Impose an ordering on created SELinuxMMAC Policy objects.

import java.util.ArrayList;

import java.util.Collections;

import java.util.Comparator;

import java.util.HashMap;

import java.util.HashSet;

import java.util.List;

 */

public final class SELinuxMMAC {

    private static final String TAG = "SELinuxMMAC";

    static final String TAG = "SELinuxMMAC";

    private static final boolean DEBUG_POLICY = false;

    private static final boolean DEBUG_POLICY_INSTALL = DEBUG_POLICY || false;

    private static final boolean DEBUG_POLICY_ORDER = DEBUG_POLICY || false;

    // All policy stanzas read from mac_permissions.xml. This is also the lock

    // to synchronize access during policy load and access attempts.

    private static final List<Policy> sPolicies = new ArrayList<Policy>();

    private static List<Policy> sPolicies = new ArrayList<>();

    // Data policy override version file.

    private static final String DATA_VERSION_FILE =

     *         were loaded successfully; no partial loading is possible.

     */

    public static boolean readInstallPolicy() {

        // Temp structure to hold the rules while we parse the xml file. We add

        // all the rules once we know there's no problems.

        // Temp structure to hold the rules while we parse the xml file

        List<Policy> policies = new ArrayList<>();

        // A separate structure to hold the default stanza. We need to add this to

        // the end of the policies list structure.

        Policy defaultPolicy = null;

        // Track sets of known policy certs so we can enforce rules across stanzas.

        Set<Set<Signature>> knownCerts = new HashSet<>();

        FileReader policyFile = null;

        XmlPullParser parser = Xml.newPullParser();

        try {

                    continue;

                }

                String tagName = parser.getName();

                if ("signer".equals(tagName)) {

                    Policy signerPolicy = readSignerOrThrow(parser);

                    // Return of a Policy instance ensures certain invariants have

                    // passed, however, we still want to do some cross policy checking.

                    // Thus, check that we haven't seen the certs in another stanza.

                    Set<Signature> certs = signerPolicy.getSignatures();

                    if (knownCerts.contains(certs)) {

                        String msg = "Separate stanzas have identical certs";

                        throw new IllegalStateException(msg);

                    }

                    knownCerts.add(certs);

                    policies.add(signerPolicy);

                } else if ("default".equals(tagName)) {

                    Policy defPolicy = readDefaultOrThrow(parser);

                    // Return of a Policy instance ensures certain invariants have

                    // passed, however, we still want to do some cross policy checking.

                    // Thus, check that we haven't already seen a default stanza.

                    if (defaultPolicy != null) {

                        String msg = "Multiple default stanzas identified";

                        throw new IllegalStateException(msg);

                    }

                    defaultPolicy = defPolicy;

                } else {

                switch (parser.getName()) {

                    case "signer":

                        policies.add(readSignerOrThrow(parser));

                        break;

                    case "default":

                        policies.add(readDefaultOrThrow(parser));

                        break;

                    default:

                        skip(parser);

                }

            }

            IoUtils.closeQuietly(policyFile);

        }

        // Add the default policy to the end if there is one. This will ensure that

        // the default stanza is consulted last when performing policy lookups.

        if (defaultPolicy != null) {

            policies.add(defaultPolicy);

        // Now sort the policy stanzas

        PolicyComparator policySort = new PolicyComparator();

        Collections.sort(policies, policySort);

        if (policySort.foundDuplicate()) {

            Slog.w(TAG, "ERROR! Duplicate entries found parsing " + MAC_PERMISSIONS);

            return false;

        }

        synchronized (sPolicies) {

            sPolicies.clear();

            sPolicies.addAll(policies);

            sPolicies = policies;

            if (DEBUG_POLICY_ORDER) {

                for (Policy policy : sPolicies) {

                    Slog.d(TAG, "Policy: " + policy.toString());

                }

            }

        }

        return true;

 * of invariants before being built and returned. Each instance can be guaranteed to

 * hold one valid policy stanza as outlined in the external/sepolicy/mac_permissions.xml

 * file.

 * </p>

 * <p>

 * The following is an example of how to use {@link Policy.PolicyBuilder} to create a

 * signer based Policy instance.

 * signer based Policy instance with only inner package name refinements.

 * </p>

 * <pre>

 * {@code

 * Policy policy = new Policy.PolicyBuilder()

 *         .addSignature("308204a8...")

 *         .addSignature("483538c8...")

 *         .setGlobalSeinfoOrThrow("paltform")

 *         .addInnerPackageMapOrThrow("com.foo.", "bar")

 *         .addInnerPackageMapOrThrow("com.foo.other", "bar")

 *         .build();

 * }

 * </pre>

 * <p>

 * An example of how to use {@link Policy.PolicyBuilder} to create a default based Policy

 * instance.

 * The following is an example of how to use {@link Policy.PolicyBuilder} to create a

 * signer based Policy instance with only a global seinfo tag.

 * </p>

 * <pre>

 * {@code

 * Policy policy = new Policy.PolicyBuilder()

 *         .addSignature("308204a8...")

 *         .addSignature("483538c8...")

 *         .setGlobalSeinfoOrThrow("paltform")

 *         .build();

 * }

 * </pre>

 * <p>

 * The following is an example of how to use {@link Policy.PolicyBuilder} to create a

 * default based Policy instance.

 * </p>

 * <pre>

 * {@code

 * Policy policy = new Policy.PolicyBuilder()

 *         .setAsDefaultPolicy()

 *         .setGlobalSeinfoOrThrow("defualt")

 *         .setGlobalSeinfoOrThrow("default")

 *         .build();

 * }

 * </pre>

        return mCerts;

    }

    /**

     * Return whether this policy object represents a default stanza.

     *

     * @return A boolean indicating if this object represents a default policy stanza.

     */

    public boolean isDefaultStanza() {

        return mDefaultStanza;

    }

    /**

     * Return whether this policy object contains package name mapping refinements.

     *

     * @return A boolean indicating if this object has inner package name mappings.

     */

    public boolean hasInnerPackages() {

        return !mPkgMap.isEmpty();

    }

    /**

     * Return the mapping of all package name refinements.

     *

     * @return A Map object whose keys are the package names and whose values are

     *         the seinfo assignments.

     */

    public Map<String, String> getInnerPackages() {

        return mPkgMap;

    }

    /**

     * Return whether the policy object has a global seinfo tag attached.

     *

     * @return A boolean indicating if this stanza has a global seinfo tag.

     */

    public boolean hasGlobalSeinfo() {

        return mSeinfo != null;

    }

    @Override

    public String toString() {

        StringBuilder sb = new StringBuilder();

        if (mDefaultStanza) {

            sb.append("defaultStanza=true ");

        }

        for (Signature cert : mCerts) {

            sb.append("cert=" + cert.toCharsString().substring(0, 11) + "... ");

        }

        if (mSeinfo != null) {

            sb.append("seinfo=" + mSeinfo);

        }

        for (String name : mPkgMap.keySet()) {

            sb.append(" " + name + "=" + mPkgMap.get(name));

        }

        return sb.toString();

    }

    /**

     * <p>

     * Determine the seinfo value to assign to an apk. The appropriate seinfo value

        }

        /**

         * Sets this stanza as a defualt stanza. All policy stanzas are assumed to

         * Sets this stanza as a default stanza. All policy stanzas are assumed to

         * be signer stanzas unless this method is explicitly called. Default stanzas

         * are treated differently with respect to allowable child tags, ordering and

         * when and how policy decisions are enforced.

         *        <ul>

         *           <li> at least one cert must be found </li>

         *           <li> either a global seinfo value is present OR at least one

         *           inner package mapping must be present. </li>

         *           inner package mapping must be present BUT not both. </li>

         *        </ul>

         *      </li>

         *    </ul>

                    String err = "Missing certs with signer tag. Expecting at least one.";

                    throw new IllegalStateException(err);

                }

                if ((p.mSeinfo == null) && (p.mPkgMap.isEmpty())) {

                    String err = "Missing seinfo OR package tags with signer tag. At " +

                            "least one must be present.";

                if (!(p.mSeinfo == null ^ p.mPkgMap.isEmpty())) {

                    String err = "Only seinfo tag XOR package tags are allowed within " +

                            "a signer stanza.";

                    throw new IllegalStateException(err);

                }

            }

        }

    }

}

/**

 * Comparision imposing an ordering on Policy objects. It is understood that Policy

 * objects can only take one of three forms and ordered according to the following

 * set of rules most specific to least.

 * <ul>

 *   <li> signer stanzas with inner package mappings </li>

 *   <li> signer stanzas with global seinfo tags </li>

 *   <li> default stanza </li>

 * </ul>

 * This comparison also checks for duplicate entries on the input selectors. Any

 * found duplicates will be flagged and can be checked with {@link #foundDuplicate}.

 */

final class PolicyComparator implements Comparator<Policy> {

    private boolean duplicateFound = false;

    public boolean foundDuplicate() {

        return duplicateFound;

    }

    @Override

    public int compare(Policy p1, Policy p2) {

        // Give precedence to signature stanzas over default stanzas

        if (p1.isDefaultStanza() != p2.isDefaultStanza()) {

            return p1.isDefaultStanza() ? 1 : -1;

        }

        // Give precedence to stanzas with inner package mappings

        if (p1.hasInnerPackages() != p2.hasInnerPackages()) {

            return p1.hasInnerPackages() ? -1 : 1;

        }

        // Check for duplicate entries

        if (p1.getSignatures().equals(p2.getSignatures())) {

            // Checks if default stanza or a signer w/o inner package names

            if (p1.hasGlobalSeinfo()) {

                duplicateFound = true;

                Slog.e(SELinuxMMAC.TAG, "Duplicate policy entry: " + p1.toString());

            }

            // Look for common inner package name mappings

            final Map<String, String> p1Packages = p1.getInnerPackages();

            final Map<String, String> p2Packages = p2.getInnerPackages();

            if (!Collections.disjoint(p1Packages.keySet(), p2Packages.keySet())) {

                duplicateFound = true;

                Slog.e(SELinuxMMAC.TAG, "Duplicate policy entry: " + p1.toString());

            }

        }

        return 0;

    }

}