assert non-NULL ptrs before calling mem funcs

The definitions of memcpy(), memmove(), and memset() state that
the behaviour is undefined if any of the pointer arguments are
NULL, and some compilers are known to make use of this to
optimise away existing NULL checks in the source.

Change-Id: I489bc256e3eac7ff41d91becb0b43aba73dbb3f9
Link: https://www.imperialviolet.org/2016/06/26/nonnull.html

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 {