Re: [U-Boot] [RFC PATCH] cmd: avb: Support A/B slots

Hi Sam,

Sorry for the late reply,

On Fri, Aug 2, 2019 at 9:57 PM Sam Protsenko semen.protsenko@linaro.org wrote:

Hi Igor, Jens,

Can you please comments on next topics:

1. With enabled A/B partitions, we have boot_a/boot_b, system_a/system_b, vendor_a/vendor_b partitions. Therefore requested_partitions[] should be slotted (which is done in this RFC patch). But this patch doesn' handle item (2) below.
2. With dynamic partitions enabled, we don't have system/vendor anymore; instead we have single "super" partitions. Therefore requested_partitions[] table contains wrong partitions list for that particular case.

This case can be handled in the latest libavb by 49936b4c010(libavb: Support vbmeta blobs in beginning of partition) [1]. Anyway, this will require to pull the latest libavb sources into U-boot.

Question: can we allow user to select which partition to verify, instead of trying to verify hard-coded partitions from requested_partitions[] table? This would solve both (1) and (2) items. But I'm not sure about next possible issues: a. Wouldn't it break chain of trust somehow?

It wont. If the user can obtain access to U-boot shell or edit U-boot env, the chain of trust is already broken (he can just wipe off `avb_verify` cmd invocation and that's it). But anyway, at first, check this solution [1].

b. Is it ok to run avb_slot_verify() several times (one time per one partition?

If (a) or (b) is of any concern, then maybe we can provide a way for the user to pass any number of arguments to 'avb verify', like this:

=> avb verify boot_a super_a dtbo_a

so help synopsis for 'avb verify' can be like this:

avb verify <partition> ...

What do you think about this? Which would be the best course of action to fix both issues (1) and (2)?

Thanks.

Signed-off-by: Sam Protsenko semen.protsenko@linaro.org

cmd/avb.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/cmd/avb.c b/cmd/avb.c index 3f6fd763a0..d1942d6605 100644 --- a/cmd/avb.c +++ b/cmd/avb.c @@ -235,6 +235,7 @@ int do_avb_verify_part(cmd_tbl_t *cmdtp, int flag, AvbSlotVerifyData *out_data; char *cmdline; char *extra_args;

•   char *slot_suffix = "";
  
    bool unlocked = false;
    int res = CMD_RET_FAILURE;
  

@@ -244,9 +245,12 @@ int do_avb_verify_part(cmd_tbl_t *cmdtp, int flag, return CMD_RET_FAILURE; }

•   if (argc != 1)
  

•   if (argc < 1 || argc > 2)
            return CMD_RET_USAGE;
  
  

•   if (argc == 2)
  

•           slot_suffix = argv[1];
  

•   printf("## Android Verified Boot 2.0 version %s\n",
           avb_version_string());
  
  

@@ -259,7 +263,7 @@ int do_avb_verify_part(cmd_tbl_t *cmdtp, int flag, slot_result = avb_slot_verify(avb_ops, requested_partitions,

•                           "",
  

•                           slot_suffix,
                            unlocked,
                            AVB_HASHTREE_ERROR_MODE_RESTART_AND_INVALIDATE,
                            &out_data);
  

@@ -419,7 +423,7 @@ static cmd_tbl_t cmd_avb[] = { U_BOOT_CMD_MKENT(read_part, 5, 0, do_avb_read_part, "", ""), U_BOOT_CMD_MKENT(read_part_hex, 4, 0, do_avb_read_part_hex, "", ""), U_BOOT_CMD_MKENT(write_part, 5, 0, do_avb_write_part, "", ""),

•   U_BOOT_CMD_MKENT(verify, 1, 0, do_avb_verify_part, "", ""),
  

•   U_BOOT_CMD_MKENT(verify, 2, 0, do_avb_verify_part, "", ""),
  

#ifdef CONFIG_OPTEE_TA_AVB U_BOOT_CMD_MKENT(read_pvalue, 3, 0, do_avb_read_pvalue, "", ""), U_BOOT_CMD_MKENT(write_pvalue, 3, 0, do_avb_write_pvalue, "", ""), @@ -462,6 +466,7 @@ U_BOOT_CMD( "avb read_pvalue <name> <bytes> - read a persistent value <name>\n" "avb write_pvalue <name> <value> - write a persistent value <name>\n" #endif

•   "avb verify - run verification process using hash data\n"
  

•   "avb verify [slot_suffix] - run verification process using hash data\n"
    "    from vbmeta structure\n"
  

•   "    [slot_suffix] - _a, _b, etc (if vbmeta partition is slotted)\n"
    );
  

-- 2.20.1

Thanks

[1] https://android.googlesource.com/platform/external/avb/+/49936b4c0109411fdd3...