crypto: propagate errors from TLS session I/O callbacks

GNUTLS doesn't know how to perform I/O on anything other than plain
FDs, so the TLS session provides it with some I/O callbacks. The
GNUTLS API design requires these callbacks to return a unix errno
value, which means we're currently loosing the useful QEMU "Error"
object.

This changes the I/O callbacks in QEMU to stash the "Error" object
in the QCryptoTLSSession class, and fetch it when seeing an I/O
error returned from GNUTLS, thus preserving useful error messages.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

1 files changed, 8 insertions, 10 deletions

diff --git a/io/channel-tls.c b/io/channel-tls.c
index 9d8bb158d1..aab630e5ae 100644
--- a/io/channel-tls.c
+++ b/io/channel-tls.c
@@ -28,17 +28,16 @@
 
 static ssize_t qio_channel_tls_write_handler(const char *buf,
                                              size_t len,
-                                             void *opaque)
+                                             void *opaque,
+                                             Error **errp)
 {
     QIOChannelTLS *tioc = QIO_CHANNEL_TLS(opaque);
     ssize_t ret;
 
-    ret = qio_channel_write(tioc->master, buf, len, NULL);
+    ret = qio_channel_write(tioc->master, buf, len, errp);
     if (ret == QIO_CHANNEL_ERR_BLOCK) {
-        errno = EAGAIN;
-        return -1;
+        return QCRYPTO_TLS_SESSION_ERR_BLOCK;
     } else if (ret < 0) {
-        errno = EIO;
         return -1;
     }
     return ret;
@@ -46,17 +45,16 @@ static ssize_t qio_channel_tls_write_handler(const char *buf,
 
 static ssize_t qio_channel_tls_read_handler(char *buf,
                                             size_t len,
-                                            void *opaque)
+                                            void *opaque,
+                                            Error **errp)
 {
     QIOChannelTLS *tioc = QIO_CHANNEL_TLS(opaque);
     ssize_t ret;
 
-    ret = qio_channel_read(tioc->master, buf, len, NULL);
+    ret = qio_channel_read(tioc->master, buf, len, errp);
     if (ret == QIO_CHANNEL_ERR_BLOCK) {
-        errno = EAGAIN;
-        return -1;
+        return QCRYPTO_TLS_SESSION_ERR_BLOCK;
     } else if (ret < 0) {
-        errno = EIO;
         return -1;
     }
     return ret;