Apple Developer Connection Student Program/ADC Tools Sampler CD Disk 3 1999.iso/Metrowerks CodeWarrior/Java Support/Java_Source/Java2/src/java/io/FilePermission.java

Java Source | 1999-05-28 | 20.9 KB | 721 lines | [TEXT/CWIE]

/*
 * @(#)FilePermission.java    1.56 98/09/28
 *
 * Copyright 1997, 1998 by Sun Microsystems, Inc.,
 * 901 San Antonio Road, Palo Alto, California, 94303, U.S.A.
 * All rights reserved.
 *
 * This software is the confidential and proprietary information
 * of Sun Microsystems, Inc. ("Confidential Information").  You
 * shall not disclose such Confidential Information and shall use
 * it only in accordance with the terms of the license agreement
 * you entered into with Sun.
 */

package java.io;

import java.security.*;
import java.util.Enumeration;
import java.util.Vector;
import java.util.StringTokenizer;

/**
 * This class represents access to a file or directory.  A FilePermission consists
 * of a pathname and a set of actions valid for that pathname.
 * <P>
 * Pathname is the pathname of the file or directory granted the specified
 * actions. A pathname that ends in "/*" (where "/" is
 * the file separator character, <code>File.separatorChar</code>) indicates
 * all the files and directories contained in that directory. A pathname
 * that ends with "/-" indicates (recursively) all files
 * and subdirectories contained in that directory. A pathname consisting of
 * the special token "<<ALL FILES>>" matches <bold>any</bold> file.
 * <P>
 * Note: A pathname consisting of a single "*" indicates all the files
 * in the current directory, while a pathname consisting of a single "-"
 * indicates all the files in the current directory and
 * (recursively) all files and subdirectories contained in the current
 * directory.
 * <P>
 * The actions to be granted are passed to the constructor in a string containing
 * a list of one or more comma-separated keywords. The possible keywords are
 * "read", "write", "execute", and "delete". Their meaning is defined as follows:
 * <P>
 * <DL>
 *    <DT> read <DD> read permission
 *    <DT> write <DD> write permission
 *    <DT> execute
 *    <DD> execute permission. Allows <code>Runtime.exec</code> to
 *         be called. Corresponds to <code>SecurityManager.checkExec</code>.
 *    <DT> delete
 *    <DD> delete permission. Allows <code>File.delete</code> to
 *         be called. Corresponds to <code>SecurityManager.checkDelete</code>.
 * </DL>
 * <P>
 * The actions string is converted to lowercase before processing.
 * <P>
 * Be careful when granting FilePermissions. Think about the implications
 * of granting read and especially write access to various files and
 * directories. The "<<ALL FILES>>" permission with write action is
 * especially dangerous. This grants permission to write to the entire
 * file system. One thing this effectively allows is replacement of the
 * system binary, including the JVM runtime environment.
 *
 * <p>Please note: Code can always read a file from the same
 * directory it's in (or a subdirectory of that directory); it does not
 * need explicit permission to do so.
 *
 * @see java.security.Permission
 * @see java.security.Permissions
 * @see java.security.PermissionCollection
 *
 * @version 1.56 99/03/26
 *
 * @author Marianne Mueller
 * @author Roland Schemers
 */

public final class FilePermission extends Permission implements Serializable {

    /**
     * Execute action.
     */
    private final static int EXECUTE = 0x1;
    /**
     * Write action.
     */
    private final static int WRITE   = 0x2;
    /**
     * Read action.
     */
    private final static int READ    = 0x4;
    /**
     * Delete action.
     */
    private final static int DELETE  = 0x8;

    /**
     * All actions (read,write,execute,delete)
     */
    private final static int ALL     = READ|WRITE|EXECUTE|DELETE;
    /**
     * No actions.
     */
    private final static int NONE    = 0x0;

    // the actions mask
    private transient int mask;

    // does path indicate a directory? (wildcard or recursive)
    private transient boolean directory;

    // is it a recursive directory specification?
    private transient boolean recursive;

    /**
     * the actions string.
     *
     * @serial
     */
    private String actions; // Left null as long as possible, then
                            // created and re-used in the getAction function.

    // canonicalized dir path. In the case of
    // directories, it is the name "/blah/*" or "/blah/-" without
    // the last character (the "*" or "-").

    private transient String cpath;

    // static Strings used by init(int mask)
    private static final String RECURSIVE = "-";
    private static final String WILD = "*";
    private static final String SEP_RECURSIVE = File.separator+RECURSIVE;
    private static final String SEP_WILD = File.separator+WILD;

/*
    public String toString()
    {
        StringBuffer sb = new StringBuffer();
    sb.append("***\n");
    sb.append("cpath = "+cpath+"\n");
    sb.append("mask = "+mask+"\n");
    sb.append("actions = "+getActions()+"\n");
    sb.append("directory = "+directory+"\n");
    sb.append("recursive = "+recursive+"\n");
    sb.append("***\n");
    return sb.toString();
    }
*/

    /**
     * initialize a FilePermission object. Common to all constructors.
     * Also called during de-serialization.
     *
     * @param mask the actions mask to use.
     *
     */

    private void init(int mask)
    {

    if ((mask & ALL) != mask)
        throw new IllegalArgumentException("invalid actions mask");

    if (mask == NONE)
        throw new IllegalArgumentException("invalid actions mask");

    if (getName() == null)
        throw new IllegalArgumentException("name can't be null");

    this.mask = mask;

    cpath = getName();

    if (cpath.equals("<<ALL FILES>>")) {
        directory = true;
        recursive = true;
        cpath = "";
        return;
    }

    if (cpath.endsWith(SEP_RECURSIVE) || cpath.equals(RECURSIVE)) {
        directory = true;
        recursive = true;
        cpath = cpath.substring(0, cpath.length()-1);
    } else if (cpath.endsWith(SEP_WILD) || cpath.equals(WILD)) {
        directory = true;
        //recursive = false;
        cpath = cpath.substring(0, cpath.length()-1);
    } else {
        // overkill since they are initialized to false, but
        // commented out here to remind us...
        //directory = false;
        //recursive = false;
    }

    if (cpath.equals("")) {
        cpath = (String) java.security.AccessController.doPrivileged(
               new sun.security.action.GetPropertyAction("user.dir"));
    }

    // store only the canonical cpath if possible

    // need a doPrivileged block as getCanonicalPath
    // might attempt to access user.dir to turn a relative
    // path into an absolute path.
    cpath = (String)
        AccessController.doPrivileged(
            new java.security.PrivilegedAction() {
        public Object run() {
        try {
            File file = new File(cpath);
            String canonical_path = file.getCanonicalPath();
            if (directory &&
            (!canonical_path.endsWith(File.separator))) {
            return canonical_path + File.separator;
            } else {
            return canonical_path;
            }
        } catch (IOException ioe) {
            // ignore if we can't canonicalize path?
        }
        return cpath;
        }
    });

    // XXX: at this point the path should be absolute. die if it isn't?
    }

    /**
     * Creates a new FilePermission object with the specified actions.
     * <i>path</i> is the pathname of a
     * file or directory, and <i>actions</i> contains a comma-separated list of the
     * desired actions granted on the file or directory. Possible actions are
     * "read", "write", "execute", and "delete".
     *
     * <p>A pathname that ends in "/*" (where "/" is
     * the file separator character, <code>File.separatorChar</code>) indicates
     * a directory and all the files contained in that directory. A pathname
     * that ends with "/-" indicates a directory and (recursively) all files
     * and subdirectories contained in that directory. The special pathname
     * "<<ALL FILES>>" matches all files.
     *
     * <p>A pathname consisting of a single "*" indicates all the files
     * in the current directory, while a pathname consisting of a single "-"
     * indicates all the files in the current directory and
     * (recursively) all files and subdirectories contained in the current
     * directory.
     *
     * @param path the pathname of the file/directory.
     * @param actions the action string.
     */

    public FilePermission(String path, String actions)
    {
    super(path);
    init(getMask(actions));
    }

    /**
     * Creates a new FilePermission object using an action mask.
     * More efficient than the FilePermission(String, String) constructor.
     * Can be used from within
     * code that needs to create a FilePermission object to pass into the
     * <code>implies</code> method.
     *
     * @param path the pathname of the file/directory.
     * @param mask the action mask to use.
     */

    // package private for use by the FilePermissionCollection add method
    FilePermission(String path, int mask)
    {
    super(path);
    init(mask);
    }

    /**
     * Checks if this FilePermission object "implies" the specified permission.
     * <P>
     * More specifically, this method returns true if:<p>
     * <ul>
     * <li> <i>p</i> is an instanceof FilePermission,<p>
     * <li> <i>p</i>'s actions are a proper subset of this
     * object's actions, and <p>
     * <li> <i>p</i>'s pathname is implied by this object's
     *      pathname. For example, "/tmp/*" implies "/tmp/foo", since
     *      "/tmp/*" encompasses the "/tmp" directory and all files in that
     *      directory, including the one named "foo".
     * </ul>
     * @param p the permission to check against.
     *
     * @return true if the specified permission is implied by this object,
     * false if not.
     */
    public boolean implies(Permission p) {
    if (!(p instanceof FilePermission))
        return false;

    FilePermission that = (FilePermission) p;

    // we get the effective mask. i.e., the "and" of this and that.
    // They must be equal to that.mask for implies to return true.

    return ((this.mask & that.mask) == that.mask) && impliesIgnoreMask(that);
    }

    /**
     * Checks if the Permission's actions are a proper subset of the
     * this object's actions. Returns the effective mask iff the
     * this FilePermission's path also implies that FilePermission's path.
     *
     * @param that the FilePermission to check against.
     * @param exact return immediatly if the masks are not equal
     * @return the effective mask
     */
    boolean impliesIgnoreMask(FilePermission that) {
    if (this.directory) {
        if (this.recursive) {
        // make sure that.path is longer then path so
        // something like /foo/- does not imply /foo
        if (that.directory) {
            return (that.cpath.length() >= this.cpath.length()) &&
                that.cpath.startsWith(this.cpath);
        }  else {
            return ((that.cpath.length() > this.cpath.length()) &&
                that.cpath.startsWith(this.cpath));
        }
        } else {
        if (that.directory) {
            // if the permission passed in is a directory
            // specification, make sure that a non-recursive
            // permission (i.e., this object) can't imply a recursive
            // permission.
            if (that.recursive)
            return false;
            else
            return (this.cpath.equals(that.cpath));
        } else {
            int last = that.cpath.lastIndexOf(File.separatorChar);
            if (last == -1)
            return false;
            else {
            String base = that.cpath.substring(0, last+1);
            return (this.cpath.equals(base));
            }
        }
        }
    } else {
        return (this.cpath.equals(that.cpath));
    }
    }

    /**
     * Checks two FilePermission objects for equality. Checks that <i>obj</i> is
     * a FilePermission, and has the same pathname and actions as this object.
     * <P>
     * @param obj the object we are testing for equality with this object.
     * @return true if obj is a FilePermission, and has the same pathname and
     * actions as this FilePermission object.
     */
    public boolean equals(Object obj) {
    if (obj == this)
        return true;

    if (! (obj instanceof FilePermission))
        return false;

    FilePermission that = (FilePermission) obj;

    return (this.mask == that.mask) &&
        this.cpath.equals(that.cpath) &&
        (this.directory == that.directory) &&
        (this.recursive == that.recursive);
    }

    /**
     * Returns the hash code value for this object.
     *
     * @return a hash code value for this object.
     */

    public int hashCode() {
    return this.cpath.hashCode();
    }

    /**
     * Converts an actions String to an actions mask.
     *
     * @param action the action string.
     * @return the actions mask.
     */
    private static int getMask(String actions) {

    int mask = NONE;

    if (actions == null) {
        return mask;
    }

    char[] a = actions.toCharArray();

    int i = a.length - 1;
    if (i < 0)
        return mask;

    while (i != -1) {
        char c;

        // skip whitespace
        while ((i!=-1) && ((c = a[i]) == ' ' ||
                   c == '\r' ||
                   c == '\n' ||
                   c == '\f' ||
                   c == '\t'))
        i--;

        // check for the known strings
        int matchlen;

        if (i >= 3 && (a[i-3] == 'r' || a[i-3] == 'R') &&
              (a[i-2] == 'e' || a[i-2] == 'E') &&
              (a[i-1] == 'a' || a[i-1] == 'A') &&
              (a[i] == 'd' || a[i] == 'D'))
        {
        matchlen = 4;
        mask |= READ;

        } else if (i >= 4 && (a[i-4] == 'w' || a[i-4] == 'W') &&
                 (a[i-3] == 'r' || a[i-3] == 'R') &&
                 (a[i-2] == 'i' || a[i-2] == 'I') &&
                 (a[i-1] == 't' || a[i-1] == 'T') &&
                 (a[i] == 'e' || a[i] == 'E'))
        {
        matchlen = 5;
        mask |= WRITE;

        } else if (i >= 6 && (a[i-6] == 'e' || a[i-6] == 'E') &&
                         (a[i-5] == 'x' || a[i-5] == 'X') &&
                 (a[i-4] == 'e' || a[i-4] == 'E') &&
                 (a[i-3] == 'c' || a[i-3] == 'C') &&
                 (a[i-2] == 'u' || a[i-2] == 'U') &&
                 (a[i-1] == 't' || a[i-1] == 'T') &&
                 (a[i] == 'e' || a[i] == 'E'))
        {
        matchlen = 7;
        mask |= EXECUTE;

        } else if (i >= 5 && (a[i-5] == 'd' || a[i-5] == 'D') &&
                 (a[i-4] == 'e' || a[i-4] == 'E') &&
                 (a[i-3] == 'l' || a[i-3] == 'L') &&
                 (a[i-2] == 'e' || a[i-2] == 'E') &&
                 (a[i-1] == 't' || a[i-1] == 'T') &&
                 (a[i] == 'e' || a[i] == 'E'))
        {
        matchlen = 6;
        mask |= DELETE;

        } else {
        // parse error
        throw new IllegalArgumentException(
            "invalid permission: " + actions);
        }

        // make sure we didn't just match the tail of a word
        // like "ackbarfaccept".  Also, skip to the comma.
        boolean seencomma = false;
        while (i >= matchlen && !seencomma) {
        switch(a[i-matchlen]) {
        case ',':
            seencomma = true;
            /*FALLTHROUGH*/
        case ' ': case '\r': case '\n':
        case '\f': case '\t':
            break;
        default:
            throw new IllegalArgumentException(
                "invalid permission: " + actions);
        }
        i--;
        }

        // point i at the location of the comma minus one (or -1).
        i -= matchlen;
    }

    return mask;
    }

    /**
     * Return the current action mask. Used by the FilePermissionCollection.
     *
     * @return the actions mask.
     */

    int getMask() {
    return mask;
    }

    /**
     * Return the canonical string representation of the actions.
     * Always returns present actions in the following order:
     * read, write, execute, delete.
     *
     * @return the canonical string representation of the actions.
     */
    private static String getActions(int mask)
    {
    StringBuffer sb = new StringBuffer();
        boolean comma = false;

    if ((mask & READ) == READ) {
        comma = true;
        sb.append("read");
    }

    if ((mask & WRITE) == WRITE) {
        if (comma) sb.append(',');
            else comma = true;
        sb.append("write");
    }

    if ((mask & EXECUTE) == EXECUTE) {
        if (comma) sb.append(',');
            else comma = true;
        sb.append("execute");
    }

    if ((mask & DELETE) == DELETE) {
        if (comma) sb.append(',');
            else comma = true;
        sb.append("delete");
    }

    return sb.toString();
    }

    /**
     * Returns the "canonical string representation" of the actions.
     * That is, this method always returns present actions in the following order:
     * read, write, execute, delete. For example, if this FilePermission object
     * allows both write and read actions, a call to <code>getActions</code>
     * will return the string "read,write".
     *
     * @return the canonical string representation of the actions.
     */
    public String getActions()
    {
    if (actions == null)
        actions = getActions(this.mask);

    return actions;
    }


    /**
     * Returns a new PermissionCollection object for storing FilePermission
     * objects.
     * <p>
     * FilePermission objects must be stored in a manner that allows them
     * to be inserted into the collection in any order, but that also enables the
     * PermissionCollection <code>implies</code>
     * method to be implemented in an efficient (and consistent) manner.
     *
     * <p>For example, if you have two FilePermissions:
     * <OL>
     * <LI>  <code>"/tmp/-", "read"</code>
     * <LI>  <code>"/tmp/scratch/foo", "write"</code>
     * </OL>
     *
     * <p>and you are calling the <code>implies</code> method with the FilePermission:
     *
     * <pre>
     *   "/tmp/scratch/foo", "read,write",
     * </pre>
     *
     * then the <code>implies</code> function must
     * take into account both the "/tmp/-" and "/tmp/scratch/foo"
     * permissions, so the effective permission is "read,write",
     * and <code>implies</code> returns true. The "implies" semantics for
     * FilePermissions are handled properly by the PermissionCollection object
     * returned by this <code>newPermissionCollection</code> method.
     *
     * @return a new PermissionCollection object suitable for storing
     * FilePermissions.
     */

    public PermissionCollection newPermissionCollection() {
    return new FilePermissionCollection();
    }

    /**
     * WriteObject is called to save the state of the FilePermission
     * to a stream. The actions are serialized, and the superclass
     * takes care of the name.
     */
    private synchronized void writeObject(java.io.ObjectOutputStream s)
        throws IOException
    {
    // Write out the actions. The superclass takes care of the name
    // call getActions to make sure actions field is initialized
    if (actions == null)
        getActions();
    s.defaultWriteObject();
    }

    /**
     * readObject is called to restore the state of the FilePermission from
     * a stream.
     */
    private synchronized void readObject(java.io.ObjectInputStream s)
         throws IOException, ClassNotFoundException
    {
    // Read in the actions, then restore everything else by calling init.
    s.defaultReadObject();
    init(getMask(actions));
    }
}

/**
 * A FilePermissionCollection stores a set of FilePermission permissions.
 * FilePermission objects
 * must be stored in a manner that allows them to be inserted in any
 * order, but enable the implies function to evaluate the implies
 * method.
 * For example, if you have two FilePermissions:
 * <OL>
 * <LI> "/tmp/-", "read"
 * <LI> "/tmp/scratch/foo", "write"
 * </OL>
 * And you are calling the implies function with the FilePermission:
 * "/tmp/scratch/foo", "read,write", then the implies function must
 * take into account both the /tmp/- and /tmp/scratch/foo
 * permissions, so the effective permission is "read,write".
 *
 * @see java.security.Permission
 * @see java.security.Permissions
 * @see java.security.PermissionCollection
 *
 * @version 1.56 99/03/26
 *
 * @author Marianne Mueller
 * @author Roland Schemers
 */

final class FilePermissionCollection extends PermissionCollection
implements Serializable {

    private Vector permissions;

    /**
     * Create an empty FilePermissions object.
     *
     */

    public FilePermissionCollection() {
    permissions = new Vector();
    }

    /**
     * Adds a permission to the FilePermissions. The key for the hash is
     * permission.path.
     *
     * @param permission the Permission object to add.
     */

    public void add(Permission permission)
    {
    if (! (permission instanceof FilePermission))
        throw new IllegalArgumentException("invalid permission: "+
                           permission);
    permissions.addElement(permission);
    }

    /**
     * Check and see if this set of permissions implies the permissions
     * expressed in "permission".
     *
     * @param p the Permission object to compare
     *
     * @return true if "permission" is a proper subset of a permission in
     * the set, false if not.
     */

    public boolean implies(Permission permission)
    {
    if (! (permission instanceof FilePermission))
           return false;

    FilePermission fp = (FilePermission) permission;

    int desired = fp.getMask();
    int effective = 0;
    int needed = desired;

    Enumeration e = permissions.elements();

    while (e.hasMoreElements()) {
        FilePermission x = (FilePermission) e.nextElement();
        if (((needed & x.getMask()) != 0) && x.impliesIgnoreMask(fp)) {
        effective |=  x.getMask();
        if ((effective & desired) == desired)
            return true;
        needed = (desired ^ effective);
        }
    }
    return false;
    }

    /**
     * Returns an enumeration of all the FilePermission objects in the
     * container.
     *
     * @return an enumeration of all the FilePermission objects.
     */

    public Enumeration elements()
    {
    return permissions.elements();
    }
}