546 lines
20 KiB
Plaintext
546 lines
20 KiB
Plaintext
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=pod
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=head1 NAME
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SSL_CTX_set_options, SSL_set_options, SSL_CTX_clear_options,
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SSL_clear_options, SSL_CTX_get_options, SSL_get_options,
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SSL_get_secure_renegotiation_support - manipulate SSL options
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=head1 SYNOPSIS
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#include <openssl/ssl.h>
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uint64_t SSL_CTX_set_options(SSL_CTX *ctx, uint64_t options);
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uint64_t SSL_set_options(SSL *ssl, uint64_t options);
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uint64_t SSL_CTX_clear_options(SSL_CTX *ctx, uint64_t options);
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uint64_t SSL_clear_options(SSL *ssl, uint64_t options);
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uint64_t SSL_CTX_get_options(const SSL_CTX *ctx);
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uint64_t SSL_get_options(const SSL *ssl);
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long SSL_get_secure_renegotiation_support(SSL *ssl);
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=head1 DESCRIPTION
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SSL_CTX_set_options() adds the options set via bit-mask in B<options> to B<ctx>.
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Options already set before are not cleared!
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SSL_set_options() adds the options set via bit-mask in B<options> to B<ssl>.
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Options already set before are not cleared!
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SSL_CTX_clear_options() clears the options set via bit-mask in B<options>
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to B<ctx>.
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SSL_clear_options() clears the options set via bit-mask in B<options> to B<ssl>.
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SSL_CTX_get_options() returns the options set for B<ctx>.
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SSL_get_options() returns the options set for B<ssl>.
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SSL_get_secure_renegotiation_support() indicates whether the peer supports
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secure renegotiation.
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Note, this is implemented via a macro.
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=head1 NOTES
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The behaviour of the SSL library can be changed by setting several options.
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The options are coded as bit-masks and can be combined by a bitwise B<or>
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operation (|).
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SSL_CTX_set_options() and SSL_set_options() affect the (external)
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protocol behaviour of the SSL library. The (internal) behaviour of
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the API can be changed by using the similar
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L<SSL_CTX_set_mode(3)> and SSL_set_mode() functions.
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During a handshake, the option settings of the SSL object are used. When
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a new SSL object is created from a context using SSL_new(), the current
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option setting is copied. Changes to B<ctx> do not affect already created
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SSL objects. SSL_clear() does not affect the settings.
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The following B<bug workaround> options are available:
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=over 4
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=item SSL_OP_CRYPTOPRO_TLSEXT_BUG
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Add server-hello extension from the early version of cryptopro draft
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when GOST ciphersuite is negotiated. Required for interoperability with CryptoPro
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CSP 3.x.
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=item SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
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Disables a countermeasure against a SSL 3.0/TLS 1.0 protocol
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vulnerability affecting CBC ciphers, which cannot be handled by some
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broken SSL implementations. This option has no effect for connections
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using other ciphers.
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=item SSL_OP_SAFARI_ECDHE_ECDSA_BUG
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Don't prefer ECDHE-ECDSA ciphers when the client appears to be Safari on OS X.
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OS X 10.8..10.8.3 has broken support for ECDHE-ECDSA ciphers.
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=item SSL_OP_TLSEXT_PADDING
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Adds a padding extension to ensure the ClientHello size is never between
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256 and 511 bytes in length. This is needed as a workaround for some
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implementations.
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=item SSL_OP_ALL
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All of the above bug workarounds.
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=back
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It is usually safe to use B<SSL_OP_ALL> to enable the bug workaround
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options if compatibility with somewhat broken implementations is
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desired.
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The following B<modifying> options are available:
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=over 4
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=item SSL_OP_ALLOW_CLIENT_RENEGOTIATION
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Client-initiated renegotiation is disabled by default. Use
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this option to enable it.
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=item SSL_OP_ALLOW_NO_DHE_KEX
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In TLSv1.3 allow a non-(ec)dhe based key exchange mode on resumption. This means
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that there will be no forward secrecy for the resumed session.
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=item SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
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Allow legacy insecure renegotiation between OpenSSL and unpatched clients or
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servers. See the B<SECURE RENEGOTIATION> section for more details.
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=item SSL_OP_CIPHER_SERVER_PREFERENCE
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When choosing a cipher, use the server's preferences instead of the client
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preferences. When not set, the SSL server will always follow the clients
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preferences. When set, the SSL/TLS server will choose following its
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own preferences.
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=item SSL_OP_CISCO_ANYCONNECT
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Use Cisco's version identifier of DTLS_BAD_VER when establishing a DTLSv1
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connection. Only available when using the deprecated DTLSv1_client_method() API.
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=item SSL_OP_CLEANSE_PLAINTEXT
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By default TLS and QUIC SSL objects keep a copy of received plaintext
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application data in a static buffer until it is overwritten by the
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next portion of data. When enabling SSL_OP_CLEANSE_PLAINTEXT
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deciphered application data is cleansed by calling OPENSSL_cleanse(3)
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after passing data to the application. Data is also cleansed when
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releasing the connection (e.g. L<SSL_free(3)>).
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Since OpenSSL only cleanses internal buffers, the application is still
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responsible for cleansing all other buffers. Most notably, this
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applies to buffers passed to functions like L<SSL_read(3)>,
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L<SSL_peek(3)> but also like L<SSL_write(3)>.
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TLS connections do not buffer data to be sent in plaintext. QUIC stream
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objects do buffer plaintext data to be sent and this option will also cause
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that data to be cleansed when it is discarded.
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This option can be set differently on individual QUIC stream objects and
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has no effect on QUIC connection objects (except where a default stream is
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being used).
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=item SSL_OP_COOKIE_EXCHANGE
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Turn on Cookie Exchange as described in RFC4347 Section 4.2.1. Only affects
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DTLS connections.
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=item SSL_OP_DISABLE_TLSEXT_CA_NAMES
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Disable TLS Extension CA Names. You may want to disable it for security reasons
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or for compatibility with some Windows TLS implementations crashing when this
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extension is larger than 1024 bytes.
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=item SSL_OP_ENABLE_KTLS
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Enable the use of kernel TLS. In order to benefit from kernel TLS OpenSSL must
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have been compiled with support for it, and it must be supported by the
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negotiated ciphersuites and extensions. The specific ciphersuites and extensions
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that are supported may vary by platform and kernel version.
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The kernel TLS data-path implements the record layer, and the encryption
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algorithm. The kernel will utilize the best hardware
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available for encryption. Using the kernel data-path should reduce the memory
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footprint of OpenSSL because no buffering is required. Also, the throughput
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should improve because data copy is avoided when user data is encrypted into
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kernel memory instead of the usual encrypt then copy to kernel.
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Kernel TLS might not support all the features of OpenSSL. For instance,
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renegotiation, and setting the maximum fragment size is not possible as of
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Linux 4.20.
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Note that with kernel TLS enabled some cryptographic operations are performed
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by the kernel directly and not via any available OpenSSL Providers. This might
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be undesirable if, for example, the application requires all cryptographic
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operations to be performed by the FIPS provider.
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=item SSL_OP_ENABLE_KTLS_TX_ZEROCOPY_SENDFILE
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With this option, sendfile() will use the zerocopy mode, which gives a
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performance boost when used with KTLS hardware offload. Note that invalid TLS
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records might be transmitted if the file is changed while being sent. This
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option has no effect if B<SSL_OP_ENABLE_KTLS> is not enabled.
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This option only applies to Linux. KTLS sendfile on FreeBSD doesn't offer an
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option to disable zerocopy and always runs in this mode.
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=item SSL_OP_ENABLE_MIDDLEBOX_COMPAT
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If set then dummy Change Cipher Spec (CCS) messages are sent in TLSv1.3. This
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has the effect of making TLSv1.3 look more like TLSv1.2 so that middleboxes that
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do not understand TLSv1.3 will not drop the connection. Regardless of whether
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this option is set or not CCS messages received from the peer will always be
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ignored in TLSv1.3. This option is set by default. To switch it off use
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SSL_clear_options(). A future version of OpenSSL may not set this by default.
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=item SSL_OP_IGNORE_UNEXPECTED_EOF
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Some TLS implementations do not send the mandatory close_notify alert on
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shutdown. If the application tries to wait for the close_notify alert but the
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peer closes the connection without sending it, an error is generated. When this
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option is enabled the peer does not need to send the close_notify alert and a
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closed connection will be treated as if the close_notify alert was received.
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You should only enable this option if the protocol running over TLS
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can detect a truncation attack itself, and that the application is checking for
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that truncation attack.
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For more information on shutting down a connection, see L<SSL_shutdown(3)>.
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=item SSL_OP_LEGACY_SERVER_CONNECT
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Allow legacy insecure renegotiation between OpenSSL and unpatched servers
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B<only>. See the B<SECURE RENEGOTIATION> section for more details.
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=item SSL_OP_NO_ANTI_REPLAY
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By default, when a server is configured for early data (i.e., max_early_data > 0),
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OpenSSL will switch on replay protection. See L<SSL_read_early_data(3)> for a
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description of the replay protection feature. Anti-replay measures are required
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to comply with the TLSv1.3 specification. Some applications may be able to
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mitigate the replay risks in other ways and in such cases the built in OpenSSL
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functionality is not required. Those applications can turn this feature off by
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setting this option. This is a server-side option only. It is ignored by
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clients.
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=item SSL_OP_NO_TX_CERTIFICATE_COMPRESSION
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Normally clients and servers will transparently attempt to negotiate the
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RFC8879 certificate compression option on TLSv1.3 connections.
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If this option is set, the certificate compression extension is ignored
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upon receipt and compressed certificates will not be sent to the peer.
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=item SSL_OP_NO_RX_CERTIFICATE_COMPRESSION
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Normally clients and servers will transparently attempt to negotiate the
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RFC8879 certificate compression option on TLSv1.3 connections.
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If this option is set, the certificate compression extension will not be sent
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and compressed certificates will not be accepted from the peer.
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=item SSL_OP_NO_COMPRESSION
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Do not use TLS record compression even if it is supported. This option is set by
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default. To switch it off use SSL_clear_options(). Note that TLS record
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compression is not recommended and is not available at security level 2 or
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above. From OpenSSL 3.2 the default security level is 2, so clearing this option
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will have no effect without also changing the default security level. See
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L<SSL_CTX_set_security_level(3)>.
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=item SSL_OP_NO_ENCRYPT_THEN_MAC
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Normally clients and servers will transparently attempt to negotiate the
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RFC7366 Encrypt-then-MAC option on TLS and DTLS connection.
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If this option is set, Encrypt-then-MAC is disabled. Clients will not
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propose, and servers will not accept the extension.
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=item SSL_OP_NO_EXTENDED_MASTER_SECRET
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Normally clients and servers will transparently attempt to negotiate the
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RFC7627 Extended Master Secret option on TLS and DTLS connection.
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If this option is set, Extended Master Secret is disabled. Clients will
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not propose, and servers will not accept the extension.
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=item SSL_OP_NO_QUERY_MTU
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Do not query the MTU. Only affects DTLS connections.
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=item SSL_OP_NO_RENEGOTIATION
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Disable all renegotiation in TLSv1.2 and earlier. Do not send HelloRequest
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messages, and ignore renegotiation requests via ClientHello.
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=item SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
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When performing renegotiation as a server, always start a new session
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(i.e., session resumption requests are only accepted in the initial
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handshake). This option is not needed for clients.
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=item SSL_OP_NO_SSLv3, SSL_OP_NO_TLSv1, SSL_OP_NO_TLSv1_1,
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SSL_OP_NO_TLSv1_2, SSL_OP_NO_TLSv1_3, SSL_OP_NO_DTLSv1, SSL_OP_NO_DTLSv1_2
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These options turn off the SSLv3, TLSv1, TLSv1.1, TLSv1.2 or TLSv1.3 protocol
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versions with TLS or the DTLSv1, DTLSv1.2 versions with DTLS,
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respectively.
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As of OpenSSL 1.1.0, these options are deprecated, use
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L<SSL_CTX_set_min_proto_version(3)> and
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L<SSL_CTX_set_max_proto_version(3)> instead.
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=item SSL_OP_NO_TICKET
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SSL/TLS supports two mechanisms for resuming sessions: session ids and stateless
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session tickets.
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When using session ids a copy of the session information is
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cached on the server and a unique id is sent to the client. When the client
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wishes to resume it provides the unique id so that the server can retrieve the
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session information from its cache.
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When using stateless session tickets the server uses a session ticket encryption
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key to encrypt the session information. This encrypted data is sent to the
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client as a "ticket". When the client wishes to resume it sends the encrypted
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data back to the server. The server uses its key to decrypt the data and resume
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the session. In this way the server can operate statelessly - no session
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information needs to be cached locally.
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The TLSv1.3 protocol only supports tickets and does not directly support session
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ids. However, OpenSSL allows two modes of ticket operation in TLSv1.3: stateful
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and stateless. Stateless tickets work the same way as in TLSv1.2 and below.
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Stateful tickets mimic the session id behaviour available in TLSv1.2 and below.
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The session information is cached on the server and the session id is wrapped up
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in a ticket and sent back to the client. When the client wishes to resume, it
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presents a ticket in the same way as for stateless tickets. The server can then
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extract the session id from the ticket and retrieve the session information from
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its cache.
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By default OpenSSL will use stateless tickets. The SSL_OP_NO_TICKET option will
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cause stateless tickets to not be issued. In TLSv1.2 and below this means no
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ticket gets sent to the client at all. In TLSv1.3 a stateful ticket will be
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sent. This is a server-side option only.
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In TLSv1.3 it is possible to suppress all tickets (stateful and stateless) from
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being sent by calling L<SSL_CTX_set_num_tickets(3)> or
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L<SSL_set_num_tickets(3)>.
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=item SSL_OP_PRIORITIZE_CHACHA
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When SSL_OP_CIPHER_SERVER_PREFERENCE is set, temporarily reprioritize
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ChaCha20-Poly1305 ciphers to the top of the server cipher list if a
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ChaCha20-Poly1305 cipher is at the top of the client cipher list. This helps
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those clients (e.g. mobile) use ChaCha20-Poly1305 if that cipher is anywhere
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in the server cipher list; but still allows other clients to use AES and other
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ciphers. Requires B<SSL_OP_CIPHER_SERVER_PREFERENCE>.
|
||
|
|
|
||
|
|
=item SSL_OP_TLS_ROLLBACK_BUG
|
||
|
|
|
||
|
|
Disable version rollback attack detection.
|
||
|
|
|
||
|
|
During the client key exchange, the client must send the same information
|
||
|
|
about acceptable SSL/TLS protocol levels as during the first hello. Some
|
||
|
|
clients violate this rule by adapting to the server's answer. (Example:
|
||
|
|
the client sends a SSLv2 hello and accepts up to SSLv3.1=TLSv1, the server
|
||
|
|
only understands up to SSLv3. In this case the client must still use the
|
||
|
|
same SSLv3.1=TLSv1 announcement. Some clients step down to SSLv3 with respect
|
||
|
|
to the server's answer and violate the version rollback protection.)
|
||
|
|
|
||
|
|
=back
|
||
|
|
|
||
|
|
The following options no longer have any effect but their identifiers are
|
||
|
|
retained for compatibility purposes:
|
||
|
|
|
||
|
|
=over 4
|
||
|
|
|
||
|
|
=item SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
|
||
|
|
|
||
|
|
=item SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
|
||
|
|
|
||
|
|
=item SSL_OP_SSLEAY_080_CLIENT_DH_BUG
|
||
|
|
|
||
|
|
=item SSL_OP_TLS_D5_BUG
|
||
|
|
|
||
|
|
=item SSL_OP_TLS_BLOCK_PADDING_BUG
|
||
|
|
|
||
|
|
=item SSL_OP_MSIE_SSLV2_RSA_PADDING
|
||
|
|
|
||
|
|
=item SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
|
||
|
|
|
||
|
|
=item SSL_OP_MICROSOFT_SESS_ID_BUG
|
||
|
|
|
||
|
|
=item SSL_OP_NETSCAPE_CHALLENGE_BUG
|
||
|
|
|
||
|
|
=item SSL_OP_PKCS1_CHECK_1
|
||
|
|
|
||
|
|
=item SSL_OP_PKCS1_CHECK_2
|
||
|
|
|
||
|
|
=item SSL_OP_SINGLE_DH_USE
|
||
|
|
|
||
|
|
=item SSL_OP_SINGLE_ECDH_USE
|
||
|
|
|
||
|
|
=item SSL_OP_EPHEMERAL_RSA
|
||
|
|
|
||
|
|
=item SSL_OP_NETSCAPE_CA_DN_BUG
|
||
|
|
|
||
|
|
=item SSL_OP_NETSCAPE_DEMO_CIPHER_CHANGE_BUG
|
||
|
|
|
||
|
|
=back
|
||
|
|
|
||
|
|
=head1 SECURE RENEGOTIATION
|
||
|
|
|
||
|
|
OpenSSL always attempts to use secure renegotiation as
|
||
|
|
described in RFC5746. This counters the prefix attack described in
|
||
|
|
CVE-2009-3555 and elsewhere.
|
||
|
|
|
||
|
|
This attack has far reaching consequences which application writers should be
|
||
|
|
aware of. In the description below an implementation supporting secure
|
||
|
|
renegotiation is referred to as I<patched>. A server not supporting secure
|
||
|
|
renegotiation is referred to as I<unpatched>.
|
||
|
|
|
||
|
|
The following sections describe the operations permitted by OpenSSL's secure
|
||
|
|
renegotiation implementation.
|
||
|
|
|
||
|
|
=head2 Patched client and server
|
||
|
|
|
||
|
|
Connections and renegotiation are always permitted by OpenSSL implementations.
|
||
|
|
|
||
|
|
=head2 Unpatched client and patched OpenSSL server
|
||
|
|
|
||
|
|
The initial connection succeeds but client renegotiation is denied by the
|
||
|
|
server with a B<no_renegotiation> warning alert if TLS v1.0 is used or a fatal
|
||
|
|
B<handshake_failure> alert in SSL v3.0.
|
||
|
|
|
||
|
|
If the patched OpenSSL server attempts to renegotiate a fatal
|
||
|
|
B<handshake_failure> alert is sent. This is because the server code may be
|
||
|
|
unaware of the unpatched nature of the client.
|
||
|
|
|
||
|
|
If the option B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION> is set then
|
||
|
|
renegotiation B<always> succeeds.
|
||
|
|
|
||
|
|
=head2 Patched OpenSSL client and unpatched server
|
||
|
|
|
||
|
|
If the option B<SSL_OP_LEGACY_SERVER_CONNECT> or
|
||
|
|
B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION> is set then initial connections
|
||
|
|
and renegotiation between patched OpenSSL clients and unpatched servers
|
||
|
|
succeeds. If neither option is set then initial connections to unpatched
|
||
|
|
servers will fail.
|
||
|
|
|
||
|
|
Setting the option B<SSL_OP_LEGACY_SERVER_CONNECT> has security implications;
|
||
|
|
clients that are willing to connect to servers that do not implement
|
||
|
|
RFC 5746 secure renegotiation are subject to attacks such as
|
||
|
|
CVE-2009-3555.
|
||
|
|
|
||
|
|
OpenSSL client applications wishing to ensure they can connect to unpatched
|
||
|
|
servers should always B<set> B<SSL_OP_LEGACY_SERVER_CONNECT>
|
||
|
|
|
||
|
|
OpenSSL client applications that want to ensure they can B<not> connect to
|
||
|
|
unpatched servers (and thus avoid any security issues) should always B<clear>
|
||
|
|
B<SSL_OP_LEGACY_SERVER_CONNECT> using SSL_CTX_clear_options() or
|
||
|
|
SSL_clear_options().
|
||
|
|
|
||
|
|
The difference between the B<SSL_OP_LEGACY_SERVER_CONNECT> and
|
||
|
|
B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION> options is that
|
||
|
|
B<SSL_OP_LEGACY_SERVER_CONNECT> enables initial connections and secure
|
||
|
|
renegotiation between OpenSSL clients and unpatched servers B<only>, while
|
||
|
|
B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION> allows initial connections
|
||
|
|
and renegotiation between OpenSSL and unpatched clients or servers.
|
||
|
|
|
||
|
|
=head2 Applicability of options to QUIC connections and streams
|
||
|
|
|
||
|
|
These options apply to SSL objects referencing a QUIC connection:
|
||
|
|
|
||
|
|
=over 4
|
||
|
|
|
||
|
|
=item SSL_OP_ALLOW_NO_DHE_KEX
|
||
|
|
|
||
|
|
=item SSL_OP_NO_TX_CERTIFICATE_COMPRESSION
|
||
|
|
|
||
|
|
=item SSL_OP_NO_RX_CERTIFICATE_COMPRESSION
|
||
|
|
|
||
|
|
=item SSL_OP_NO_TICKET
|
||
|
|
|
||
|
|
=item SSL_OP_PRIORITIZE_CHACHA
|
||
|
|
|
||
|
|
=back
|
||
|
|
|
||
|
|
These options apply to SSL objects referencing a QUIC stream:
|
||
|
|
|
||
|
|
=over 4
|
||
|
|
|
||
|
|
=item SSL_OP_CLEANSE_PLAINTEXT
|
||
|
|
|
||
|
|
=back
|
||
|
|
|
||
|
|
Options on QUIC connections are initialized from the options set on SSL_CTX
|
||
|
|
before a QUIC connection SSL object is created. Options on QUIC streams are
|
||
|
|
initialised from the options configured on the QUIC connection SSL object
|
||
|
|
they are created from.
|
||
|
|
|
||
|
|
Setting options which relate to QUIC streams on a QUIC connection SSL object has
|
||
|
|
no direct effect on the QUIC connection SSL object itself, but will change the
|
||
|
|
options set on the default stream (if there is one) and will also determine the
|
||
|
|
default options set on any future streams which are created.
|
||
|
|
|
||
|
|
Other options not mentioned above do not have an effect and will be ignored.
|
||
|
|
|
||
|
|
Options which relate to QUIC streams may also be set directly on QUIC stream SSL
|
||
|
|
objects. Setting connection-related options on such an object has no effect.
|
||
|
|
|
||
|
|
=head1 RETURN VALUES
|
||
|
|
|
||
|
|
SSL_CTX_set_options() and SSL_set_options() return the new options bit-mask
|
||
|
|
after adding B<options>.
|
||
|
|
|
||
|
|
SSL_CTX_clear_options() and SSL_clear_options() return the new options bit-mask
|
||
|
|
after clearing B<options>.
|
||
|
|
|
||
|
|
SSL_CTX_get_options() and SSL_get_options() return the current bit-mask.
|
||
|
|
|
||
|
|
SSL_get_secure_renegotiation_support() returns 1 is the peer supports
|
||
|
|
secure renegotiation and 0 if it does not.
|
||
|
|
|
||
|
|
=head1 SEE ALSO
|
||
|
|
|
||
|
|
L<ssl(7)>, L<SSL_new(3)>, L<SSL_clear(3)>, L<SSL_shutdown(3)>
|
||
|
|
L<SSL_CTX_set_tmp_dh_callback(3)>,
|
||
|
|
L<SSL_CTX_set_min_proto_version(3)>,
|
||
|
|
L<openssl-dhparam(1)>
|
||
|
|
|
||
|
|
=head1 HISTORY
|
||
|
|
|
||
|
|
The attempt to always try to use secure renegotiation was added in
|
||
|
|
OpenSSL 0.9.8m.
|
||
|
|
|
||
|
|
The B<SSL_OP_PRIORITIZE_CHACHA> and B<SSL_OP_NO_RENEGOTIATION> options
|
||
|
|
were added in OpenSSL 1.1.1.
|
||
|
|
|
||
|
|
The B<SSL_OP_NO_EXTENDED_MASTER_SECRET> and B<SSL_OP_IGNORE_UNEXPECTED_EOF>
|
||
|
|
options were added in OpenSSL 3.0.
|
||
|
|
|
||
|
|
The B<SSL_OP_> constants and the corresponding parameter and return values
|
||
|
|
of the affected functions were changed to C<uint64_t> type in OpenSSL 3.0.
|
||
|
|
For that reason it is no longer possible use the B<SSL_OP_> macro values
|
||
|
|
in preprocessor C<#if> conditions. However it is still possible to test
|
||
|
|
whether these macros are defined or not.
|
||
|
|
|
||
|
|
=head1 COPYRIGHT
|
||
|
|
|
||
|
|
Copyright 2001-2023 The OpenSSL Project Authors. All Rights Reserved.
|
||
|
|
|
||
|
|
Licensed under the Apache License 2.0 (the "License"). You may not use
|
||
|
|
this file except in compliance with the License. You can obtain a copy
|
||
|
|
in the file LICENSE in the source distribution or at
|
||
|
|
L<https://www.openssl.org/source/license.html>.
|
||
|
|
|
||
|
|
=cut
|