Fix race condition in NewSessionTicket

If a NewSessionTicket is received by a multi-threaded client when
attempting to reuse a previous ticket then a race condition can occur
potentially leading to a double free of the ticket data.

CVE-2015-1791

This also fixes RT#3808 where a session ID is changed for a session already
in the client session cache. Since the session ID is the key to the cache
this breaks the cache access.

Parts of this patch were inspired by this Akamai change:
https://github.com/akamai/openssl/commit/c0bf69a791239ceec64509f9f19fcafb2461b0d3

Reviewed-by: Rich Salz <rsalz@openssl.org>
(cherry picked from commit 27c76b9b8010b536687318739c6f631ce4194688)

Conflicts:
	ssl/ssl.h
	ssl/ssl_err.c

5 files changed, 107 insertions, 0 deletions

diff --git a/ssl/s3_clnt.c b/ssl/s3_clnt.c
index 118856fe6a..8d035f7cfa 100644
--- a/ssl/s3_clnt.c
+++ b/ssl/s3_clnt.c
@@ -1722,6 +1722,38 @@ int ssl3_get_new_session_ticket(SSL *s)
     }
 
     p = d = (unsigned char *)s->init_msg;
+
+    if (s->session->session_id_length > 0) {
+        int i = s->session_ctx->session_cache_mode;
+        SSL_SESSION *new_sess;
+        /*
+         * We reused an existing session, so we need to replace it with a new
+         * one
+         */
+        if (i & SSL_SESS_CACHE_CLIENT) {
+            /*
+             * Remove the old session from the cache
+             */
+            if (i & SSL_SESS_CACHE_NO_INTERNAL_STORE) {
+                if (s->session_ctx->remove_session_cb != NULL)
+                    s->session_ctx->remove_session_cb(s->session_ctx,
+                                                      s->session);
+            } else {
+                /* We carry on if this fails */
+                SSL_CTX_remove_session(s->session_ctx, s->session);
+            }
+        }
+
+        if ((new_sess = ssl_session_dup(s->session, 0)) == 0) {
+            al = SSL_AD_INTERNAL_ERROR;
+            SSLerr(SSL_F_SSL3_GET_NEW_SESSION_TICKET, ERR_R_MALLOC_FAILURE);
+            goto f_err;
+        }
+
+        SSL_SESSION_free(s->session);
+        s->session = new_sess;
+    }
+
     n2l(p, s->session->tlsext_tick_lifetime_hint);
     n2s(p, ticklen);
     /* ticket_lifetime_hint + ticket_length + ticket */
diff --git a/ssl/ssl.h b/ssl/ssl.h
index ee9944f9cb..2dcc3b8e95 100644
--- a/ssl/ssl.h
+++ b/ssl/ssl.h
@@ -1945,6 +1945,7 @@ void ERR_load_SSL_strings(void);
 # define SSL_F_SSL_READ                                   223
 # define SSL_F_SSL_RSA_PRIVATE_DECRYPT                    187
 # define SSL_F_SSL_RSA_PUBLIC_ENCRYPT                     188
+# define SSL_F_SSL_SESSION_DUP                            348
 # define SSL_F_SSL_SESSION_NEW                            189
 # define SSL_F_SSL_SESSION_PRINT_FP                       190
 # define SSL_F_SSL_SESS_CERT_NEW                          225
diff --git a/ssl/ssl_err.c b/ssl/ssl_err.c
index c8745914d7..65c8f61e78 100644
--- a/ssl/ssl_err.c
+++ b/ssl/ssl_err.c
@@ -279,6 +279,7 @@ static ERR_STRING_DATA SSL_str_functs[] = {
     {ERR_FUNC(SSL_F_SSL_READ), "SSL_read"},
     {ERR_FUNC(SSL_F_SSL_RSA_PRIVATE_DECRYPT), "SSL_RSA_PRIVATE_DECRYPT"},
     {ERR_FUNC(SSL_F_SSL_RSA_PUBLIC_ENCRYPT), "SSL_RSA_PUBLIC_ENCRYPT"},
+    {ERR_FUNC(SSL_F_SSL_SESSION_DUP), "ssl_session_dup"},
     {ERR_FUNC(SSL_F_SSL_SESSION_NEW), "SSL_SESSION_new"},
     {ERR_FUNC(SSL_F_SSL_SESSION_PRINT_FP), "SSL_SESSION_print_fp"},
     {ERR_FUNC(SSL_F_SSL_SESS_CERT_NEW), "SSL_SESS_CERT_NEW"},
diff --git a/ssl/ssl_locl.h b/ssl/ssl_locl.h
index 9fa209d247..038554f0d6 100644
--- a/ssl/ssl_locl.h
+++ b/ssl/ssl_locl.h
@@ -760,6 +760,7 @@ int ssl_set_peer_cert_type(SESS_CERT *c, int type);
 int ssl_get_new_session(SSL *s, int session);
 int ssl_get_prev_session(SSL *s, unsigned char *session, int len,
                          const unsigned char *limit);
+SSL_SESSION *ssl_session_dup(SSL_SESSION *src, int ticket);
 int ssl_cipher_id_cmp(const SSL_CIPHER *a, const SSL_CIPHER *b);
 int ssl_cipher_ptr_id_cmp(const SSL_CIPHER *const *ap,
                           const SSL_CIPHER *const *bp);
diff --git a/ssl/ssl_sess.c b/ssl/ssl_sess.c
index fc312968f8..9baa090d82 100644
--- a/ssl/ssl_sess.c
+++ b/ssl/ssl_sess.c
@@ -135,6 +135,78 @@ SSL_SESSION *SSL_SESSION_new(void)
     return (ss);
 }
 
+/*
+ * Create a new SSL_SESSION and duplicate the contents of |src| into it. If
+ * ticket == 0 then no ticket information is duplicated, otherwise it is.
+ */
+SSL_SESSION *ssl_session_dup(SSL_SESSION *src, int ticket)
+{
+    SSL_SESSION *dest;
+
+    dest = OPENSSL_malloc(sizeof(*src));
+    if (dest == NULL) {
+        goto err;
+    }
+    memcpy(dest, src, sizeof(*dest));
+
+#ifndef OPENSSL_NO_KRB5
+    dest->krb5_client_princ_len = dest->krb5_client_princ_len;
+    if (src->krb5_client_princ_len > 0)
+        memcpy(dest->krb5_client_princ, src->krb5_client_princ,
+               src->krb5_client_princ_len);
+#endif
+
+    if (src->sess_cert != NULL)
+        CRYPTO_add(&src->sess_cert->references, 1, CRYPTO_LOCK_SSL_SESS_CERT);
+
+    if (src->peer != NULL)
+        CRYPTO_add(&src->peer->references, 1, CRYPTO_LOCK_X509);
+
+    dest->references = 1;
+
+    if(src->ciphers != NULL) {
+        dest->ciphers = sk_SSL_CIPHER_dup(src->ciphers);
+        if (dest->ciphers == NULL)
+            goto err;
+    } else {
+        dest->ciphers = NULL;
+    }
+
+    if (!CRYPTO_dup_ex_data(CRYPTO_EX_INDEX_SSL_SESSION,
+                                            &dest->ex_data, &src->ex_data)) {
+        goto err;
+    }
+
+    /* We deliberately don't copy the prev and next pointers */
+    dest->prev = NULL;
+    dest->next = NULL;
+
+#ifndef OPENSSL_NO_TLSEXT
+    if (src->tlsext_hostname) {
+        dest->tlsext_hostname = BUF_strdup(src->tlsext_hostname);
+        if (dest->tlsext_hostname == NULL) {
+            goto err;
+        }
+    } else {
+        dest->tlsext_hostname = NULL;
+    }
+#endif
+
+    if (ticket != 0) {
+        dest->tlsext_tick_lifetime_hint = src->tlsext_tick_lifetime_hint;
+        dest->tlsext_ticklen = src->tlsext_ticklen;
+        if((dest->tlsext_tick = OPENSSL_malloc(src->tlsext_ticklen)) == NULL) {
+            goto err;
+        }
+    }
+
+    return dest;
+err:
+    SSLerr(SSL_F_SSL_SESSION_DUP, ERR_R_MALLOC_FAILURE);
+    SSL_SESSION_free(dest);
+    return NULL;
+}
+
 const unsigned char *SSL_SESSION_get_id(const SSL_SESSION *s,
                                         unsigned int *len)
 {