8277489: Rewrite JAAS UnixLoginModule with FFM

wangweij · TheRealMDoerr · wangweij · commit eda15aa19c36 · 2026-01-22T12:16:09.000Z
Co-authored-by: Martin Doerr &lt;mdoerr@openjdk.org&gt;
Reviewed-by: mdoerr, ascarpino, erikj
diff --git a/make/modules/jdk.security.auth/Lib.gmk b/make/modules/jdk.security.auth/Lib.gmk
@@ -31,13 +31,14 @@ include LibCommon.gmk
 ## Build libjaas
 ################################################################################
 
-$(eval $(call SetupJdkLibrary, BUILD_LIBJAAS, \
-    NAME := jaas, \
-    OPTIMIZATION := LOW, \
-    EXTRA_HEADER_DIRS := java.base:libjava, \
-    LIBS_windows := advapi32.lib mpr.lib netapi32.lib user32.lib, \
-))
-
-TARGETS += $(BUILD_LIBJAAS)
+ifeq ($(call isTargetOs, windows), true)
+  $(eval $(call SetupJdkLibrary, BUILD_LIBJAAS, \
+      NAME := jaas, \
+      OPTIMIZATION := LOW, \
+      EXTRA_HEADER_DIRS := java.base:libjava, \
+      LIBS_windows := advapi32.lib mpr.lib netapi32.lib user32.lib, \
+  ))
 
+  TARGETS += $(BUILD_LIBJAAS)
+endif
 ################################################################################
diff --git a/src/java.base/share/classes/module-info.java b/src/java.base/share/classes/module-info.java
@@ -274,7 +274,8 @@
         jdk.httpserver,
         jdk.jlink,
         jdk.jpackage,
-        jdk.net;
+        jdk.net,
+        jdk.security.auth;
     exports sun.net to
         java.net.http,
         jdk.naming.dns;
diff --git a/src/jdk.security.auth/share/classes/com/sun/security/auth/module/UnixLoginModule.java b/src/jdk.security.auth/share/classes/com/sun/security/auth/module/UnixLoginModule.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2026, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -26,14 +26,14 @@
 package com.sun.security.auth.module;
 
 import java.util.*;
-import java.io.IOException;
 import javax.security.auth.*;
 import javax.security.auth.callback.*;
 import javax.security.auth.login.*;
 import javax.security.auth.spi.*;
 import com.sun.security.auth.UnixPrincipal;
 import com.sun.security.auth.UnixNumericUserPrincipal;
 import com.sun.security.auth.UnixNumericGroupPrincipal;
+import jdk.internal.util.OperatingSystem;
 
 /**
  * This {@code LoginModule} imports a user's Unix
@@ -121,20 +121,34 @@ public void initialize(Subject subject, CallbackHandler callbackHandler,
      */
     public boolean login() throws LoginException {
 
-        long[] unixGroups = null;
+        // Fail immediately on Windows to avoid cygwin-like functions
+        // being loaded, which are not supported.
+        if (OperatingSystem.isWindows()) {
+            throw new FailedLoginException
+                    ("Failed in attempt to import " +
+                            "the underlying system identity information" +
+                            " on " + System.getProperty("os.name"));
+        }
 
         try {
             ss = new UnixSystem();
-        } catch (UnsatisfiedLinkError ule) {
+        } catch (ExceptionInInitializerError | UnsatisfiedLinkError ule) {
+            // Errors could happen in either static blocks or the constructor,
+            // both have a cause.
             succeeded = false;
-            throw new FailedLoginException
+            var error = new FailedLoginException
                                 ("Failed in attempt to import " +
                                 "the underlying system identity information" +
                                 " on " + System.getProperty("os.name"));
+            if (ule.getCause() != null) {
+                error.initCause(ule.getCause());
+            }
+            throw error;
         }
         userPrincipal = new UnixPrincipal(ss.getUsername());
         UIDPrincipal = new UnixNumericUserPrincipal(ss.getUid());
         GIDPrincipal = new UnixNumericGroupPrincipal(ss.getGid(), true);
+        long[] unixGroups = null;
         if (ss.getGroups() != null && ss.getGroups().length > 0) {
             unixGroups = ss.getGroups();
             for (int i = 0; i < unixGroups.length; i++) {
@@ -150,9 +164,11 @@ public boolean login() throws LoginException {
                     "succeeded importing info: ");
             System.out.println("\t\t\tuid = " + ss.getUid());
             System.out.println("\t\t\tgid = " + ss.getGid());
-            unixGroups = ss.getGroups();
-            for (int i = 0; i < unixGroups.length; i++) {
-                System.out.println("\t\t\tsupp gid = " + unixGroups[i]);
+            System.out.println("\t\t\tusername = " + ss.getUsername());
+            if (unixGroups != null) {
+                for (int i = 0; i < unixGroups.length; i++) {
+                    System.out.println("\t\t\tsupp gid = " + unixGroups[i]);
+                }
             }
         }
         succeeded = true;
diff --git a/src/jdk.security.auth/share/classes/com/sun/security/auth/module/UnixSystem.java b/src/jdk.security.auth/share/classes/com/sun/security/auth/module/UnixSystem.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2026, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -25,38 +25,194 @@
 
 package com.sun.security.auth.module;
 
+import jdk.internal.util.Architecture;
+import jdk.internal.util.OperatingSystem;
+
+import java.lang.foreign.AddressLayout;
+import java.lang.foreign.Arena;
+import java.lang.foreign.FunctionDescriptor;
+import java.lang.foreign.GroupLayout;
+import java.lang.foreign.Linker;
+import java.lang.foreign.MemoryLayout;
+import java.lang.foreign.MemorySegment;
+import java.lang.foreign.StructLayout;
+import java.lang.foreign.SymbolLookup;
+import java.lang.foreign.ValueLayout;
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.VarHandle;
+
+import static java.lang.foreign.MemoryLayout.PathElement.groupElement;
+
 /**
  * This class implementation retrieves and makes available Unix
  * UID/GID/groups information for the current user.
  *
  * @since 1.4
  */
+@SuppressWarnings("restricted")
 public class UnixSystem {
 
-    private native void getUnixInfo();
-
-    // Warning: the following 4 fields are used by Unix.c
-
-    /** The current username. */
+    /**
+     * The current username.
+     */
     protected String username;
 
-    /** The current user ID. */
+    /**
+     * The current user ID.
+     */
     protected long uid;
 
-    /** The current group ID. */
+    /**
+     * The current group ID.
+     */
     protected long gid;
 
-    /** The current list of groups. */
+    /**
+     * The current list of groups.
+     */
     protected long[] groups;
 
+    private static final Linker LINKER = Linker.nativeLinker();
+    private static final SymbolLookup SYMBOL_LOOKUP = SymbolLookup.loaderLookup()
+            .or(LINKER.defaultLookup());
+
+    private static final ValueLayout.OfByte C_CHAR
+            = (ValueLayout.OfByte) LINKER.canonicalLayouts().get("char");
+    private static final ValueLayout.OfInt C_INT
+            = (ValueLayout.OfInt) LINKER.canonicalLayouts().get("int");
+    private static final ValueLayout.OfLong C_LONG
+            = (ValueLayout.OfLong) LINKER.canonicalLayouts().get("long");
+    private static final AddressLayout C_POINTER
+            = ((AddressLayout) LINKER.canonicalLayouts().get("void*"))
+            .withTargetLayout(MemoryLayout.sequenceLayout(java.lang.Long.MAX_VALUE, C_CHAR));
+    private static final ValueLayout C_SIZE_T
+            = (ValueLayout) LINKER.canonicalLayouts().get("size_t");
+
+    private static final StructLayout CAPTURE_STATE_LAYOUT
+            = Linker.Option.captureStateLayout();
+    private static final VarHandle VH_errno = CAPTURE_STATE_LAYOUT.varHandle(
+            MemoryLayout.PathElement.groupElement("errno"));
+
+    private static final MethodHandle MH_strerror
+            = LINKER.downcallHandle(SYMBOL_LOOKUP.findOrThrow("strerror"),
+                    FunctionDescriptor.of(C_POINTER, C_INT));
+
+    private static final MethodHandle MH_getgroups
+            = LINKER.downcallHandle(SYMBOL_LOOKUP.findOrThrow("getgroups"),
+                    FunctionDescriptor.of(C_INT, C_INT, C_POINTER),
+                    Linker.Option.captureCallState("errno"));
+    private static final MethodHandle MH_getuid
+            = LINKER.downcallHandle(SYMBOL_LOOKUP.findOrThrow("getuid"),
+                    FunctionDescriptor.of(C_INT));
+
+    // Some architectures require appropriate zero or sign extension to 64 bit.
+    // Use long directly before https://bugs.openjdk.org/browse/JDK-8336664 is resolved.
+    private static final boolean calling_convention_requires_int_as_long
+            = Architecture.isPPC64() || Architecture.isPPC64LE() || Architecture.isS390();
+
+    // getpwuid_r does not work on AIX, instead we use another similar function
+    // extern int _posix_getpwuid_r(uid_t, struct passwd *, char *, int, struct passwd **)
+    private static final MethodHandle MH_getpwuid_r
+            = LINKER.downcallHandle(SYMBOL_LOOKUP.findOrThrow(
+                            OperatingSystem.isAix() ? "_posix_getpwuid_r" : "getpwuid_r"),
+                    FunctionDescriptor.of(C_INT,
+                            calling_convention_requires_int_as_long ? C_LONG : C_INT,
+                            C_POINTER, C_POINTER,
+                            OperatingSystem.isAix() ? C_INT : C_SIZE_T,
+                            C_POINTER));
+
+    private static final GroupLayout ML_passwd = MemoryLayout.structLayout(
+            C_POINTER.withName("pw_name"),
+            C_POINTER.withName("pw_passwd"),
+            C_INT.withName("pw_uid"),
+            C_INT.withName("pw_gid"),
+            // Different platforms have different fields in `struct passwd`.
+            // While we don't need those fields here, the struct needs to be
+            // big enough to avoid buffer overflow when `getpwuid_r` is called.
+            MemoryLayout.paddingLayout(100));
+
+    private static final VarHandle VH_pw_uid
+            = ML_passwd.varHandle(groupElement("pw_uid"));
+    private static final VarHandle VH_pw_gid
+            = ML_passwd.varHandle(groupElement("pw_gid"));
+    private static final VarHandle VH_pw_name
+            = ML_passwd.varHandle(groupElement("pw_name"));
+
+    // The buffer size for the getpwuid_r function:
+    // 1. sysconf(_SC_GETPW_R_SIZE_MAX) on macOS is 4096 and 1024 on Linux,
+    //    so we choose a bigger one.
+    // 2. We do not call sysconf() here because even _SC_GETPW_R_SIZE_MAX
+    //    could be different on different platforms.
+    // 3. We choose int instead of long because the buffer_size argument
+    //    might be `int` or `long` and converting from `long` to `int`
+    //    requires an explicit cast.
+    private static final int GETPW_R_SIZE_MAX = 4096;
+
     /**
      * Instantiate a {@code UnixSystem} and load
      * the native library to access the underlying system information.
      */
-    @SuppressWarnings("restricted")
     public UnixSystem() {
-        System.loadLibrary("jaas");
-        getUnixInfo();
+        // The FFM code has only been tested on multiple platforms
+        // (including macOS, Linux, AIX, etc) and might fail on other
+        // *nix systems. Especially, the `passwd` struct could be defined
+        // differently. I've checked several and an extra 100 chars at the
+        // end seems enough.
+        try (Arena scope = Arena.ofConfined()) {
+            MemorySegment capturedState = scope.allocate(CAPTURE_STATE_LAYOUT);
+            int groupnum = (int) MH_getgroups.invokeExact(capturedState, 0, MemorySegment.NULL);
+            if (groupnum == -1) {
+                throw new RuntimeException("getgroups returns " + groupnum);
+            }
+
+            var gs = scope.allocate(C_INT, groupnum);
+            groupnum = (int) MH_getgroups.invokeExact(capturedState, groupnum, gs);
+            if (groupnum == -1) {
+                var errno = (int) VH_errno.get(capturedState, 0L);
+                var errMsg = (MemorySegment) MH_strerror.invokeExact(errno);
+                throw new RuntimeException("getgroups returns " + groupnum
+                        + ". Reason: " + errMsg.reinterpret(Long.MAX_VALUE).getString(0));
+            }
+
+            groups = new long[groupnum];
+            for (int i = 0; i < groupnum; i++) {
+                groups[i] = Integer.toUnsignedLong(gs.getAtIndex(C_INT, i));
+            }
+
+            var pwd = scope.allocate(ML_passwd);
+            var result = scope.allocate(C_POINTER);
+            var buffer = scope.allocate(GETPW_R_SIZE_MAX);
+
+            long tmpUid = Integer.toUnsignedLong((int) MH_getuid.invokeExact());
+
+            // Do not call invokeExact because the type of buffer_size is not
+            // always long in the underlying system.
+            int out;
+            if (calling_convention_requires_int_as_long) {
+                out = (int) MH_getpwuid_r.invoke(
+                        tmpUid, pwd, buffer, GETPW_R_SIZE_MAX, result);
+            } else {
+                out = (int) MH_getpwuid_r.invoke(
+                        (int) tmpUid, pwd, buffer, GETPW_R_SIZE_MAX, result);
+            }
+            if (out != 0) {
+                // If ERANGE (Result too large) is detected in a new platform,
+                // consider adjusting GETPW_R_SIZE_MAX.
+                var err = (MemorySegment) MH_strerror.invokeExact(out);
+                throw new RuntimeException(err.reinterpret(Long.MAX_VALUE).getString(0));
+            } else if (result.get(ValueLayout.ADDRESS, 0).equals(MemorySegment.NULL)) {
+                throw new RuntimeException("the requested entry is not found");
+            } else {
+                // uid_t and gid_t were defined unsigned.
+                uid = Integer.toUnsignedLong((int) VH_pw_uid.get(pwd, 0L));
+                gid = Integer.toUnsignedLong((int) VH_pw_gid.get(pwd, 0L));
+                username = ((MemorySegment) VH_pw_name.get(pwd, 0L)).getString(0);
+            }
+        } catch (Throwable t) {
+            var error = new UnsatisfiedLinkError("FFM calls failed");
+            error.initCause(t);
+            throw error;
+        }
     }
 
     /**
diff --git a/src/jdk.security.auth/unix/native/libjaas/Unix.c b/src/jdk.security.auth/unix/native/libjaas/Unix.c
diff --git a/test/jdk/com/sun/security/auth/module/AllPlatforms.java b/test/jdk/com/sun/security/auth/module/AllPlatforms.java
