nspawn/dissect: automatically discover dm-verity verity partitions

This adds support for discovering and making use of properly tagged dm-verity
data integrity partitions. This extends both systemd-nspawn and systemd-dissect
with a new --root-hash= switch that takes the root hash to use for the root
partition, and is otherwise fully automatic.

Verity partitions are discovered automatically by GPT table type UUIDs, as
listed in
https://www.freedesktop.org/wiki/Specifications/DiscoverablePartitionsSpec/
(which I updated prior to this change, to include new UUIDs for this purpose.

mkosi with https://github.com/systemd/mkosi/pull/39 applied may generate images
that carry the necessary integrity data. With that PR and this commit, the
following simply lines suffice to boot up an integrity-protected container image:

```
 # mkdir test
 # cd test
 # mkosi --verity
 # systemd-nspawn -i ./image.raw -bn
```

Note that mkosi writes the image file to "image.raw" next to a a file
"image.roothash" that contains the root hash. systemd-nspawn will look for that
file and use it if it exists, in case --root-hash= is not specified explicitly.

1 files changed, 16 insertions, 4 deletions

diff --git a/src/shared/dissect-image.h b/src/shared/dissect-image.h
index 69484eb32c..902c8d4a37 100644
--- a/src/shared/dissect-image.h
+++ b/src/shared/dissect-image.h
@@ -45,10 +45,20 @@ enum  {
         PARTITION_SRV,
         PARTITION_ESP,
         PARTITION_SWAP,
+        PARTITION_ROOT_VERITY, /* verity data for the PARTITION_ROOT partition */
+        PARTITION_ROOT_SECONDARY_VERITY, /* verity data for the PARTITION_ROOT_SECONDARY partition */
         _PARTITION_DESIGNATOR_MAX,
         _PARTITION_DESIGNATOR_INVALID = -1
 };
 
+static inline int PARTITION_VERITY_OF(int p) {
+        if (p == PARTITION_ROOT)
+                return PARTITION_ROOT_VERITY;
+        if (p == PARTITION_ROOT_SECONDARY)
+                return PARTITION_ROOT_SECONDARY_VERITY;
+        return _PARTITION_DESIGNATOR_INVALID;
+}
+
 typedef enum DissectImageFlags {
         DISSECT_IMAGE_READ_ONLY = 1,
         DISSECT_IMAGE_DISCARD_ON_LOOP = 2,   /* Turn on "discard" if on loop device and file system supports it */
@@ -57,17 +67,19 @@ typedef enum DissectImageFlags {
 } DissectImageFlags;
 
 struct DissectedImage {
-        bool encrypted;
+        bool encrypted:1;
+        bool verity:1;     /* verity available and usable */
+        bool can_verity:1; /* verity available, but not necessarily used */
         DissectedPartition partitions[_PARTITION_DESIGNATOR_MAX];
 };
 
-int dissect_image(int fd, DissectedImage **ret);
+int dissect_image(int fd, const void *root_hash, size_t root_hash_size, DissectedImage **ret);
 
 DissectedImage* dissected_image_unref(DissectedImage *m);
 DEFINE_TRIVIAL_CLEANUP_FUNC(DissectedImage*, dissected_image_unref);
 
-int dissected_image_decrypt(DissectedImage *m, const char *passphrase, DissectImageFlags flags, DecryptedImage **ret);
-int dissected_image_decrypt_interactively(DissectedImage *m, const char *passphrase, DissectImageFlags flags, DecryptedImage **ret);
+int dissected_image_decrypt(DissectedImage *m, const char *passphrase, const void *root_hash, size_t root_hash_size, DissectImageFlags flags, DecryptedImage **ret);
+int dissected_image_decrypt_interactively(DissectedImage *m, const char *passphrase, const void *root_hash, size_t root_hash_size, DissectImageFlags flags, DecryptedImage **ret);
 int dissected_image_mount(DissectedImage *m, const char *dest, DissectImageFlags flags);
 
 DecryptedImage* decrypted_image_unref(DecryptedImage *p);