Make Transforms Unidirectional

Convert the IpSecTransform from being a bi-directional
pair of SAs to a unidirectional single SA. This CL
also removes the concept of "direction from SAs meaning
that a IpSecTransform may now be applied to a socket
in either direction.

-Make transforms unidirectional
-Add Convert allocateSpi() to use destination rather
 than direction and remote address
-Remove directionality from builders for IpSecTransform
-Change applyTransportModeTransform() to take a
 direction in which to apply the transform object.
-Additional minor naming updates
-Restrict IpSecConfig to only print keys on eng builds
-Move DIRECTION constants to IpSecManager
-Add sourceAddress parameter to IpSecTransform to provide
 additional guarantees about the source address of data;
 (explicit failure rather than implicit failure).
-Move SPI to the build() method of IpSecTransform

Bug: 71717213
Test: runtest frameworks-net, CTS - IpSecManagerTest
Change-Id: I0824b37f443f4b8c62536d9801238c63ed8f2a1c

5 files changed, 215 insertions, 260 deletions

diff --git a/core/java/android/net/IIpSecService.aidl b/core/java/android/net/IIpSecService.aidl
index d9b57db18071..3fe531fd7960 100644
--- a/core/java/android/net/IIpSecService.aidl
+++ b/core/java/android/net/IIpSecService.aidl
@@ -31,7 +31,7 @@ import android.os.ParcelFileDescriptor;
 interface IIpSecService
 {
     IpSecSpiResponse allocateSecurityParameterIndex(
-            int direction, in String remoteAddress, int requestedSpi, in IBinder binder);
+            in String destinationAddress, int requestedSpi, in IBinder binder);
 
     void releaseSecurityParameterIndex(int resourceId);
 
@@ -43,7 +43,7 @@ interface IIpSecService
 
     void deleteTransportModeTransform(int transformId);
 
-    void applyTransportModeTransform(in ParcelFileDescriptor socket, int transformId);
+    void applyTransportModeTransform(in ParcelFileDescriptor socket, int direction, int transformId);
 
-    void removeTransportModeTransform(in ParcelFileDescriptor socket, int transformId);
+    void removeTransportModeTransforms(in ParcelFileDescriptor socket, int transformId);
 }
diff --git a/core/java/android/net/IpSecAlgorithm.java b/core/java/android/net/IpSecAlgorithm.java
index 7d752e89e6f6..c69a4d4c0bee 100644
--- a/core/java/android/net/IpSecAlgorithm.java
+++ b/core/java/android/net/IpSecAlgorithm.java
@@ -256,13 +256,19 @@ public final class IpSecAlgorithm implements Parcelable {
         return getName().equals(AUTH_CRYPT_AES_GCM);
     }
 
+    // Because encryption keys are sensitive and userdebug builds are used by large user pools
+    // such as beta testers, we only allow sensitive info such as keys on eng builds.
+    private static boolean isUnsafeBuild() {
+        return Build.IS_DEBUGGABLE && Build.IS_ENG;
+    }
+
     @Override
     public String toString() {
         return new StringBuilder()
                 .append("{mName=")
                 .append(mName)
                 .append(", mKey=")
-                .append(Build.IS_DEBUGGABLE ? HexDump.toHexString(mKey) : "<hidden>")
+                .append(isUnsafeBuild() ? HexDump.toHexString(mKey) : "<hidden>")
                 .append(", mTruncLenBits=")
                 .append(mTruncLenBits)
                 .append("}")
diff --git a/core/java/android/net/IpSecConfig.java b/core/java/android/net/IpSecConfig.java
index f54ceb5c142a..80b0af33735b 100644
--- a/core/java/android/net/IpSecConfig.java
+++ b/core/java/android/net/IpSecConfig.java
@@ -32,59 +32,29 @@ public final class IpSecConfig implements Parcelable {
     // MODE_TRANSPORT or MODE_TUNNEL
     private int mMode = IpSecTransform.MODE_TRANSPORT;
 
-    // Needs to be valid only for tunnel mode
     // Preventing this from being null simplifies Java->Native binder
-    private String mLocalAddress = "";
+    private String mSourceAddress = "";
 
     // Preventing this from being null simplifies Java->Native binder
-    private String mRemoteAddress = "";
+    private String mDestinationAddress = "";
 
     // The underlying Network that represents the "gateway" Network
     // for outbound packets. It may also be used to select packets.
     private Network mNetwork;
 
-    /**
-     * This class captures the parameters that specifically apply to inbound or outbound traffic.
-     */
-    public static class Flow {
-        // Minimum requirements for identifying a transform
-        // SPI identifying the IPsec flow in packet processing
-        // and a remote IP address
-        private int mSpiResourceId = IpSecManager.INVALID_RESOURCE_ID;
-
-        // Encryption Algorithm
-        private IpSecAlgorithm mEncryption;
-
-        // Authentication Algorithm
-        private IpSecAlgorithm mAuthentication;
-
-        // Authenticated Encryption Algorithm
-        private IpSecAlgorithm mAuthenticatedEncryption;
-
-        @Override
-        public String toString() {
-            return new StringBuilder()
-                    .append("{mSpiResourceId=")
-                    .append(mSpiResourceId)
-                    .append(", mEncryption=")
-                    .append(mEncryption)
-                    .append(", mAuthentication=")
-                    .append(mAuthentication)
-                    .append(", mAuthenticatedEncryption=")
-                    .append(mAuthenticatedEncryption)
-                    .append("}")
-                    .toString();
-        }
-
-        static boolean equals(IpSecConfig.Flow lhs, IpSecConfig.Flow rhs) {
-            if (lhs == null || rhs == null) return (lhs == rhs);
-            return (lhs.mSpiResourceId == rhs.mSpiResourceId
-                    && IpSecAlgorithm.equals(lhs.mEncryption, rhs.mEncryption)
-                    && IpSecAlgorithm.equals(lhs.mAuthentication, rhs.mAuthentication));
-        }
-    }
+    // Minimum requirements for identifying a transform
+    // SPI identifying the IPsec SA in packet processing
+    // and a destination IP address
+    private int mSpiResourceId = IpSecManager.INVALID_RESOURCE_ID;
+
+    // Encryption Algorithm
+    private IpSecAlgorithm mEncryption;
+
+    // Authentication Algorithm
+    private IpSecAlgorithm mAuthentication;
 
-    private final Flow[] mFlow = new Flow[] {new Flow(), new Flow()};
+    // Authenticated Encryption Algorithm
+    private IpSecAlgorithm mAuthenticatedEncryption;
 
     // For tunnel mode IPv4 UDP Encapsulation
     // IpSecTransform#ENCAP_ESP_*, such as ENCAP_ESP_OVER_UDP_IKE
@@ -100,36 +70,37 @@ public final class IpSecConfig implements Parcelable {
         mMode = mode;
     }
 
-    /** Set the local IP address for Tunnel mode */
-    public void setLocalAddress(String localAddress) {
-        mLocalAddress = localAddress;
+    /** Set the source IP addres for this IPsec transform */
+    public void setSourceAddress(String sourceAddress) {
+        mSourceAddress = sourceAddress;
     }
 
-    /** Set the remote IP address for this IPsec transform */
-    public void setRemoteAddress(String remoteAddress) {
-        mRemoteAddress = remoteAddress;
+    /** Set the destination IP address for this IPsec transform */
+    public void setDestinationAddress(String destinationAddress) {
+        mDestinationAddress = destinationAddress;
     }
 
-    /** Set the SPI for a given direction by resource ID */
-    public void setSpiResourceId(int direction, int resourceId) {
-        mFlow[direction].mSpiResourceId = resourceId;
+    /** Set the SPI by resource ID */
+    public void setSpiResourceId(int resourceId) {
+        mSpiResourceId = resourceId;
     }
 
-    /** Set the encryption algorithm for a given direction */
-    public void setEncryption(int direction, IpSecAlgorithm encryption) {
-        mFlow[direction].mEncryption = encryption;
+    /** Set the encryption algorithm */
+    public void setEncryption(IpSecAlgorithm encryption) {
+        mEncryption = encryption;
     }
 
-    /** Set the authentication algorithm for a given direction */
-    public void setAuthentication(int direction, IpSecAlgorithm authentication) {
-        mFlow[direction].mAuthentication = authentication;
+    /** Set the authentication algorithm */
+    public void setAuthentication(IpSecAlgorithm authentication) {
+        mAuthentication = authentication;
     }
 
-    /** Set the authenticated encryption algorithm for a given direction */
-    public void setAuthenticatedEncryption(int direction, IpSecAlgorithm authenticatedEncryption) {
-        mFlow[direction].mAuthenticatedEncryption = authenticatedEncryption;
+    /** Set the authenticated encryption algorithm */
+    public void setAuthenticatedEncryption(IpSecAlgorithm authenticatedEncryption) {
+        mAuthenticatedEncryption = authenticatedEncryption;
     }
 
+    /** Set the underlying network that will carry traffic for this transform */
     public void setNetwork(Network network) {
         mNetwork = network;
     }
@@ -155,28 +126,28 @@ public final class IpSecConfig implements Parcelable {
         return mMode;
     }
 
-    public String getLocalAddress() {
-        return mLocalAddress;
+    public String getSourceAddress() {
+        return mSourceAddress;
     }
 
-    public int getSpiResourceId(int direction) {
-        return mFlow[direction].mSpiResourceId;
+    public int getSpiResourceId() {
+        return mSpiResourceId;
     }
 
-    public String getRemoteAddress() {
-        return mRemoteAddress;
+    public String getDestinationAddress() {
+        return mDestinationAddress;
     }
 
-    public IpSecAlgorithm getEncryption(int direction) {
-        return mFlow[direction].mEncryption;
+    public IpSecAlgorithm getEncryption() {
+        return mEncryption;
     }
 
-    public IpSecAlgorithm getAuthentication(int direction) {
-        return mFlow[direction].mAuthentication;
+    public IpSecAlgorithm getAuthentication() {
+        return mAuthentication;
     }
 
-    public IpSecAlgorithm getAuthenticatedEncryption(int direction) {
-        return mFlow[direction].mAuthenticatedEncryption;
+    public IpSecAlgorithm getAuthenticatedEncryption() {
+        return mAuthenticatedEncryption;
     }
 
     public Network getNetwork() {
@@ -209,17 +180,13 @@ public final class IpSecConfig implements Parcelable {
     @Override
     public void writeToParcel(Parcel out, int flags) {
         out.writeInt(mMode);
-        out.writeString(mLocalAddress);
-        out.writeString(mRemoteAddress);
+        out.writeString(mSourceAddress);
+        out.writeString(mDestinationAddress);
         out.writeParcelable(mNetwork, flags);
-        out.writeInt(mFlow[IpSecTransform.DIRECTION_IN].mSpiResourceId);
-        out.writeParcelable(mFlow[IpSecTransform.DIRECTION_IN].mEncryption, flags);
-        out.writeParcelable(mFlow[IpSecTransform.DIRECTION_IN].mAuthentication, flags);
-        out.writeParcelable(mFlow[IpSecTransform.DIRECTION_IN].mAuthenticatedEncryption, flags);
-        out.writeInt(mFlow[IpSecTransform.DIRECTION_OUT].mSpiResourceId);
-        out.writeParcelable(mFlow[IpSecTransform.DIRECTION_OUT].mEncryption, flags);
-        out.writeParcelable(mFlow[IpSecTransform.DIRECTION_OUT].mAuthentication, flags);
-        out.writeParcelable(mFlow[IpSecTransform.DIRECTION_OUT].mAuthenticatedEncryption, flags);
+        out.writeInt(mSpiResourceId);
+        out.writeParcelable(mEncryption, flags);
+        out.writeParcelable(mAuthentication, flags);
+        out.writeParcelable(mAuthenticatedEncryption, flags);
         out.writeInt(mEncapType);
         out.writeInt(mEncapSocketResourceId);
         out.writeInt(mEncapRemotePort);
@@ -231,22 +198,15 @@ public final class IpSecConfig implements Parcelable {
 
     private IpSecConfig(Parcel in) {
         mMode = in.readInt();
-        mLocalAddress = in.readString();
-        mRemoteAddress = in.readString();
+        mSourceAddress = in.readString();
+        mDestinationAddress = in.readString();
         mNetwork = (Network) in.readParcelable(Network.class.getClassLoader());
-        mFlow[IpSecTransform.DIRECTION_IN].mSpiResourceId = in.readInt();
-        mFlow[IpSecTransform.DIRECTION_IN].mEncryption =
-                (IpSecAlgorithm) in.readParcelable(IpSecAlgorithm.class.getClassLoader());
-        mFlow[IpSecTransform.DIRECTION_IN].mAuthentication =
-                (IpSecAlgorithm) in.readParcelable(IpSecAlgorithm.class.getClassLoader());
-        mFlow[IpSecTransform.DIRECTION_IN].mAuthenticatedEncryption =
-                (IpSecAlgorithm) in.readParcelable(IpSecAlgorithm.class.getClassLoader());
-        mFlow[IpSecTransform.DIRECTION_OUT].mSpiResourceId = in.readInt();
-        mFlow[IpSecTransform.DIRECTION_OUT].mEncryption =
+        mSpiResourceId = in.readInt();
+        mEncryption =
                 (IpSecAlgorithm) in.readParcelable(IpSecAlgorithm.class.getClassLoader());
-        mFlow[IpSecTransform.DIRECTION_OUT].mAuthentication =
+        mAuthentication =
                 (IpSecAlgorithm) in.readParcelable(IpSecAlgorithm.class.getClassLoader());
-        mFlow[IpSecTransform.DIRECTION_OUT].mAuthenticatedEncryption =
+        mAuthenticatedEncryption =
                 (IpSecAlgorithm) in.readParcelable(IpSecAlgorithm.class.getClassLoader());
         mEncapType = in.readInt();
         mEncapSocketResourceId = in.readInt();
@@ -260,10 +220,10 @@ public final class IpSecConfig implements Parcelable {
         strBuilder
                 .append("{mMode=")
                 .append(mMode == IpSecTransform.MODE_TUNNEL ? "TUNNEL" : "TRANSPORT")
-                .append(", mLocalAddress=")
-                .append(mLocalAddress)
-                .append(", mRemoteAddress=")
-                .append(mRemoteAddress)
+                .append(", mSourceAddress=")
+                .append(mSourceAddress)
+                .append(", mDestinationAddress=")
+                .append(mDestinationAddress)
                 .append(", mNetwork=")
                 .append(mNetwork)
                 .append(", mEncapType=")
@@ -274,10 +234,14 @@ public final class IpSecConfig implements Parcelable {
                 .append(mEncapRemotePort)
                 .append(", mNattKeepaliveInterval=")
                 .append(mNattKeepaliveInterval)
-                .append(", mFlow[OUT]=")
-                .append(mFlow[IpSecTransform.DIRECTION_OUT])
-                .append(", mFlow[IN]=")
-                .append(mFlow[IpSecTransform.DIRECTION_IN])
+                .append("{mSpiResourceId=")
+                .append(mSpiResourceId)
+                .append(", mEncryption=")
+                .append(mEncryption)
+                .append(", mAuthentication=")
+                .append(mAuthentication)
+                .append(", mAuthenticatedEncryption=")
+                .append(mAuthenticatedEncryption)
                 .append("}");
 
         return strBuilder.toString();
@@ -299,17 +263,18 @@ public final class IpSecConfig implements Parcelable {
     public static boolean equals(IpSecConfig lhs, IpSecConfig rhs) {
         if (lhs == null || rhs == null) return (lhs == rhs);
         return (lhs.mMode == rhs.mMode
-                && lhs.mLocalAddress.equals(rhs.mLocalAddress)
-                && lhs.mRemoteAddress.equals(rhs.mRemoteAddress)
+                && lhs.mSourceAddress.equals(rhs.mSourceAddress)
+                && lhs.mDestinationAddress.equals(rhs.mDestinationAddress)
                 && ((lhs.mNetwork != null && lhs.mNetwork.equals(rhs.mNetwork))
                         || (lhs.mNetwork == rhs.mNetwork))
                 && lhs.mEncapType == rhs.mEncapType
                 && lhs.mEncapSocketResourceId == rhs.mEncapSocketResourceId
                 && lhs.mEncapRemotePort == rhs.mEncapRemotePort
                 && lhs.mNattKeepaliveInterval == rhs.mNattKeepaliveInterval
-                && IpSecConfig.Flow.equals(lhs.mFlow[IpSecTransform.DIRECTION_OUT],
-                        rhs.mFlow[IpSecTransform.DIRECTION_OUT])
-                && IpSecConfig.Flow.equals(lhs.mFlow[IpSecTransform.DIRECTION_IN],
-                        rhs.mFlow[IpSecTransform.DIRECTION_IN]));
+                && lhs.mSpiResourceId == rhs.mSpiResourceId
+                && IpSecAlgorithm.equals(lhs.mEncryption, rhs.mEncryption)
+                && IpSecAlgorithm.equals(
+                        lhs.mAuthenticatedEncryption, rhs.mAuthenticatedEncryption)
+                && IpSecAlgorithm.equals(lhs.mAuthentication, rhs.mAuthentication));
     }
 }
diff --git a/core/java/android/net/IpSecManager.java b/core/java/android/net/IpSecManager.java
index 34cfa9b2153d..67d4fcac97d6 100644
--- a/core/java/android/net/IpSecManager.java
+++ b/core/java/android/net/IpSecManager.java
@@ -17,6 +17,7 @@ package android.net;
 
 import static com.android.internal.util.Preconditions.checkNotNull;
 
+import android.annotation.IntDef;
 import android.annotation.NonNull;
 import android.annotation.SystemService;
 import android.annotation.TestApi;
@@ -33,6 +34,8 @@ import dalvik.system.CloseGuard;
 
 import java.io.FileDescriptor;
 import java.io.IOException;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
 import java.net.DatagramSocket;
 import java.net.InetAddress;
 import java.net.Socket;
@@ -53,6 +56,23 @@ public final class IpSecManager {
     private static final String TAG = "IpSecManager";
 
     /**
+     * For direction-specific attributes of an {@link IpSecTransform}, indicates that an attribute
+     * applies to traffic towards the host.
+     */
+    public static final int DIRECTION_IN = 0;
+
+    /**
+     * For direction-specific attributes of an {@link IpSecTransform}, indicates that an attribute
+     * applies to traffic from the host.
+     */
+    public static final int DIRECTION_OUT = 1;
+
+    /** @hide */
+    @IntDef(value = {DIRECTION_IN, DIRECTION_OUT})
+    @Retention(RetentionPolicy.SOURCE)
+    public @interface PolicyDirection {}
+
+    /**
      * The Security Parameter Index (SPI) 0 indicates an unknown or invalid index.
      *
      * <p>No IPsec packet may contain an SPI of 0.
@@ -125,7 +145,7 @@ public final class IpSecManager {
      */
     public static final class SecurityParameterIndex implements AutoCloseable {
         private final IIpSecService mService;
-        private final InetAddress mRemoteAddress;
+        private final InetAddress mDestinationAddress;
         private final CloseGuard mCloseGuard = CloseGuard.get();
         private int mSpi = INVALID_SECURITY_PARAMETER_INDEX;
         private int mResourceId = INVALID_RESOURCE_ID;
@@ -164,14 +184,14 @@ public final class IpSecManager {
         }
 
         private SecurityParameterIndex(
-                @NonNull IIpSecService service, int direction, InetAddress remoteAddress, int spi)
+                @NonNull IIpSecService service, InetAddress destinationAddress, int spi)
                 throws ResourceUnavailableException, SpiUnavailableException {
             mService = service;
-            mRemoteAddress = remoteAddress;
+            mDestinationAddress = destinationAddress;
             try {
                 IpSecSpiResponse result =
                         mService.allocateSecurityParameterIndex(
-                                direction, remoteAddress.getHostAddress(), spi, new Binder());
+                                destinationAddress.getHostAddress(), spi, new Binder());
 
                 if (result == null) {
                     throw new NullPointerException("Received null response from IpSecService");
@@ -216,25 +236,23 @@ public final class IpSecManager {
     }
 
     /**
-     * Reserve a random SPI for traffic bound to or from the specified remote address.
+     * Reserve a random SPI for traffic bound to or from the specified destination address.
      *
      * <p>If successful, this SPI is guaranteed available until released by a call to {@link
      * SecurityParameterIndex#close()}.
      *
-     * @param direction {@link IpSecTransform#DIRECTION_IN} or {@link IpSecTransform#DIRECTION_OUT}
-     * @param remoteAddress address of the remote. SPIs must be unique for each remoteAddress
+     * @param destinationAddress the destination address for traffic bearing the requested SPI.
+     *     For inbound traffic, the destination should be an address currently assigned on-device.
      * @return the reserved SecurityParameterIndex
-     * @throws ResourceUnavailableException indicating that too many SPIs are currently allocated
-     *     for this user
-     * @throws SpiUnavailableException indicating that a particular SPI cannot be reserved
+     * @throws {@link #ResourceUnavailableException} indicating that too many SPIs are
+     *     currently allocated for this user
      */
-    public SecurityParameterIndex allocateSecurityParameterIndex(
-            int direction, InetAddress remoteAddress) throws ResourceUnavailableException {
+    public SecurityParameterIndex allocateSecurityParameterIndex(InetAddress destinationAddress)
+            throws ResourceUnavailableException {
         try {
             return new SecurityParameterIndex(
                     mService,
-                    direction,
-                    remoteAddress,
+                    destinationAddress,
                     IpSecManager.INVALID_SECURITY_PARAMETER_INDEX);
         } catch (SpiUnavailableException unlikely) {
             throw new ResourceUnavailableException("No SPIs available");
@@ -242,26 +260,27 @@ public final class IpSecManager {
     }
 
     /**
-     * Reserve the requested SPI for traffic bound to or from the specified remote address.
+     * Reserve the requested SPI for traffic bound to or from the specified destination address.
      *
      * <p>If successful, this SPI is guaranteed available until released by a call to {@link
      * SecurityParameterIndex#close()}.
      *
-     * @param direction {@link IpSecTransform#DIRECTION_IN} or {@link IpSecTransform#DIRECTION_OUT}
-     * @param remoteAddress address of the remote. SPIs must be unique for each remoteAddress
+     * @param destinationAddress the destination address for traffic bearing the requested SPI.
+     *     For inbound traffic, the destination should be an address currently assigned on-device.
      * @param requestedSpi the requested SPI, or '0' to allocate a random SPI
      * @return the reserved SecurityParameterIndex
-     * @throws ResourceUnavailableException indicating that too many SPIs are currently allocated
-     *     for this user
-     * @throws SpiUnavailableException indicating that the requested SPI could not be reserved
+     * @throws {@link #ResourceUnavailableException} indicating that too many SPIs are
+     *     currently allocated for this user
+     * @throws {@link #SpiUnavailableException} indicating that the requested SPI could not be
+     *     reserved
      */
     public SecurityParameterIndex allocateSecurityParameterIndex(
-            int direction, InetAddress remoteAddress, int requestedSpi)
+            InetAddress destinationAddress, int requestedSpi)
             throws SpiUnavailableException, ResourceUnavailableException {
         if (requestedSpi == IpSecManager.INVALID_SECURITY_PARAMETER_INDEX) {
             throw new IllegalArgumentException("Requested SPI must be a valid (non-zero) SPI");
         }
-        return new SecurityParameterIndex(mService, direction, remoteAddress, requestedSpi);
+        return new SecurityParameterIndex(mService, destinationAddress, requestedSpi);
     }
 
     /**
@@ -269,14 +288,14 @@ public final class IpSecManager {
      *
      * <p>This applies transport mode encapsulation to the given socket. Once applied, I/O on the
      * socket will be encapsulated according to the parameters of the {@code IpSecTransform}. When
-     * the transform is removed from the socket by calling {@link #removeTransportModeTransform},
+     * the transform is removed from the socket by calling {@link #removeTransportModeTransforms},
      * unprotected traffic can resume on that socket.
      *
      * <p>For security reasons, the destination address of any traffic on the socket must match the
      * remote {@code InetAddress} of the {@code IpSecTransform}. Attempts to send traffic to any
      * other IP address will result in an IOException. In addition, reads and writes on the socket
      * will throw IOException if the user deactivates the transform (by calling {@link
-     * IpSecTransform#close()}) without calling {@link #removeTransportModeTransform}.
+     * IpSecTransform#close()}) without calling {@link #removeTransportModeTransforms}.
      *
      * <h4>Rekey Procedure</h4>
      *
@@ -287,14 +306,15 @@ public final class IpSecManager {
      * in-flight packets have been received.
      *
      * @param socket a stream socket
+     * @param direction the policy direction either {@link #DIRECTION_IN} or {@link #DIRECTION_OUT}
      * @param transform a transport mode {@code IpSecTransform}
      * @throws IOException indicating that the transform could not be applied
-     * @hide
      */
-    public void applyTransportModeTransform(Socket socket, IpSecTransform transform)
+    public void applyTransportModeTransform(
+            Socket socket, int direction, IpSecTransform transform)
             throws IOException {
         try (ParcelFileDescriptor pfd = ParcelFileDescriptor.fromSocket(socket)) {
-            applyTransportModeTransform(pfd, transform);
+            applyTransportModeTransform(pfd, direction, transform);
         }
     }
 
@@ -303,14 +323,14 @@ public final class IpSecManager {
      *
      * <p>This applies transport mode encapsulation to the given socket. Once applied, I/O on the
      * socket will be encapsulated according to the parameters of the {@code IpSecTransform}. When
-     * the transform is removed from the socket by calling {@link #removeTransportModeTransform},
+     * the transform is removed from the socket by calling {@link #removeTransportModeTransforms},
      * unprotected traffic can resume on that socket.
      *
      * <p>For security reasons, the destination address of any traffic on the socket must match the
      * remote {@code InetAddress} of the {@code IpSecTransform}. Attempts to send traffic to any
      * other IP address will result in an IOException. In addition, reads and writes on the socket
      * will throw IOException if the user deactivates the transform (by calling {@link
-     * IpSecTransform#close()}) without calling {@link #removeTransportModeTransform}.
+     * IpSecTransform#close()}) without calling {@link #removeTransportModeTransforms}.
      *
      * <h4>Rekey Procedure</h4>
      *
@@ -321,14 +341,14 @@ public final class IpSecManager {
      * in-flight packets have been received.
      *
      * @param socket a datagram socket
+     * @param direction the policy direction either DIRECTION_IN or DIRECTION_OUT
      * @param transform a transport mode {@code IpSecTransform}
      * @throws IOException indicating that the transform could not be applied
-     * @hide
      */
-    public void applyTransportModeTransform(DatagramSocket socket, IpSecTransform transform)
-            throws IOException {
+    public void applyTransportModeTransform(
+            DatagramSocket socket, int direction, IpSecTransform transform) throws IOException {
         try (ParcelFileDescriptor pfd = ParcelFileDescriptor.fromDatagramSocket(socket)) {
-            applyTransportModeTransform(pfd, transform);
+            applyTransportModeTransform(pfd, direction, transform);
         }
     }
 
@@ -337,14 +357,14 @@ public final class IpSecManager {
      *
      * <p>This applies transport mode encapsulation to the given socket. Once applied, I/O on the
      * socket will be encapsulated according to the parameters of the {@code IpSecTransform}. When
-     * the transform is removed from the socket by calling {@link #removeTransportModeTransform},
+     * the transform is removed from the socket by calling {@link #removeTransportModeTransforms},
      * unprotected traffic can resume on that socket.
      *
      * <p>For security reasons, the destination address of any traffic on the socket must match the
      * remote {@code InetAddress} of the {@code IpSecTransform}. Attempts to send traffic to any
      * other IP address will result in an IOException. In addition, reads and writes on the socket
      * will throw IOException if the user deactivates the transform (by calling {@link
-     * IpSecTransform#close()}) without calling {@link #removeTransportModeTransform}.
+     * IpSecTransform#close()}) without calling {@link #removeTransportModeTransforms}.
      *
      * <h4>Rekey Procedure</h4>
      *
@@ -355,24 +375,27 @@ public final class IpSecManager {
      * in-flight packets have been received.
      *
      * @param socket a socket file descriptor
+     * @param direction the policy direction either DIRECTION_IN or DIRECTION_OUT
      * @param transform a transport mode {@code IpSecTransform}
      * @throws IOException indicating that the transform could not be applied
      */
-    public void applyTransportModeTransform(FileDescriptor socket, IpSecTransform transform)
+    public void applyTransportModeTransform(
+            FileDescriptor socket, int direction, IpSecTransform transform)
             throws IOException {
         // We dup() the FileDescriptor here because if we don't, then the ParcelFileDescriptor()
         // constructor takes control and closes the user's FD when we exit the method
         // This is behaviorally the same as the other versions, but the PFD constructor does not
         // dup() automatically, whereas PFD.fromSocket() and PDF.fromDatagramSocket() do dup().
         try (ParcelFileDescriptor pfd = ParcelFileDescriptor.dup(socket)) {
-            applyTransportModeTransform(pfd, transform);
+            applyTransportModeTransform(pfd, direction, transform);
         }
     }
 
     /* Call down to activate a transform */
-    private void applyTransportModeTransform(ParcelFileDescriptor pfd, IpSecTransform transform) {
+    private void applyTransportModeTransform(
+            ParcelFileDescriptor pfd, int direction, IpSecTransform transform) throws IOException {
         try {
-            mService.applyTransportModeTransform(pfd, transform.getResourceId());
+            mService.applyTransportModeTransform(pfd, direction, transform.getResourceId());
         } catch (RemoteException e) {
             throw e.rethrowFromSystemServer();
         }
@@ -407,12 +430,11 @@ public final class IpSecManager {
      * @param socket a socket that previously had a transform applied to it
      * @param transform the IPsec Transform that was previously applied to the given socket
      * @throws IOException indicating that the transform could not be removed from the socket
-     * @hide
      */
-    public void removeTransportModeTransform(Socket socket, IpSecTransform transform)
+    public void removeTransportModeTransforms(Socket socket, IpSecTransform transform)
             throws IOException {
         try (ParcelFileDescriptor pfd = ParcelFileDescriptor.fromSocket(socket)) {
-            removeTransportModeTransform(pfd, transform);
+            removeTransportModeTransforms(pfd, transform);
         }
     }
 
@@ -430,12 +452,11 @@ public final class IpSecManager {
      * @param socket a socket that previously had a transform applied to it
      * @param transform the IPsec Transform that was previously applied to the given socket
      * @throws IOException indicating that the transform could not be removed from the socket
-     * @hide
      */
-    public void removeTransportModeTransform(DatagramSocket socket, IpSecTransform transform)
+    public void removeTransportModeTransforms(DatagramSocket socket, IpSecTransform transform)
             throws IOException {
         try (ParcelFileDescriptor pfd = ParcelFileDescriptor.fromDatagramSocket(socket)) {
-            removeTransportModeTransform(pfd, transform);
+            removeTransportModeTransforms(pfd, transform);
         }
     }
 
@@ -454,17 +475,17 @@ public final class IpSecManager {
      * @param transform the IPsec Transform that was previously applied to the given socket
      * @throws IOException indicating that the transform could not be removed from the socket
      */
-    public void removeTransportModeTransform(FileDescriptor socket, IpSecTransform transform)
+    public void removeTransportModeTransforms(FileDescriptor socket, IpSecTransform transform)
             throws IOException {
         try (ParcelFileDescriptor pfd = ParcelFileDescriptor.dup(socket)) {
-            removeTransportModeTransform(pfd, transform);
+            removeTransportModeTransforms(pfd, transform);
         }
     }
 
     /* Call down to remove a transform */
-    private void removeTransportModeTransform(ParcelFileDescriptor pfd, IpSecTransform transform) {
+    private void removeTransportModeTransforms(ParcelFileDescriptor pfd, IpSecTransform transform) {
         try {
-            mService.removeTransportModeTransform(pfd, transform.getResourceId());
+            mService.removeTransportModeTransforms(pfd, transform.getResourceId());
         } catch (RemoteException e) {
             throw e.rethrowFromSystemServer();
         }
diff --git a/core/java/android/net/IpSecTransform.java b/core/java/android/net/IpSecTransform.java
index 102ba6d94faa..7b9b4830929d 100644
--- a/core/java/android/net/IpSecTransform.java
+++ b/core/java/android/net/IpSecTransform.java
@@ -38,13 +38,11 @@ import java.lang.annotation.RetentionPolicy;
 import java.net.InetAddress;
 
 /**
- * This class represents an IPsec transform, which comprises security associations in one or both
- * directions.
+ * This class represents a transform, which roughly corresponds to an IPsec Security Association.
  *
  * <p>Transforms are created using {@link IpSecTransform.Builder}. Each {@code IpSecTransform}
- * object encapsulates the properties and state of an inbound and outbound IPsec security
- * association. That includes, but is not limited to, algorithm choice, key material, and allocated
- * system resources.
+ * object encapsulates the properties and state of an IPsec security association. That includes,
+ * but is not limited to, algorithm choice, key material, and allocated system resources.
  *
  * @see <a href="https://tools.ietf.org/html/rfc4301">RFC 4301, Security Architecture for the
  *     Internet Protocol</a>
@@ -52,23 +50,6 @@ import java.net.InetAddress;
 public final class IpSecTransform implements AutoCloseable {
     private static final String TAG = "IpSecTransform";
 
-    /**
-     * For direction-specific attributes of an {@link IpSecTransform}, indicates that an attribute
-     * applies to traffic towards the host.
-     */
-    public static final int DIRECTION_IN = 0;
-
-    /**
-     * For direction-specific attributes of an {@link IpSecTransform}, indicates that an attribute
-     * applies to traffic from the host.
-     */
-    public static final int DIRECTION_OUT = 1;
-
-    /** @hide */
-    @IntDef(value = {DIRECTION_IN, DIRECTION_OUT})
-    @Retention(RetentionPolicy.SOURCE)
-    public @interface TransformDirection {}
-
     /** @hide */
     public static final int MODE_TRANSPORT = 0;
 
@@ -170,7 +151,7 @@ public final class IpSecTransform implements AutoCloseable {
      *
      * <p>Deactivating a transform while it is still applied to a socket will result in errors on
      * that socket. Make sure to remove transforms by calling {@link
-     * IpSecManager#removeTransportModeTransform}. Note, removing an {@code IpSecTransform} from a
+     * IpSecManager#removeTransportModeTransforms}. Note, removing an {@code IpSecTransform} from a
      * socket will not deactivate it (because one transform may be applied to multiple sockets).
      *
      * <p>It is safe to call this method on a transform that has already been deactivated.
@@ -272,85 +253,49 @@ public final class IpSecTransform implements AutoCloseable {
         private IpSecConfig mConfig;
 
         /**
-         * Set the encryption algorithm for the given direction.
-         *
-         * <p>If encryption is set for a direction without also providing an SPI for that direction,
-         * creation of an {@code IpSecTransform} will fail when attempting to build the transform.
+         * Set the encryption algorithm.
          *
          * <p>Encryption is mutually exclusive with authenticated encryption.
          *
-         * @param direction either {@link #DIRECTION_IN} or {@link #DIRECTION_OUT}
          * @param algo {@link IpSecAlgorithm} specifying the encryption to be applied.
          */
-        public IpSecTransform.Builder setEncryption(
-                @TransformDirection int direction, IpSecAlgorithm algo) {
+        public IpSecTransform.Builder setEncryption(@NonNull IpSecAlgorithm algo) {
             // TODO: throw IllegalArgumentException if algo is not an encryption algorithm.
-            mConfig.setEncryption(direction, algo);
+            Preconditions.checkNotNull(algo);
+            mConfig.setEncryption(algo);
             return this;
         }
 
         /**
-         * Set the authentication (integrity) algorithm for the given direction.
-         *
-         * <p>If authentication is set for a direction without also providing an SPI for that
-         * direction, creation of an {@code IpSecTransform} will fail when attempting to build the
-         * transform.
+         * Set the authentication (integrity) algorithm.
          *
          * <p>Authentication is mutually exclusive with authenticated encryption.
          *
-         * @param direction either {@link #DIRECTION_IN} or {@link #DIRECTION_OUT}
          * @param algo {@link IpSecAlgorithm} specifying the authentication to be applied.
          */
-        public IpSecTransform.Builder setAuthentication(
-                @TransformDirection int direction, IpSecAlgorithm algo) {
+        public IpSecTransform.Builder setAuthentication(@NonNull IpSecAlgorithm algo) {
             // TODO: throw IllegalArgumentException if algo is not an authentication algorithm.
-            mConfig.setAuthentication(direction, algo);
+            Preconditions.checkNotNull(algo);
+            mConfig.setAuthentication(algo);
             return this;
         }
 
         /**
-         * Set the authenticated encryption algorithm for the given direction.
-         *
-         * <p>If an authenticated encryption algorithm is set for a given direction without also
-         * providing an SPI for that direction, creation of an {@code IpSecTransform} will fail when
-         * attempting to build the transform.
+         * Set the authenticated encryption algorithm.
          *
-         * <p>The Authenticated Encryption (AE) class of algorithms are also known as Authenticated
-         * Encryption with Associated Data (AEAD) algorithms, or Combined mode algorithms (as
-         * referred to in <a href="https://tools.ietf.org/html/rfc4301">RFC 4301</a>).
+         * <p>The Authenticated Encryption (AE) class of algorithms are also known as
+         * Authenticated Encryption with Associated Data (AEAD) algorithms, or Combined mode
+         * algorithms (as referred to in
+         * <a href="https://tools.ietf.org/html/rfc4301">RFC 4301</a>).
          *
          * <p>Authenticated encryption is mutually exclusive with encryption and authentication.
          *
-         * @param direction either {@link #DIRECTION_IN} or {@link #DIRECTION_OUT}
          * @param algo {@link IpSecAlgorithm} specifying the authenticated encryption algorithm to
          *     be applied.
          */
-        public IpSecTransform.Builder setAuthenticatedEncryption(
-                @TransformDirection int direction, IpSecAlgorithm algo) {
-            mConfig.setAuthenticatedEncryption(direction, algo);
-            return this;
-        }
-
-        /**
-         * Set the SPI for the given direction.
-         *
-         * <p>Because IPsec operates at the IP layer, this 32-bit identifier uniquely identifies
-         * packets to a given destination address. To prevent SPI collisions, values should be
-         * reserved by calling {@link IpSecManager#allocateSecurityParameterIndex}.
-         *
-         * <p>If the SPI and algorithms are omitted for one direction, traffic in that direction
-         * will not be encrypted or authenticated.
-         *
-         * @param direction either {@link #DIRECTION_IN} or {@link #DIRECTION_OUT}
-         * @param spi a unique {@link IpSecManager.SecurityParameterIndex} to identify transformed
-         *     traffic
-         */
-        public IpSecTransform.Builder setSpi(
-                @TransformDirection int direction, IpSecManager.SecurityParameterIndex spi) {
-            if (spi.getResourceId() == INVALID_RESOURCE_ID) {
-                throw new IllegalArgumentException("Invalid SecurityParameterIndex");
-            }
-            mConfig.setSpiResourceId(direction, spi.getResourceId());
+        public IpSecTransform.Builder setAuthenticatedEncryption(@NonNull IpSecAlgorithm algo) {
+            Preconditions.checkNotNull(algo);
+            mConfig.setAuthenticatedEncryption(algo);
             return this;
         }
 
@@ -363,7 +308,8 @@ public final class IpSecTransform implements AutoCloseable {
          * @hide
          */
         @SystemApi
-        public IpSecTransform.Builder setUnderlyingNetwork(Network net) {
+        public IpSecTransform.Builder setUnderlyingNetwork(@NonNull Network net) {
+            Preconditions.checkNotNull(net);
             mConfig.setNetwork(net);
             return this;
         }
@@ -382,7 +328,8 @@ public final class IpSecTransform implements AutoCloseable {
          *     encapsulated traffic. In the case of IKEv2, this should be port 4500.
          */
         public IpSecTransform.Builder setIpv4Encapsulation(
-                IpSecManager.UdpEncapsulationSocket localSocket, int remotePort) {
+                @NonNull IpSecManager.UdpEncapsulationSocket localSocket, int remotePort) {
+            Preconditions.checkNotNull(localSocket);
             mConfig.setEncapType(ENCAP_ESPINUDP);
             if (localSocket.getResourceId() == INVALID_RESOURCE_ID) {
                 throw new IllegalArgumentException("Invalid UdpEncapsulationSocket");
@@ -419,24 +366,33 @@ public final class IpSecTransform implements AutoCloseable {
          * will not affect any network traffic until it has been applied to one or more sockets.
          *
          * @see IpSecManager#applyTransportModeTransform
-         * @param remoteAddress the remote {@code InetAddress} of traffic on sockets that will use
-         *     this transform
+         * @param sourceAddress the source {@code InetAddress} of traffic on sockets that will use
+         *     this transform; this address must belong to the Network used by all sockets that
+         *     utilize this transform; if provided, then only traffic originating from the
+         *     specified source address will be processed.
+         * @param spi a unique {@link IpSecManager.SecurityParameterIndex} to identify transformed
+         *     traffic
          * @throws IllegalArgumentException indicating that a particular combination of transform
          *     properties is invalid
-         * @throws IpSecManager.ResourceUnavailableException indicating that too many transforms are
-         *     active
+         * @throws IpSecManager.ResourceUnavailableException indicating that too many transforms
+         *     are active
          * @throws IpSecManager.SpiUnavailableException indicating the rare case where an SPI
          *     collides with an existing transform
          * @throws IOException indicating other errors
          */
-        public IpSecTransform buildTransportModeTransform(InetAddress remoteAddress)
+        public IpSecTransform buildTransportModeTransform(
+                @NonNull InetAddress sourceAddress,
+                @NonNull IpSecManager.SecurityParameterIndex spi)
                 throws IpSecManager.ResourceUnavailableException,
                         IpSecManager.SpiUnavailableException, IOException {
-            if (remoteAddress == null) {
-                throw new IllegalArgumentException("Remote address may not be null or empty!");
+            Preconditions.checkNotNull(sourceAddress);
+            Preconditions.checkNotNull(spi);
+            if (spi.getResourceId() == INVALID_RESOURCE_ID) {
+                throw new IllegalArgumentException("Invalid SecurityParameterIndex");
             }
             mConfig.setMode(MODE_TRANSPORT);
-            mConfig.setRemoteAddress(remoteAddress.getHostAddress());
+            mConfig.setSourceAddress(sourceAddress.getHostAddress());
+            mConfig.setSpiResourceId(spi.getResourceId());
             // FIXME: modifying a builder after calling build can change the built transform.
             return new IpSecTransform(mContext, mConfig).activate();
         }
@@ -445,26 +401,33 @@ public final class IpSecTransform implements AutoCloseable {
          * Build and return an {@link IpSecTransform} object as a Tunnel Mode Transform. Some
          * parameters have interdependencies that are checked at build time.
          *
-         * @param localAddress the {@link InetAddress} that provides the local endpoint for this
+         * @param sourceAddress the {@link InetAddress} that provides the source address for this
          *     IPsec tunnel. This is almost certainly an address belonging to the {@link Network}
          *     that will originate the traffic, which is set as the {@link #setUnderlyingNetwork}.
-         * @param remoteAddress the {@link InetAddress} representing the remote endpoint of this
-         *     IPsec tunnel.
+         * @param spi a unique {@link IpSecManager.SecurityParameterIndex} to identify transformed
+         *     traffic
          * @throws IllegalArgumentException indicating that a particular combination of transform
          *     properties is invalid.
+         * @throws IpSecManager.ResourceUnavailableException indicating that too many transforms
+         *     are active
+         * @throws IpSecManager.SpiUnavailableException indicating the rare case where an SPI
+         *     collides with an existing transform
+         * @throws IOException indicating other errors
          * @hide
          */
         public IpSecTransform buildTunnelModeTransform(
-                InetAddress localAddress, InetAddress remoteAddress) {
-            if (localAddress == null) {
-                throw new IllegalArgumentException("Local address may not be null or empty!");
-            }
-            if (remoteAddress == null) {
-                throw new IllegalArgumentException("Remote address may not be null or empty!");
+                @NonNull InetAddress sourceAddress,
+                @NonNull IpSecManager.SecurityParameterIndex spi)
+                throws IpSecManager.ResourceUnavailableException,
+                        IpSecManager.SpiUnavailableException, IOException {
+            Preconditions.checkNotNull(sourceAddress);
+            Preconditions.checkNotNull(spi);
+            if (spi.getResourceId() == INVALID_RESOURCE_ID) {
+                throw new IllegalArgumentException("Invalid SecurityParameterIndex");
             }
-            mConfig.setLocalAddress(localAddress.getHostAddress());
-            mConfig.setRemoteAddress(remoteAddress.getHostAddress());
             mConfig.setMode(MODE_TUNNEL);
+            mConfig.setSourceAddress(sourceAddress.getHostAddress());
+            mConfig.setSpiResourceId(spi.getResourceId());
             return new IpSecTransform(mContext, mConfig);
         }