BIO_f_zlib: Properly handle BIO_CTRL_PENDING and BIO_CTRL_WPENDING calls.

There can be data to write in output buffer and data to read that were
not yet read in the input stream.

Fixes #9866

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9877)

diff --git a/crypto/comp/c_zlib.c b/crypto/comp/c_zlib.c
index 78219f202d8b82ee8d8a4d6ae8f865c9ebabec33..1dd7d679981081ca43b20920b65e48fe23033425 100644 (file)
--- a/crypto/comp/c_zlib.c
+++ b/crypto/comp/c_zlib.c
@@ -598,6 +598,28 @@ static long bio_zlib_ctrl(BIO *b, int cmd, long num, void *ptr)
         BIO_copy_next_retry(b);
         break;
 
+    case BIO_CTRL_WPENDING:
+        if (ctx->obuf == NULL)
+            return 0;
+
+        if (ctx->odone) {
+            ret = ctx->ocount;
+        } else {
+            ret = ctx->ocount;
+            if (ret == 0)
+                /* Unknown amount pending but we are not finished */
+                ret = 1;
+        }
+        if (ret == 0)
+            ret = BIO_ctrl(next, cmd, num, ptr);
+        break;
+
+    case BIO_CTRL_PENDING:
+        ret = ctx->zin.avail_in;
+        if (ret == 0)
+            ret = BIO_ctrl(next, cmd, num, ptr);
+        break;
+
     default:
         ret = BIO_ctrl(next, cmd, num, ptr);
         break;