Codebase list openssl / 3b8e97a
Zero memory in CRYPTO_secure_malloc. This commit destroys the free list pointers which would otherwise be present in the returned memory blocks. This in turn helps prevent information leakage from the secure memory area. Note: CRYPTO_secure_malloc is not guaranteed to return zeroed memory: before the secure memory system is initialised or if it isn't implemented. Reviewed-by: Tim Hudson <tjh@openssl.org> Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com> (Merged from https://github.com/openssl/openssl/pull/7011) Pauli 5 years ago
2 changed file(s) with 55 addition(s) and 5 deletion(s). Raw diff Collapse all Expand all
+11
-5
crypto/mem_sec.c less more
136136
137137 void *CRYPTO_secure_zalloc(size_t num, const char *file, int line)
138138 {
139 void *ret = CRYPTO_secure_malloc(num, file, line);
140
141 if (ret != NULL)
142 memset(ret, 0, num);
143 return ret;
139 #ifdef IMPLEMENTED
140 if (secure_mem_initialized)
141 /* CRYPTO_secure_malloc() zeroes allocations when it is implemented */
142 return CRYPTO_secure_malloc(num, file, line);
143 #endif
144 return CRYPTO_zalloc(num, file, line);
144145 }
145146
146147 void CRYPTO_secure_free(void *ptr, const char *file, int line)
587588
588589 OPENSSL_assert(WITHIN_ARENA(chunk));
589590
591 /* zero the free list header as a precaution against information leakage */
592 memset(chunk, 0, sizeof(SH_LIST));
593
590594 return chunk;
591595 }
592596
619623
620624 list--;
621625
626 /* Zero the higher addressed block's free list pointers */
627 memset(ptr > buddy ? ptr : buddy, 0, sizeof(SH_LIST));
622628 if (ptr > buddy)
623629 ptr = buddy;
624630
+44
-0
test/secmemtest.c less more
128128 #endif
129129 }
130130
131 static int test_sec_mem_clear(void)
132 {
133 #if defined(OPENSSL_SYS_LINUX) || defined(OPENSSL_SYS_UNIX)
134 const int size = 64;
135 unsigned char *p = NULL;
136 int i, res = 0;
137
138 if (!TEST_true(CRYPTO_secure_malloc_init(4096, 32))
139 || !TEST_ptr(p = OPENSSL_secure_malloc(size)))
140 goto err;
141
142 for (i = 0; i < size; i++)
143 if (!TEST_uchar_eq(p[i], 0))
144 goto err;
145
146 for (i = 0; i < size; i++)
147 p[i] = (unsigned char)(i + ' ' + 1);
148
149 OPENSSL_secure_free(p);
150
151 /*
152 * A deliberate use after free here to verify that the memory has been
153 * cleared properly. Since secure free doesn't return the memory to
154 * libc's memory pool, it technically isn't freed. However, the header
155 * bytes have to be skipped and these consist of two pointers in the
156 * current implementation.
157 */
158 for (i = sizeof(void *) * 2; i < size; i++)
159 if (!TEST_uchar_eq(p[i], 0))
160 return 0;
161
162 res = 1;
163 p = NULL;
164
165 err:
166 OPENSSL_secure_free(p);
167 CRYPTO_secure_malloc_done();
168 return res;
169 #else
170 return 1;
171 #endif
172 }
173
131174 int setup_tests(void)
132175 {
133176 ADD_TEST(test_sec_mem);
177 ADD_TEST(test_sec_mem_clear);
134178 return 1;
135179 }