1SSL_COMP_add_compression_method(3)  OpenSSL SSL_COMP_add_compression_method(3)
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NAME

6       SSL_COMP_add_compression_method - handle SSL/TLS integrated compression
7       methods
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SYNOPSIS

10        #include <openssl/ssl.h>
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12        int SSL_COMP_add_compression_method(int id, COMP_METHOD *cm);
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DESCRIPTION

15       SSL_COMP_add_compression_method() adds the compression method cm with
16       the identifier id to the list of available compression methods. This
17       list is globally maintained for all SSL operations within this
18       application.  It cannot be set for specific SSL_CTX or SSL objects.
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NOTES

21       The TLS standard (or SSLv3) allows the integration of compression
22       methods into the communication. The TLS RFC does however not specify
23       compression methods or their corresponding identifiers, so there is
24       currently no compatible way to integrate compression with unknown
25       peers. It is therefore currently not recommended to integrate
26       compression into applications. Applications for non-public use may
27       agree on certain compression methods. Using different compression
28       methods with the same identifier will lead to connection failure.
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30       An OpenSSL client speaking a protocol that allows compression (SSLv3,
31       TLSv1) will unconditionally send the list of all compression methods
32       enabled with SSL_COMP_add_compression_method() to the server during the
33       handshake.  Unlike the mechanisms to set a cipher list, there is no
34       method available to restrict the list of compression method on a per
35       connection basis.
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37       An OpenSSL server will match the identifiers listed by a client against
38       its own compression methods and will unconditionally activate
39       compression when a matching identifier is found. There is no way to
40       restrict the list of compression methods supported on a per connection
41       basis.
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43       The OpenSSL library has the compression methods COMP_rle() and (when
44       especially enabled during compilation) COMP_zlib() available.
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WARNINGS

47       Once the identities of the compression methods for the TLS protocol
48       have been standardized, the compression API will most likely be
49       changed. Using it in the current state is not recommended.
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RETURN VALUES

52       SSL_COMP_add_compression_method() may return the following values:
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54       0   The operation succeeded.
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56       1   The operation failed. Check the error queue to find out the reason.
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SEE ALSO

59       ssl(3)
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631.0.0e                            2003-11-29SSL_COMP_add_compression_method(3)
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