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dissect: optionally allow attaching images that do not qualify as DDIs with --attach

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It's nice to use --attach since it validates our images. So far, it
strictly insisted on checking that the image was a DDI however, which
limits its use for certain usecases.

Add "--relax" to address this limitation.
This commit is contained in:
Lennart Poettering
2026-09-22 16:04:26 +02:00
committed by Luca Boccassi
parent efa16c7f31
commit b0edc60661
4 changed files with 58 additions and 19 deletions
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src/dissect/dissect.c
+30 -17
View File
@@ -109,6 +109,7 @@ static RuntimeScope arg_runtime_scope = _RUNTIME_SCOPE_INVALID;
static bool arg_all = false;
static uid_t arg_uid_base = UID_INVALID;
static bool arg_quiet = false;
static bool arg_relax = false;
static ImageFilter *arg_image_filter = NULL;
static int arg_copy_ownership = -1;
@@ -355,6 +356,10 @@ static int parse_argv(int argc, char *argv[]) {
arg_loop_ref_auto = true;
break;
OPTION_LONG("relax", NULL, "Skip DDI validation, attach image as it is"):
arg_relax = true;
break;
OPTION_LONG("image-policy", "POLICY", "Specify image dissection policy"):
r = parse_image_policy_argument(opts.arg, &arg_image_policy);
if (r < 0)
@@ -707,6 +712,10 @@ static int parse_argv(int argc, char *argv[]) {
return r;
}
if (arg_relax && arg_action != ACTION_ATTACH)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
"The --relax switch is only supported in combination with --attach.");
SET_FLAG(arg_flags, DISSECT_IMAGE_ALLOW_INTERACTIVE_AUTH, isatty_safe(STDIN_FILENO));
return 1;
@@ -1809,19 +1818,16 @@ static int action_discover(void) {
return table_print_with_pager(t, arg_json_format_flags, arg_pager_flags, arg_legend);
}
static int action_attach(DissectedImage *m, LoopDevice *d) {
static int action_attach(LoopDevice *d) {
int r;
assert(m);
assert(d);
r = loop_device_set_autoclear(d, false);
if (r < 0)
return log_error_errno(r, "Failed to disable auto-clear logic on loopback device: %m");
r = dissected_image_relinquish(m);
if (r < 0)
return log_error_errno(r, "Failed to relinquish DM and loopback block devices: %m");
loop_device_relinquish(d);
if (!arg_quiet)
puts(d->node);
@@ -1997,7 +2003,7 @@ static int run(int argc, char *argv[]) {
;
}
if (arg_image) {
if (arg_image && !arg_relax) {
r = verity_settings_load(
&arg_verity_settings,
arg_image,
@@ -2053,19 +2059,26 @@ static int run(int argc, char *argv[]) {
log_warning_errno(r, "Failed to set loop reference string to '%s', ignoring: %m", arg_loop_ref);
}
r = dissect_loop_device_and_warn(
d,
&arg_verity_settings,
/* mount_options= */ NULL,
arg_image_policy,
arg_image_filter,
arg_flags,
&m);
if (r < 0)
return r;
/* Unless --relax is specified we insist that the image qualifies as DDI:
* dissecting it validates it against the image policy and waits until the
* kernel created the per-partition block devices, so that callers may
* access them immediately after we return. With --relax we skip dissection
* entirely, and attach the image as it is. */
if (!arg_relax) {
r = dissect_loop_device_and_warn(
d,
&arg_verity_settings,
/* mount_options= */ NULL,
arg_image_policy,
arg_image_filter,
arg_flags,
&m);
if (r < 0)
return r;
}
if (arg_action == ACTION_ATTACH)
return action_attach(m, d);
return action_attach(d);
r = dissected_image_load_verity_sig_partition(
m,