In ssl3_read_bytes(), do not process more than three consecutive TLS

records, otherwise a peer can potentially cause us to loop indefinately.
Return with an SSL_ERROR_WANT_READ instead, so that the caller can choose
when they want to handle further processing for this connection.

ok beck@ miod@

1 files changed, 24 insertions, 4 deletions

diff --git a/src/lib/libssl/s3_pkt.c b/src/lib/libssl/s3_pkt.c
index 0e97be6728..8d4212d4a1 100644
--- a/src/lib/libssl/s3_pkt.c
+++ b/src/lib/libssl/s3_pkt.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: s3_pkt.c,v 1.58 2016/07/10 23:07:34 tedu Exp $ */
+/* $OpenBSD: s3_pkt.c,v 1.59 2016/11/03 16:23:30 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -839,10 +839,11 @@ ssl3_write_pending(SSL *s, int type, const unsigned char *buf, unsigned int len)
 int
 ssl3_read_bytes(SSL *s, int type, unsigned char *buf, int len, int peek)
 {
-        int al, i, j, ret;
+        void (*cb)(const SSL *ssl, int type2, int val) = NULL;
+        int al, i, j, ret, rrcount = 0;
         unsigned int n;
         SSL3_RECORD *rr;
-        void (*cb)(const SSL *ssl, int type2, int val) = NULL;
+        BIO *bio;
 
         if (s->s3->rbuf.buf == NULL) /* Not initialized yet */
                 if (!ssl3_setup_read_buffer(s))
@@ -896,7 +897,27 @@ ssl3_read_bytes(SSL *s, int type, unsigned char *buf, int len, int peek)
                         return (-1);
                 }
         }
+
 start:
+        /*
+         * Do not process more than three consecutive records, otherwise the
+         * peer can cause us to loop indefinitely. Instead, return with an
+         * SSL_ERROR_WANT_READ so the caller can choose when to handle further
+         * processing. In the future, the total number of non-handshake and
+         * non-application data records per connection should probably also be
+         * limited...
+         */
+        if (rrcount++ >= 3) {
+                if ((bio = SSL_get_rbio(s)) == NULL) {
+                        SSLerr(SSL_F_SSL3_READ_BYTES, ERR_R_INTERNAL_ERROR);
+                        return -1;
+                }
+                BIO_clear_retry_flags(bio);
+                BIO_set_retry_read(bio);
+                s->rwstate = SSL_READING;
+                return -1;
+        }
+
         s->rwstate = SSL_NOTHING;
 
         /*
@@ -1050,7 +1071,6 @@ start:
                                 if (!(s->mode & SSL_MODE_AUTO_RETRY)) {
                                         if (s->s3->rbuf.left == 0) {
                                                 /* no read-ahead left? */
-                                                BIO *bio;
                         /* In the case where we try to read application data,
                          * but we trigger an SSL handshake, we return -1 with
                          * the retry option set.  Otherwise renegotiation may