Add krun_add_disk2 API

Adds an enum that describes the supported disk image variants.

Adds the `krun_add_disk2` API that requires the user to specify the
format of the disk image they're providing.

The following formats are supported:
- KRUN_DISK_FORMAT_RAW
- KRUN_DISK_FORMAT_QCOW2

Signed-off-by: Jake Correnti <[email protected]>

Author: jakecorrenti

include/libkrun.h

@@ -95,16 +95,25 @@ int32_t krun_set_root_disk(uint32_t ctx_id, const char *disk_path);
 int32_t krun_set_data_disk(uint32_t ctx_id, const char *disk_path);
 
 /**
- * Adds a disk image to be used as a general partition for the microVM.
+ * Adds a disk image to be used as a general partition for the microVM. The only supported image
+ * format is "raw".
  *
  * This API is mutually exclusive with the deprecated krun_set_root_disk and
  * krun_set_data_disk methods and must not be used together.
  *
+ * SECURITY NOTE:
+ * Libkrun is not responsible for probing the disk image provided, as probing a disk image should
+ * be avoided. However, if one must probe the disk image, it falls onto the user. The disk image
+ * must only be probed once, and the probe of the image must be done before the first boot of the
+ * microVM.
+ *
+ * The disk image is assumed to be a Raw disk image, and trust is put into the user to
+ * correctly and securely probe the disk image, if at all.
+ *
  * Arguments:
  *  "ctx_id"    - the configuration context ID.
  *  "block_id"  - a null-terminated string representing the partition.
- *  "disk_path" - a null-terminated string representing the path leading to the disk image that
- *                contains the root file-system.
+ *  "disk_path" - a null-terminated string representing the path leading to the disk image.
  *  "read_only" - whether the mount should be read-only. Required if the caller does not have
  *                write permissions (for disk images in /usr/share).
  *
@@ -113,6 +122,49 @@ int32_t krun_set_data_disk(uint32_t ctx_id, const char *disk_path);
  */
 int32_t krun_add_disk(uint32_t ctx_id, const char *block_id, const char *disk_path, bool read_only);
 
+/* Supported disk image formats */
+#define KRUN_DISK_FORMAT_RAW 0
+#define KRUN_DISK_FORMAT_QCOW2 1
+/**
+ * Adds a disk image to be used as a general partition for the microVM. The supported
+ * image formats are: "raw" and "qcow2".
+ *
+ * This API is mutually exclusive with the deprecated krun_set_root_disk and
+ * krun_set_data_disk methods and must not be used together.
+ *
+ * SECURITY NOTE:
+ * Libkrun is not responsible for probing the disk image provided, as probing a disk image should
+ * be avoided. However, if one must probe the disk image, it falls onto the user. The disk image
+ * must only be probed once, and the probe of the image must be done before the first boot of the
+ * microVM. 
+ *
+ * The disk image may be in the Raw or Qcow2 format, but trust is put into the user to
+ * correctly and securely probe the disk image, if at all.
+ *
+ * It is possible for a Raw disk image to be probed, and have the guest write a Qcow2
+ * image header into the Raw file's first sector. If the disk image is then re-probed, and the
+ * user tells libkrun it is a Qcow2, then libkrun will boot the disk image as a Qcow2. Qcow2
+ * files can, and will, open other files. The guest will most likely have access to the data in those
+ * files, essentially giving the guest access to any file on the host system the disk emulation
+ * has access to.
+ *
+ * Arguments:
+ *  "ctx_id"      - the configuration context ID.
+ *  "block_id"    - a null-terminated string representing the partition.
+ *  "disk_path"   - a null-terminated string representing the path leading to the disk image.
+ *  "disk_format" - the disk image format (i.e. KRUN_DISK_FORMAT_{RAW, QCOW2})
+ *  "read_only"   - whether the mount should be read-only. Required if the caller does not have
+ *                  write permissions (for disk images in /usr/share).
+ *
+ * Returns:
+ *  Zero on success or a negative error number on failure.
+ */
+int32_t krun_add_disk2(uint32_t ctx_id,
+                       const char *block_id,
+                       const char *disk_path,
+                       uint32_t disk_format,
+                       bool read_only);
+
 /**
  * NO LONGER SUPPORTED. DO NOT USE.
  *

src/libkrun/src/lib.rs

@@ -534,6 +534,53 @@ pub unsafe extern "C" fn krun_add_disk(
     KRUN_SUCCESS
 }
 
+#[allow(clippy::missing_safety_doc)]
+#[no_mangle]
+#[cfg(feature = "blk")]
+pub unsafe extern "C" fn krun_add_disk2(
+    ctx_id: u32,
+    c_block_id: *const c_char,
+    c_disk_path: *const c_char,
+    disk_format: u32,
+    read_only: bool,
+) -> i32 {
+    let disk_path = match CStr::from_ptr(c_disk_path).to_str() {
+        Ok(disk) => disk,
+        Err(_) => return -libc::EINVAL,
+    };
+
+    let block_id = match CStr::from_ptr(c_block_id).to_str() {
+        Ok(block_id) => block_id,
+        Err(_) => return -libc::EINVAL,
+    };
+
+    let format = match disk_format {
+        0 => ImageType::Raw,
+        1 => ImageType::Qcow2,
+        _ => {
+            // Do not continue if the user cannot specify a valid disk format
+            return -libc::EINVAL;
+        }
+    };
+
+    match CTX_MAP.lock().unwrap().entry(ctx_id) {
+        Entry::Occupied(mut ctx_cfg) => {
+            let cfg = ctx_cfg.get_mut();
+            let block_device_config = BlockDeviceConfig {
+                block_id: block_id.to_string(),
+                cache_type: CacheType::Writeback,
+                disk_image_path: disk_path.to_string(),
+                disk_image_format: format,
+                is_disk_read_only: read_only,
+            };
+            cfg.add_block_cfg(block_device_config);
+        }
+        Entry::Vacant(_) => return -libc::ENOENT,
+    }
+
+    KRUN_SUCCESS
+}
+
 #[allow(clippy::missing_safety_doc)]
 #[no_mangle]
 #[cfg(feature = "blk")]