[PATCH v2 2/2] bootstd: android: Allow boot with AVB failures when unlocked

[Mattijs Korpershoek]

When the bootloader is UNLOCKED, it should be possible to boot Android
even if AVB reports verification errors [1].

This allows developers to flash modified partitions on
userdebug/engineering builds.

Developers can do so on unlocked devices with:
$ fastboot flash --disable-verity --disable-verification vbmeta vbmeta.img

In such case, bootmeth_android refuses to boot.

Allow the boot to continue when the device is UNLOCKED and AVB reports
verification errors.

[1] https://source.android.com/docs/security/features/verifiedboot/boot-flow#unlocked-devices
Fixes: 125d9f3306ea ("bootstd: Add a bootmeth for Android")
Signed-off-by: Mattijs Korpershoek <mkorpershoek at baylibre.com>
---
 boot/bootmeth_android.c | 37 ++++++++++++++++++++++++-------------
 1 file changed, 24 insertions(+), 13 deletions(-)

diff --git a/boot/bootmeth_android.c b/boot/bootmeth_android.c
index 2cd167f80280801618a317a65e93a10e70a0d9ee..dc9aad1633bb7a6d577013bfa0f939343f2e066b 100644
--- a/boot/bootmeth_android.c
+++ b/boot/bootmeth_android.c
@@ -407,17 +407,26 @@ static int run_avb_verification(struct bootflow *bflow)
 				 AVB_HASHTREE_ERROR_MODE_RESTART_AND_INVALIDATE,
 				 &out_data);
 
-	if (result != AVB_SLOT_VERIFY_RESULT_OK) {
-		printf("Verification failed, reason: %s\n",
-		       str_avb_slot_error(result));
-		avb_slot_verify_data_free(out_data);
-		return log_msg_ret("avb verify", -EIO);
-	}
-
-	if (unlocked)
-		boot_state = AVB_ORANGE;
-	else
+	if (!unlocked) {
+		/* When device is locked, we only accept AVB_SLOT_VERIFY_RESULT_OK */
+		if (result != AVB_SLOT_VERIFY_RESULT_OK) {
+			printf("Verification failed, reason: %s\n",
+			       str_avb_slot_error(result));
+			avb_slot_verify_data_free(out_data);
+			return log_msg_ret("avb verify", -EIO);
+		}
 		boot_state = AVB_GREEN;
+	} else {
+		/* When device is unlocked, we also accept verification errors */
+		if (result != AVB_SLOT_VERIFY_RESULT_OK &&
+		    result != AVB_SLOT_VERIFY_RESULT_ERROR_VERIFICATION) {
+			printf("Unlocked verification failed, reason: %s\n",
+			       str_avb_slot_error(result));
+			avb_slot_verify_data_free(out_data);
+			return log_msg_ret("avb verify unlocked", -EIO);
+		}
+		boot_state = AVB_ORANGE;
+	}
 
 	extra_args = avb_set_state(avb_ops, boot_state);
 	if (extra_args) {
@@ -427,9 +436,11 @@ static int run_avb_verification(struct bootflow *bflow)
 			goto free_out_data;
 	}
 
-	ret = avb_append_commandline(bflow, out_data->cmdline);
-	if (ret < 0)
-		goto free_out_data;
+	if (result == AVB_SLOT_VERIFY_RESULT_OK) {
+		ret = avb_append_commandline(bflow, out_data->cmdline);
+		if (ret < 0)
+			goto free_out_data;
+	}
 
 	return 0;
 

-- 
2.47.1