1 /* SPDX-License-Identifier: BSD-2-Clause */
2 /*
3 * Copyright (c) 2014, STMicroelectronics International N.V.
4 */
5
6 /*
7 * This file provides extensions for functions not defined in <string.h>
8 */
9
10 #ifndef STRING_EXT_H
11 #define STRING_EXT_H
12
13 #include <stddef.h>
14 #include <sys/cdefs.h>
15
16 /*
17 * Copy src to string dst of siz size. At most siz-1 characters
18 * will be copied. Always NUL terminates (unless siz == 0).
19 * Returns strlen(src); if retval >= siz, truncation occurred.
20 */
21 size_t strlcpy(char *dst, const char *src, size_t size);
22 size_t strlcat(char *dst, const char *src, size_t size);
23
24 /* A constant-time version of memcmp() */
25 int consttime_memcmp(const void *p1, const void *p2, size_t nb);
26
27 /* Deprecated. For backward compatibility. */
buf_compare_ct(const void * s1,const void * s2,size_t n)28 static inline int buf_compare_ct(const void *s1, const void *s2, size_t n)
29 {
30 return consttime_memcmp(s1, s2, n);
31 }
32
33 /* Variant of strdup() that uses nex_malloc() instead of malloc() */
34 char *nex_strdup(const char *s);
35
36 /*
37 * Like memset(s, 0, count) but prevents the compiler from optimizing the call
38 * away. Such "dead store elimination" optimizations typically occur when
39 * clearing a *local* variable that is not used after it is cleared; but
40 * link-time optimization (LTO) can also trigger code elimination in other
41 * circumstances. See "Dead Store Elimination (Still) Considered Harmful" [1]
42 * for details and examples (and note that the Cland compiler enables LTO by
43 * default!).
44 *
45 * [1] https://www.usenix.org/system/files/conference/usenixsecurity17/sec17-yang.pdf
46 *
47 * Practically speaking:
48 *
49 * - Use memzero_explicit() to *clear* (as opposed to initialize) *sensitive*
50 * data (such as keys, passwords, cryptographic state);
51 * - Otherwise, use memset().
52 */
53 void memzero_explicit(void *s, size_t count);
54
55 #endif /* STRING_EXT_H */
56