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Delay creating s->session until resumption is resolved.

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When not offering to resume a session, the client populates s->session with a
fresh SSL_SESSION before the ServerHello is processed and, in DTLS_ANY_VERSION,
before the version is even determined. Don't create a fresh SSL_SESSION until
we know we are doing a full handshake.

This brings ssl3_send_client_hello closer to ssl23_client_hello in behavior. It
also fixes ssl_version in the client in DTLS_ANY_VERSION.

SSLv23_client_method is largely unchanged. If no session is offered, s->session
continues to be NULL until the ServerHello is received. The one difference is
that s->session isn't populated until the entire ServerHello is received,
rather than just the first half, in the case of a fragmented ServerHello. Apart
from info_callback, no external hooks get called between those points, so this
shouldn't expose new missing NULL checks.

The other client methods change significantly to match SSLv23_client_method's
behavior. For TLS, any exposed missing NULL checks are also in
SSLv23_client_method (and version-specific methods are already weird), so that
should be safe. For DTLS, I've verified that accesses in d1_*.c either handle
NULL or are after the ServerHello.

Change-Id: Idcae6bd242480e28a57dbba76ce67f1ac1ae1d1d
Reviewed-on: https://boringssl-review.googlesource.com/2404
Reviewed-by: Adam Langley <agl@google.com>
This commit is contained in:
David Benjamin 2014-11-23 04:20:17 -05:00 committed by Adam Langley
parent 8b8c006564
commit 81ea0bf538
2 changed files with 20 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
ssl/s23_clnt.c
View File

@ -555,12 +555,6 @@ static int ssl23_get_server_hello(SSL *s)
goto err; goto err;
} }
s->init_num=0; s->init_num=0;
/* If there was no session to resume, now that the final version is
* determined, insert a fresh one. */
if (s->session == NULL && !ssl_get_new_session(s,0))
goto err;
return(SSL_connect(s)); return(SSL_connect(s));
err: err:
return(-1); return(-1);

39
ssl/s3_clnt.c
View File

@ -148,6 +148,7 @@
* OTHERWISE. * OTHERWISE.
*/ */
#include <assert.h>
#include <stdio.h> #include <stdio.h>
#include <openssl/buf.h> #include <openssl/buf.h>
@ -627,15 +628,6 @@ int ssl3_send_client_hello(SSL *s)
buf=(unsigned char *)s->init_buf->data; buf=(unsigned char *)s->init_buf->data;
if (s->state == SSL3_ST_CW_CLNT_HELLO_A) if (s->state == SSL3_ST_CW_CLNT_HELLO_A)
{ {
SSL_SESSION *sess = s->session;
if (sess == NULL ||
sess->ssl_version != s->version ||
!sess->session_id_length ||
sess->not_resumable)
{
if (!ssl_get_new_session(s,0))
goto err;
}
if (s->method->version == DTLS_ANY_VERSION) if (s->method->version == DTLS_ANY_VERSION)
{ {
/* Determine which DTLS version to use */ /* Determine which DTLS version to use */
@ -666,6 +658,18 @@ int ssl3_send_client_hello(SSL *s)
} }
s->client_version = s->version; s->client_version = s->version;
} }
/* If the configured session was created at a version
* higher than our maximum version, drop it. */
if (s->session &&
(s->session->session_id_length == 0 ||
s->session->not_resumable ||
(!SSL_IS_DTLS(s) && s->session->ssl_version > s->version) ||
(SSL_IS_DTLS(s) && s->session->ssl_version < s->version)))
{
SSL_set_session(s, NULL);
}
/* else use the pre-loaded session */ /* else use the pre-loaded session */
p=s->s3->client_random; p=s->s3->client_random;
@ -727,7 +731,7 @@ int ssl3_send_client_hello(SSL *s)
p+=SSL3_RANDOM_SIZE; p+=SSL3_RANDOM_SIZE;
/* Session ID */ /* Session ID */
if (s->new_session) if (s->new_session || s->session == NULL)
i=0; i=0;
else else
i=s->session->session_id_length; i=s->session->session_id_length;
@ -868,7 +872,8 @@ int ssl3_get_server_hello(SSL *s)
/* Copy over the server random. */ /* Copy over the server random. */
memcpy(s->s3->server_random, CBS_data(&server_random), SSL3_RANDOM_SIZE); memcpy(s->s3->server_random, CBS_data(&server_random), SSL3_RANDOM_SIZE);
if (CBS_len(&session_id) != 0 && assert(s->session == NULL || s->session->session_id_length > 0);
if (s->session != NULL &&
CBS_mem_equal(&session_id, CBS_mem_equal(&session_id,
s->session->session_id, s->session->session_id_length)) s->session->session_id, s->session->session_id_length))
{ {
@ -884,16 +889,12 @@ int ssl3_get_server_hello(SSL *s)
} }
else else
{ {
/* The session wasn't resumed. */ /* The session wasn't resumed. Create a fresh SSL_SESSION to
* fill out. */
s->hit = 0; s->hit = 0;
/* If we were trying for session-id reuse, make a new if (!ssl_get_new_session(s, 0))
* SSL_SESSION so we don't stuff up other people */
if (s->session->session_id_length > 0)
{ {
if (!ssl_get_new_session(s,0)) goto f_err;
{
goto f_err;
}
} }
/* Note: session_id could be empty. */ /* Note: session_id could be empty. */
s->session->session_id_length = CBS_len(&session_id); s->session->session_id_length = CBS_len(&session_id);