[nginx] SSL: avoid reading on pending SSL_write_early_data().

[Sergey Kandaurov]

details:   https://hg.nginx.org/nginx/rev/294162223c7c
branches:  
changeset: 7431:294162223c7c
user:      Sergey Kandaurov <pluknet at nginx.com>
date:      Tue Dec 18 15:15:15 2018 +0300
description:
SSL: avoid reading on pending SSL_write_early_data().

If SSL_write_early_data() returned SSL_ERROR_WANT_WRITE, stop further reading
using a newly introduced c->ssl->write_blocked flag, as otherwise this would
result in SSL error "ssl3_write_bytes:bad length".  Eventually, normal reading
will be restored by read event posted from successful SSL_write_early_data().

While here, place "SSL_write_early_data: want write" debug on the path.

diffstat:

 src/event/ngx_event_openssl.c |  20 ++++++++++++++++++++
 src/event/ngx_event_openssl.h |   1 +
 2 files changed, 21 insertions(+), 0 deletions(-)

diffs (62 lines):

diff -r 286ae954009d -r 294162223c7c src/event/ngx_event_openssl.c
--- a/src/event/ngx_event_openssl.c	Fri Dec 14 18:11:06 2018 +0300
+++ b/src/event/ngx_event_openssl.c	Tue Dec 18 15:15:15 2018 +0300
@@ -1839,6 +1839,10 @@ ngx_ssl_recv_early(ngx_connection_t *c, 
         buf += 1;
     }
 
+    if (c->ssl->write_blocked) {
+        return NGX_AGAIN;
+    }
+
     /*
      * SSL_read_early_data() may return data in parts, so try to read
      * until SSL_read_early_data() would return no data
@@ -2339,6 +2343,11 @@ ngx_ssl_write_early(ngx_connection_t *c,
             ngx_post_event(c->read, &ngx_posted_events);
         }
 
+        if (c->ssl->write_blocked) {
+            c->ssl->write_blocked = 0;
+            ngx_post_event(c->read, &ngx_posted_events);
+        }
+
         c->sent += written;
 
         return written;
@@ -2352,6 +2361,9 @@ ngx_ssl_write_early(ngx_connection_t *c,
 
     if (sslerr == SSL_ERROR_WANT_WRITE) {
 
+        ngx_log_debug0(NGX_LOG_DEBUG_EVENT, c->log, 0,
+                       "SSL_write_early_data: want write");
+
         if (c->ssl->saved_read_handler) {
 
             c->read->handler = c->ssl->saved_read_handler;
@@ -2365,6 +2377,14 @@ ngx_ssl_write_early(ngx_connection_t *c,
             ngx_post_event(c->read, &ngx_posted_events);
         }
 
+        /*
+         * OpenSSL 1.1.1a fails to handle SSL_read_early_data()
+         * if an SSL_write_early_data() call blocked on writing,
+         * see https://github.com/openssl/openssl/issues/7757
+         */
+
+        c->ssl->write_blocked = 1;
+
         c->write->ready = 0;
         return NGX_AGAIN;
     }
diff -r 286ae954009d -r 294162223c7c src/event/ngx_event_openssl.h
--- a/src/event/ngx_event_openssl.h	Fri Dec 14 18:11:06 2018 +0300
+++ b/src/event/ngx_event_openssl.h	Tue Dec 18 15:15:15 2018 +0300
@@ -98,6 +98,7 @@ struct ngx_ssl_connection_s {
     unsigned                    try_early_data:1;
     unsigned                    in_early:1;
     unsigned                    early_preread:1;
+    unsigned                    write_blocked:1;
 };