crypto.utils source code

1 module crypto.utils;
2 
3 /*
4 The MIT License (MIT)
5 
6 Copyright (c) 2019 DarkRiDDeR
7 
8 Permission is hereby granted, free of charge, to any person obtaining a copy
9 of this software and associated documentation files (the "Software"), to deal
10 in the Software without restriction, including without limitation the rights
11 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
12 copies of the Software, and to permit persons to whom the Software is
13 furnished to do so, subject to the following conditions:
14 
15 The above copyright notice and this permission notice shall be included in all
16 copies or substantial portions of the Software.
17 
18 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
19 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
20 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
21 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
22 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
23 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
24 SOFTWARE.
25 */
26 
27 /**
28 * Fills a block of memory with zeros. It is designed to be a more secure version of ZeroMemory.
29 *
30 * !!! function secureZeroMemory processes data by byte.
31 *
32 * Use this function instead of ZeroMemory when you want to ensure that your data will be overwritten promptly,
33 * as some compilers can optimize a call to ZeroMemory by removing it entirely.
34 */
35 void secureZeroMemory(void* p, in size_t length) pure nothrow @nogc
36 {
37     version (D_InlineAsm_X86_64)
38     {
39         asm pure nothrow @nogc
40         {
41             mov RBX, [p];
42             mov RDX, p;
43             mov RCX, length;
44             iter:
45             xor RBX, RBX;
46             mov [RDX], RBX;
47             inc RDX;
48             loop iter;
49         }
50     }
51     else version (D_InlineAsm_X86)
52     {
53         asm pure nothrow @nogc
54         {
55             mov EBX, [p];
56             mov EDX, p;
57             mov ECX, length;
58             iter:
59             xor EBX, EBX;
60             mov [EDX], EBX;
61             inc EDX;
62             loop iter;
63         }
64     }
65     else version (LDC)
66     {
67         import ldc.intrinsics : llvm_memset;
68         llvm_memset(p, 0, length, true); // The "true" means volatile.
69     }
70     else
71     {
72         static if (__VERSION__ >= 2089)
73             import core..volatile : volatileStore;
74         else
75             import core.bitop : volatileStore;
76         static void zero(void* p, size_t remaining) @nogc nothrow
77         {
78             for (; remaining != 0 && (cast(size_t) p) % size_t.alignof != 0; ++p, --remaining)
79                 volatileStore(cast(ubyte*) p, ubyte(0));
80             for (; remaining >= size_t.sizeof; p += size_t.sizeof, remaining -= size_t.sizeof)
81                 volatileStore(cast(size_t*) p, size_t(0));
82             for (; remaining != 0; ++p, --remaining)
83                 volatileStore(cast(ubyte*) p, ubyte(0));
84         }
85         // Workaround because volatileStore is not annotated "pure".
86         (cast(void function(void*, size_t) @nogc nothrow pure) &zero)(p, length);
87     }
88 }
89 
90 void secureZeroMemory(void[] ar) pure nothrow @nogc
91 {
92     if (ar.length == 0)
93     {
94         return;
95     }
96 
97     secureZeroMemory(ar.ptr, ar.length);
98 }
99 
100 unittest
101 {
102     auto ar = new ubyte[255];
103     auto ar2 = ar.dup;
104 
105     foreach (i, ref e; ar2)
106         e = cast(ubyte)i;
107     assert(ar != ar2);
108 
109     secureZeroMemory(ar2.ptr, ar2.length);
110     assert(ar == ar2);
111 
112 
113     uint[] i  = [0, 0, 0,  0, 0 ];
114     uint[] i2 = [8, 5, 99, 5, 99];
115     // !!! function secureZeroMemory processes data by byte. Therefore, it is wrong:
116     secureZeroMemory(i2.ptr, i2.length);
117     assert(i != i2);
118     // Need to calculate the length:
119     secureZeroMemory(i2.ptr, uint.sizeof * i2.length);
120     assert(i == i2);
121 
122     // or use a cast to type void[]
123     i2 = [8, 5, 99, 5, 99];
124     secureZeroMemory(cast(void[])i2);
125     assert(i == i2);
126 }