ssl: workaround for new behavior of SSL_read() in OpenSSL >= 1.1.0c

Commit 4880672a9b41 of OpenSSL[1] (which then was backported to 1.1.0
branch at 122580ef71e4) changed the bahavior of SSL_read(): it now
returns -1 in the case the underlying BIO reaches EOF unexpectedly. This
means, it is possible that rb_sys_fail() is called with errno == 0,
resulting in [BUG].

So, as a workaround, let's distinguish IO error from the underlying BIO
and EOF in violation of SSL/TLS protocol with the value of errno.

[1] https://git.openssl.org/?p=openssl.git;a=commit;h=4880672a9b41a09a0984b55e219f02a2de7ab75e

1 files changed, 14 insertions, 4 deletions

diff --git a/ext/openssl/ossl_ssl.c b/ext/openssl/ossl_ssl.c
index cf1502eb..6931e998 100644
--- a/ext/openssl/ossl_ssl.c
+++ b/ext/openssl/ossl_ssl.c
@@ -1706,11 +1706,21 @@ ossl_ssl_read_internal(int argc, VALUE *argv, VALUE self, int nonblock)
                 rb_io_wait_readable(FPTR_TO_FD(fptr));
 		continue;
 	    case SSL_ERROR_SYSCALL:
-		if(ERR_peek_error() == 0 && nread == 0) {
-		    if (no_exception_p(opts)) { return Qnil; }
-		    rb_eof_error();
+		if (!ERR_peek_error()) {
+		    /*
+		     * XXX: OpenSSL commit 4880672a9b41 (backported to 1.1.0c)
+		     * changed SSL_read() to return -1 on unexpected EOF because
+		     * it's not retryable, contrary to the manpage.
+		     * Remove this comment (and maybe fix the condition) when
+		     * the manpage or the implementation is fixed.
+		     */
+		    if (errno)
+			rb_sys_fail(0);
+		    else {
+			if (no_exception_p(opts)) { return Qnil; }
+			rb_eof_error();
+		    }
 		}
-		rb_sys_fail(0);
 	    default:
 		ossl_raise(eSSLError, "SSL_read");
 	    }