grantSignaturePermission method in PackageManagerService java file

PackageManagerService.java

private boolean grantSignaturePermission(String perm, PackageParser.Package pkg,
                                          BasePermission bp, HashSet<String> origPermissions) {
        boolean allowed;
        allowed = (compareSignatures(
                bp.packageSetting.signatures.mSignatures, pkg.mSignatures)
                        == PackageManager.SIGNATURE_MATCH)
                || (compareSignatures(mPlatformPackage.mSignatures, pkg.mSignatures)
                        == PackageManager.SIGNATURE_MATCH);
        if (!allowed && (bp.protectionLevel
                & PermissionInfo.PROTECTION_FLAG_SYSTEM) != 0) {
            if (isSystemApp(pkg)) {
                // For updated system applications, a system permission
                // is granted only if it had been defined by the original application.
                if (isUpdatedSystemApp(pkg)) {
                    final PackageSetting sysPs = mSettings
                            .getDisabledSystemPkgLPr(pkg.packageName);
                    final GrantedPermissions origGp = sysPs.sharedUser != null
                            ? sysPs.sharedUser : sysPs;

                    if (origGp.grantedPermissions.contains(perm)) {
                        // If the original was granted this permission, we take
                        // that grant decision as read and propagate it to the
                        // update.
                        allowed = true;
                    } else {
                        // The system apk may have been updated with an older
                        // version of the one on the data partition, but which
                        // granted a new system permission that it didn't have
                        // before.  In this case we do want to allow the app to
                        // now get the new permission if the ancestral apk is
                        // privileged to get it.
                        if (sysPs.pkg != null && sysPs.isPrivileged()) {
                            for (int j=0;
                                    j<sysPs.pkg.requestedPermissions.size(); j++) {
                                if (perm.equals(
                                        sysPs.pkg.requestedPermissions.get(j))) {
                                    allowed = true;
                                    break;
                                }
                            }
                        }
                    }
                } else {
                    allowed = isPrivilegedApp(pkg);
                }
            }
        }
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// HERE