Index: src/lib/crypto/Makefile.in
===================================================================
--- src/lib/crypto/Makefile.in	(revision 23398)
+++ src/lib/crypto/Makefile.in	(working copy)
@@ -22,6 +22,7 @@
 	$(srcdir)/t_hmac.c	\
 	$(srcdir)/t_pkcs5.c	\
 	$(srcdir)/t_cts.c	\
+	$(srcdir)/t_short.c	\
 	$(srcdir)/vectors.c
 
 ##DOSBUILDTOP = ..\..
@@ -184,12 +185,13 @@
 
 clean-unix:: clean-liblinks clean-libs clean-libobjs
 
-check-unix:: t_nfold t_encrypt t_prf t_prng t_hmac t_pkcs5
+check-unix:: t_nfold t_encrypt t_prf t_prng t_hmac t_pkcs5 t_short
 	$(RUN_SETUP) $(VALGRIND) ./t_nfold
 	$(RUN_SETUP) $(VALGRIND) ./t_encrypt
 	$(RUN_SETUP) $(VALGRIND) ./t_prng <$(srcdir)/t_prng.seed >t_prng.output && \
 	diff t_prng.output $(srcdir)/t_prng.expected
 	$(RUN_SETUP) $(VALGRIND) ./t_hmac
+	$(RUN_SETUP) $(VALGRIND) ./t_short
 
 #	$(RUN_SETUP) $(VALGRIND) ./t_pkcs5
 
@@ -218,10 +220,14 @@
 	$(CC_LINK) -o $@ t_cts.$(OBJEXT) \
 		$(K5CRYPTO_LIB) $(COM_ERR_LIB) $(SUPPORT_LIB)
 
+t_short$(EXEEXT): t_short.$(OBJEXT) $(CRYPTO_DEPLIB) $(SUPPORT_DEPLIB)
+	$(CC_LINK) -o $@ t_short.$(OBJEXT) \
+		$(K5CRYPTO_LIB) $(COM_ERR_LIB) $(SUPPORT_LIB)
 
 clean::
 	$(RM) t_nfold.o t_nfold t_encrypt t_encrypt.o t_prng.o t_prng \
-		t_hmac.o t_hmac t_pkcs5.o t_pkcs5 pbkdf2.o t_prf t_prf.o
+		t_hmac.o t_hmac t_pkcs5.o t_pkcs5 pbkdf2.o t_prf t_prf.o \
+		t_short t_short.o
 	-$(RM) t_prng.output
 
 all-windows::
@@ -761,6 +767,15 @@
   $(SRCTOP)/include/krb5/locate_plugin.h $(SRCTOP)/include/krb5/preauth_plugin.h \
   $(SRCTOP)/include/port-sockets.h $(SRCTOP)/include/socket-utils.h \
   $(srcdir)/hash_provider/hash_provider.h t_cts.c
+t_short.so t_short.po $(OUTPRE)t_short.$(OBJEXT): $(BUILDTOP)/include/autoconf.h \
+  $(BUILDTOP)/include/krb5/krb5.h $(BUILDTOP)/include/osconf.h \
+  $(BUILDTOP)/include/profile.h $(COM_ERR_DEPS) $(SRCTOP)/include/k5-err.h \
+  $(SRCTOP)/include/k5-int-pkinit.h $(SRCTOP)/include/k5-int.h \
+  $(SRCTOP)/include/k5-platform.h $(SRCTOP)/include/k5-plugin.h \
+  $(SRCTOP)/include/k5-thread.h $(SRCTOP)/include/krb5.h \
+  $(SRCTOP)/include/krb5/locate_plugin.h $(SRCTOP)/include/krb5/preauth_plugin.h \
+  $(SRCTOP)/include/port-sockets.h $(SRCTOP)/include/socket-utils.h \
+  t_short.c
 vectors.so vectors.po $(OUTPRE)vectors.$(OBJEXT): $(BUILDTOP)/include/autoconf.h \
   $(BUILDTOP)/include/krb5/krb5.h $(BUILDTOP)/include/osconf.h \
   $(BUILDTOP)/include/profile.h $(COM_ERR_DEPS) $(SRCTOP)/include/k5-err.h \
Index: src/lib/crypto/arcfour/arcfour.c
===================================================================
--- src/lib/crypto/arcfour/arcfour.c	(revision 23398)
+++ src/lib/crypto/arcfour/arcfour.c	(working copy)
@@ -203,6 +203,12 @@
   keylength = enc->keylength;
   hashsize = hash->hashsize;
 
+  /* Verify input and output lengths. */
+  if (input->length < hashsize + CONFOUNDERLENGTH)
+    return KRB5_BAD_MSIZE;
+  if (output->length < input->length - hashsize - CONFOUNDERLENGTH)
+    return KRB5_BAD_MSIZE;
+
   d1.length=keybytes;
   d1.data=malloc(d1.length);
   if (d1.data == NULL)
Index: src/lib/crypto/enc_provider/aes.c
===================================================================
--- src/lib/crypto/enc_provider/aes.c	(revision 23398)
+++ src/lib/crypto/enc_provider/aes.c	(working copy)
@@ -94,9 +94,11 @@
     nblocks = (input->length + BLOCK_SIZE - 1) / BLOCK_SIZE;
 
     if (nblocks == 1) {
-	/* XXX Used for DK function.  */
+	/* Used when deriving keys. */
+	if (input->length < BLOCK_SIZE)
+	    return KRB5_BAD_MSIZE;
 	enc(output->data, input->data, &ctx);
-    } else {
+    } else if (nblocks > 1) {
 	unsigned int nleft;
 
 	for (blockno = 0; blockno < nblocks - 2; blockno++) {
@@ -149,9 +151,9 @@
 
     if (nblocks == 1) {
 	if (input->length < BLOCK_SIZE)
-	    abort();
+	    return KRB5_BAD_MSIZE;
 	dec(output->data, input->data, &ctx);
-    } else {
+    } else if (nblocks > 1) {
 
 	for (blockno = 0; blockno < nblocks - 2; blockno++) {
 	    dec(tmp2, input->data + blockno * BLOCK_SIZE, &ctx);
Index: src/lib/crypto/dk/dk_decrypt.c
===================================================================
--- src/lib/crypto/dk/dk_decrypt.c	(revision 23398)
+++ src/lib/crypto/dk/dk_decrypt.c	(working copy)
@@ -89,6 +89,12 @@
     else if (hmacsize > hashsize)
 	return KRB5KRB_AP_ERR_BAD_INTEGRITY;
 
+    /* Verify input and output lengths. */
+    if (input->length < blocksize + hmacsize)
+	return KRB5_BAD_MSIZE;
+    if (output->length < input->length - blocksize - hmacsize)
+	return KRB5_BAD_MSIZE;
+
     enclen = input->length - hmacsize;
 
     if ((kedata = (unsigned char *) malloc(keylength)) == NULL)
Index: src/lib/crypto/raw/raw_decrypt.c
===================================================================
--- src/lib/crypto/raw/raw_decrypt.c	(revision 23398)
+++ src/lib/crypto/raw/raw_decrypt.c	(working copy)
@@ -34,5 +34,7 @@
 		 const krb5_data *ivec, const krb5_data *input,
 		 krb5_data *output)
 {
+    if (output->length < input->length)
+	return KRB5_BAD_MSIZE;
     return((*(enc->decrypt))(key, ivec, input, output));
 }
Index: src/lib/crypto/t_short.c
===================================================================
--- src/lib/crypto/t_short.c	(revision 0)
+++ src/lib/crypto/t_short.c	(revision 0)
@@ -0,0 +1,112 @@
+/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
+/*
+ * lib/crypto/crypto_tests/t_short.c
+ *
+ * Copyright (C) 2009 by the Massachusetts Institute of Technology.
+ * All rights reserved.
+ *
+ * Export of this software from the United States of America may
+ *   require a specific license from the United States Government.
+ *   It is the responsibility of any person or organization contemplating
+ *   export to obtain such a license before exporting.
+ *
+ * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
+ * distribute this software and its documentation for any purpose and
+ * without fee is hereby granted, provided that the above copyright
+ * notice appear in all copies and that both that copyright notice and
+ * this permission notice appear in supporting documentation, and that
+ * the name of M.I.T. not be used in advertising or publicity pertaining
+ * to distribution of the software without specific, written prior
+ * permission.  Furthermore if you modify this software you must label
+ * your software as modified software and not distribute it in such a
+ * fashion that it might be confused with the original M.I.T. software.
+ * M.I.T. makes no representations about the suitability of
+ * this software for any purpose.  It is provided "as is" without express
+ * or implied warranty.
+ *
+ * Tests the outcome of decrypting overly short tokens.  This program can be
+ * run under a tool like valgrind to detect bad memory accesses; when run
+ * normally by the test suite, it verifies that each operation returns
+ * KRB5_BAD_MSIZE.
+ */
+
+#include "k5-int.h"
+
+krb5_enctype interesting_enctypes[] = {
+    ENCTYPE_DES_CBC_CRC,
+    ENCTYPE_DES_CBC_MD4,
+    ENCTYPE_DES_CBC_MD5,
+    ENCTYPE_DES3_CBC_SHA1,
+    ENCTYPE_ARCFOUR_HMAC,
+    ENCTYPE_ARCFOUR_HMAC_EXP,
+    ENCTYPE_AES256_CTS_HMAC_SHA1_96,
+    ENCTYPE_AES128_CTS_HMAC_SHA1_96,
+    0
+};
+
+/* Abort if an operation unexpectedly fails. */
+static void
+x(krb5_error_code code)
+{
+    if (code != 0)
+        abort();
+}
+
+/* Abort if a decrypt operation doesn't have the expected result. */
+static void
+check_decrypt_result(krb5_error_code code, size_t len, size_t min_len)
+{
+    if (len < min_len) {
+        /* Undersized tokens should always result in BAD_MSIZE. */
+        if (code != KRB5_BAD_MSIZE)
+            abort();
+    } else {
+        /* Min-size tokens should succeed or fail the integrity check. */
+        if (code != 0 && code != KRB5KRB_AP_ERR_BAD_INTEGRITY)
+            abort();
+    }
+}
+
+static void
+test_enctype(krb5_enctype enctype)
+{
+    krb5_error_code ret;
+    krb5_keyblock keyblock;
+    krb5_enc_data input;
+    krb5_data output;
+    size_t min_len, len;
+
+    printf("Testing enctype %d\n", (int) enctype);
+    x(krb5_c_encrypt_length(NULL, enctype, 0, &min_len));
+    x(krb5_c_make_random_key(NULL, enctype, &keyblock));
+    input.enctype = enctype;
+
+    /* Try each length up to the minimum length. */
+    for (len = 0; len <= min_len; len++) {
+        input.ciphertext.data = calloc(len, 1);
+        input.ciphertext.length = len;
+        output.data = calloc(len, 1);
+        output.length = len;
+
+        /* Attempt a normal decryption. */
+        ret = krb5_c_decrypt(NULL, &keyblock, 0, NULL, &input, &output);
+        check_decrypt_result(ret, len, min_len);
+
+        free(input.ciphertext.data);
+        free(output.data);
+    }
+}
+
+int
+main(int argc, char **argv)
+{
+    int i;
+    krb5_data notrandom;
+
+    notrandom.data = "notrandom";
+    notrandom.length = 9;
+    krb5_c_random_seed(NULL, &notrandom);
+    for (i = 0; interesting_enctypes[i]; i++)
+        test_enctype(interesting_enctypes[i]);
+    return 0;
+}
Index: src/lib/crypto/old/old_decrypt.c
===================================================================
--- src/lib/crypto/old/old_decrypt.c	(revision 23398)
+++ src/lib/crypto/old/old_decrypt.c	(working copy)
@@ -45,8 +45,10 @@
     blocksize = enc->block_size;
     hashsize = hash->hashsize;
 
+    /* Verify input and output lengths. */
+    if (input->length < blocksize + hashsize || input->length % blocksize != 0)
+	return(KRB5_BAD_MSIZE);
     plainsize = input->length - blocksize - hashsize;
-
     if (arg_output->length < plainsize)
 	return(KRB5_BAD_MSIZE);