rbd: add support for getting password from QCryptoSecret object

Currently RBD passwords must be provided on the command line
via

  $QEMU -drive file=rbd:pool/image:id=myname:\
               key=QVFDVm41aE82SHpGQWhBQXEwTkN2OGp0SmNJY0UrSE9CbE1RMUE=:\
               auth_supported=cephx

This is insecure because the key is visible in the OS process
listing.

This adds support for an 'password-secret' parameter in the RBD
parameters that can be used with the QCryptoSecret object to
provide the password via a file:

  echo "QVFDVm41aE82SHpGQWhBQXEwTkN2OGp0SmNJY0UrSE9CbE1RMUE=" > poolkey.b64
  $QEMU -object secret,id=secret0,file=poolkey.b64,format=base64 \
        -drive driver=rbd,filename=rbd:pool/image:id=myname:\
               auth_supported=cephx,password-secret=secret0

Reviewed-by: Josh Durgin <jdurgin@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-id: 1453385961-10718-2-git-send-email-berrange@redhat.com
Signed-off-by: Jeff Cody <jcody@redhat.com>

block/rbd.c

@@ -16,6 +16,7 @@
 #include "qemu-common.h"
 #include "qemu/error-report.h"
 #include "block/block_int.h"
+#include "crypto/secret.h"
 
 #include <rbd/librbd.h>
 
@@ -228,6 +229,27 @@ static char *qemu_rbd_parse_clientname(const char *conf, char *clientname)
     return NULL;
 }
 
+
+static int qemu_rbd_set_auth(rados_t cluster, const char *secretid,
+                             Error **errp)
+{
+    if (secretid == 0) {
+        return 0;
+    }
+
+    gchar *secret = qcrypto_secret_lookup_as_base64(secretid,
+                                                    errp);
+    if (!secret) {
+        return -1;
+    }
+
+    rados_conf_set(cluster, "key", secret);
+    g_free(secret);
+
+    return 0;
+}
+
+
 static int qemu_rbd_set_conf(rados_t cluster, const char *conf,
                              bool only_read_conf_file,
                              Error **errp)
@@ -299,10 +321,13 @@ static int qemu_rbd_create(const char *filename, QemuOpts *opts, Error **errp)
     char conf[RBD_MAX_CONF_SIZE];
     char clientname_buf[RBD_MAX_CONF_SIZE];
     char *clientname;
+    const char *secretid;
     rados_t cluster;
     rados_ioctx_t io_ctx;
     int ret;
 
+    secretid = qemu_opt_get(opts, "password-secret");
+
     if (qemu_rbd_parsename(filename, pool, sizeof(pool),
                            snap_buf, sizeof(snap_buf),
                            name, sizeof(name),
@@ -350,6 +375,11 @@ static int qemu_rbd_create(const char *filename, QemuOpts *opts, Error **errp)
         return -EIO;
     }
 
+    if (qemu_rbd_set_auth(cluster, secretid, errp) < 0) {
+        rados_shutdown(cluster);
+        return -EIO;
+    }
+
     if (rados_connect(cluster) < 0) {
         error_setg(errp, "error connecting");
         rados_shutdown(cluster);
@@ -423,6 +453,11 @@ static QemuOptsList runtime_opts = {
             .type = QEMU_OPT_STRING,
             .help = "Specification of the rbd image",
         },
+        {
+            .name = "password-secret",
+            .type = QEMU_OPT_STRING,
+            .help = "ID of secret providing the password",
+        },
         { /* end of list */ }
     },
 };
@@ -436,6 +471,7 @@ static int qemu_rbd_open(BlockDriverState *bs, QDict *options, int flags,
     char conf[RBD_MAX_CONF_SIZE];
     char clientname_buf[RBD_MAX_CONF_SIZE];
     char *clientname;
+    const char *secretid;
     QemuOpts *opts;
     Error *local_err = NULL;
     const char *filename;
@@ -450,6 +486,7 @@ static int qemu_rbd_open(BlockDriverState *bs, QDict *options, int flags,
     }
 
     filename = qemu_opt_get(opts, "filename");
+    secretid = qemu_opt_get(opts, "password-secret");
 
     if (qemu_rbd_parsename(filename, pool, sizeof(pool),
                            snap_buf, sizeof(snap_buf),
@@ -488,6 +525,11 @@ static int qemu_rbd_open(BlockDriverState *bs, QDict *options, int flags,
         }
     }
 
+    if (qemu_rbd_set_auth(s->cluster, secretid, errp) < 0) {
+        r = -EIO;
+        goto failed_shutdown;
+    }
+
     /*
      * Fallback to more conservative semantics if setting cache
      * options fails. Ignore errors from setting rbd_cache because the
@@ -919,6 +961,11 @@ static QemuOptsList qemu_rbd_create_opts = {
             .type = QEMU_OPT_SIZE,
             .help = "RBD object size"
         },
+        {
+            .name = "password-secret",
+            .type = QEMU_OPT_STRING,
+            .help = "ID of secret providing the password",
+        },
         { /* end of list */ }
     }
 };