Android系统替换证书

证书说明README

build/target/product/security/README

For detailed information on key types and image signing, please see:

https://source.android.com/devices/tech/ota/sign_builds.html

The test keys in this directory are used in development only and should
NEVER be used to sign packages in publicly released images (as that would
open a major security hole).

key generation
--------------

The following commands were used to generate the test key pairs:

  development/tools/make_key testkey  '/C=US/ST=California/L=Mountain View/O=Android/OU=Android/CN=Android/emailAddress=android@android.com'
  development/tools/make_key platform '/C=US/ST=California/L=Mountain View/O=Android/OU=Android/CN=Android/emailAddress=android@android.com'
  development/tools/make_key shared   '/C=US/ST=California/L=Mountain View/O=Android/OU=Android/CN=Android/emailAddress=android@android.com'
  development/tools/make_key media    '/C=US/ST=California/L=Mountain View/O=Android/OU=Android/CN=Android/emailAddress=android@android.com'

signing using the openssl commandline (for boot/system images)
--------------------------------------------------------------

1. convert pk8 format key to pem format
   % openssl pkcs8 -inform DER -nocrypt -in testkey.pk8 -out testkey.pem

2. create a signature using the pem format key
   % openssl dgst -binary -sha1 -sign testkey.pem FILE > FILE.sig

extracting public keys for embedding
------------------------------------

dumpkey.jar is a Java tool that takes an x.509 certificate in PEM format as
input and prints a C structure to standard output:

    $ java -jar out/host/linux-x86/framework/dumpkey.jar build/target/product/security/testkey.x509.pem
    {64,0xc926ad21,{1795090719,2141396315,950055447,2581568430,4268923165,1920809988,546586521,3498997798,1776797858,3740060814,1805317999,1429410244,129622599,1422441418,1783893377,1222374759,2563319927,323993566,28517732,609753416,1826472888,215237850,4261642700,4049082591,3228462402,774857746,154822455,2497198897,2758199418,3019015328,2794777644,87251430,2534927978,120774784,571297800,3695899472,2479925187,3811625450,3401832990,2394869647,3267246207,950095497,555058928,414729973,1136544882,3044590084,465547824,4058146728,2731796054,1689838846,3890756939,1048029507,895090649,247140249,178744550,3547885223,3165179243,109881576,3944604415,1044303212,3772373029,2985150306,3737520932,3599964420},{3437017481,3784475129,2800224972,3086222688,251333580,2131931323,512774938,325948880,2657486437,2102694287,3820568226,792812816,1026422502,2053275343,2800889200,3113586810,165549746,4273519969,4065247892,1902789247,772932719,3941848426,3652744109,216871947,3164400649,1942378755,3996765851,1055777370,964047799,629391717,2232744317,3910558992,191868569,2758883837,3682816752,2997714732,2702529250,3570700455,3776873832,3924067546,3555689545,2758825434,1323144535,61311905,1997411085,376844204,213777604,4077323584,9135381,1625809335,2804742137,2952293945,1117190829,4237312782,1825108855,3013147971,1111251351,2568837572,1684324211,2520978805,367251975,810756730,2353784344,1175080310}}

This is called by build/make/core/Makefile to incorporate the OTA signing keys
into the recovery image.

在BoradConfig中定义参数
device/qcom/msm8937_32/BoardConfig.mk

BOARD_PROPERTY_OVERRIDES_SPLIT_ENABLED := true

替换原生证书 将里面build/target/product/security

#生成证书
subject='/C=US/ST=California/L=Mountain View/O=Android/OU=Android/CN=Android/emailAddress=android@android.com'
mkdir ~/.android-certs
for x in releasekey platform shared media networkstack; do \
    ./development/tools/make_key ~/.android-certs/$x "$subject"; \
  done

系统默认key配置
build/make/core/Makefile

# The "test-keys" tag marks builds signed with the old test keys,
# which are available in the SDK.  "dev-keys" marks builds signed with
# non-default dev keys (usually private keys from a vendor directory).
# Both of these tags will be removed and replaced with "release-keys"
# when the target-files is signed in a post-build step.
ifeq ($(DEFAULT_SYSTEM_DEV_CERTIFICATE),build/target/product/security/testkey)
BUILD_KEYS := test-keys
else
	BUILD_KEYS := release-keys
endif

Makefile 里面定义otacerts 证书，校验升级包是否正确

# -----------------------------------------------------------------
# Build a keystore with the authorized keys in it, used to verify the
# authenticity of downloaded OTA packages.
#
# This rule adds to ALL_DEFAULT_INSTALLED_MODULES, so it needs to come
# before the rules that use that variable to build the image.
ALL_DEFAULT_INSTALLED_MODULES += $(TARGET_OUT_ETC)/security/otacerts.zip
$(TARGET_OUT_ETC)/security/otacerts.zip: KEY_CERT_PAIR := $(DEFAULT_KEY_CERT_PAIR)
$(TARGET_OUT_ETC)/security/otacerts.zip: $(addsuffix .x509.pem,$(DEFAULT_KEY_CERT_PAIR)) | $(ZIPTIME)
	$(hide) rm -f $@
	$(hide) mkdir -p $(dir $@)
	$(hide) zip -qjX $@ $<
	$(remove-timestamps-from-package)

#ota包签名

# Keys authorized to sign OTA packages this build will accept.  The
# build always uses dev-keys for this; release packaging tools will
# substitute other keys for this one.
OTA_PUBLIC_KEYS := $(DEFAULT_SYSTEM_DEV_CERTIFICATE).x509.pem

# Generate a file containing the keys that will be read by the
# recovery binary.
RECOVERY_INSTALL_OTA_KEYS := \
	$(call intermediates-dir-for,PACKAGING,ota_keys)/keys
DUMPKEY_JAR := $(HOST_OUT_JAVA_LIBRARIES)/dumpkey.jar
$(RECOVERY_INSTALL_OTA_KEYS): PRIVATE_OTA_PUBLIC_KEYS := $(OTA_PUBLIC_KEYS)
$(RECOVERY_INSTALL_OTA_KEYS): extra_keys := $(patsubst %,%.x509.pem,$(PRODUCT_EXTRA_RECOVERY_KEYS))
$(RECOVERY_INSTALL_OTA_KEYS): $(OTA_PUBLIC_KEYS) $(DUMPKEY_JAR) $(extra_keys)
	@echo "DumpPublicKey: $@ <= $(PRIVATE_OTA_PUBLIC_KEYS) $(extra_keys)"
	@rm -rf $@
	@mkdir -p $(dir $@)
	$(JAVA) -jar $(DUMPKEY_JAR) $(PRIVATE_OTA_PUBLIC_KEYS) $(extra_keys) > $@

DEFAULT_SYSTEM_DEV_CERTIFICATE 赋值

build/make/core/config.mk

# The default key if not set as LOCAL_CERTIFICATE
ifdef PRODUCT_DEFAULT_DEV_CERTIFICATE
  DEFAULT_SYSTEM_DEV_CERTIFICATE := $(PRODUCT_DEFAULT_DEV_CERTIFICATE)
else
  DEFAULT_SYSTEM_DEV_CERTIFICATE := build/target/product/security/releasekey
endif

在API 28基础上修改selinux keys配置

system/sepolicy/private/keys.conf
system/sepolicy/prebuilts/api/28.0/private/keys.conf

查看apk证书
keytool -printcert -jarfile ***.apk