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Avoid issuing multiple tickets with TLS 1.3

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With the upcoming OpenSSL 1.1.1 release TLS 1.3 is supported, and
multiple tickets are issued for each full handshake, this is
counter-productive for SMTP, so we ask OpenSSL to mint just one
ticket.
This commit is contained in:
Viktor Dukhovni
2018-08-15 00:53:59 -04:00
parent 4ccf5fbaf6
commit b72af0bdf1
2 changed files with 20 additions and 1 deletions
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5
postfix/src/tls/tls.h
View File

@@ -107,6 +107,11 @@ extern const char *str_tls_level(int);
#define TLS_method SSLv23_method #define TLS_method SSLv23_method
#define TLS_client_method SSLv23_client_method #define TLS_client_method SSLv23_client_method
#define TLS_server_method SSLv23_server_method #define TLS_server_method SSLv23_server_method
#endif
/* Backwards compatibility with OpenSSL < 1.1.1 */
#if OPENSSL_VERSION_NUMBER < 0x1010100fUL
#define SSL_CTX_set_num_tickets(ctx, num) ((void)0)
#endif #endif
/* SSL_CIPHER_get_name() got constified in 0.9.7g */ /* SSL_CIPHER_get_name() got constified in 0.9.7g */

16
postfix/src/tls/tls_server.c
View File

@@ -502,8 +502,22 @@ TLS_APPL_STATE *tls_server_init(const TLS_SERVER_INIT_PROPS *props)
ticketable = 0; ticketable = 0;
} }
} }
if (ticketable) if (ticketable) {
SSL_CTX_set_tlsext_ticket_key_cb(server_ctx, ticket_cb); SSL_CTX_set_tlsext_ticket_key_cb(server_ctx, ticket_cb);
/*
* OpenSSL 1.1.1 introduces support for TLS 1.3, which can issue more
* than one ticket per handshake. While this may be appropriate for
* communication between browsers and webservers, it is not terribly
* useful for MTAs, many of which other than Postfix don't do TLS
* session caching at all, and Postfix has no mechanism for storing
* multiple session tickets, if more than one sent, the second clobbers
* the first. OpenSSL 1.1.1 servers default to issuing two tickets for
* non-resumption handshakes, we reduce this to one. Our ticket
* decryption callback already (since 2.11) asks OpenSSL to avoid
* issuing new tickets when the presented ticket is re-usable.
*/
SSL_CTX_set_num_tickets(server_ctx, 1);
}
#endif #endif
if (!ticketable) if (!ticketable)
off |= SSL_OP_NO_TICKET; off |= SSL_OP_NO_TICKET;