 1/n-1 BEAST mitigation.
zero_n
- Perform 0/n BEAST mitigation.
disabled
- Disable BEAST mitigation.
Warning!
Using {beast_mitigation, disabled}
makes SSL or TLS
vulnerable to the BEAST attack.
TLS/DTLS OPTION DESCRIPTIONS - CLIENT SIDE
The following options are client-specific or have a slightly different meaning in the client than in the server:
{verify, verify_type()}
In mode verify_none
the default behavior is to allow
all x509-path validation errors. See also option verify_fun
.
{reuse_sessions, boolean()}
Specifies if the client is to try to reuse sessions when possible.
{cacerts, [public_key:der_encoded()]}
The DER-encoded trusted certificates. If this option
is supplied it overrides option cacertfile
.
{cacertfile, path()}
Path to a file containing PEM-encoded CA certificates. The CA certificates are used during server authentication and when building the client certificate chain.
{alpn_advertised_protocols, [binary()]}
The list of protocols supported by the client to be sent to the server to be used for an Application-Layer Protocol Negotiation (ALPN). If the server supports ALPN then it will choose a protocol from this list; otherwise it will fail the connection with a "no_application_protocol" alert. A server that does not support ALPN will ignore this value.
The list of protocols must not contain an empty binary.
The negotiated protocol can be retrieved using the negotiated_protocol/1
function.
{client_preferred_next_protocols, {Precedence :: server | client, ClientPrefs :: [binary()]}}
{client_preferred_next_protocols, {Precedence :: server | client, ClientPrefs :: [binary()], Default :: binary()}}
Indicates that the client is to try to perform Next Protocol Negotiation.
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.
{psk_identity, string()}
Specifies the identity the client presents to the server.
The matching secret is found by calling user_lookup_fun
.
{srp_identity, {Username :: string(), Password :: string()}
Specifies the username and password to use to authenticate to the server.
{server_name_indication, HostName :: hostname()}
Specify the hostname to be used in TLS Server Name Indication extension.
If not specified it will default to the Host
argument of connect/[3,4]
unless it is of type inet:ipaddress().
The HostName
will also be used in the hostname verification of the peer certificate using
public_key:pkix_verify_hostname/2.
{server_name_indication, disable}
Prevents the Server Name Indication extension from being sent and disables the hostname verification check public_key:pkix_verify_hostname/2
{customize_hostname_check, Options::list()}
Customizes the hostname verification of the peer certificate, as different protocols that use TLS such as HTTP or LDAP may want to do it differently, for possible options see public_key:pkix_verify_hostname/3
{fallback, boolean()}
Send special cipher suite TLS_FALLBACK_SCSV to avoid undesired TLS version downgrade. Defaults to false
Warning!
Note this option is not needed in normal TLS usage and should not be used to implement new clients. But legacy clients that retries connections in the following manner
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.
{signature_algs, [{hash(), ecdsa | rsa | dsa}]}
In addition to the algorithms negotiated by the cipher
suite used for key exchange, payload encryption, message
authentication and pseudo random calculation, the TLS signature
algorithm extension
[
%% 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
TLS/DTLS OPTION DESCRIPTIONS - SERVER SIDE
The following options are server-specific or have a slightly different meaning in the server than in the client:
{cacerts, [public_key:der_encoded()]}
The DER-encoded trusted certificates. If this option
is supplied it overrides option cacertfile
.
{cacertfile, path()}
Path to a file containing PEM-encoded CA certificates. The CA certificates are used to build the server certificate chain and for client authentication. The CAs are also used in the list of acceptable client CAs passed to the client when a certificate is requested. Can be omitted if there is no need to verify the client and if there are no intermediate CAs for the server certificate.
{dh, public_key:der_encoded()}
The DER-encoded Diffie-Hellman parameters. If specified,
it overrides option dhfile
.
{dhfile, path()}
Path to a file containing PEM-encoded Diffie Hellman parameters to be used by the server if a cipher suite using Diffie Hellman key exchange is negotiated. If not specified, default parameters are used.
{verify, verify_type()}
A server only does x509-path validation in mode verify_peer
,
as it then sends a certificate request to the client
(this message is not sent if the verify option is verify_none
).
You can then also want to specify option fail_if_no_peer_cert
.
{fail_if_no_peer_cert, boolean()}
Used together with {verify, verify_peer}
by an TLS/DTLS server.
If set to true
, the server fails if the client does not have
a certificate to send, that is, sends an empty certificate. If set to
false
, it fails only if the client sends an invalid
certificate (an empty certificate is considered valid). Defaults to false.
{reuse_sessions, boolean()}
Specifies if the server is to agree to reuse sessions
when requested by the clients. See also option reuse_session
.
{reuse_session, fun(SuggestedSessionId,
PeerCert, Compression, CipherSuite) -> boolean()}
Enables the TLS/DTLS server to have a local policy
for deciding if a session is to be reused or not.
Meaningful only if reuse_sessions
is set to true
.
SuggestedSessionId
is a binary()
, PeerCert
is
a DER-encoded certificate, Compression
is an enumeration integer,
and CipherSuite
is of type ciphersuite()
.
{alpn_preferred_protocols, [binary()]}
Indicates the server will try to perform Application-Layer Protocol Negotiation (ALPN).
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.
{next_protocols_advertised, Protocols :: [binary()]}
List of protocols to send to the client if the client indicates that
it supports the Next Protocol extension. The client can select a protocol
that is not on this list. The list of protocols must not contain an empty
binary. If the server negotiates a Next Protocol, it can be accessed
using the negotiated_next_protocol/1
method.
{psk_identity, string()}
Specifies the server identity hint, which the server presents to the client.
{log_alert, boolean()}
If set to false
, error reports are not displayed.
{honor_cipher_order, boolean()}
If set to true
, use the server preference for cipher
selection. If set to false
(the default), use the client
preference.
{sni_hosts, [{hostname(), [ssl_option()]}]}
If the server receives a SNI (Server Name Indication) from the client
matching a host listed in the sni_hosts
option, the specific options for
that host will override previously specified options.
The option sni_fun
, and sni_hosts
are mutually exclusive.
{sni_fun, SNIfun::fun()}
If the server receives a SNI (Server Name Indication) from the client,
the given function will be called to retrieve [ssl_option()]
for the indicated server.
These options will be merged into predefined [ssl_option()]
.
The function should be defined as:
fun(ServerName :: string()) -> [ssl_option()]
and can be specified as a fun or as named fun module:function/1
The option sni_fun
, and sni_hosts
are mutually exclusive.
{client_renegotiation, boolean()}
false
. The default value is true
.
Note that disabling renegotiation can result in long-lived connections
becoming unusable due to limits on the number of messages the underlying
cipher suite can encipher.
{honor_cipher_order, boolean()}
{honor_ecc_order, boolean()}
{signature_algs, [{hash(), ecdsa | rsa | dsa}]}
The algorithms specified by this option will be the ones accepted by the server in a signature algorithm negotiation, introduced in TLS-1.2. The algorithms will also be offered to the client if a client certificate is requested. For more details see the corresponding client option.
General
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:
{ssl, Socket, Data}
{ssl_closed, Socket}
{ssl_error, Socket, Reason}
A Timeout
argument specifies a time-out in milliseconds. The
default value for argument Timeout
is infinity
.
Functions
append_cipher_suites(Deferred, Suites) -> ciphers()
Deferred = ciphers() | cipher_filters()
Suites = ciphers()
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()
Type = erlang | openssl | all
Deprecated in OTP 21, use cipher_suites/2 instead.
cipher_suites(Supported, Version) -> ciphers()
Supported = default | all | anonymous
Version = protocol_version()
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}
Socket = socket()
SslOptions = [{handshake, hello| full} | ssl_option()]
Timeout = integer() | infinity
SslSocket = sslsocket()
Ext = hello_extensions()
Reason = term()
Upgrades a gen_tcp
, or equivalent,
connected socket to an TLS socket, that is, performs the
client-side TLS handshake.
Note!
If the option verify
is set to verify_peer
the option server_name_indication
shall also be specified,
if it is not no Server Name Indication extension will be sent,
and public_key:pkix_verify_hostname/2
will be called with the IP-address of the connection as ReferenceID
, which is proably not what you want.
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}
Host = host()
Port = integer()
Options = [option()]
Timeout = integer() | infinity
SslSocket = sslsocket()
Reason = term()
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.
Note!
According to good practices certificates should not use IP-addresses as "server names". It would be very surprising if this happen outside a closed network.
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}
SslSocket = sslsocket()
Reason = term()
Closes an TLS/DTLS connection.
close(SslSocket, How) -> ok | {ok, port()} | {error, Reason}
SslSocket = sslsocket()
How = timeout() | {NewController::pid(), timeout()}
Reason = term()
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}
SslSocket = sslsocket()
NewOwner = pid()
Reason = term()
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}
SslSocket = sslsocket()
Item = protocol | cipher_suite | sni_hostname | ecc | session_id | atom()
Result = [{Item::atom(), Value::term()}]
Reason = term()
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}
SslSocket = sslsocket()
Items = [Item]
Item = protocol | cipher_suite | sni_hostname | ecc | session_id | client_random | server_random | master_secret | atom()
Result = [{Item::atom(), Value::term()}]
Reason = term()
Returns the requested information items about the connection, if they are defined.
Note!
If only undefined options are requested the resulting list can be empty.
filter_cipher_suites(Suites, Filters) -> ciphers()
Suites = ciphers()
Filters = cipher_filters()
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()
Reason = term()
Presents the error returned by an SSL function as a printable string.
getopts(SslSocket, OptionNames) -> {ok, [socketoption()]} | {error, Reason}
Socket = sslsocket()
OptionNames = [atom()]
Gets the values of the specified socket options.
getstat(SslSocket) -> {ok, OptionValues} | {error, inet:posix()}
getstat(SslSocket, OptionNames) -> {ok, OptionValues} | {error, inet:posix()}
SslSocket = sslsocket()
OptionNames = [atom()]
OptionValues = [{inet:stat_option(), integer()}]
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}
HsSocket = SslSocket = sslsocket()
Timeout = integer()
Reason = term()
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}
Socket = socket() | sslsocket()
SslSocket = sslsocket()
Ext = hello_extensions()
SslOptions = [{handshake, hello| full} | ssl_option()]
Timeout = integer()
Reason = term()
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.
Warning!
The Socket
shall be in passive mode ({active,
false}) before calling this function or else the behavior of this function
is undefined.
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
SslSocket = sslsocket()
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}
HsSocket = SslSocket = sslsocket()
SslOptions = [ssl_option()]
Timeout = integer()
Reason = term()
Continue the SSL/TLS handshake possiby with new, additional or changed options.
listen(Port, Options) -> {ok, ListenSocket} | {error, Reason}
Port = integer()
Options = options()
ListenSocket = sslsocket()
Creates an SSL listen socket.
negotiated_protocol(SslSocket) -> {ok, Protocol} | {error, protocol_not_negotiated}
SslSocket = sslsocket()
Protocol = binary()
Returns the protocol negotiated through ALPN or NPN extensions.
peercert(SslSocket) -> {ok, Cert} | {error, Reason}
SslSocket = 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(SslSocket) -> {ok, {Address, Port}} | {error, Reason}
SslSocket = sslsocket()
Address = ipaddress()
Port = integer()
Returns the address and port number of the peer.
prepend_cipher_suites(Preferred, Suites) -> ciphers()
Preferred = ciphers() | cipher_filters()
Suites = ciphers()
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()}
Socket = sslsocket()
Secret = binary() | master_secret
Label = binary()
Seed = [binary() | prf_random()]
WantedLength = non_neg_integer()
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}
SslSocket = sslsocket()
Length = integer()
Timeout = integer()
Data = [char()] | binary()
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}
SslSocket = 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(SslSocket, Data) -> ok | {error, Reason}
SslSocket = sslsocket()
Data = iodata()
Writes Data
to Socket
.
A notable return value is {error, closed}
indicating that
the socket is closed.
setopts(SslSocket, Options) -> ok | {error, Reason}
SslSocket = sslsocket()
Options = [socketoption]()
Sets options according to Options
for socket
Socket
.
shutdown(SslSocket, How) -> ok | {error, Reason}
SslSocket = sslsocket()
How = read | write | read_write
Reason = reason()
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}
SslSocket = sslsocket()
Timeout = integer()
Reason = term()
Deprecated in OTP 21, use handshake/[1,2] instead.
Note!
handshake/[1,2] always returns a new socket.
ssl_accept(Socket, SslOptions) ->
ssl_accept(Socket, SslOptions, Timeout) -> {ok, Socket} | ok | {error, Reason}
Socket = socket() | sslsocket()
SslOptions = [ssl_option()]
Timeout = integer()
Reason = term()
Deprecated in OTP 21, use handshake/[2,3] instead.
Note!
handshake/[2,3] always returns a new socket.
sockname(SslSocket) -> {ok, {Address, Port}} | {error, Reason}
SslSocket = sslsocket()
Address = ipaddress()
Port = integer()
Returns the local address and port number of socket
Socket
.
start() ->
start(Type) -> ok | {error, Reason}
Type = permanent | transient | temporary
Starts the SSL application. Default type
is temporary
.
stop() -> ok
Stops the SSL application.
suite_to_str(CipherSuite) -> String
CipherSuite = erl_cipher_suite()
String = string()
Returns the string representation of a cipher suite.
transport_accept(ListenSocket) ->
transport_accept(ListenSocket, Timeout) -> {ok, SslSocket} | {error, Reason}
ListenSocket = SslSocket = 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 is to be passed to
handshake/[2,3]
to complete handshaking, that is,
establishing the SSL/TLS/DTLS connection.
Warning!
The socket returned can only be used with handshake/[2,3]. 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() -> [versions_info()]
versions_info() = {app_vsn, string()} | {supported | available, [ssl_tls_protocol()]} | {supported_dtls | available_dtls, [dtls_protocol()]}
Returns version information relevant for the SSL application.
app_vsn
supported
supported_dtls
available
available_dtls