SSL_COMP_add_compression_method(3) - NetBSD Manual Pages

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SSL_COMP_add_compression_method(3)  OpenSSL SSL_COMP_add_compression_method(3)

SSL_COMP_add_compression_method - handle SSL/TLS integrated compression methods
libcrypto, -lcrypto
#include <openssl/ssl.h> int SSL_COMP_add_compression_method(int id, COMP_METHOD *cm);
SSL_COMP_add_compression_method() adds the compression method cm with the identifier id to the list of available compression methods. This list is globally maintained for all SSL operations within this applica- tion. It cannot be set for specific SSL_CTX or SSL objects.
The TLS standard (or SSLv3) allows the integration of compression meth- ods into the communication. The TLS RFC does however not specify com- pression methods or their corresponding identifiers, so there is cur- rently no compatible way to integrate compression with unknown peers. It is therefore currently not recommended to integrate compression into applications. Applications for non-public use may agree on certain com- pression methods. Using different compression methods with the same identifier will lead to connection failure. An OpenSSL client speaking a protocol that allows compression (SSLv3, TLSv1) will unconditionally send the list of all compression methods enabled with SSL_COMP_add_compression_method() to the server during the handshake. Unlike the mechanisms to set a cipher list, there is no method available to restrict the list of compression method on a per connection basis. An OpenSSL server will match the identifiers listed by a client against its own compression methods and will unconditionally activate compres- sion when a matching identifier is found. There is no way to restrict the list of compression methods supported on a per connection basis. The OpenSSL library has the compression methods COMP_rle() and (when especially enabled during compilation) COMP_zlib() available.
Once the identities of the compression methods for the TLS protocol have been standardized, the compression API will most likely be changed. Using it in the current state is not recommended.
SSL_COMP_add_compression_method() may return the following values: 0 The operation succeeded. 1 The operation failed. Check the error queue to find out the reason.
ssl(3) 3rd Berkeley Distribution 0.9.7d SSL_COMP_add_compression_method(3)
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