diff --git a/lib/asn1/der_copy.c b/lib/asn1/der_copy.c
index bd3d2404a..6e42e29b3 100644
--- a/lib/asn1/der_copy.c
+++ b/lib/asn1/der_copy.c
@@ -99,11 +99,15 @@ int ASN1CALL
 der_copy_printable_string (const heim_printable_string *from,
 		       heim_printable_string *to)
 {
-    to->length = from->length;
-    to->data   = malloc(to->length + 1);
-    if(to->data == NULL)
+    assert(from->length == 0 || (from->length > 0 && from->data != NULL));
+    to->data = malloc(from->length + 1);
+    if (to->data == NULL) {
+	to->length = 0;
 	return ENOMEM;
-    memcpy(to->data, from->data, to->length);
+    }
+    to->length = from->length;
+    if (to->length > 0)
+	memcpy(to->data, from->data, to->length);
     ((char *)to->data)[to->length] = '\0';
     return 0;
 }
@@ -118,11 +122,18 @@ der_copy_ia5_string (const heim_ia5_string *from,
 int ASN1CALL
 der_copy_bmp_string (const heim_bmp_string *from, heim_bmp_string *to)
 {
-    to->length = from->length;
-    to->data   = malloc(to->length * sizeof(to->data[0]));
-    if(to->length != 0 && to->data == NULL)
+    assert(from->length == 0 || (from->length > 0 && from->data != NULL));
+    if (from->length == 0)
+	to->data = calloc(1, 1);
+    else
+	to->data = malloc(from->length * sizeof(from->data[0]));
+    if (to->data == NULL) {
+	to->length = 0;
 	return ENOMEM;
-    memcpy(to->data, from->data, to->length * sizeof(to->data[0]));
+    }
+    to->length = from->length;
+    if (to->length > 0)
+	memcpy(to->data, from->data, to->length * sizeof(to->data[0]));
     return 0;
 }
 
@@ -130,11 +141,18 @@ int ASN1CALL
 der_copy_universal_string (const heim_universal_string *from,
 			   heim_universal_string *to)
 {
-    to->length = from->length;
-    to->data   = malloc(to->length * sizeof(to->data[0]));
-    if(to->length != 0 && to->data == NULL)
+    assert(from->length == 0 || (from->length > 0 && from->data != NULL));
+    if (from->length == 0)
+	to->data = calloc(1, 1);
+    else
+	to->data = malloc(from->length * sizeof(from->data[0]));
+    if (to->data == NULL) {
+	to->length = 0;
 	return ENOMEM;
-    memcpy(to->data, from->data, to->length * sizeof(to->data[0]));
+    }
+    to->length = from->length;
+    if (to->length > 0)
+	memcpy(to->data, from->data, to->length * sizeof(to->data[0]));
     return 0;
 }
 
@@ -148,26 +166,36 @@ der_copy_visible_string (const heim_visible_string *from,
 int ASN1CALL
 der_copy_octet_string (const heim_octet_string *from, heim_octet_string *to)
 {
-    to->length = from->length;
-    if (from->data == NULL) {
-        to->data = NULL;
-        return 0;
-    }
-    to->data = malloc(to->length);
-    if (to->length != 0 && to->data == NULL)
+    assert(from->length == 0 || (from->length > 0 && from->data != NULL));
+    if (from->length == 0)
+	to->data = calloc(1, 1);
+    else
+	to->data = malloc(from->length);
+    if (to->data == NULL) {
+	to->length = 0;
 	return ENOMEM;
-    memcpy(to->data, from->data, to->length);
+    }
+    to->length = from->length;
+    if (to->length > 0)
+	memcpy(to->data, from->data, to->length);
     return 0;
 }
 
 int ASN1CALL
 der_copy_heim_integer (const heim_integer *from, heim_integer *to)
 {
-    to->length = from->length;
-    to->data   = malloc(to->length);
-    if(to->length != 0 && to->data == NULL)
+    assert(from->length == 0 || (from->length > 0 && from->data != NULL));
+    if (from->length == 0)
+	to->data = calloc(1, 1);
+    else
+	to->data = malloc(from->length);
+    if (to->data == NULL) {
+	to->length = 0;
 	return ENOMEM;
-    memcpy(to->data, from->data, to->length);
+    }
+    to->length = from->length;
+    if (to->length > 0)
+	memcpy(to->data, from->data, to->length);
     to->negative = from->negative;
     return 0;
 }
@@ -175,10 +203,20 @@ der_copy_heim_integer (const heim_integer *from, heim_integer *to)
 int ASN1CALL
 der_copy_oid (const heim_oid *from, heim_oid *to)
 {
-    to->length     = from->length;
-    to->components = malloc(to->length * sizeof(*to->components));
-    if (to->length != 0 && to->components == NULL)
+    if (from->length == 0) {
+	to->length = 0;
+	to->components = calloc(1, sizeof(*from->components));
+	if (to->components == NULL)
+	    return ENOMEM;
+	return 0;
+    }
+    assert(from->components != NULL);
+    to->components = malloc(from->length * sizeof(*from->components));
+    if (to->components == NULL) {
+	to->length = 0;
 	return ENOMEM;
+    }
+    to->length = from->length;
     memcpy(to->components, from->components,
 	   to->length * sizeof(*to->components));
     return 0;
@@ -189,11 +227,19 @@ der_copy_bit_string (const heim_bit_string *from, heim_bit_string *to)
 {
     size_t len;
 
+    assert(from->length == 0 || (from->length > 0 && from->data != NULL));
+
     len = (from->length + 7) / 8;
-    to->length = from->length;
-    to->data   = malloc(len);
-    if(len != 0 && to->data == NULL)
+    if (len == 0)
+	to->data = calloc(1, 1);
+    else
+	to->data = malloc(len);
+    if (to->data == NULL) {
+	to->length = 0;
 	return ENOMEM;
-    memcpy(to->data, from->data, len);
+    }
+    to->length = from->length;
+    if (len > 0)
+	memcpy(to->data, from->data, len);
     return 0;
 }
diff --git a/lib/asn1/der_get.c b/lib/asn1/der_get.c
index 152d2527f..c12f81700 100644
--- a/lib/asn1/der_get.c
+++ b/lib/asn1/der_get.c
@@ -174,6 +174,8 @@ der_get_general_string (const unsigned char *p, size_t len,
     const unsigned char *p1;
     char *s;
 
+    assert(p != NULL);
+
     if (size)
 	*size = 0;
 
@@ -220,6 +222,8 @@ int ASN1CALL
 der_get_printable_string(const unsigned char *p, size_t len,
 			 heim_printable_string *str, size_t *size)
 {
+    assert(p != NULL);
+
     if (size)
 	*size = 0;
 
@@ -233,6 +237,7 @@ der_get_printable_string(const unsigned char *p, size_t len,
 	gen_data_zero(str);
 	return ENOMEM;
     }
+
     memcpy(str->data, p, len);
     ((char *)str->data)[len] = '\0';
     if(size) *size = len;
@@ -252,6 +257,8 @@ der_get_bmp_string (const unsigned char *p, size_t len,
 {
     size_t i;
 
+    assert(p != NULL);
+
     if (size)
 	*size = 0;
 
@@ -291,6 +298,8 @@ der_get_universal_string (const unsigned char *p, size_t len,
 {
     size_t i;
 
+    assert(p != NULL);
+
     if (size)
 	*size = 0;
 
@@ -334,14 +343,23 @@ int ASN1CALL
 der_get_octet_string (const unsigned char *p, size_t len,
 		      heim_octet_string *data, size_t *size)
 {
+    assert(p != NULL);
+
     if (size)
 	*size = 0;
-    data->length = len;
-    data->data = malloc(len);
-    if (data->data == NULL && data->length != 0)
+
+    if (len == 0)
+	data->data = malloc(1);
+    else
+	data->data = malloc(len);
+    if (data->data == NULL) {
+	data->length = 0;
 	return ENOMEM;
+    }
+    data->length = len;
     memcpy (data->data, p, len);
-    if(size) *size = len;
+    if (size)
+	*size = len;
     return 0;
 }
 
@@ -355,6 +373,8 @@ der_get_octet_string_ber (const unsigned char *p, size_t len,
     unsigned int tag, depth = 0;
     size_t l, datalen, oldlen = len;
 
+    assert(p != NULL);
+
     if (size)
 	*size = 0;
 
@@ -431,6 +451,8 @@ der_get_heim_integer (const unsigned char *p, size_t len,
     if (len == 0)
 	return 0;
 
+    assert(p != NULL);
+
     if (p[0] & 0x80) {
 	unsigned char *q;
 	int carry = 1;
@@ -511,6 +533,8 @@ der_get_time (const unsigned char *p, size_t len,
     char *times;
     int e;
 
+    assert(p != NULL);
+
     if (size)
 	*size = 0;
 
@@ -549,6 +573,8 @@ der_get_oid (const unsigned char *p, size_t len,
     size_t n;
     size_t oldlen = len;
 
+    assert(p != NULL);
+
     if (size)
 	*size = 0;
 
@@ -562,8 +588,10 @@ der_get_oid (const unsigned char *p, size_t len,
 	return ERANGE;
 
     data->components = malloc((len + 1) * sizeof(data->components[0]));
-    if (data->components == NULL)
+    if (data->components == NULL) {
+	data->length = 0;
 	return ENOMEM;
+    }
     data->components[0] = (*p) / 40;
     data->components[1] = (*p) % 40;
     --len;
@@ -605,6 +633,9 @@ der_get_tag (const unsigned char *p, size_t len,
 
     if (len < 1)
 	return ASN1_MISSING_FIELD;
+
+    assert(p != NULL);
+
     *cls = (Der_class)(((*p) >> 6) & 0x03);
     *type = (Der_type)(((*p) >> 5) & 0x01);
     *tag = (*p) & 0x1f;
@@ -731,6 +762,8 @@ int ASN1CALL
 der_get_bit_string (const unsigned char *p, size_t len,
 		    heim_bit_string *data, size_t *size)
 {
+    assert(p != NULL);
+
     if (size)
 	*size = 0;
 
@@ -750,8 +783,10 @@ der_get_bit_string (const unsigned char *p, size_t len,
     if (len - 1 > 0) {
 	data->length = (len - 1) * 8;
 	data->data = malloc(len - 1);
-	if (data->data == NULL)
+	if (data->data == NULL) {
+	    data->length = 0;
 	    return ENOMEM;
+	}
 	memcpy (data->data, p + 1, len - 1);
 	data->length -= p[0];
     } else {
diff --git a/lib/asn1/der_put.c b/lib/asn1/der_put.c
index a9c485e3b..8fbd6f3da 100644
--- a/lib/asn1/der_put.c
+++ b/lib/asn1/der_put.c
@@ -246,9 +246,11 @@ int ASN1CALL
 der_put_general_string (unsigned char *p, size_t len,
 			const heim_general_string *str, size_t *size)
 {
-    size_t slen = strlen(*str);
+    size_t slen;
 
+    assert(p != NULL && str != NULL && *str != NULL && size != NULL);
     *size = 0;
+    slen = strlen(*str);
     if (len < slen)
 	return ASN1_OVERFLOW;
     p -= slen;
@@ -284,6 +286,8 @@ der_put_bmp_string (unsigned char *p, size_t len,
 {
     size_t i;
 
+    assert(p != NULL && data != NULL);
+
     if (size)
 	*size = 0;
 
@@ -333,6 +337,8 @@ int ASN1CALL
 der_put_octet_string (unsigned char *p, size_t len,
 		      const heim_octet_string *data, size_t *size)
 {
+    assert(p != NULL && data != NULL && size != NULL);
+
     *size = 0;
     if (len < data->length)
 	return ASN1_OVERFLOW;
@@ -346,9 +352,11 @@ int ASN1CALL
 der_put_heim_integer (unsigned char *p, size_t len,
 		     const heim_integer *data, size_t *size)
 {
-    unsigned char *buf = data->data;
+    unsigned char *buf;
     int hibitset = 0;
 
+    assert(p != NULL);
+
     if (size)
 	*size = 0;
 
@@ -363,6 +371,8 @@ der_put_heim_integer (unsigned char *p, size_t len,
     if (len < data->length)
 	return ASN1_OVERFLOW;
 
+    assert(data->data != NULL);
+    buf = data->data;
     len -= data->length;
 
     if (data->negative) {
@@ -486,6 +496,8 @@ der_replace_tag(const unsigned char *p, size_t len,
     size_t payload_len, l, tag_len, len_len;
     int e;
 
+    assert(p != NULL && out != NULL && outlen != NULL);
+
     e = der_get_tag(p, len, &found_class, &found_type, &found_tag, &l);
     if (e)
         return e;
@@ -531,6 +543,8 @@ der_encode_implicit(unsigned char *p, size_t len,
     unsigned char *p2;
     int e;
 
+    assert(p != NULL && size != NULL);
+
     /* Attempt to encode in place */
     e = encoder(p, len, obj, size);
     if (e == 0) {
@@ -655,9 +669,12 @@ int ASN1CALL
 der_put_bit_string (unsigned char *p, size_t len,
 		    const heim_bit_string *data, size_t *size)
 {
-    size_t data_size = (data->length + 7) / 8;
+    size_t data_size;
+
+    assert(p != NULL && data != NULL && size != NULL);
 
     *size = 0;
+    data_size = (data->length + 7) / 8;
     if (len < data_size + 1)
 	return ASN1_OVERFLOW;
     p -= data_size + 1;
@@ -674,9 +691,12 @@ der_put_bit_string (unsigned char *p, size_t len,
 int
 _heim_der_set_sort(const void *a1, const void *a2)
 {
-    const heim_octet_string *s1 = a1, *s2 = a2;
+    const heim_octet_string *s1, *s2;
     int ret;
 
+    assert(a1 != NULL && a2 != NULL);
+    s1 = a1;
+    s2 = a2;
     ret = memcmp(s1->data, s2->data,
 		 s1->length < s2->length ? s1->length : s2->length);
     if (ret != 0)
diff --git a/lib/gssapi/krb5/arcfour.c b/lib/gssapi/krb5/arcfour.c
index 0cdfc0582..8931b32e1 100644
--- a/lib/gssapi/krb5/arcfour.c
+++ b/lib/gssapi/krb5/arcfour.c
@@ -167,10 +167,13 @@ arcfour_mic_cksum_iov(krb5_context context,
 	    continue;
 	}
 
-	memcpy(ptr + ofs,
-	       iov[i].buffer.value,
-	       iov[i].buffer.length);
-	ofs += iov[i].buffer.length;
+	if (iov[i].buffer.length > 0) {
+	    assert(iov[i].buffer.value != NULL);
+	    memcpy(ptr + ofs,
+		   iov[i].buffer.value,
+		   iov[i].buffer.length);
+	    ofs += iov[i].buffer.length;
+	}
     }
 
     if (padding) {
diff --git a/lib/krb5/pac.c b/lib/krb5/pac.c
index 2b2e0b5a4..c73b65196 100644
--- a/lib/krb5/pac.c
+++ b/lib/krb5/pac.c
@@ -35,6 +35,7 @@
 
 #include <heimbasepriv.h>
 #include <wind.h>
+#include <assert.h>
 
 struct PAC_INFO_BUFFER {
     uint32_t type;
@@ -382,6 +383,8 @@ krb5_pac_add_buffer(krb5_context context, krb5_pac p,
     size_t len, offset, header_end, old_end;
     uint32_t i;
 
+    assert(data->length > 0 && data->data != NULL);
+
     len = p->pac->numbuffers;
 
     ptr = realloc(p->pac,
@@ -1101,7 +1104,7 @@ build_logon_name(krb5_context context,
 	    krb5_set_error_message(context, ret, "Principal %s is not valid UTF-8", s);
 	    free(s);
 	    return ret;
-	} else 
+	} else
 	    free(s);
 
 	s2_len = (ucs2_len + 1) * 2;
diff --git a/lib/krb5/store_emem.c b/lib/krb5/store_emem.c
index d44cb1bfd..6a3908f74 100644
--- a/lib/krb5/store_emem.c
+++ b/lib/krb5/store_emem.c
@@ -33,6 +33,7 @@
 
 #include "krb5_locl.h"
 #include "store-int.h"
+#include <assert.h>
 
 typedef struct emem_storage{
     unsigned char *base;
@@ -45,6 +46,9 @@ static ssize_t
 emem_fetch(krb5_storage *sp, void *data, size_t size)
 {
     emem_storage *s = (emem_storage*)sp->data;
+
+    assert(data != NULL && s->ptr != NULL);
+
     if((size_t)(s->base + s->len - s->ptr) < size)
 	size = s->base + s->len - s->ptr;
     memmove(data, s->ptr, size);
@@ -55,7 +59,17 @@ emem_fetch(krb5_storage *sp, void *data, size_t size)
 static ssize_t
 emem_store(krb5_storage *sp, const void *data, size_t size)
 {
-    emem_storage *s = (emem_storage*)sp->data;
+    emem_storage *s;
+
+    if (size == 0) {
+	sp->seek(sp, 0, SEEK_CUR);
+	return 0;
+    }
+
+    s = (emem_storage*)sp->data;
+
+    assert(data != NULL);
+
     if(size > (size_t)(s->base + s->size - s->ptr)){
 	void *base;
 	size_t sz, off;
@@ -139,6 +153,9 @@ static void
 emem_free(krb5_storage *sp)
 {
     emem_storage *s = sp->data;
+
+    assert(s->base != NULL);
+
     memset_s(s->base, s->len, 0, s->len);
     free(s->base);
 }