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NAME
ssl - Interface Functions for Secure Socket Layer
DESCRIPTION
This module contains interface functions for the SSL/TLS/DTLS protocol. For detailed information about
the supported standards see ssl(7).
DATA TYPES
Types used in SSL/TLS/DTLS
socket() = gen_tcp:socket()
sslsocket() = any()
An opaque reference to the TLS/DTLS connection, may be used for equality matching.
tls_option() = tls_client_option() | tls_server_option()
tls_client_option() =
client_option() |
common_option() |
socket_option() |
transport_option()
tls_server_option() =
server_option() |
common_option() |
socket_option() |
transport_option()
socket_option() =
gen_tcp:connect_option() |
gen_tcp:listen_option() |
gen_udp:option()
The default socket options are [{mode,list},{packet, 0},{header, 0},{active, true}].
For valid options, see the inet(3erl), gen_tcp(3erl) and gen_udp(3erl) manual pages in Kernel.
Note that stream oriented options such as packet are only relevant for SSL/TLS and not DTLS
active_msgs() =
{ssl, sslsocket(), Data :: binary() | list()} |
{ssl_closed, sslsocket()} |
{ssl_error, sslsocket(), Reason :: any()} |
{ssl_passive, sslsocket()}
When a 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 as described above.
The ssl_passive message is sent only when the socket is in {active, N} mode and the counter
dropped to 0. It indicates that the socket has transitioned to passive ({active, false}) mode.
transport_option() =
{cb_info,
{CallbackModule :: atom(),
DataTag :: atom(),
ClosedTag :: atom(),
ErrTag :: atom()}} |
{cb_info,
{CallbackModule :: atom(),
DataTag :: atom(),
ClosedTag :: atom(),
ErrTag :: atom(),
PassiveTag :: atom()}}
Defaults to {gen_tcp, tcp, tcp_closed, tcp_error, tcp_passive} for TLS (for backward compatibility
a four tuple will be converted to a five tuple with the last element "second_element"_passive) and
{gen_udp, udp, udp_closed, udp_error} for DTLS (might also be changed to five tuple in the
future). Can be used to customize the transport layer. The tag values should be the values used by
the underlying transport in its active mode messages. 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.
host() = hostname() | ip_address()
hostname() = string()
ip_address() = inet:ip_address()
protocol_version() = tls_version() | dtls_version()
tls_version() = 'tlsv1.2' | 'tlsv1.3' | tls_legacy_version()
dtls_version() = 'dtlsv1.2' | dtls_legacy_version()
tls_legacy_version() = tlsv1 | 'tlsv1.1' | sslv3
dtls_legacy_version() = dtlsv1
prf_random() = client_random | server_random
verify_type() = verify_none | verify_peer
ciphers() = [erl_cipher_suite()] | string()
erl_cipher_suite() =
#{key_exchange := kex_algo(),
cipher := cipher(),
mac := hash() | aead,
prf := hash() | default_prf}
cipher() =
aes_128_cbc | aes_256_cbc | aes_128_gcm | aes_256_gcm |
aes_128_ccm | aes_256_ccm | aes_128_ccm_8 | aes_256_ccm_8 |
chacha20_poly1305 |
legacy_cipher()
legacy_cipher() = rc4_128 | des_cbc | '3des_ede_cbc'
cipher_filters() =
[{key_exchange | cipher | mac | prf, algo_filter()}]
hash() = sha | sha2() | legacy_hash()
sha2() = sha224 | sha256 | sha384 | sha512
legacy_hash() = md5
old_cipher_suite() =
{kex_algo(), cipher(), hash()} |
{kex_algo(), cipher(), hash() | aead, hash()}
signature_algs() = [{hash(), sign_algo()}]
sign_algo() = rsa | dsa | ecdsa
sign_scheme() =
rsa_pkcs1_sha256 | rsa_pkcs1_sha384 | rsa_pkcs1_sha512 |
ecdsa_secp256r1_sha256 | ecdsa_secp384r1_sha384 |
ecdsa_secp521r1_sha512 | rsa_pss_rsae_sha256 |
rsa_pss_rsae_sha384 | rsa_pss_rsae_sha512 |
rsa_pss_pss_sha256 | rsa_pss_pss_sha384 | rsa_pss_pss_sha512 |
rsa_pkcs1_sha1 | ecdsa_sha1
group() =
secp256r1 | secp384r1 | secp521r1 | ffdhe2048 | ffdhe3072 |
ffdhe4096 | ffdhe6144 | ffdhe8192
kex_algo() =
rsa | dhe_rsa | dhe_dss | ecdhe_ecdsa | ecdh_ecdsa |
ecdh_rsa | srp_rsa | srp_dss | psk | dhe_psk | rsa_psk |
dh_anon | ecdh_anon | srp_anon | any
algo_filter() =
fun((kex_algo() | cipher() | hash() | aead | default_prf) ->
true | false)
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
psk_identity() = string()
srp_identity() = {Username :: string(), Password :: string()}
srp_param_type() =
srp_1024 | srp_1536 | srp_2048 | srp_3072 | srp_4096 |
srp_6144 | srp_8192
app_level_protocol() = binary()
protocol_extensions() =
#{renegotiation_info => binary(),
signature_algs => signature_algs(),
alpn => app_level_protocol(),
srp => binary(),
next_protocol => app_level_protocol(),
ec_point_formats => [0..2],
elliptic_curves => [public_key:oid()],
sni => hostname()}
error_alert() =
{tls_alert, {tls_alert(), Description :: string()}}
tls_alert() =
close_notify | unexpected_message | bad_record_mac |
record_overflow | handshake_failure | bad_certificate |
unsupported_certificate | certificate_revoked |
certificate_expired | certificate_unknown |
illegal_parameter | unknown_ca | access_denied |
decode_error | decrypt_error | export_restriction |
protocol_version | insufficient_security | internal_error |
inappropriate_fallback | user_canceled | no_renegotiation |
unsupported_extension | certificate_unobtainable |
unrecognized_name | bad_certificate_status_response |
bad_certificate_hash_value | unknown_psk_identity |
no_application_protocol
reason() = any()
TLS/DTLS OPTION DESCRIPTIONS - COMMON for SERVER and CLIENT
common_option() =
{protocol, protocol()} |
{handshake, handshake_completion()} |
{cert, cert()} |
{certfile, cert_pem()} |
{key, key()} |
{keyfile, key_pem()} |
{password, key_password()} |
{ciphers, cipher_suites()} |
{eccs, [named_curve()]} |
{signature_algs_cert, signature_schemes()} |
{supported_groups, supported_groups()} |
{secure_renegotiate, secure_renegotiation()} |
{depth, allowed_cert_chain_length()} |
{verify_fun, custom_verify()} |
{crl_check, crl_check()} |
{crl_cache, crl_cache_opts()} |
{max_handshake_size, handshake_size()} |
{partial_chain, root_fun()} |
{versions, protocol_versions()} |
{user_lookup_fun, custom_user_lookup()} |
{log_level, logging_level()} |
{log_alert, log_alert()} |
{hibernate_after, hibernate_after()} |
{padding_check, padding_check()} |
{beast_mitigation, beast_mitigation()} |
{ssl_imp, ssl_imp()}
protocol() = tls | dtls
Choose TLS or DTLS protocol for the transport layer security. Defaults to tls. For DTLS other
transports than UDP are not yet supported.
handshake_completion() = 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.
cert_pem() = file:filename()
Path to a file containing the user certificate on PEM format.
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.
key_pem() = file:filename()
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.
key_password() = string()
String containing the user's password. Only used if the private keyfile is password-protected.
cipher_suites() = ciphers()
A list of cipher suites that should be supported
The function ssl:cipher_suites/2 can be used to find all cipher suites that are supported by
default and all cipher suites that may be configured.
If you compose your own cipher_suites() make sure they are filtered for cryptolib support
ssl:filter_cipher_suites/2 Additionaly the functions ssl:append_cipher_suites/2 ,
ssl:prepend_cipher_suites/2, ssl:suite_to_str/1, ssl:str_to_suite/1, and
ssl:suite_to_openssl_str/1 also exist to help creating customized cipher suite lists.
Note:
Note that TLS-1.3 and TLS-1.2 cipher suites are not overlapping sets of cipher suites so to
support both these versions cipher suites from both versions need to be included. If supporting
TLS-1.3 versions prior to TLS-1.2 can not be supported.
Non-default cipher suites including anonymous cipher suites (PRE TLS-1.3) are supported for
interop/testing purposes and may be used by adding them to your cipher suite list. Note that they
must also be supported/enabled by the peer to actually be used.
signature_schemes() = [sign_scheme()]
In addition to the signature_algorithms extension from TLS 1.2, TLS 1.3 (RFC 5246 Section
4.2.3)adds the signature_algorithms_cert extension which enables having special requirements on
the signatures used in the certificates that differs from the requirements on digital signatures
as a whole. If this is not required this extension is not needed.
The client will send a signature_algorithms_cert extension (ClientHello), if TLS version 1.3 or
later is used, and the signature_algs_cert option is explicitly specified. By default, only the
signature_algs extension is sent.
The signature schemes shall be ordered according to the client's preference (favorite choice
first).
supported_groups() = [group()]
TLS 1.3 introduces the "supported_groups" extension that is used for negotiating the Diffie-
Hellman parameters in a TLS 1.3 handshake. Both client and server can specify a list of parameters
that they are willing to use.
If it is not specified it will use a default list ([x25519, x448, secp256r1, secp384r1]) that is
filtered based on the installed crypto library version.
secure_renegotiation() = boolean()
Specifies if to reject renegotiation attempt that does not live up to RFC 5746. By default
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 RFC 5746.
allowed_cert_chain_length() = 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.
custom_verify() =
{Verifyfun :: function(), InitialUserState :: any()}
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:
check is only performed on the peer certificate.
best_effort:
if certificate revocation status cannot be determined it will be accepted as valid.
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(3erl).
crl_cache_opts() = [any()]
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.
root_fun() = function()
fun(Chain::[public_key:der_encoded()]) ->
{trusted_ca, DerCert::public_key:der_encoded()} | 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.
protocol_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(7).
custom_user_lookup() =
{Lookupfun :: function(), UserState :: any()}
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 RFC 2945 and RFC
5054: crypto:sha([Salt, crypto:sha([Username, <<$:>>, Password])])
session_id() = binary()
Identifies a TLS session.
log_alert() = boolean()
If set to false, TLS/DTLS Alert reports are not displayed. Deprecated in OTP 22, use {log_level,
logging_level()} instead.
logging_level() = logger:level()
Specifies the log level for a TLS/DTLS connection. Alerts are logged on notice level, which is the
default level. The level debug triggers verbose logging of TLS/DTLS protocol messages. See also
ssl(7)
hibernate_after() = timeout()
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.
handshake_size() = integer()
Integer (24 bits unsigned). Used to limit the size of valid TLS handshake packets to avoid DoS
attacks. Defaults to 256*1024.
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-3.0 or TLS-1.0 vulnerable to the BEAST attack.
ssl_imp() = new | old
Deprecated since OTP-17, has no affect.
TLS/DTLS OPTION DESCRIPTIONS - CLIENT
client_option() =
{verify, client_verify_type()} |
{reuse_session, client_reuse_session()} |
{reuse_sessions, client_reuse_sessions()} |
{cacerts, client_cacerts()} |
{cacertfile, client_cafile()} |
{alpn_advertised_protocols, client_alpn()} |
{client_preferred_next_protocols,
client_preferred_next_protocols()} |
{psk_identity, client_psk_identity()} |
{srp_identity, client_srp_identity()} |
{server_name_indication, sni()} |
{customize_hostname_check, customize_hostname_check()} |
{signature_algs, client_signature_algs()} |
{fallback, fallback()}
client_verify_type() = verify_type()
In mode verify_none the default behavior is to allow all x509-path validation errors. See also
option verify_fun.
client_reuse_session() = session_id()
Reuses a specific session earlier saved with the option {reuse_sessions, save} since OTP-21.3
client_reuse_sessions() = boolean() | save
When save is specified a new connection will be negotiated and saved for later reuse. The session
ID can be fetched with connection_information/2 and used with the client option reuse_session The
boolean value true specifies that if possible, automatized session reuse will be performed. If a
new session is created, and is unique in regard to previous stored sessions, it will be saved for
possible later reuse. Since OTP-21.3
client_cacerts() = [public_key:der_encoded()]
The DER-encoded trusted certificates. If this option is supplied it overrides option cacertfile.
client_cafile() = file:filename()
Path to a file containing PEM-encoded CA certificates. The CA certificates are used during server
authentication and when building the client certificate chain.
client_alpn() = [app_level_protocol()]
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 :: [app_level_protocol()]} |
{Precedence :: server | client,
ClientPrefs :: [app_level_protocol()],
Default :: app_level_protocol()}
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.
client_psk_identity() = psk_identity()
Specifies the identity the client presents to the server. The matching secret is found by calling
user_lookup_fun
client_srp_identity() = srp_identity()
Specifies the username and password to use to authenticate to the server.
sni() = hostname() | disable
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.
The special value 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() = 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.
client_signature_algs() = signature_algs()
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 Section 7.4.1.4.1 in RFC 5246 may be used, from TLS 1.2, to negotiate which signature
algorithm to use during the TLS handshake. If no lower TLS versions than 1.2 are supported, the
client will send a TLS signature algorithm extension with the algorithms specified by this option.
Defaults to
[
%% 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
server_option() =
{cacerts, server_cacerts()} |
{cacertfile, server_cafile()} |
{dh, dh_der()} |
{dhfile, dh_file()} |
{verify, server_verify_type()} |
{fail_if_no_peer_cert, fail_if_no_peer_cert()} |
{reuse_sessions, server_reuse_sessions()} |
{reuse_session, server_reuse_session()} |
{alpn_preferred_protocols, server_alpn()} |
{next_protocols_advertised, server_next_protocol()} |
{psk_identity, server_psk_identity()} |
{honor_cipher_order, boolean()} |
{sni_hosts, sni_hosts()} |
{sni_fun, sni_fun()} |
{honor_cipher_order, honor_cipher_order()} |
{honor_ecc_order, honor_ecc_order()} |
{client_renegotiation, client_renegotiation()} |
{signature_algs, server_signature_algs()}
server_cacerts() = [public_key:der_encoded()]
The DER-encoded trusted certificates. If this option is supplied it overrides option cacertfile.
server_cafile() = file:filename()
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_der() = binary()
The DER-encoded Diffie-Hellman parameters. If specified, it overrides option dhfile.
Warning:
The dh_der option is not supported by TLS 1.3. Use the supported_groups option instead.
dh_file() = file:filename()
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.
Warning:
The dh_file option is not supported by TLS 1.3. Use the supported_groups option instead.
server_verify_type() = 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.
server_reuse_sessions() = boolean()
The boolean value true specifies that the server will agree to reuse sessions. Setting it to false
will result in an empty session table, that is no sessions will be reused. See also option
reuse_session
server_reuse_session() = function()
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().
server_alpn() = [app_level_protocol()]
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.
server_next_protocol() = [app_level_protocol()]
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.
server_psk_identity() = psk_identity()
Specifies the server identity hint, which the server presents to the client.
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(), [server_option() | common_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() = function()
If the server receives a SNI (Server Name Indication) from the client, the given function will be
called to retrieve [server_option()] for the indicated server. These options will be merged into
predefined [server_option()] list. The function should be defined as: fun(ServerName :: string())
-> [server_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()
In protocols that support client-initiated renegotiation, the cost of resources of such an
operation is higher for the server than the client. This can act as a vector for denial of service
attacks. The SSL application already takes measures to counter-act such attempts, but client-
initiated renegotiation can be strictly disabled by setting this option to 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()
If true, use the server's preference for cipher selection. If false (the default), use the
client's preference.
honor_ecc_order() = boolean()
If true, use the server's preference for ECC curve selection. If false (the default), use the
client's preference.
server_signature_algs() = signature_algs()
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.
EXPORTS
append_cipher_suites(Deferred, Suites) -> ciphers()
Types:
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() -> [old_cipher_suite()] | [string()]
cipher_suites(Type) -> [old_cipher_suite() | string()]
Types:
Type = erlang | openssl | all
Deprecated in OTP 21, use cipher_suites/2 instead.
cipher_suites(Supported, Version) -> ciphers()
Types:
Supported = default | all | anonymous
Version = protocol_version()
Returns all default or all supported (except anonymous), or all anonymous cipher suites for a TLS
version
Note:
The cipher suites returned by this function are the cipher suites that the OTP ssl application can
support provided that they are supported by the cryptolib linked with the OTP crypto application.
Use ssl:filter_cipher_suites(Suites, []). to filter the list for the current cryptolib. Note that
cipher suites may be filtered out because they are too old or too new depending on the cryptolib
cipher_suites(Supported, Version, StringType :: rfc | openssl) ->
[string()]
Types:
Supported = default | all | anonymous
Version = protocol_version()
Same as cipher_suites/2 but lists RFC or OpenSSL string names instead of erl_cipher_suite()
eccs() -> NamedCurves
eccs(Version) -> NamedCurves
Types:
Version = protocol_version()
NamedCurves = [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(TCPSocket, TLSOptions) ->
{ok, sslsocket()} |
{error, reason()} |
{option_not_a_key_value_tuple, any()}
connect(TCPSocket, TLSOptions, Timeout) ->
{ok, sslsocket()} | {error, reason()}
Types:
TCPSocket = socket()
TLSOptions = [tls_client_option()]
Timeout = timeout()
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.
If the option active is set to once, true or an integer value, the process owning the sslsocket
will receive messages of type active_msgs()
connect(Host, Port, TLSOptions) ->
{ok, sslsocket()} |
{ok, sslsocket(), Ext :: protocol_extensions()} |
{error, reason()} |
{option_not_a_key_value_tuple, any()}
connect(Host, Port, TLSOptions, Timeout) ->
{ok, sslsocket()} |
{ok, sslsocket(), Ext :: protocol_extensions()} |
{error, reason()} |
{option_not_a_key_value_tuple, any()}
Types:
Host = host()
Port = inet:port_number()
TLSOptions = [tls_client_option()]
Timeout = timeout()
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.
If the option active is set to once, true or an integer value, the process owning the sslsocket
will receive messages of type active_msgs()
close(SslSocket) -> ok | {error, Reason}
Types:
SslSocket = sslsocket()
Reason = any()
Closes an TLS/DTLS connection.
close(SslSocket, How) -> ok | {ok, port()} | {error, Reason}
Types:
SslSocket = sslsocket()
How = timeout() | {NewController :: pid(), timeout()}
Reason = any()
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}
Types:
SslSocket = sslsocket()
NewOwner = pid()
Reason = any()
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()}
Types:
SslSocket = sslsocket()
Result = [{OptionName, OptionValue}]
OptionName = atom()
OptionValue = any()
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.
Note:
The legacy Item = cipher_suite is still supported and returns the cipher suite on its
(undocumented) legacy format. It should be replaced by selected_cipher_suite.
connection_information(SslSocket, Items) ->
{ok, Result} | {error, reason()}
Types:
SslSocket = sslsocket()
Items = [OptionName]
Result = [{OptionName, OptionValue}]
OptionName = atom()
OptionValue = any()
Returns the requested information items about the connection, if they are defined.
Note that client_random, server_random and master_secret are values that affect the security of
connection. Meaningful atoms, not specified above, are the ssl option names.
Note:
If only undefined options are requested the resulting list can be empty.
filter_cipher_suites(Suites, Filters) -> Ciphers
Types:
Suites = ciphers()
Filters = cipher_filters()
Ciphers = ciphers()
Removes cipher suites if any of the filter functions returns false for any part of the cipher
suite. If no filter function is supplied for some part the default behaviour regards it as if
there was a filter function that returned true. For examples see Customizing cipher suits
Additionaly this function also filters the cipher suites to exclude cipher suites not supported by
the cryptolib used by the OTP crypto application. That is calling ssl:filter_cipher_suites(Suites,
[]) will be equivalent to only applying the filters for cryptolib support.
format_error(Reason :: {error, Reason}) -> string()
Types:
Reason = any()
Presents the error returned by an SSL function as a printable string.
getopts(SslSocket, OptionNames) ->
{ok, [gen_tcp:option()]} | {error, reason()}
Types:
SslSocket = sslsocket()
OptionNames = [gen_tcp:option_name()]
Gets the values of the specified socket options.
getstat(SslSocket) -> {ok, OptionValues} | {error, inet:posix()}
getstat(SslSocket, Options) ->
{ok, OptionValues} | {error, inet:posix()}
Types:
SslSocket = sslsocket()
Options = [inet:stat_option()]
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) ->
{ok, SslSocket} |
{ok, SslSocket, Ext} |
{error, Reason}
handshake(HsSocket, Timeout) ->
{ok, SslSocket} |
{ok, SslSocket, Ext} |
{error, Reason}
Types:
HsSocket = sslsocket()
Timeout = timeout()
SslSocket = sslsocket()
Ext = protocol_extensions()
Reason = closed | timeout | error_alert()
Performs the SSL/TLS/DTLS server-side handshake.
Returns a new TLS/DTLS socket if the handshake is successful.
If the option active is set to once, true or an integer value, the process owning the sslsocket
will receive messages of type active_msgs()
handshake(Socket, Options) ->
{ok, SslSocket} |
{ok, SslSocket, Ext} |
{error, Reason}
handshake(Socket, Options, Timeout) ->
{ok, SslSocket} |
{ok, SslSocket, Ext} |
{error, Reason}
Types:
Socket = socket() | sslsocket()
SslSocket = sslsocket()
Options = [server_option()]
Timeout = timeout()
Ext = protocol_extensions()
Reason = closed | timeout | {options, any()} | error_alert()
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.
If the option active is set to once, true or an integer value, the process owning the sslsocket
will receive messages of type active_msgs()
handshake_cancel(Sslsocket :: #sslsocket{}) -> any()
Cancel the handshake with a fatal USER_CANCELED alert.
handshake_continue(HsSocket, Options) ->
{ok, SslSocket} | {error, Reason}
handshake_continue(HsSocket, Options, Timeout) ->
{ok, SslSocket} | {error, Reason}
Types:
HsSocket = sslsocket()
Options = [tls_client_option() | tls_server_option()]
Timeout = timeout()
SslSocket = sslsocket()
Reason = closed | timeout | error_alert()
Continue the SSL/TLS handshake possiby with new, additional or changed options.
listen(Port, Options) -> {ok, ListenSocket} | {error, reason()}
Types:
Port = inet:port_number()
Options = [tls_server_option()]
ListenSocket = sslsocket()
Creates an SSL listen socket.
negotiated_protocol(SslSocket) -> {ok, Protocol} | {error, Reason}
Types:
SslSocket = sslsocket()
Protocol = binary()
Reason = protocol_not_negotiated
Returns the protocol negotiated through ALPN or NPN extensions.
peercert(SslSocket) -> {ok, Cert} | {error, reason()}
Types:
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()}
Types:
SslSocket = sslsocket()
Address = inet:ip_address()
Port = inet:port_number()
Returns the address and port number of the peer.
prepend_cipher_suites(Preferred, Suites) -> ciphers()
Types:
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(SslSocket, Secret, Label, Seed, WantedLength) ->
{ok, binary()} | {error, reason()}
Types:
SslSocket = sslsocket()
Secret = binary() | master_secret
Label = binary()
Seed = [binary() | prf_random()]
WantedLength = integer() >= 0
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) -> {ok, Data} | {error, reason()}
recv(SslSocket, Length, Timeout) -> {ok, Data} | {error, reason()}
Types:
SslSocket = sslsocket()
Length = integer()
Data = binary() | list() | HttpPacket
Timeout = timeout()
HttpPacket = any()
See the description of HttpPacket in erlang:decode_packet/3 in ERTS.
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()}
Types:
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()}
Types:
SslSocket = sslsocket()
Data = iodata()
Writes Data to SslSocket.
A notable return value is {error, closed} indicating that the socket is closed.
setopts(SslSocket, Options) -> ok | {error, reason()}
Types:
SslSocket = sslsocket()
Options = [gen_tcp:option()]
Sets options according to Options for socket SslSocket.
shutdown(SslSocket, How) -> ok | {error, reason()}
Types:
SslSocket = sslsocket()
How = read | write | read_write
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) -> ok | {error, Reason}
ssl_accept(Socket, TimeoutOrOptions) ->
ok | {ok, sslsocket()} | {error, Reason}
Types:
Socket = sslsocket() | socket()
TimeoutOrOptions = timeout() | [tls_server_option()]
Reason = timeout | closed | {options, any()} | error_alert()
Deprecated in OTP 21, use handshake/[1,2] instead.
Note:
handshake/[1,2] always returns a new socket.
ssl_accept(Socket, Options, Timeout) ->
ok | {ok, sslsocket()} | {error, Reason}
Types:
Socket = sslsocket() | socket()
Options = [tls_server_option()]
Timeout = timeout()
Reason = timeout | closed | {options, any()} | error_alert()
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()}
Types:
SslSocket = sslsocket()
Address = inet:ip_address()
Port = inet:port_number()
Returns the local address and port number of socket SslSocket.
start() -> ok | {error, reason()}
start(Type) -> ok | {error, Reason}
Starts the SSL application. Default type is temporary.
stop() -> ok
Stops the SSL application.
str_to_suite(CipherSuiteName) -> erl_cipher_suite()
Types:
CipherSuiteName =
string() |
{error, {not_recognized, CipherSuiteName :: string()}}
Converts an RFC or OpenSSL name string to an erl_cipher_suite() Returns an error if the cipher
suite is not supported or the name is not a valid cipher suite name.
suite_to_openssl_str(CipherSuite) -> string()
Types:
CipherSuite = erl_cipher_suite()
Converts erl_cipher_suite() to OpenSSL name string.
PRE TLS-1.3 these names differ for RFC names
suite_to_str(CipherSuite) -> string()
Types:
CipherSuite = erl_cipher_suite()
Converts erl_cipher_suite() to RFC name string.
transport_accept(ListenSocket) ->
{ok, SslSocket} | {error, reason()}
transport_accept(ListenSocket, Timeout) ->
{ok, SslSocket} | {error, reason()}
Types:
ListenSocket = sslsocket()
Timeout = timeout()
SslSocket = sslsocket()
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:
Most API functions require that the TLS/DTLS connection is established to work as expected.
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() -> [VersionInfo]
Types:
VersionInfo =
{ssl_app, string()} |
{supported | available, [tls_version()]} |
{supported_dtls | available_dtls, [dtls_version()]}
Returns version information relevant for the SSL application.
app_vsn:
The application version of the SSL application.
supported:
SSL/TLS versions supported by default. Overridden by a version option on connect/[2,3,4],
listen/2, and ssl_accept/[1,2,3]. For the negotiated SSL/TLS version, see
connection_information/1 .
supported_dtls:
DTLS versions supported by default. Overridden by a version option on connect/[2,3,4],
listen/2, and ssl_accept/[1,2,3]. For the negotiated DTLS version, see
connection_information/1 .
available:
All SSL/TLS versions supported by the SSL application. TLS 1.2 requires sufficient support
from the Crypto application.
available_dtls:
All DTLS versions supported by the SSL application. DTLS 1.2 requires sufficient support from
the Crypto application.
SEE ALSO
inet(3erl) and gen_tcp(3erl) gen_udp(3erl)