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package ssl
Functions for making encrypted communications using the Secure Socket Layer (SSL). These are mostly bindings to the openssl library.
OpenSSL version
val native_library_version : versionExceptions and errors
type ssl_error = | Error_none(*No error happened. This is never raised and should disappear in future versions.
*)| Error_ssl(*A non-recoverable, fatal error in the SSL library occurred, usually a protocol error. The OpenSSL error queue contains more information on the error. If this error occurs then no further I/O operations should be performed on the connection and SSL_shutdown() must not be called.
*)| Error_want_read(*The operation did not complete; the same TLS/SSL I/O function should be called again later.
*)| Error_want_write(*The operation did not complete; the same TLS/SSL I/O function should be called again later.
*)| Error_want_x509_lookup(*The operation did not complete because an application callback set by
*)set_client_cert_cbhas asked to be called again. The TLS/SSL I/O function should be called again later. Details depend on the application.| Error_syscall(*Some I/O error occurred. The OpenSSL error queue may contain more information on the error.
*)| Error_zero_return(*The TLS/SSL connection has been closed. If the protocol version is SSL 3.0 or TLS 1.0, this result code is returned only if a closure alert has occurred in the protocol, i.e. if the connection has been closed cleanly. Note that in this case
*)Error_zero_returndoes not necessarily indicate that the underlying transport has been closed.| Error_want_connect(*The operation did not complete; the same TLS/SSL I/O function should be called again later.
*)| Error_want_accept(*The operation did not complete; the same TLS/SSL I/O function should be called again later.
*)| Error_want_async(*The operation did not complete because an asynchronous engine is still processing data. The TLS/SSL I/O function should be called again later. The function must be called from the same thread that the original call was made from.
*)| Error_want_async_job(*The asynchronous job could not be started because there were no async jobs available in the pool. The application should retry the operation after a currently executing asynchronous operation for the current thread has completed.
*)| Error_want_client_hello_cb(*The operation did not complete because an application callback set by SSL_CTX_set_client_hello_cb() has asked to be called again. The TLS/SSL I/O function should be called again later. Details depend on the application.
*)| Error_want_retry_verify(*See https://www.openssl.org/docs/manmaster/man3/SSL_CTX_set_verify.html
*)
An ssl error has occurred (see SSL_get_error(3ssl) for details).
exception Connection_error of ssl_errorThe connection could not be made with the SSL service.
exception Accept_error of ssl_errorFailed to accept an SSL connection.
exception Read_error of ssl_errorAn error occurred while reading data.
exception Write_error of ssl_errorAn error occurred while writing data.
An error occurred while flushing a socket. Flush_error true means that the operation should be retried.
type verify_error = | Error_v_unable_to_get_issuer_cert(*The issuer certificate could not be found: this occurs if the issuer certificate of an untrusted certificate cannot be found.
*)| Error_v_unable_to_get_ctl(*The CRL of a certificate could not be found.
*)| Error_v_unable_to_decrypt_cert_signature(*The certificate signature could not be decrypted. This means that the actual signature value could not be determined rather than it not matching the expected value, this is only meaningful for RSA keys.
*)| Error_v_unable_to_decrypt_CRL_signature(*The CRL signature could not be decrypted: this means that the actual signature value could not be determined rather than it not matching the expected value. Unused.
*)| Error_v_unable_to_decode_issuer_public_key(*The public key in the certificate SubjectPublicKeyInfo could not be read.
*)| Error_v_cert_signature_failure(*The signature of the certificate is invalid.
*)| Error_v_CRL_signature_failure(*The signature of the certificate is invalid.
*)| Error_v_cert_not_yet_valid(*The certificate is not yet valid: the notBefore date is after the current time.
*)| Error_v_cert_has_expired(*The certificate has expired: that is the notAfter date is before the current time.
*)| Error_v_CRL_not_yet_valid(*The CRL is not yet valid.
*)| Error_v_CRL_has_expired(*The CRL has expired.
*)| Error_v_error_in_cert_not_before_field(*The certificate notBefore field contains an invalid time.
*)| Error_v_error_in_cert_not_after_field(*The certificate notAfter field contains an invalid time.
*)| Error_v_error_in_CRL_last_update_field(*The CRL lastUpdate field contains an invalid time.
*)| Error_v_error_in_CRL_next_update_field(*The CRL nextUpdate field contains an invalid time.
*)| Error_v_out_of_mem(*An error occurred trying to allocate memory. This should never happen.
*)| Error_v_depth_zero_self_signed_cert(*The passed certificate is self signed and the same certificate cannot be found in the list of trusted certificates.
*)| Error_v_self_signed_cert_in_chain(*The certificate chain could be built up using the untrusted certificates but the root could not be found locally.
*)| Error_v_unable_to_get_issuer_cert_locally(*The issuer certificate of a locally looked up certificate could not be found. This normally means the list of trusted certificates is not complete.
*)| Error_v_unable_to_verify_leaf_signature(*No signatures could be verified because the chain contains only one certificate and it is not self signed.
*)| Error_v_cert_chain_too_long(*The certificate chain length is greater than the supplied maximum depth. Unused.
*)| Error_v_cert_revoked(*The certificate has been revoked.
*)| Error_v_invalid_CA(*A CA certificate is invalid. Either it is not a CA or its extensions are not consistent with the supplied purpose.
*)| Error_v_path_length_exceeded(*The basicConstraints pathlength parameter has been exceeded.
*)| Error_v_invalid_purpose(*The supplied certificate cannot be used for the specified purpose.
*)| Error_v_cert_untrusted(*The root CA is not marked as trusted for the specified purpose.
*)| Error_v_cert_rejected(*The root CA is marked to reject the specified purpose.
*)| Error_v_subject_issuer_mismatch(*The current candidate issuer certificate was rejected because its subject name did not match the issuer name of the current certificate.
*)| Error_v_akid_skid_mismatch(*The current candidate issuer certificate was rejected because its subject key identifier was present and did not match the authority key identifier current certificate.
*)| Error_v_akid_issuer_serial_mismatch(*The current candidate issuer certificate was rejected because its issuer name and serial number was present and did not match the authority key identifier of the current certificate.
*)| Error_v_keyusage_no_certsign(*The current candidate issuer certificate was rejected because its keyUsage extension does not permit certificate signing.
*)| Error_v_application_verification(*An application specific error. Unused.
*)
Why did the certificate verification fail?
exception Verify_error of verify_errorAn error occurred while verifying the certificate.
Communication
Initialize SSL functions. Should be called before calling any other function. The parameter thread_safe should be set to true if you use threads in you application (the same effect can achieved by calling Ssl_threads.init first.
Retrieve a human-readable message that corresponds to the earliest error code from the thread's error queue and removes the entry.
module Error : sig ... endThreads
You should not have to use those functions. They are only here for internal use (they are needed to make the openssl library thread-safe, see the Ssl_threads module).
Contexts
A context. A context should be created by a server or client once per program life-time and holds mainly default values for the SSL structures which are later created for the connections.
val create_context : protocol -> context_type -> contextCreate a context.
set_min_protocol_version ctx proto sets the minimum supported protocol version for ctx to proto.
set_max_protocol_version ctx proto sets the maximum supported protocol version for ctx to proto.
get_min_protocol_version ctx sets the minimum supported protocol version for ctx to proto.
get_max_protocol_version ctx proto sets the maximum supported protocol version for ctx to proto.
val add_extra_chain_cert : context -> string -> unitAdd an additional certificate to the extra chain certificates associated with the ctx. Extra chain certificates will be sent to the peer for verification and are sent in order following the end entity certificate. The value should be contents of the certificate as string in PEM format.
val add_cert_to_store : context -> string -> unitAdd a certificate to the ctx trust storage. The value should be contents of the certificate as string in PEM format.
val use_certificate : context -> string -> string -> unituse_certificate ctx cert privkey makes the context ctx use cert as * certificate's file name (in PEM format) and privkey as private key file * name.
val use_certificate_from_string : context -> string -> string -> unitUse a certificate whose contents is given as argument (you should use instead use_certificate if you want to read the certificate from a file).
val set_password_callback : context -> (bool -> string) -> unitSet the callback function called to get passwords for encrypted PEM files. * The callback function takes a boolean argument which indicates if it's used * for reading/decryption (false) or writing/encryption (true).
val set_client_CA_list_from_file : context -> string -> unitSet the list of CAs sent to the client when requesting a client certificate.
val client_verify_callback : verify_callbackClient's verification callback. Warning: this might change in the future.
Set verbosity of client_verify_callback
val set_verify : context -> verify_mode list -> verify_callback option -> unitSet the verify mode and callback, see SSL_CTX_set_verify(3). * Warning: this might change in the future.
val set_verify_depth : context -> int -> unitSet the maximum depth for the certificate chain verification that shall be allowed.
val set_context_alpn_protos : context -> string list -> unitSet the list of supported ALPN protocols for negotiation to the context.
val set_context_alpn_select_callback :
context ->
(string list -> string option) ->
unitSet the callback to allow server to select the preferred protocol from client's available protocols.
Ciphers
A cipher. It holds the algorithm information for a particular cipher which * are a core part of the SSL/TLS protocol.
Disable all protocols from the list. * Note that SSLv23 disables both SSLv2 and SSLv3 (as opposed to all the * protocols). *
val set_cipher_list : context -> string -> unitSet the list of available ciphers for a context. See man ciphers(1) for the format of the string.
val honor_cipher_order : context -> unitWhen choosing a cipher, use the server's preferences instead of the client * preferences. When not set, the SSL server will always follow the clients * preferences. When set, the SSLv3/TLSv1 server will choose following its * own preferences. Because of the different protocol, for SSLv2 the server * will send its list of preferences to the client and the client chooses.
val init_dh_from_file : context -> string -> unitInit DH parameters from file
val init_ec_from_named_curve : context -> string -> unitInit EC curve from curve name
val get_cipher_description : cipher -> stringGet a description of a cipher.
val get_cipher_name : cipher -> stringGet the name of a cipher.
val get_cipher_version : cipher -> stringGet the version of a cipher.
Get the version used for the connection. As per the OpenSSL documentation, should only be called after the initial handshake has been completed. Prior to that the results returned from these functions may be unreliable.
Certificates
val read_certificate : string -> certificateread_certificate fname reads the certificate in the file fname.
val write_certificate : string -> certificate -> unitval get_certificate : socket -> certificateGet the certificate used by a socket.
val get_issuer : certificate -> stringGet the issuer of a certificate.
val get_subject : certificate -> stringGet the subject of a certificate.
val get_start_date : certificate -> Unix.tmGet the start date of a certificate.
val get_expiration_date : certificate -> Unix.tmGet the expiration date of a certificate.
val load_verify_locations : context -> string -> string -> unitload_verify_locations ctxt cafile capath specifies the locations for the context ctx, at which CA certificates for verification purposes are located. cafile should be the name of a CA certificates file in PEM format and capath should be the name of a directory which contains CA certificates in PEM format. Empty strings can be used in order not to specify on of the parameters (but not both).
val set_default_verify_paths : context -> boolSpecifies that the default locations from which CA certificates are loaded should be used. Returns true on success.
val get_verify_result : socket -> intGet the verification result.
Get a human readable verification error message for the verification error Its input should be the result of calling get_verify_result.
val digest : [ `SHA1 | `SHA256 | `SHA384 ] -> certificate -> stringGet the digest of the certificate as a binary string, using the SHA1, SHA256 or SHA384 hashing algorithm.
Creating, connecting, closing and configuring sockets
val set_client_SNI_hostname : socket -> string -> unitSet the hostname the client is attempting to connect to using the Server * Name Indication (SNI) TLS extension.
val set_alpn_protos : socket -> string list -> unitSet the list of supported ALPN protocols for negotiation to the connection.
val get_negotiated_alpn_protocol : socket -> string optionGet the negotiated protocol from the connection.
val verify : socket -> unitCheck the result of the verification of the X509 certificate presented by the peer, if any. Raises a verify_error on failure.
val set_hostflags : socket -> x509_check_flag list -> unitval set_host : socket -> string -> unitval set_ip : socket -> string -> unitSet the expected ip address to be verified. Ip address is dotted decimal quad for IPv4 and colon-separated hexadecimal for IPv6. The condensed "::" notation is supported for IPv6 addresses.
val file_descr_of_socket : socket -> Unix.file_descrGet the file descriptor associated with a socket. It is primarily useful for selecting on it; you should not write or read on it.
I/O on SSL sockets
The main SSL communication functions that can block if sockets are in blocking mode. This set of functions releases the OCaml runtime lock, which can require extra copying of application data. The module Runtime_lock provided below lifts this limitation by never releasing the OCaml runtime lock.
val connect : socket -> unitConnect an SSL socket.
val accept : socket -> unitAccept an SSL connection.
Open an SSL connection with the specified context.
val close_notify : socket -> boolSend close notify to the peer. This is SSL_shutdown(3). * returns true if shutdown is finished, false in case close_notify * needs to be called a second time.
val shutdown_connection : socket -> unitClose an SSL connection opened with open_connection.
val shutdown : socket -> unitClose a SSL connection. * Send close notify to the peer and wait for close notify from peer.
val flush : socket -> unitFlush an SSL connection.
val read : socket -> Bytes.t -> int -> int -> intread sock buf off len receives data from a connected SSL socket.
read_into_bigarray sock ba off len receives data from a connected SSL socket. This function releases the runtime while the read takes place.
val write : socket -> Bytes.t -> int -> int -> intwrite sock buf off len sends data over a connected SSL socket.
val write_substring : socket -> string -> int -> int -> intwrite_substring sock str off len sends data over a connected SSL socket.
write_bigarray sock ba off len sends data over a connected SSL socket. This function releases the runtime while the read takes place.
High-level communication functions
val input_string : socket -> stringInput a string on an SSL socket.
val output_string : socket -> string -> unitWrite a string on an SSL socket.
val input_char : socket -> charInput a character on an SSL socket.
val output_char : socket -> char -> unitWrite a char on an SSL socket.
val input_int : socket -> intInput an integer on an SSL socket.
val output_int : socket -> int -> unitWrite an integer on an SSL socket.
module Runtime_lock : sig ... endRuntime_lock is an equivalent, signature compatible, equivalent to the Ssl module, with one difference: the OCaml runtime lock isn't released before calling the underlying SSL primitives. Multiple systhreads cannot, therefore, run concurrently.
This function is deprecated. Use Runtime_lock.read_into_bigarray instead.