ssl
Module
ssl
Module Summary
Interface Functions for Secure Socket Layer
Description
This module contains interface functions for the SSL/TLS protocol. For detailed information about the supported standards see ssl(6)
.
Data types
The following data types are used in the functions for SSL:
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)
andgen_tcp(3)
manual pages in Kernel. 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}
| {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}
. Can be used to customize the transport layer. The callback module must implement a reliable transport protocol, behave asgen_tcp
, and have functions corresponding toinet:setopts/2
,inet:getopts/2
,inet:peername/1
,inet:sockname/1
, andinet:port/1
. The callbackgen_tcp
is treated specially and callsinet
directly.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() =
sslv3 | tlsv1 | 'tlsv1.1' | 'tlsv1.2'
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
SSL 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. DTLS over other transports than UDP are not yet supported.{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
andCrypto's Users Guide
. If this option is supplied, it overrides optionkeyfile
.{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 (RFC 4279
andRFC 5487
), Secure Remote Password (RFC 5054
), RC4 cipher suites, and anonymous cipher suites only work if explicitly enabled by this option; they are supported/enabled by the peer also. Anonymous cipher suites are supported for testing purposes only and are not be used when security matters.{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
RFC 5746
. By defaultsecure_renegotiate
is set tofalse
, that is, secure renegotiation is used if possible, but it falls back to insecure renegotiation if the peer does not supportRFC 5746
. {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
orvalid
as second argument to the verification fun. See thepublic_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/SSL 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/SSL 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
inverify_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 modeverify_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}
whereReason
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 tofalse
.peer
- check is only performed on the peer certificate.
best_effort
- if certificate revocation status can not 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(3)
. {crl_cache, {Module :: atom(), {DbHandle :: internal | term(), Args :: list()}}}
-
Specify how to perform lookup and caching of certificate revocation lists.
Module
defaults tossl_crl_cache
withDbHandle
beinginternal
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 in
X509 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
, whereN
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 utilityc_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 whosenextUpdate
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
. If the environment option is not set, it defaults to all versions, except SSL-3.0, supported by the SSL application. See alsossl(6).
{hibernate_after, integer()|undefined}
When an integer-value is specified,
ssl_connection
goes into hibernation after the specified number of milliseconds of inactivity, thus reducing its memory footprint. Whenundefined
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 toRFC 2945
andRFC 5054
: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.WarningUsing
{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.WarningUsing
{beast_mitigation, disabled}
makes SSL or TLS vulnerable to the BEAST attack.
Ssl 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 optionverify_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 ofconnect/[3,4]
unless it is of type inet:ipaddress().The
HostName
will also be used in the hostname verification of the peer certificate usingpublic_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
{fallback, boolean()}
-
Send special cipher suite TLS_FALLBACK_SCSV to avoid undesired TLS version downgrade. Defaults to false
WarningNote 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
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
Ssl 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 isverify_none
). You can then also want to specify optionfail_if_no_peer_cert
.{fail_if_no_peer_cert, boolean()}
-
Used together with
{verify, verify_peer}
by an SSL server. If set totrue
, the server fails if the client does not have a certificate to send, that is, sends an empty certificate. If set tofalse
, 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 SSL server to have a local policy for deciding if a session is to be reused or not. Meaningful only if
reuse_sessions
is set totrue
.SuggestedSessionId
is abinary()
,PeerCert
is a DER-encoded certificate,Compression
is an enumeration integer, andCipherSuite
is of typeciphersuite()
.{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 tofalse
(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 optionsni_fun
, andsni_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 namedfun module:function/1
The optionsni_fun
, andsni_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 istrue
. 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.
{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
. {v2_hello_compatible, boolean()}
- If true, the server accepts clients that send hello messages on SSL-2.0 format but offers supported SSL/TLS versions. Defaults to false, that is the server will not interoperate with clients that offers SSL-2.0.
General
When an 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 time-out in milliseconds. The default value for argument Timeout
is infinity
.
Exports
append_cipher_suites(Deferred, Suites) -> ciphers()
Types
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()
Types
Returns a list of supported cipher suites. This function will become deprecated in OTP 21, and replaced by ssl:cipher-suites/2
cipher_suites()
is equivalent to cipher_suites(erlang).
Type openssl
is provided for backwards compatibility with the old SSL, which used OpenSSL. cipher_suites(all)
returns all available cipher suites. The cipher suites not present in cipher_suites(erlang)
but included in cipher_suites(all)
are not used unless explicitly configured by the user.
cipher_suites(Supported, Version) -> ciphers()
Types
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} | {error, Reason}
Types
Upgrades a gen_tcp
, or equivalent, connected socket to an SSL socket, that is, performs the client-side ssl handshake.
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.
connect(Host, Port, Options) ->
connect(Host, Port, Options, Timeout) -> {ok, SslSocket} | {error, Reason}
Types
Opens an SSL 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 possibilitis of the public_key:pkix_verify_hostname/2
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.
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.
close(SslSocket) -> ok | {error, Reason}
Types
Closes an SSL connection.
close(SslSocket, How) -> ok | {ok, port()} | {error, Reason}
Types
Closes or downgrades an SSL 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
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
Meaningful atoms, not specified above, are the ssl option names.
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}
Types
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.
Returns the requested information items about the connection, if they are defined.
If only undefined options are requested the resulting list can be empty.
filter_cipher_suites(Suites, Filters) -> ciphers()
Types
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()
Types
Presents the error returned by an SSL function as a printable string.
getopts(Socket, OptionNames) -> {ok, [socketoption()]} | {error, Reason}
Types
Gets the values of the specified socket options.
getstat(Socket) -> {ok, OptionValues} | {error, inet:posix()}
getstat(Socket, OptionNames) -> {ok, OptionValues} | {error, inet:posix()}
Types
Gets one or more statistic options for the underlying TCP socket.
See inet:getstat/2 for statistic options description.
listen(Port, Options) -> {ok, ListenSocket} | {error, Reason}
Types
Creates an SSL listen socket.
negotiated_protocol(Socket) -> {ok, Protocol} | {error, protocol_not_negotiated}
Types
Returns the protocol negotiated through ALPN or NPN extensions.
peercert(Socket) -> {ok, Cert} | {error, Reason}
Types
The peer certificate is returned as a DER-encoded binary. The certificate can be decoded with public_key:pkix_decode_cert/2
.
peername(Socket) -> {ok, {Address, Port}} | {error, Reason}
Types
Returns the address and port number of the peer.
prepend_cipher_suites(Preferred, Suites) -> ciphers()
Types
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()}
Types
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 connections; {error, undefined}
is returned for SSLv3 connections.
recv(Socket, Length) ->
recv(Socket, Length, Timeout) -> {ok, Data} | {error, Reason}
Types
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(Socket) -> ok | {error, Reason}
Types
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(Socket, Data) -> ok | {error, Reason}
Types
Writes Data
to Socket
.
A notable return value is {error, closed}
indicating that the socket is closed.
setopts(Socket, Options) -> ok | {error, Reason}
Types
Sets options according to Options
for socket Socket
.
shutdown(Socket, How) -> ok | {error, Reason}
Types
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(Socket) ->
ssl_accept(Socket, Timeout) -> ok | {error, Reason}
Types
Performs the SSL/TLS server-side handshake.
Socket
is a socket as returned by ssl:transport_accept/[1,2]
ssl_accept(Socket, SslOptions) ->
ssl_accept(Socket, SslOptions, Timeout) -> {ok, Socket} | ok | {error, Reason}
Types
If Socket
is a socket()
: upgrades a gen_tcp
, or equivalent, socket to an SSL socket, that is, performs the SSL/TLS server-side handshake and returns the SSL socket.
The listen socket is to be in mode {active, false}
before telling the client that the server is ready to upgrade by calling this function, else the upgrade succeeds or does not succeed depending on timing.
If Socket
is an sslsocket()
: provides extra SSL/TLS options to those specified in ssl:listen/2
and then performs the SSL/TLS handshake.
sockname(Socket) -> {ok, {Address, Port}} | {error, Reason}
Types
Returns the local address and port number of socket Socket
.
start() ->
start(Type) -> ok | {error, Reason}
Types
Starts the SSL application. Default type is temporary
.
stop() -> ok
Stops the SSL application.
transport_accept(ListenSocket) ->
transport_accept(ListenSocket, Timeout) -> {ok, NewSocket} | {error, Reason}
Types
Accepts an incoming connection request on a listen socket. ListenSocket
must be a socket returned from ssl:listen/2
. The socket returned is to be passed to ssl:ssl_accept[2,3]
to complete handshaking, that is, establishing the SSL/TLS connection.
The socket returned can only be used with ssl:ssl_accept[2,3]
. No traffic can be sent or received before that call.
The accepted socket inherits the options set for ListenSocket
in ssl: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()]
Types
Returns version information relevant for the SSL application.
app_vsn
- The application version of the SSL application.
supported
- TLS/SSL versions supported by default. Overridden by a version option on
connect/[2,3,4]
,listen/2
, andssl_accept/[1,2,3]
. For the negotiated TLS/SSL version, seessl:connection_information/1
. available
- All TLS/SSL versions supported by the SSL application. TLS 1.2 requires sufficient support from the Crypto application.
See also
inet(3)
and gen_tcp(3)
© 2010–2017 Ericsson AB
Licensed under the Apache License, Version 2.0.