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Diffstat (limited to 'doc/cha-gtls-app.texi')
| -rw-r--r-- | doc/cha-gtls-app.texi | 56 |
1 files changed, 26 insertions, 30 deletions
diff --git a/doc/cha-gtls-app.texi b/doc/cha-gtls-app.texi index 4abeef856a..63843124c8 100644 --- a/doc/cha-gtls-app.texi +++ b/doc/cha-gtls-app.texi @@ -1688,36 +1688,32 @@ the discussion in @ref{Safe renegotiation}). Several TLS ciphersuites require additional parameters that need to be generated or provided by the application. The Diffie-Hellman based ciphersuites (ANON-DH or DHE), require -the group parameters to be provided. Those can either be -be generated on the fly using @funcref{gnutls_dh_params_generate2} -or imported from pregenerated data using @funcref{gnutls_dh_params_import_pkcs3}. -The parameters can be used in a @acronym{TLS} session by calling -@funcref{gnutls_certificate_set_dh_params} or -@funcref{gnutls_anon_set_server_dh_params} for anonymous sessions. - -@showfuncD{gnutls_dh_params_generate2,gnutls_dh_params_import_pkcs3,gnutls_certificate_set_dh_params,gnutls_anon_set_server_dh_params} - -Due to the time-consuming calculations required for the generation -of Diffie-Hellman parameters we suggest against performing generation -of them within an application. The @code{certtool} tool can be used to -generate or export known safe values that can be stored in code -or in a configuration file to provide the ability to replace. We also -recommend the usage of @funcref{gnutls_sec_param_to_pk_bits} -(see @ref{Selecting cryptographic key sizes}) to determine -the bit size of the generated parameters. - -Note that the information stored in the generated PKCS #3 structure -changed with GnuTLS 3.0.9. Since that version the @code{privateValueLength} -member of the structure is set, allowing the server utilizing the -parameters to use keys of the size of the security parameter. This -provides better performance in key exchange. - -To allow renewal of the parameters within an application without -accessing the credentials, which are a shared structure, -an alternative interface is available using a callback function. - -@showfuncdesc{gnutls_certificate_set_params_function} - +the group parameters to be provided. +These parameters can be specified in a @acronym{TLS} credentials +structure by calling +@funcref{gnutls_certificate_set_known_dh_params}, +@funcref{gnutls_anon_set_server_known_dh_params}, or +@funcref{gnutls_psk_set_server_known_dh_params}, depending on the type +of the credentials. + +@showfuncC{gnutls_certificate_set_known_dh_params,gnutls_anon_set_server_known_dh_params,gnutls_psk_set_server_known_dh_params} + +The functions above will set DH parameters pre-configured in the library +based on the security level provided. The GnuTLS' included parameters are +the FFDHE parameters from @xcite{RFC7919}. + +@subsubsection Legacy parameter generation +Note that older than 3.5.6 versions of GnuTLS provided functions +to generate or import arbitrary DH parameters from a file. This +practice is still supported but discouraged in current versions. + +@showfuncC{gnutls_dh_params_generate2,gnutls_dh_params_import_pkcs3,gnutls_certificate_set_dh_params} + +For old applications which require explicit DH parameters, we recommend +using @code{certtool} (of GnuTLS 3.5.6) with the @code{--get-dh-params} +option to obtain the FFDHE parameters descussed above. The output +parameters of the tool are in PKCS#3 format and can be imported by +most existing applications. @node Deriving keys for other applications/protocols @subsection Deriving keys for other applications/protocols |