1 This directory contains the core Android SELinux policy configuration. 2 It defines the domains and types for the AOSP services and apps common to 3 all devices. Device-specific policy should be placed under a 4 separate device/<vendor>/<board>/sepolicy subdirectory and linked 5 into the policy build as described below. 6 7 Policy Generation: 8 9 Additional, per device, policy files can be added into the 10 policy build. These files should have each line including the 11 final line terminated by a newline character (0x0A). This 12 will allow files to be concatenated and processed whenever 13 the m4(1) macro processor is called by the build process. 14 Adding the newline will also make the intermediate text files 15 easier to read when debugging build failures. The sets of file, 16 service and property contexts files will automatically have a 17 newline inserted between each file as these are common failure 18 points. 19 20 These device policy files can be configured through the use of 21 the BOARD_SEPOLICY_DIRS variable. This variable should be set 22 in the BoardConfig.mk file in the device or vendor directories. 23 24 BOARD_SEPOLICY_DIRS contains a list of directories to search 25 for additional policy files. Order matters in this list. 26 For example, if you have 2 instances of widget.te files in the 27 BOARD_SEPOLICY_DIRS search path, then the first one found (at the 28 first search dir containing the file) will be concatenated first. 29 Reviewing out/target/product/<device>/etc/sepolicy_intermediates/policy.conf 30 will help sort out ordering issues. 31 32 Example BoardConfig.mk Usage: 33 From the Tuna device BoardConfig.mk, device/samsung/tuna/BoardConfig.mk 34 35 BOARD_SEPOLICY_DIRS += device/samsung/tuna/sepolicy 36 37 Additionally, OEMs can specify BOARD_SEPOLICY_M4DEFS to pass arbitrary m4 38 definitions during the build. A definition consists of a string in the form 39 of macro-name=value. Spaces must NOT be present. This is useful for building modular 40 policies, policy generation, conditional file paths, etc. It is supported in 41 the following file types: 42 * All *.te and SE Linux policy files as passed to checkpolicy 43 * file_contexts 44 * service_contexts 45 * property_contexts 46 * keys.conf 47 48 Example BoardConfig.mk Usage: 49 BOARD_SEPOLICY_M4DEFS += btmodule=foomatic \ 50 btdevice=/dev/gps 51 52 SPECIFIC POLICY FILE INFORMATION 53 54 mac_permissions.xml: 55 ABOUT: 56 The mac_permissions.xml file is used for controlling the mmac solutions 57 as well as mapping a public base16 signing key with an arbitrary seinfo 58 string. Details of the files contents can be found in a comment at the 59 top of that file. The seinfo string, previously mentioned, is the same string 60 that is referenced in seapp_contexts. 61 62 It is important to note the final processed version of this file 63 is stripped of comments and whitespace. This is to preserve space on the 64 system.img. If one wishes to view it in a more human friendly format, 65 the "tidy" or "xmllint" command will assist you. 66 67 TOOLING: 68 insertkeys.py 69 Is a helper script for mapping arbitrary tags in the signature stanzas of 70 mac_permissions.xml to public keys found in pem files. This script takes 71 a mac_permissions.xml file(s) and configuration file in order to operate. 72 Details of the configuration file (keys.conf) can be found in the subsection 73 keys.conf. This tool is also responsible for stripping the comments and 74 whitespace during processing. 75 76 keys.conf 77 The keys.conf file is used for controlling the mapping of "tags" found in 78 the mac_permissions.xml signature stanzas with actual public keys found in 79 pem files. The configuration file is processed via m4. 80 81 The script allows for mapping any string contained in TARGET_BUILD_VARIANT 82 with specific path to a pem file. Typically TARGET_BUILD_VARIANT is either 83 user, eng or userdebug. Additionally, one can specify "ALL" to map a path to 84 any string specified in TARGET_BUILD_VARIANT. All tags are matched verbatim 85 and all options are matched lowercase. The options are "tolowered" automatically 86 for the user, it is convention to specify tags and options in all uppercase 87 and tags start with @. The option arguments can also use environment variables 88 via the familiar $VARIABLE syntax. This is often useful for setting a location 89 to ones release keys. 90 91 Often times, one will need to integrate an application that was signed by a separate 92 organization and may need to extract the pem file for the insertkeys/keys.conf tools. 93 Extraction of the public key in the pem format is possible via openssl. First you need 94 to unzip the apk, once it is unzipped, cd into the META_INF directory and then execute 95 openssl pkcs7 -inform DER -in CERT.RSA -out CERT.pem -outform PEM -print_certs 96 On some occasions CERT.RSA has a different name, and you will need to adjust for that. 97 After extracting the pem, you can rename it, and configure keys.conf and 98 mac_permissions.xml to pick up the change. You MUST open the generated pem file in a text 99 editor and strip out anything outside the opening and closing scissor lines. Failure to do 100 so WILL cause a compile time issue thrown by insertkeys.py 101 102 NOTE: The pem files are base64 encoded and PackageManagerService, mac_permissions.xml 103 and setool all use base16 encodings. 104
