[Qemu-block] [PATCH 1/2] block: Add "json-file:" pseudo protocol

[Fam Zheng]

When opening the image, "json-file:/path/to/json/file" has the same as
"json-file:$(cat /path/to/json/file)". The advantage is that sensitive
information that would be exposed in /proc/$PID/cmdline or log files,
is no longer visible this way.

Signed-off-by: Fam Zheng <address@hidden>
---
 block.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 52 insertions(+), 6 deletions(-)

diff --git a/block.c b/block.c
index e9f40dc..785f317 100644
--- a/block.c
+++ b/block.c
@@ -962,10 +962,6 @@ static QDict *parse_json_filename(const char *filename, 
Error **errp)
 {
     QObject *options_obj;
     QDict *options;
-    int ret;
-
-    ret = strstart(filename, "json:", &filename);
-    assert(ret);
 
     options_obj = qobject_from_json(filename);
     if (!options_obj) {
@@ -985,6 +981,36 @@ static QDict *parse_json_filename(const char *filename, 
Error **errp)
     return options;
 }
 
+static char *read_json_file(const char *filename, Error **errp)
+{
+    BlockDriverState *file = NULL;
+    QDict *options;
+    int r;
+    int64_t sectors;
+    char *buf;
+
+    options = qdict_new();
+    qdict_put(options, "driver",
+              qstring_from_str("raw"));
+    r = bdrv_open(&file, filename, NULL, options, 0, errp);
+    if (r) {
+        return NULL;
+    }
+    sectors = DIV_ROUND_UP(bdrv_getlength(file), BDRV_SECTOR_SIZE);
+    if (sectors > (1024 * 1024 / BDRV_SECTOR_SIZE)) {
+        error_setg(errp, "JSON file is too large");
+        return NULL;
+    }
+    buf = g_malloc0(sectors << BDRV_SECTOR_BITS);
+    r = bdrv_read(file, 0, (uint8_t *)buf, sectors);
+    if (r) {
+        error_setg(errp, "Failed to read JSON file");
+        g_free(buf);
+        return NULL;
+    }
+    return buf;
+}
+
 /*
  * Fills in default options for opening images and converts the legacy
  * filename/flags pair to option QDict entries.
@@ -1002,8 +1028,28 @@ static int bdrv_fill_options(QDict **options, const char 
**pfilename,
     Error *local_err = NULL;
 
     /* Parse json: pseudo-protocol */
-    if (filename && g_str_has_prefix(filename, "json:")) {
-        QDict *json_options = parse_json_filename(filename, &local_err);
+    if (filename &&
+        (g_str_has_prefix(filename, "json:") ||
+         g_str_has_prefix(filename, "json-file:"))) {
+        char *json_str;
+        QDict *json_options;
+        int ret;
+
+        if (g_str_has_prefix(filename, "json-file:")) {
+            strstart(filename, "json-file:", &filename);
+            json_str = read_json_file(filename, &local_err);
+            if (local_err) {
+                error_propagate(errp, local_err);
+                return -EIO;
+            }
+        } else {
+            ret = strstart(filename, "json:", &filename);
+            assert(ret);
+
+            json_str = g_strdup(filename);
+        }
+        json_options = parse_json_filename(json_str, &local_err);
+        g_free(json_str);
         if (local_err) {
             error_propagate(errp, local_err);
             return -EINVAL;
-- 
2.4.3