VeraCrypt
aboutsummaryrefslogtreecommitdiff
path: root/src/Crypto/rdseed_ml.asm
blob: 60704230ee746e0f170846a12e4043cb6b93cd3b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
;; rdrand.asm - written and placed in public domain by Jeffrey Walton and Uri Blumenthal.
;;              Copyright assigned to the Crypto++ project.

;; This ASM file provides RDSEED to downlevel Microsoft tool chains.
;; Everything "just works" under Visual Studio. Other platforms will
;; have to run MASM/MASM-64 and then link to the object files.

;; set ASFLAGS=/nologo /D_M_X86 /W3 /Cx /Zi /safeseh
;; set ASFLAGS64=/nologo /D_M_X64 /W3 /Cx /Zi
;; "C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\bin\ml.exe" %ASFLAGS% /Fo rdrand-x86.obj /c rdrand.asm
;; "C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\bin\amd64\ml64.exe" %ASFLAGS64% /Fo rdrand-x64.obj /c rdrand.asm

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

TITLE    MASM_RDSEED_GenerateBlock source file
SUBTITLE Microsoft specific ASM code to utilize RDSEED for down level Microsoft toolchains

PUBLIC MASM_RDSEED_GenerateBlock

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;; C/C++ Function prototypes (both are fastcall)
;;   X86:
;;      extern "C" void __fastcall MASM_RDSEED_GenerateBlock(byte* ptr, size_t size);
;;   X64:
;;      extern "C" void __fastcall MASM_RDSEED_GenerateBlock(byte* ptr, size_t size);

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

IFDEF _M_X86    ;; Set via the command line

.486
.MODEL FLAT

;; Fastcall calling conventions exports
ALIAS <@MASM_RDSEED_GenerateBlock@8> = <MASM_RDSEED_GenerateBlock>

ENDIF

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

IFDEF _M_X86    ;; Set via the command line

.CODE
ALIGN   8
OPTION PROLOGUE:NONE
OPTION EPILOGUE:NONE

;; No need for Load_Arguments due to fastcall
;;   ECX (in): arg1, byte* buffer
;;   EDX (in): arg2, size_t bsize

MASM_RDSEED_GenerateBlock PROC   ;; arg1:DWORD, arg2:DWORD

    MWSIZE EQU 04h    ;; machine word size
    buffer EQU ecx
    bsize  EQU edx

            ;; Top of While loop
RDSEED_GenerateBlock_Top:

            ;; Check remaining size
    cmp     bsize, 0
    je      RDSEED_GenerateBlock_Return

RDSEED_Call_EAX:
            ;; RDSEED is not available prior to VS2012. Just emit
            ;;   the byte codes using DB. This is `rdseed eax`.
    DB      0Fh, 0C7h, 0F8h

            ;; If CF=1, the number returned by RDSEED is valid.
            ;; If CF=0, a random number was not available.

            ;; Retry immediately
    jnc     RDSEED_Call_EAX

RDSEED_succeeded:

    cmp     bsize, MWSIZE
    jb      RDSEED_Partial_Machine_Word

RDSEED_Full_Machine_Word:

    mov     DWORD PTR [buffer], eax
    add     buffer, MWSIZE        ;; No need for Intel Core 2 slow workarounds, like
    sub     bsize, MWSIZE         ;;   `lea buffer,[buffer+MWSIZE]` for faster adds

            ;; Continue
    jmp     RDSEED_GenerateBlock_Top

            ;; 1,2,3 bytes remain
RDSEED_Partial_Machine_Word:

            ;; Test bit 1 to see if size is at least 2
    test    bsize, 2
    jz      RDSEED_Bit_1_Not_Set

    mov     WORD PTR [buffer], ax
    shr     eax, 16
    add     buffer, 2

RDSEED_Bit_1_Not_Set:

            ;; Test bit 0 to see if size is at least 1
    test    bsize, 1
    jz      RDSEED_Bit_0_Not_Set

    mov     BYTE PTR [buffer], al
    ;; shr     ax, 8
    ;; add     buffer, 1

RDSEED_Bit_0_Not_Set:

            ;; We've hit all the bits

RDSEED_GenerateBlock_Return:

            ;; Clear artifacts
    xor     eax, eax
    ret

MASM_RDSEED_GenerateBlock ENDP

ENDIF    ;; _M_X86

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

IFDEF _M_X64    ;; Set via the command line

.CODE
ALIGN   16
OPTION PROLOGUE:NONE
OPTION EPILOGUE:NONE

;; No need for Load_Arguments due to fastcall
;;   RCX (in): arg1, byte* buffer
;;   RDX (in): arg2, size_t bsize

MASM_RDSEED_GenerateBlock PROC   ;; arg1:QWORD, arg2:QWORD

    MWSIZE EQU 08h    ;; machine word size
    buffer EQU rcx
    bsize  EQU rdx

            ;; Top of While loop
RDSEED_GenerateBlock_Top:

            ;; Check remaining size
    cmp     bsize, 0
    je      RDSEED_GenerateBlock_Return

RDSEED_Call_RAX:
            ;; RDSEED is not available prior to VS2012. Just emit
            ;;   the byte codes using DB. This is `rdseed rax`.
    DB      048h, 0Fh, 0C7h, 0F8h

            ;; If CF=1, the number returned by RDSEED is valid.
            ;; If CF=0, a random number was not available.

            ;; Retry immediately
    jnc     RDSEED_Call_RAX

RDSEED_succeeded:

    cmp     bsize, MWSIZE
    jb      RDSEED_Partial_Machine_Word

RDSEED_Full_Machine_Word:

    mov     QWORD PTR [buffer], rax
    add     buffer, MWSIZE
    sub     bsize, MWSIZE

            ;; Continue
    jmp     RDSEED_GenerateBlock_Top

            ;; 1,2,3,4,5,6,7 bytes remain
RDSEED_Partial_Machine_Word:

            ;; Test bit 2 to see if size is at least 4
    test    bsize, 4
    jz      RDSEED_Bit_2_Not_Set

    mov     DWORD PTR [buffer], eax
    shr     rax, 32
    add     buffer, 4

RDSEED_Bit_2_Not_Set:

            ;; Test bit 1 to see if size is at least 2
    test    bsize, 2
    jz      RDSEED_Bit_1_Not_Set

    mov     WORD PTR [buffer], ax
    shr     eax, 16
    add     buffer, 2

RDSEED_Bit_1_Not_Set:

            ;; Test bit 0 to see if size is at least 1
    test    bsize, 1
    jz      RDSEED_Bit_0_Not_Set

    mov     BYTE PTR [buffer], al
    ;; shr     ax, 8
    ;; add     buffer, 1

RDSEED_Bit_0_Not_Set:

            ;; We've hit all the bits

RDSEED_GenerateBlock_Return:

            ;; Clear artifacts
    xor     rax, rax
    ret

MASM_RDSEED_GenerateBlock ENDP

ENDIF    ;; _M_X64

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

END