Dump the root digest of hashtree for dm-verity partitions
It's requested by the partner engineering team to uniquely
identify a partition.
Bug: 197973981
Test: boot the device and check props
Change-Id: I0f7aa34dd0087f0698fe90b9df6c0eae06fc4f5d
diff --git a/fs_mgr/fs_mgr.cpp b/fs_mgr/fs_mgr.cpp
index 5f15aad..002b302 100644
--- a/fs_mgr/fs_mgr.cpp
+++ b/fs_mgr/fs_mgr.cpp
@@ -2231,16 +2231,16 @@
return false;
}
-std::string fs_mgr_get_hashtree_algorithm(const android::fs_mgr::FstabEntry& entry) {
+std::optional<HashtreeInfo> fs_mgr_get_hashtree_info(const android::fs_mgr::FstabEntry& entry) {
if (!entry.fs_mgr_flags.verify && !entry.fs_mgr_flags.avb) {
- return "";
+ return {};
}
DeviceMapper& dm = DeviceMapper::Instance();
std::string device = GetVerityDeviceName(entry);
std::vector<DeviceMapper::TargetInfo> table;
if (dm.GetState(device) == DmDeviceState::INVALID || !dm.GetTableInfo(device, &table)) {
- return "";
+ return {};
}
for (const auto& target : table) {
if (strcmp(target.spec.target_type, "verity") != 0) {
@@ -2256,14 +2256,15 @@
std::vector<std::string> tokens = android::base::Split(target.data, " \t\r\n");
if (tokens[0] != "0" && tokens[0] != "1") {
LOG(WARNING) << "Unrecognized device mapper version in " << target.data;
- return "";
+ return {};
}
- // Hashtree algorithm is the 8th token in the output
- return android::base::Trim(tokens[7]);
+ // Hashtree algorithm & root digest are the 8th & 9th token in the output.
+ return HashtreeInfo{.algorithm = android::base::Trim(tokens[7]),
+ .root_digest = android::base::Trim(tokens[8])};
}
- return "";
+ return {};
}
bool fs_mgr_verity_is_check_at_most_once(const android::fs_mgr::FstabEntry& entry) {
diff --git a/fs_mgr/include/fs_mgr.h b/fs_mgr/include/fs_mgr.h
index 4d3ecc9..21c9989 100644
--- a/fs_mgr/include/fs_mgr.h
+++ b/fs_mgr/include/fs_mgr.h
@@ -22,6 +22,7 @@
#include <linux/dm-ioctl.h>
#include <functional>
+#include <optional>
#include <string>
#include <fstab/fstab.h>
@@ -68,6 +69,13 @@
bool userdata_mounted;
};
+struct HashtreeInfo {
+ // The hash algorithm used to build the merkle tree.
+ std::string algorithm;
+ // The root digest of the merkle tree.
+ std::string root_digest;
+};
+
// fs_mgr_mount_all() updates fstab entries that reference device-mapper.
// Returns a |MountAllResult|. The first element is one of the FS_MNG_MNTALL_* return codes
// defined above, and the second element tells whether this call to fs_mgr_mount_all was responsible
@@ -88,9 +96,9 @@
bool fs_mgr_load_verity_state(int* mode);
// Returns true if verity is enabled on this particular FstabEntry.
bool fs_mgr_is_verity_enabled(const android::fs_mgr::FstabEntry& entry);
-// Returns the hash algorithm used to build the hashtree of this particular FstabEntry. Returns an
-// empty string if the input isn't a dm-verity entry, or if there is an error.
-std::string fs_mgr_get_hashtree_algorithm(const android::fs_mgr::FstabEntry& entry);
+// Returns the verity hashtree information of this particular FstabEntry. Returns std::nullopt
+// if the input isn't a dm-verity entry, or if there is an error.
+std::optional<HashtreeInfo> fs_mgr_get_hashtree_info(const android::fs_mgr::FstabEntry& entry);
bool fs_mgr_swapon_all(const android::fs_mgr::Fstab& fstab);
bool fs_mgr_update_logical_partition(android::fs_mgr::FstabEntry* entry);
diff --git a/init/builtins.cpp b/init/builtins.cpp
index 7633d9c..994eed9 100644
--- a/init/builtins.cpp
+++ b/init/builtins.cpp
@@ -894,9 +894,11 @@
std::string partition = entry.mount_point == "/" ? "system" : Basename(entry.mount_point);
SetProperty("partition." + partition + ".verified", std::to_string(mode));
- std::string hash_alg = fs_mgr_get_hashtree_algorithm(entry);
- if (!hash_alg.empty()) {
- SetProperty("partition." + partition + ".verified.hash_alg", hash_alg);
+ auto hashtree_info = fs_mgr_get_hashtree_info(entry);
+ if (hashtree_info) {
+ SetProperty("partition." + partition + ".verified.hash_alg", hashtree_info->algorithm);
+ SetProperty("partition." + partition + ".verified.root_digest",
+ hashtree_info->root_digest);
}
}
