repart: derive verity salt and uuid from seed

diff --git a/src/partition/repart.c b/src/partition/repart.c
index 829d80ddf0de6c48d8f06ad2015721fc4eb86a4a..c87f42346dbb1cc6826edae4175fe0b90ba67c88 100644 (file)
--- a/src/partition/repart.c
+++ b/src/partition/repart.c
@@ -207,7 +207,8 @@ typedef struct Partition {
         sd_id128_t current_uuid, new_uuid;
         bool new_uuid_is_set;
         char *current_label, *new_label;
-        sd_id128_t fs_uuid, luks_uuid;
+        sd_id128_t fs_uuid, luks_uuid, verity_uuid;
+        uint8_t verity_salt[SHA256_DIGEST_SIZE];
 
         bool dropped;
         bool factory_reset;
@@ -2188,6 +2189,12 @@ static int derive_uuid(sd_id128_t base, const char *token, sd_id128_t *ret) {
         return 0;
 }
 
+static void derive_salt(sd_id128_t base, const char *token, uint8_t ret[static SHA256_DIGEST_SIZE]) {
+        assert(token);
+
+        hmac_sha256(base.bytes, sizeof(base.bytes), token, strlen(token), ret);
+}
+
 static int context_load_partition_table(Context *context) {
         _cleanup_(fdisk_unref_contextp) struct fdisk_context *c = NULL;
         _cleanup_(fdisk_unref_tablep) struct fdisk_table *t = NULL;
@@ -3900,7 +3907,7 @@ static int partition_format_verity_hash(
         cryptsetup_enable_logging(cd);
 
         r = sym_crypt_format(
-                        cd, CRYPT_VERITY, NULL, NULL, NULL, NULL, 0,
+                        cd, CRYPT_VERITY, NULL, NULL, SD_ID128_TO_UUID_STRING(p->verity_uuid), NULL, 0,
                         &(struct crypt_params_verity){
                                 .data_device = data_node,
                                 .flags = CRYPT_VERITY_CREATE_HASH,
@@ -3908,7 +3915,8 @@ static int partition_format_verity_hash(
                                 .hash_type = 1,
                                 .data_block_size = context->sector_size,
                                 .hash_block_size = context->sector_size,
-                                .salt_size = 32,
+                                .salt_size = sizeof(p->verity_salt),
+                                .salt = (const char*)p->verity_salt,
                         });
         if (r < 0) {
                 /* libcryptsetup reports non-descriptive EIO errors for every I/O failure. Luckily, it
@@ -4870,6 +4878,15 @@ static int context_acquire_partition_uuids_and_labels(Context *context) {
                                 return r;
                 }
 
+                /* Derive the verity salt and verity superblock UUID from the seed to keep them reproducible */
+                if (p->verity == VERITY_HASH) {
+                        derive_salt(context->seed, "verity-salt", p->verity_salt);
+
+                        r = derive_uuid(context->seed, "verity-uuid", &p->verity_uuid);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to acquire verity uuid: %m");
+                }
+
                 if (!isempty(p->current_label)) {
                         /* never change initialized labels */
                         r = free_and_strdup_warn(&p->new_label, p->current_label);