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SSL_CONF_cmd

NAME

SSL_CONF_cmd_value_type, SSL_CONF_cmd - send configuration command

SYNOPSIS

#include <openssl/ssl.h>

int SSL_CONF_cmd(SSL_CONF_CTX *ctx, const char *option, const char *value);
int SSL_CONF_cmd_value_type(SSL_CONF_CTX *ctx, const char *option);

DESCRIPTION

The function SSL_CONF_cmd() performs configuration operation option with optional parameter value on ctx. Its purpose is to simplify application configuration of SSL_CTX or SSL structures by providing a common framework for command line options or configuration files.

SSL_CONF_cmd_value_type() returns the type of value that option refers to.

SUPPORTED COMMAND LINE COMMANDS

Currently supported option names for command lines (i.e. when the flag SSL_CONF_FLAG_CMDLINE is set) are listed below. Note: all option names are case sensitive. Unless otherwise stated commands can be used by both clients and servers and the value parameter is not used. The default prefix for command line commands is - and that is reflected below.

  • -bugs

    Various bug workarounds are set, same as setting SSL_OP_ALL.

  • -no_comp

    Disables support for SSL/TLS compression, same as setting SSL_OP_NO_COMPRESSION. As of OpenSSL 1.1.0, compression is off by default.

  • -comp

    Enables support for SSL/TLS compression, same as clearing SSL_OP_NO_COMPRESSION. This command was introduced in OpenSSL 1.1.0. As of OpenSSL 1.1.0, compression is off by default. TLS compression can only be used in security level 1 or lower. From OpenSSL 3.2.0 and above the default security level is 2, so this option will have no effect without also changing the security level. See SSL_CTX_set_security_level(3).

  • -no_ticket

    Disables support for session tickets, same as setting SSL_OP_NO_TICKET.

  • -serverpref

    Use server and not client preference order when determining which cipher suite, signature algorithm or elliptic curve to use for an incoming connection. Equivalent to SSL_OP_CIPHER_SERVER_PREFERENCE. Only used by servers.

  • -client_renegotiation

    Allows servers to accept client-initiated renegotiation. Equivalent to setting SSL_OP_ALLOW_CLIENT_RENEGOTIATION. Only used by servers.

  • -legacy_renegotiation

    Permits the use of unsafe legacy renegotiation. Equivalent to setting SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION.

  • -no_renegotiation

    Disables all attempts at renegotiation in TLSv1.2 and earlier, same as setting SSL_OP_NO_RENEGOTIATION.

  • -no_resumption_on_reneg

    Sets SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION. Only used by servers.

  • -legacy_server_connect, -no_legacy_server_connect

    Permits or prohibits the use of unsafe legacy renegotiation for OpenSSL clients only. Equivalent to setting or clearing SSL_OP_LEGACY_SERVER_CONNECT.

  • -prioritize_chacha

    Prioritize ChaCha ciphers when the client has a ChaCha20 cipher at the top of its preference list. This usually indicates a client without AES hardware acceleration (e.g. mobile) is in use. Equivalent to SSL_OP_PRIORITIZE_CHACHA. Only used by servers. Requires -serverpref.

  • -allow_no_dhe_kex

    In TLSv1.3 allow a non-(ec)dhe based key exchange mode on resumption. This means that there will be no forward secrecy for the resumed session.

  • -prefer_no_dhe_kex

    In TLSv1.3, on resumption let the server prefer a non-(ec)dhe based key exchange mode over an (ec)dhe based one. Requires -allow_no_dhe_kex. Equivalent to SSL_OP_PREFER_NO_DHE_KEX. Only used by servers.

  • -strict

    Enables strict mode protocol handling. Equivalent to setting SSL_CERT_FLAG_TLS_STRICT.

  • -sigalgs algs

    This sets the supported signature algorithms for TLSv1.2 and TLSv1.3. For clients this value is used directly for the supported signature algorithms extension. For servers it is used to determine which signature algorithms to support.

    The algs argument should be a colon separated list of signature algorithms in order of decreasing preference of the form algorithm+hash or signature_scheme. For the default providers shipped with OpenSSL, algorithm is one of RSA, DSA or ECDSA and hash is a supported algorithm OID short name such as SHA1, SHA224, SHA256, SHA384 or SHA512. Note: algorithm and hash names are case sensitive. signature_scheme is one of the signature schemes defined in TLSv1.3, specified using the IETF name, e.g., ecdsa_secp256r1_sha256, ed25519, or rsa_pss_pss_sha256. Additional providers may make available further algorithms via the TLS-SIGALG capability. See provider-base(7).

    If this option is not set then all signature algorithms supported by all activated providers are permissible.

    Note: algorithms which specify a PKCS#1 v1.5 signature scheme (either by using RSA as the algorithm or by using one of the rsa_pkcs1_* identifiers) are ignored in TLSv1.3 and will not be negotiated.

  • -client_sigalgs algs

    This sets the supported signature algorithms associated with client authentication for TLSv1.2 and TLSv1.3. For servers the algs is used in the signature_algorithms field of a CertificateRequest message. For clients it is used to determine which signature algorithm to use with the client certificate. If a server does not request a certificate this option has no effect.

    The syntax of algs is identical to -sigalgs. If not set, then the value set for -sigalgs will be used instead.

  • -groups groups

    This sets the supported groups. For clients, the groups are sent using the supported groups extension. For servers, it is used to determine which group to use. This setting affects groups used for signatures (in TLSv1.2 and earlier) and key exchange. The first group listed will also be used for the key_share sent by a client in a TLSv1.3 ClientHello.

    The groups argument is a colon separated list of groups. The group can be either the NIST name (e.g. P-256), some other commonly used name where applicable (e.g. X25519, ffdhe2048) or an OpenSSL OID name (e.g. prime256v1). Group names are case sensitive. The list should be in order of preference with the most preferred group first.

    Groups for TLSv1.3 in the default provider are P-256, P-384, P-521, X25519, X448, ffdhe2048, ffdhe3072, ffdhe4096, ffdhe6144, ffdhe8192, brainpoolP256r1tls13, brainpoolP384r1tls13 and brainpoolP512r1tls13. Additional providers may make available further algorithms via the TLS-GROUP capability. See provider-base(7).

  • -curves groups

    This is a synonym for the -groups command.

  • -named_curve curve

    This sets the temporary curve used for ephemeral ECDH modes. Only used by servers.

  • -tx_cert_comp

    Enables support for sending TLSv1.3 compressed certificates.

  • -no_tx_cert_comp

    Disables support for sending TLSv1.3 compressed certificates.

  • -rx_cert_comp

    Enables support for receiving TLSv1.3 compressed certificates.

  • -no_rx_cert_comp

    Disables support for receiving TLSv1.3 compressed certificates.

  • -comp

    The groups argument is a curve name or the special value auto which picks an appropriate curve based on client and server preferences. The curve can be either the NIST name (e.g. P-256) or an OpenSSL OID name (e.g. prime256v1). Curve names are case sensitive.

  • -cipher ciphers

    Sets the TLSv1.2 and below ciphersuite list to ciphers. This list will be combined with any configured TLSv1.3 ciphersuites. Note: syntax checking of ciphers is currently not performed unless a SSL or SSL_CTX structure is associated with ctx.

  • -ciphersuites 1.3ciphers

    Sets the available ciphersuites for TLSv1.3 to value. This is a colon-separated list of TLSv1.3 ciphersuite names in order of preference. This list will be combined any configured TLSv1.2 and below ciphersuites. See openssl-ciphers(1) for more information.

  • -min_protocol minprot, -max_protocol maxprot

    Sets the minimum and maximum supported protocol. Currently supported protocol values are SSLv3, TLSv1, TLSv1.1, TLSv1.2, TLSv1.3 for TLS; DTLSv1, DTLSv1.2 for DTLS, and None for no limit. If either the lower or upper bound is not specified then only the other bound applies, if specified. If your application supports both TLS and DTLS you can specify any of these options twice, once with a bound for TLS and again with an appropriate bound for DTLS. To restrict the supported protocol versions use these commands rather than the deprecated alternative commands below.

  • -record_padding padding

    Controls use of TLSv1.3 record layer padding. padding is a string of the form "number[,number]" where the (required) first number is the padding block size (in octets) for application data, and the optional second number is the padding block size for handshake and alert messages. If the optional second number is omitted, the same padding will be applied to all messages.

    Padding attempts to pad TLSv1.3 records so that they are a multiple of the set length on send. A value of 0 or 1 turns off padding as relevant. Otherwise, the values must be >1 or <=16384.

  • -debug_broken_protocol

    Ignored.

  • -no_middlebox

    Turn off "middlebox compatibility", as described below.

Additional Options

The following options are accepted by SSL_CONF_cmd(), but are not processed by the OpenSSL commands.

  • -cert file

    Attempts to use file as the certificate for the appropriate context. It currently uses SSL_CTX_use_certificate_chain_file() if an SSL_CTX structure is set or SSL_use_certificate_file() with filetype PEM if an SSL structure is set. This option is only supported if certificate operations are permitted.

  • -key file

    Attempts to use file as the private key for the appropriate context. This option is only supported if certificate operations are permitted. Note: if no -key option is set then a private key is not loaded unless the flag SSL_CONF_FLAG_REQUIRE_PRIVATE is set.

  • -dhparam file

    Attempts to use file as the set of temporary DH parameters for the appropriate context. This option is only supported if certificate operations are permitted.

  • -no_ssl3, -no_tls1, -no_tls1_1, -no_tls1_2, -no_tls1_3

    Disables protocol support for SSLv3, TLSv1.0, TLSv1.1, TLSv1.2 or TLSv1.3 by setting the corresponding options SSL_OP_NO_SSLv3, SSL_OP_NO_TLSv1, SSL_OP_NO_TLSv1_1, SSL_OP_NO_TLSv1_2 and SSL_OP_NO_TLSv1_3 respectively. These options are deprecated, use -min_protocol and -max_protocol instead.

  • -anti_replay, -no_anti_replay

    Switches replay protection, on or off respectively. With replay protection on, OpenSSL will automatically detect if a session ticket has been used more than once, TLSv1.3 has been negotiated, and early data is enabled on the server. A full handshake is forced if a session ticket is used a second or subsequent time. Anti-Replay is on by default unless overridden by a configuration file and is only used by servers. Anti-replay measures are required for compliance with the TLSv1.3 specification. Some applications may be able to mitigate the replay risks in other ways and in such cases the built-in OpenSSL functionality is not required. Switching off anti-replay is equivalent to SSL_OP_NO_ANTI_REPLAY.

SUPPORTED CONFIGURATION FILE COMMANDS

Currently supported option names for configuration files (i.e., when the flag SSL_CONF_FLAG_FILE is set) are listed below. All configuration file option names are case insensitive so signaturealgorithms is recognised as well as SignatureAlgorithms. Unless otherwise stated the value names are also case insensitive.

Note: the command prefix (if set) alters the recognised option values.

  • CipherString

    Sets the ciphersuite list for TLSv1.2 and below to value. This list will be combined with any configured TLSv1.3 ciphersuites. Note: syntax checking of value is currently not performed unless an SSL or SSL_CTX structure is associated with ctx.

  • Ciphersuites

    Sets the available ciphersuites for TLSv1.3 to value. This is a colon-separated list of TLSv1.3 ciphersuite names in order of preference. This list will be combined any configured TLSv1.2 and below ciphersuites. See openssl-ciphers(1) for more information.

  • Certificate

    Attempts to use the file value as the certificate for the appropriate context. It currently uses SSL_CTX_use_certificate_chain_file() if an SSL_CTX structure is set or SSL_use_certificate_file() with filetype PEM if an SSL structure is set. This option is only supported if certificate operations are permitted.

  • PrivateKey

    Attempts to use the file value as the private key for the appropriate context. This option is only supported if certificate operations are permitted. Note: if no PrivateKey option is set then a private key is not loaded unless the SSL_CONF_FLAG_REQUIRE_PRIVATE is set.

  • ChainCAFile, ChainCAPath, VerifyCAFile, VerifyCAPath

    These options indicate a file or directory used for building certificate chains or verifying certificate chains. These options are only supported if certificate operations are permitted.

  • RequestCAFile

    This option indicates a file containing a set of certificates in PEM form. The subject names of the certificates are sent to the peer in the certificate_authorities extension for TLS 1.3 (in ClientHello or CertificateRequest) or in a certificate request for previous versions or TLS.

  • ServerInfoFile

    Attempts to use the file value in the "serverinfo" extension using the function SSL_CTX_use_serverinfo_file.

  • DHParameters

    Attempts to use the file value as the set of temporary DH parameters for the appropriate context. This option is only supported if certificate operations are permitted.

  • RecordPadding

    Controls use of TLSv1.3 record layer padding. value is a string of the form "number[,number]" where the (required) first number is the padding block size (in octets) for application data, and the optional second number is the padding block size for handshake and alert messages. If the optional second number is omitted, the same padding will be applied to all messages.

    Padding attempts to pad TLSv1.3 records so that they are a multiple of the set length on send. A value of 0 or 1 turns off padding as relevant. Otherwise, the values must be >1 or <=16384.

  • SignatureAlgorithms

    This sets the supported signature algorithms for TLSv1.2 and TLSv1.3. For clients this value is used directly for the supported signature algorithms extension. For servers it is used to determine which signature algorithms to support.

    The value argument should be a colon separated list of signature algorithms in order of decreasing preference of the form algorithm+hash or signature_scheme. For the default providers shipped with OpenSSL, algorithm is one of RSA, DSA or ECDSA and hash is a supported algorithm OID short name such as SHA1, SHA224, SHA256, SHA384 or SHA512. Note: algorithm and hash names are case sensitive. signature_scheme is one of the signature schemes defined in TLSv1.3, specified using the IETF name, e.g., ecdsa_secp256r1_sha256, ed25519, or rsa_pss_pss_sha256. Additional providers may make available further algorithms via the TLS_SIGALG capability. See "CAPABILITIES" in provider-base(7).

    If this option is not set then all signature algorithms supported by all activated providers are permissible.

    Note: algorithms which specify a PKCS#1 v1.5 signature scheme (either by using RSA as the algorithm or by using one of the rsa_pkcs1_* identifiers) are ignored in TLSv1.3 and will not be negotiated.

  • ClientSignatureAlgorithms

    This sets the supported signature algorithms associated with client authentication for TLSv1.2 and TLSv1.3. For servers the value is used in the signature_algorithms field of a CertificateRequest message. For clients it is used to determine which signature algorithm to use with the client certificate. If a server does not request a certificate this option has no effect.

    The syntax of value is identical to SignatureAlgorithms. If not set then the value set for SignatureAlgorithms will be used instead.

  • Groups

    This sets the supported groups. For clients, the groups are sent using the supported groups extension. For servers, it is used to determine which group to use. This setting affects groups used for signatures (in TLSv1.2 and earlier) and key exchange. The first group listed will also be used for the key_share sent by a client in a TLSv1.3 ClientHello.

    The value argument is a colon separated list of groups. The group can be either the NIST name (e.g. P-256), some other commonly used name where applicable (e.g. X25519, ffdhe2048) or an OpenSSL OID name (e.g. prime256v1). Group names are case sensitive. The list should be in order of preference with the most preferred group first.

    Currently supported groups for TLSv1.3 are P-256, P-384, P-521, X25519, X448, ffdhe2048, ffdhe3072, ffdhe4096, ffdhe6144, ffdhe8192.

  • Curves

    This is a synonym for the "Groups" command.

  • MinProtocol

    This sets the minimum supported SSL, TLS or DTLS version.

    Currently supported protocol values are SSLv3, TLSv1, TLSv1.1, TLSv1.2, TLSv1.3, DTLSv1 and DTLSv1.2. The SSL and TLS bounds apply only to TLS-based contexts, while the DTLS bounds apply only to DTLS-based contexts. The command can be repeated with one instance setting a TLS bound, and the other setting a DTLS bound. The value None applies to both types of contexts and disables the limits.

  • MaxProtocol

    This sets the maximum supported SSL, TLS or DTLS version.

    Currently supported protocol values are SSLv3, TLSv1, TLSv1.1, TLSv1.2, TLSv1.3, DTLSv1 and DTLSv1.2. The SSL and TLS bounds apply only to TLS-based contexts, while the DTLS bounds apply only to DTLS-based contexts. The command can be repeated with one instance setting a TLS bound, and the other setting a DTLS bound. The value None applies to both types of contexts and disables the limits.

  • Protocol

    This can be used to enable or disable certain versions of the SSL, TLS or DTLS protocol.

    The value argument is a comma separated list of supported protocols to enable or disable. If a protocol is preceded by - that version is disabled.

    All protocol versions are enabled by default. You need to disable at least one protocol version for this setting have any effect. Only enabling some protocol versions does not disable the other protocol versions.

    Currently supported protocol values are SSLv3, TLSv1, TLSv1.1, TLSv1.2, TLSv1.3, DTLSv1 and DTLSv1.2. The special value ALL refers to all supported versions.

    This can't enable protocols that are disabled using MinProtocol or MaxProtocol, but can disable protocols that are still allowed by them.

    The Protocol command is fragile and deprecated; do not use it. Use MinProtocol and MaxProtocol instead. If you do use Protocol, make sure that the resulting range of enabled protocols has no "holes", e.g. if TLS 1.0 and TLS 1.2 are both enabled, make sure to also leave TLS 1.1 enabled.

  • Options

    The value argument is a comma separated list of various flags to set. If a flag string is preceded - it is disabled. See the SSL_CTX_set_options(3) function for more details of individual options.

    Each option is listed below. Whe