Disable partial writes for early data

We don't keep track of the number of bytes written between in the
SSL_write_ex() call and the subsequent flush. If the flush needs to be
retried then we will have forgotten how many bytes actually got written.
The simplest solution is to just disable it for this scenario.

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4802)

diff --git a/ssl/ssl_lib.c b/ssl/ssl_lib.c
index 61e5ebb2d111040e465596b2a986df5daa77a345..e7867cd5c884dc4460dc9628830a0d36217f1431 100644 (file)
--- a/ssl/ssl_lib.c
+++ b/ssl/ssl_lib.c
@@ -1970,6 +1970,7 @@ int SSL_write_early_data(SSL *s, const void *buf, size_t num, size_t *written)
 {
     int ret, early_data_state;
     size_t writtmp;
+    uint32_t partialwrite;
 
     switch (s->early_data_state) {
     case SSL_EARLY_DATA_NONE:
@@ -1995,7 +1996,15 @@ int SSL_write_early_data(SSL *s, const void *buf, size_t num, size_t *written)
 
     case SSL_EARLY_DATA_WRITE_RETRY:
         s->early_data_state = SSL_EARLY_DATA_WRITING;
+        /*
+         * We disable partial write for early data because we don't keep track
+         * of how many bytes we've written between the SSL_write_ex() call and
+         * the flush if the flush needs to be retried)
+         */
+        partialwrite = s->mode & SSL_MODE_ENABLE_PARTIAL_WRITE;
+        s->mode &= ~SSL_MODE_ENABLE_PARTIAL_WRITE;
         ret = SSL_write_ex(s, buf, num, &writtmp);
+        s->mode |= partialwrite;
         if (!ret) {
             s->early_data_state = SSL_EARLY_DATA_WRITE_RETRY;
             return ret;
@@ -2007,10 +2016,6 @@ int SSL_write_early_data(SSL *s, const void *buf, size_t num, size_t *written)
         /* The buffering BIO is still in place so we need to flush it */
         if (statem_flush(s) != 1)
             return 0;
-        /*
-         * TODO(TLS1.3): Technically this may not be correct in the event of
-         * SSL_MODE_ENABLE_PARTIAL_WRITE. What should we do about this?
-         */
         *written = num;
         s->early_data_state = SSL_EARLY_DATA_WRITE_RETRY;
         return 1;