Introduce ticket support. To enable them it is enough to set a positive

lifetime with tls_config_set_session_lifetime(). This enables tickets
and uses an internal automatic rekeying mode for the ticket keys.

If multiple processes are involved the following functions can be used to make
tickets work accross all instances:
- tls_config_set_session_id() sets the session identifier
- tls_config_add_ticket_key() adds an encryption and authentication key

For now only the last 4 keys added will be used (unless they are too old).
If tls_config_add_ticket_key() is used the caller must ensure to add new keys
regularly. It is best to do this 4 times per session lifetime (which is also
the ticket key lifetime).

Since tickets break PFS it is best to minimize the session lifetime according
to needs.

With a lot of help, input and OK beck@, jsing@

1 files changed, 28 insertions, 1 deletions

diff --git a/src/lib/libtls/tls_init.3 b/src/lib/libtls/tls_init.3
index 05474016f4..f5cada93a5 100644
--- a/src/lib/libtls/tls_init.3
+++ b/src/lib/libtls/tls_init.3
@@ -1,4 +1,4 @@
-.\" $OpenBSD: tls_init.3,v 1.84 2017/01/24 01:16:26 claudio Exp $
+.\" $OpenBSD: tls_init.3,v 1.85 2017/01/24 01:48:05 claudio Exp $
 .\"
 .\" Copyright (c) 2014 Ted Unangst <tedu@openbsd.org>
 .\"
@@ -26,6 +26,7 @@
 .Nm tls_config_parse_protocols ,
 .Nm tls_config_add_keypair_file ,
 .Nm tls_config_add_keypair_mem ,
+.Nm tls_config_add_ticket_key ,
 .Nm tls_config_set_alpn ,
 .Nm tls_config_set_ca_file ,
 .Nm tls_config_set_ca_path ,
@@ -42,6 +43,8 @@
 .Nm tls_config_set_ocsp_staple_mem ,
 .Nm tls_config_set_ocsp_staple_file ,
 .Nm tls_config_set_protocols ,
+.Nm tls_config_set_session_id ,
+.Nm tls_config_set_session_lifetime ,
 .Nm tls_config_set_verify_depth ,
 .Nm tls_config_prefer_ciphers_client ,
 .Nm tls_config_prefer_ciphers_server ,
@@ -111,6 +114,8 @@
 .Ft "int"
 .Fn tls_config_add_keypair_mem "struct tls_config *config" "const uint8_t *cert" "size_t cert_len" "const uint8_t *key" "size_t key_len"
 .Ft "int"
+.Fn tls_config_add_ticket_key "struct tls_config *config" "uint32_t keyrev" "unsigned char *key" "size_t keylen"
+.Ft "int"
 .Fn tls_config_set_alpn "struct tls_config *config" "const char *alpn"
 .Ft "int"
 .Fn tls_config_set_ca_file "struct tls_config *config" "const char *ca_file"
@@ -143,6 +148,10 @@
 .Ft "int"
 .Fn tls_config_set_protocols "struct tls_config *config" "uint32_t protocols"
 .Ft "int"
+.Fn tls_config_set_session_id "struct tls_config *config" "const unsigned char *session_id" "size_t len"
+.Ft "int"
+.Fn tls_config_set_session_lifetime "struct tls_config *config" "int lifetime"
+.Ft "int"
 .Fn tls_config_set_verify_depth "struct tls_config *config" "int verify_depth"
 .Ft "void"
 .Fn tls_config_prefer_ciphers_client "struct tls_config *config"
@@ -371,6 +380,14 @@ used as an alternative certificate for Server Name Indication (server only).
 adds an additional public certificate and private key from memory,
 used as an alternative certificate for Server Name Indication (server only).
 .It
+.Fn tls_config_add_ticket_key
+adds a key used for the encryption and authentication of TLS tickets.
+By default keys are generated and rotated automatically based on their lifetime.
+This function should only be used to synchronise ticket encryption key accross
+multiple processes.
+Re-adding a known key will result in an error, unless it is the most recently
+added key.
+.It
 .Fn tls_config_set_alpn
 sets the ALPN protocols that are supported.
 The alpn string is a comma separated list of protocols, in order of preference.
@@ -447,6 +464,16 @@ Additionally, the values
 .Dv TLS_PROTOCOLS_DEFAULT
 (TLSv1.2 only) may be used.
 .It
+.Fn tls_config_set_session_id
+sets the session identifier that will be used by the TLS server when
+sessions are enabled.
+By default a random value is used.
+.It
+.Fn tls_config_set_session_lifetime
+sets the lifetime to be used for TLS sessions.
+Session support is disabled if a lifetime of zero is specified, which is the
+default.
+.It
 .Fn tls_config_set_verify_depth
 limits the number of intermediate certificates that will be followed during
 certificate validation.