commit fecef364795d098383aaaec53f1149ceeef28a42
author Steve Muckle <smuckle@google.com> Tue May 12 16:21:41 2020 -0700
committer Steve Muckle <smuckle@google.com> Sun May 17 17:01:25 2020 -0700
tree 171be39f3b88b411434d34495368d8c4a7fb4a81
parent 9dc0bba136c0f4e7b243c0f721ad5cabf76972b3

fastbootd: copy AVB footer on boot image to end of block device

If the flashed boot image is smaller than the block device, the AVB
footer will not be at the end of the partition. Although images are
normally created to match the partition size the GKI boot.img must work
on all devices, and the size of the boot partition will vary.

Copy the AVB footer to the end of the partition before flashing, if it
is not there already.

Bug: 156036850
Change-Id: I11f0c7d32d1b6c74edd4f84f815d175605280cb8
Merged-In: I11f0c7d32d1b6c74edd4f84f815d175605280cb8

fastboot/Android.bp

diff --git a/fastboot/Android.bp b/fastboot/Android.bp
index 884856d..a7cde68 100644
--- a/fastboot/Android.bp
+++ b/fastboot/Android.bp
@@ -148,6 +148,7 @@
     ],
 
     header_libs: [
+        "avb_headers",
         "libsnapshot_headers",
     ]
 }

fastboot/device/flashing.cpp

diff --git a/fastboot/device/flashing.cpp b/fastboot/device/flashing.cpp
index 7e7e507..a5f1223 100644
--- a/fastboot/device/flashing.cpp
+++ b/fastboot/device/flashing.cpp
@@ -31,6 +31,7 @@
 #include <ext4_utils/ext4_utils.h>
 #include <fs_mgr_overlayfs.h>
 #include <fstab/fstab.h>
+#include <libavb/libavb.h>
 #include <liblp/builder.h>
 #include <liblp/liblp.h>
 #include <libsnapshot/snapshot.h>
@@ -122,6 +123,27 @@
     }
 }
 
+static void CopyAVBFooter(std::vector<char>* data, const uint64_t block_device_size) {
+    if (data->size() < AVB_FOOTER_SIZE) {
+        return;
+    }
+    std::string footer;
+    uint64_t footer_offset = data->size() - AVB_FOOTER_SIZE;
+    for (int idx = 0; idx < AVB_FOOTER_MAGIC_LEN; idx++) {
+        footer.push_back(data->at(footer_offset + idx));
+    }
+    if (0 != footer.compare(AVB_FOOTER_MAGIC)) {
+        return;
+    }
+
+    // copy AVB footer from end of data to end of block device
+    uint64_t original_data_size = data->size();
+    data->resize(block_device_size, 0);
+    for (int idx = 0; idx < AVB_FOOTER_SIZE; idx++) {
+        data->at(block_device_size - 1 - idx) = data->at(original_data_size - 1 - idx);
+    }
+}
+
 int Flash(FastbootDevice* device, const std::string& partition_name) {
     PartitionHandle handle;
     if (!OpenPartition(device, partition_name, &handle)) {
@@ -131,8 +153,14 @@
     std::vector<char> data = std::move(device->download_data());
     if (data.size() == 0) {
         return -EINVAL;
-    } else if (data.size() > get_block_device_size(handle.fd())) {
+    }
+    uint64_t block_device_size = get_block_device_size(handle.fd());
+    if (data.size() > block_device_size) {
         return -EOVERFLOW;
+    } else if (data.size() < block_device_size &&
+               (partition_name == "boot" || partition_name == "boot_a" ||
+                partition_name == "boot_b")) {
+        CopyAVBFooter(&data, block_device_size);
     }
     WipeOverlayfsForPartition(device, partition_name);
     return FlashBlockDevice(handle.fd(), data);