SSL_CTX_set_cipher_list.pod 2.7 KB

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  1. =pod
  2. =head1 NAME
  3. SSL_CTX_set_cipher_list, SSL_set_cipher_list - choose list of available SSL_CIPHERs
  4. =head1 SYNOPSIS
  5. #include <openssl/ssl.h>
  6. int SSL_CTX_set_cipher_list(SSL_CTX *ctx, const char *str);
  7. int SSL_set_cipher_list(SSL *ssl, const char *str);
  8. =head1 DESCRIPTION
  9. SSL_CTX_set_cipher_list() sets the list of available ciphers for B<ctx>
  10. using the control string B<str>. The format of the string is described
  11. in L<ciphers(1)|ciphers(1)>. The list of ciphers is inherited by all
  12. B<ssl> objects created from B<ctx>.
  13. SSL_set_cipher_list() sets the list of ciphers only for B<ssl>.
  14. =head1 NOTES
  15. The control string B<str> should be universally usable and not depend
  16. on details of the library configuration (ciphers compiled in). Thus no
  17. syntax checking takes place. Items that are not recognized, because the
  18. corresponding ciphers are not compiled in or because they are mistyped,
  19. are simply ignored. Failure is only flagged if no ciphers could be collected
  20. at all.
  21. It should be noted, that inclusion of a cipher to be used into the list is
  22. a necessary condition. On the client side, the inclusion into the list is
  23. also sufficient. On the server side, additional restrictions apply. All ciphers
  24. have additional requirements. ADH ciphers don't need a certificate, but
  25. DH-parameters must have been set. All other ciphers need a corresponding
  26. certificate and key.
  27. A RSA cipher can only be chosen, when a RSA certificate is available.
  28. RSA export ciphers with a keylength of 512 bits for the RSA key require
  29. a temporary 512 bit RSA key, as typically the supplied key has a length
  30. of 1024 bit (see
  31. L<SSL_CTX_set_tmp_rsa_callback(3)|SSL_CTX_set_tmp_rsa_callback(3)>).
  32. RSA ciphers using EDH need a certificate and key and additional DH-parameters
  33. (see L<SSL_CTX_set_tmp_dh_callback(3)|SSL_CTX_set_tmp_dh_callback(3)>).
  34. A DSA cipher can only be chosen, when a DSA certificate is available.
  35. DSA ciphers always use DH key exchange and therefore need DH-parameters
  36. (see L<SSL_CTX_set_tmp_dh_callback(3)|SSL_CTX_set_tmp_dh_callback(3)>).
  37. When these conditions are not met for any cipher in the list (e.g. a
  38. client only supports export RSA ciphers with a asymmetric key length
  39. of 512 bits and the server is not configured to use temporary RSA
  40. keys), the "no shared cipher" (SSL_R_NO_SHARED_CIPHER) error is generated
  41. and the handshake will fail.
  42. =head1 RETURN VALUES
  43. SSL_CTX_set_cipher_list() and SSL_set_cipher_list() return 1 if any cipher
  44. could be selected and 0 on complete failure.
  45. =head1 SEE ALSO
  46. L<ssl(3)|ssl(3)>, L<SSL_get_ciphers(3)|SSL_get_ciphers(3)>,
  47. L<SSL_CTX_use_certificate(3)|SSL_CTX_use_certificate(3)>,
  48. L<SSL_CTX_set_tmp_rsa_callback(3)|SSL_CTX_set_tmp_rsa_callback(3)>,
  49. L<SSL_CTX_set_tmp_dh_callback(3)|SSL_CTX_set_tmp_dh_callback(3)>,
  50. L<ciphers(1)|ciphers(1)>
  51. =cut