Improve convert and dd commands

Update to

v1: https://lists.gnu.org/archive/html/qemu-devel/2017-01/msg05699.html
v2: https://lists.gnu.org/archive/html/qemu-devel/2017-02/msg00728.html
v3: https://lists.gnu.org/archive/html/qemu-devel/2017-02/msg04391.html
v4: https://lists.gnu.org/archive/html/qemu-devel/2017-04/msg02153.html
v5: https://lists.gnu.org/archive/html/qemu-devel/2017-04/msg04109.html
v6: https://lists.gnu.org/archive/html/qemu-devel/2017-05/msg00215.html

This series is in response to Max pointing out that you cannot use 'convert' for an encrypted target image.

The 'convert' and 'dd' commands need to first create the image and then open it. The bdrv_create() method takes a set of options for creating the image, which let us provide a key-secret for the encryption key. When the commands then open the new image, they don't provide any options, so the image is unable to be opened due to lack of encryption key. It is also not possible to use the --image-opts argument to provide structured options in the target image name - it must be a plain filename to satisfy the bdrv_create() API contract.

This series addresses these problems to some extent

- Adds a new --target-image-opts flag which is used to say that the target filename is using structured options. It is *only* permitted to use this when -n is also set. ie the target image must be pre-created so convert/dd don't need to run bdrv_create().

- When --target-image-opts is not used, add special case code that identifies options passed to bdrv_create() named "*key-secret" and adds them to the options used to open the new image

In future it is desirable to make --target-image-opts work even when -n is *not* given. This requires considerable work to create a new bdrv_create() API impl.

The first patch fixes a bug in the 'dd' command while the second adds support for the missing '--object' arg to 'dd', allowing it to reference secrets when opening files. The last two patches implement the new features described above for the 'convert' command.

NB, this is now rebased against the block-next branch from

git://github.com/XanClic/qemu.git

Changed in v7:

- Drop the (accidentally included) revert patch (Eric)

Changed in v6:

- Fix misc typos (Fam)
- Resolve messy conflicts wrt max/block-next (Max)

Changed in v5:

- Fix return value (Max)
- Misc doc changes (Max)
- Use error_abort (Max)

Changed in v4:

- Refactor img_open_new_file in terms of img_open_file (Kevin)

Changed in v3:

- Drop all patches affecting the 'dd' command except for the clear bug fix and the --object support. They can be re-considered once dd is rewritten to run ontop of convert.
- Use consistent return/goto style in dd command (Max)
- Fix error reporting when using compressed image and skip-create (Max)
- Unconditionally create QDict when open files (Max)

Changed in v2:

- Replace dd -n flag with support for conv=nocreat,notrunc
- Misc typos (Eric, Fam)

Daniel P. Berrange (4):
qemu-img: add support for --object with 'dd' command
qemu-img: fix --image-opts usage with dd command
qemu-img: introduce --target-image-opts for 'convert' command
qemu-img: copy *key-secret opts when opening newly created files

 qemu-img-cmds.hx |   4 +-
 qemu-img.c       | 139 ++++++++++++++++++++++++++++++++++++++++++-------------
 qemu-img.texi    |  12 ++++-
 3 files changed, 120 insertions(+), 35 deletions(-)

2.9.3

The qemu-img dd command added --image-opts support, but missed the corresponding --object support. This prevented passing secrets (eg auth passwords) needed by certain disk images.

---
 qemu-img.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

index c719636..34f49c2 100644
@@ -4086,6 +4086,7 @@ static int img_dd(int argc, char **argv)
     };
     const struct option long_options[] = {
         { "help", no_argument, 0, 'h'},
+        { "object", required_argument, 0, OPTION_OBJECT},
         { "image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
         { 0, 0, 0, 0 }
     };

@@ -4110,6 +4111,15 @@ static int img_dd(int argc, char **argv)
         case 'h':
             help();
             break;
+        case OPTION_OBJECT: {
+            QemuOpts *opts;
+            opts = qemu_opts_parse_noisily(&qemu_object_opts,
+                                           optarg, true);
+            if (!opts) {
+                ret = -1;
+                goto out;
+            }
+        }   break;
         case OPTION_IMAGE_OPTS:
             image_opts = true;
             break;

@@ -4154,6 +4164,14 @@ static int img_dd(int argc, char **argv)
         ret = -1;
         goto out;
     }
+
+    if (qemu_opts_foreach(&qemu_object_opts,
+                          user_creatable_add_opts_foreach,
+                          NULL, NULL)) {
+        ret = -1;
+        goto out;
+    }
+
     blk1 = img_open(image_opts, in.filename, fmt, 0, false, false);
 
     if (!blk1) {

2.9.3

The --image-opts flag can only be used to affect the parsing of the source image. The target image has to be specified in the traditional style regardless, since it needs to be passed to the bdrv_create() API which does not support the new style opts.

---
 qemu-img.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

index 34f49c2..d8fdcb1 100644
@@ -4239,8 +4239,13 @@ static int img_dd(int argc, char **argv)
         goto out;
     }
 
-    blk2 = img_open(image_opts, out.filename, out_fmt, BDRV_O_RDWR,
-                    false, false);
+    /* TODO, we can't honour --image-opts for the target,
+     * since it needs to be given in a format compatible
+     * with the bdrv_create() call above which does not
+     * support image-opts style.
+     */
+    blk2 = img_open_file(out.filename, out_fmt, BDRV_O_RDWR,
+                         false, false);
 
     if (!blk2) {
         ret = -1;

2.9.3

The '--image-opts' flag indicates whether the source filename includes options. The target filename has to remain in the plain filename format though, since it needs to be passed to bdrv_create(). When using --skip-create though, it would be possible to use image-opts syntax. This adds --target-image-opts to indicate that the target filename includes options. Currently this mandates use of the --skip-create flag too.

---
 qemu-img-cmds.hx |  4 +--
 qemu-img.c       | 77 +++++++++++++++++++++++++++++++++++++-------------------
 qemu-img.texi    | 12 +++++++--
 3 files changed, 63 insertions(+), 30 deletions(-)

index bf4ce59..c97572e 100644
@@ -40,9 +40,9 @@ STEXI
 ETEXI
 
 DEF("convert", img_convert,
-    "convert [--object objectdef] [--image-opts] [-c] [-p] [-q] [-n] [-f fmt] [-t cache] [-T src_cache] [-O output_fmt] [-B backing_file] [-o options] [-s snapshot_id_or_name] [-l snapshot_param] [-S sparse_size] [-m num_coroutines] [-W] filename [filename2 [...]] output_filename")
+    "convert [--object objectdef] [--image-opts] [--target-image-opts] [-c] [-p] [-q] [-n] [-f fmt] [-t cache] [-T src_cache] [-O output_fmt] [-B backing_file] [-o options] [-s snapshot_id_or_name] [-l snapshot_param] [-S sparse_size] [-m num_coroutines] [-W] filename [filename2 [...]] output_filename")
 STEXI
-@item convert [--object @var{objectdef}] [--image-opts] [-c] [-p] [-q] [-n] [-f @var{fmt}] [-t @var{cache}] [-T @var{src_cache}] [-O @var{output_fmt}] [-B @var{backing_file}] [-o @var{options}] [-s @var{snapshot_id_or_name}] [-l @var{snapshot_param}] [-S @var{sparse_size}] [-m @var{num_coroutines}] [-W] @var{filename} [@var{filename2} [...]] @var{output_filename}
+@item convert [--object @var{objectdef}] [--image-opts] [--target-image-opts] [-c] [-p] [-q] [-n] [-f @var{fmt}] [-t @var{cache}] [-T @var{src_cache}] [-O @var{output_fmt}] [-B @var{backing_file}] [-o @var{options}] [-s @var{snapshot_id_or_name}] [-l @var{snapshot_param}] [-S @var{sparse_size}] [-m @var{num_coroutines}] [-W] @var{filename} [@var{filename2} [...]] @var{output_filename}
 ETEXI
 
 DEF("dd", img_dd,

index 50a2364..5b925ec 100644
@@ -45,9 +45,17 @@ keys.
 
 @item --image-opts
 
-Indicates that the @var{filename} parameter is to be interpreted as a
+Indicates that the source @var{filename} parameter is to be interpreted as a
 full option string, not a plain filename. This parameter is mutually
-exclusive with the @var{-f} and @var{-F} parameters.
+exclusive with the @var{-f} parameter.
+
+@item --target-image-opts
+
+Indicates that the @var{output_filename} parameter(s) are to be interpreted as
+a full option string, not a plain filename. This parameter is mutually
+exclusive with the @var{-O} parameters. It is currently required to also use
+the @var{-n} parameter to skip image creation. This restriction may be relaxed
+in a future release.
 
 @item fmt
 is the disk image format. It is guessed automatically in most cases. See below

2.9.3

Sure you want to keep this, considering that there are quite some changes since v5?

[...]

[...]

[...]

This change was just automatic reindent by the editor, I'll put it back to 5.

Yes

That's a rebase / conflict resolution mistake

Regards,
Daniel

|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|

The qemu-img dd/convert commands will create an image file and then try to open it. Historically it has been possible to open new files without passing any options. With encrypted files though, the *key-secret options are mandatory, so we need to provide those options when opening the newly created file.

---
 qemu-img.c | 41 +++++++++++++++++++++++++++++++++++------
 1 file changed, 35 insertions(+), 6 deletions(-)

index 94c8cea..cbf05b4 100644
@@ -305,15 +305,17 @@ static BlockBackend *img_open_opts(const char *optstr,
 }
 
 static BlockBackend *img_open_file(const char *filename,
+                                   QDict *options,
                                    const char *fmt, int flags,
                                    bool writethrough, bool quiet)
 {
     BlockBackend *blk;
     Error *local_err = NULL;
-    QDict *options = NULL;
 
     if (fmt) {
-        options = qdict_new();
+        if (!options) {
+            options = qdict_new();
+        }
         qdict_put(options, "driver", qstring_from_str(fmt));
     }
 

@@ -332,6 +334,33 @@ static BlockBackend *img_open_file(const char *filename,
 }
 
 
+static int img_add_key_secrets(void *opaque,
+                               const char *name, const char *value,
+                               Error **errp)
+{
+    QDict *options = opaque;
+
+    if (g_str_has_suffix(name, "key-secret")) {
+        qdict_put(options, name, qstring_from_str(value));
+    }
+
+    return 0;
+}
+
+static BlockBackend *img_open_new_file(const char *filename,
+                                       QemuOpts *create_opts,
+                                       const char *fmt, int flags,
+                                       bool writethrough, bool quiet)
+{
+    QDict *options = NULL;
+
+    options = qdict_new();
+    qemu_opt_foreach(create_opts, img_add_key_secrets, options, &error_abort);
+
+    return img_open_file(filename, options, fmt, flags, writethrough, quiet);
+}
+
+
 static BlockBackend *img_open(bool image_opts,
                               const char *filename,
                               const char *fmt, int flags, bool writethrough,

@@ -351,7 +380,7 @@ static BlockBackend *img_open(bool image_opts,
         }
         blk = img_open_opts(filename, opts, flags, writethrough, quiet);
     } else {
-        blk = img_open_file(filename, fmt, flags, writethrough, quiet);
+        blk = img_open_file(filename, NULL, fmt, flags, writethrough, quiet);
     }
     return blk;
 }

@@ -2256,8 +2285,8 @@ static int img_convert(int argc, char **argv)
          * That has to wait for bdrv_create to be improved
          * to allow filenames in option syntax
          */
-        s.target = img_open_file(out_filename, out_fmt, flags,
-                                 writethrough, quiet);
+        s.target = img_open_new_file(out_filename, opts, out_fmt,
+                                     flags, writethrough, quiet);
     }
     if (!s.target) {
         ret = -1;

@@ -4269,7 +4298,7 @@ static int img_dd(int argc, char **argv)
      * with the bdrv_create() call above which does not
      * support image-opts style.
      */
-    blk2 = img_open_file(out.filename, out_fmt, BDRV_O_RDWR,
+    blk2 = img_open_file(out.filename, NULL, out_fmt, BDRV_O_RDWR,
                          false, false);
 
     if (!blk2) {

2.9.3