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Commit df6a780e authored by Chin-Ting Kuo's avatar Chin-Ting Kuo Committed by Bowgo Tsai
Browse files

Allow --disable-verification when top-level vbmeta is in 'boot' 

If top-level vbmeta struct is in 'boot' partition,
the "flags" element offset of top-level vbmeta header
from the beginning of boot partition is 123 plus
top-level vbmeta offset recorded in the boot image footer.

Bug: 139639521
Test: m fastboot
Test: fastboot --disable-verification flashall
Test: fastboot --disable-verification flash boot boot.img, checks the
      flag isn't changed if the device has vbmeta partition
Test: fastboot --disable-verification flash vbmeta vbmeta.img
Change-Id: Ibf73c9330639e971ee3873ac19f072cf7baed55b
parent cb2598e4

fastboot/Android.bp

+5 −1
Original line number Diff line number Diff line
@@ -189,7 +189,11 @@ cc_defaults { 
    // will violate ODR.

    shared_libs: [],



    header_libs: ["bootimg_headers"],

    header_libs: [

        "avb_headers",

        "bootimg_headers",

    ],



    static_libs: [

        "libziparchive",

        "libsparse",

fastboot/fastboot.cpp

+38 −8
Original line number Diff line number Diff line
@@ -51,6 +51,7 @@ 
#include <utility>

#include <vector>



#include <android-base/endian.h>

#include <android-base/file.h>

#include <android-base/macros.h>

#include <android-base/parseint.h>
@@ -59,6 +60,7 @@ 
#include <android-base/strings.h>

#include <android-base/unique_fd.h>

#include <build/version.h>

#include <libavb/libavb.h>

#include <liblp/liblp.h>

#include <platform_tools_version.h>

#include <sparse/sparse.h>
@@ -919,33 +921,50 @@ static bool load_buf(const char* fname, struct fastboot_buffer* buf) { 
    return load_buf_fd(fd.release(), buf);

}



static void rewrite_vbmeta_buffer(struct fastboot_buffer* buf) {

static void rewrite_vbmeta_buffer(struct fastboot_buffer* buf, bool vbmeta_in_boot) {

    // Buffer needs to be at least the size of the VBMeta struct which

    // is 256 bytes.

    if (buf->sz < 256) {

        return;

    }



    int fd = make_temporary_fd("vbmeta rewriting");



    std::string data;

    if (!android::base::ReadFdToString(buf->fd, &data)) {

        die("Failed reading from vbmeta");

    }



    uint64_t vbmeta_offset = 0;

    if (vbmeta_in_boot) {

        // Tries to locate top-level vbmeta from boot.img footer.

        uint64_t footer_offset = buf->sz - AVB_FOOTER_SIZE;

        if (0 != data.compare(footer_offset, AVB_FOOTER_MAGIC_LEN, AVB_FOOTER_MAGIC)) {

            die("Failed to find AVB_FOOTER at offset: %" PRId64, footer_offset);

        }

        const AvbFooter* footer = reinterpret_cast<const AvbFooter*>(data.c_str() + footer_offset);

        vbmeta_offset = be64toh(footer->vbmeta_offset);

    }

    // Ensures there is AVB_MAGIC at vbmeta_offset.

    if (0 != data.compare(vbmeta_offset, AVB_MAGIC_LEN, AVB_MAGIC)) {

        die("Failed to find AVB_MAGIC at offset: %" PRId64, vbmeta_offset);

    }



    fprintf(stderr, "Rewriting vbmeta struct at offset: %" PRId64 "\n", vbmeta_offset);



    // There's a 32-bit big endian |flags| field at offset 120 where

    // bit 0 corresponds to disable-verity and bit 1 corresponds to

    // disable-verification.

    //

    // See external/avb/libavb/avb_vbmeta_image.h for the layout of

    // the VBMeta struct.

    uint64_t flags_offset = 123 + vbmeta_offset;

    if (g_disable_verity) {

        data[123] |= 0x01;

        data[flags_offset] |= 0x01;

    }

    if (g_disable_verification) {

        data[123] |= 0x02;

        data[flags_offset] |= 0x02;

    }



    int fd = make_temporary_fd("vbmeta rewriting");

    if (!android::base::WriteStringToFd(data, fd)) {

        die("Failed writing to modified vbmeta");

    }
@@ -954,14 +973,25 @@ static void rewrite_vbmeta_buffer(struct fastboot_buffer* buf) { 
    lseek(fd, 0, SEEK_SET);

}



static bool has_vbmeta_partition() {

    std::string partition_type;

    return fb->GetVar("partition-type:vbmeta", &partition_type) == fastboot::SUCCESS ||

           fb->GetVar("partition-type:vbmeta_a", &partition_type) == fastboot::SUCCESS ||

           fb->GetVar("partition-type:vbmeta_b", &partition_type) == fastboot::SUCCESS;

}



static void flash_buf(const std::string& partition, struct fastboot_buffer *buf)

{

    sparse_file** s;



    // Rewrite vbmeta if that's what we're flashing and modification has been requested.

    if ((g_disable_verity || g_disable_verification) &&

        (partition == "vbmeta" || partition == "vbmeta_a" || partition == "vbmeta_b")) {

        rewrite_vbmeta_buffer(buf);

    if (g_disable_verity || g_disable_verification) {

        if (partition == "vbmeta" || partition == "vbmeta_a" || partition == "vbmeta_b") {

            rewrite_vbmeta_buffer(buf, false /* vbmeta_in_boot */);

        } else if (!has_vbmeta_partition() &&

                   (partition == "boot" || partition == "boot_a" || partition == "boot_b")) {

            rewrite_vbmeta_buffer(buf, true /* vbmeta_in_boot */ );

        }

    }



    switch (buf->type) {