/src/botan/src/lib/rng/processor_rng/processor_rng.cpp
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1 | | /* |
2 | | * (C) 2016,2019,2020 Jack Lloyd |
3 | | * |
4 | | * Botan is released under the Simplified BSD License (see license.txt) |
5 | | */ |
6 | | |
7 | | #include <botan/processor_rng.h> |
8 | | #include <botan/internal/loadstor.h> |
9 | | #include <botan/internal/cpuid.h> |
10 | | |
11 | | #if defined(BOTAN_TARGET_CPU_IS_X86_FAMILY) && !defined(BOTAN_USE_GCC_INLINE_ASM) |
12 | | #include <immintrin.h> |
13 | | #endif |
14 | | |
15 | | namespace Botan { |
16 | | |
17 | | namespace { |
18 | | |
19 | | #if defined(BOTAN_TARGET_CPU_IS_X86_FAMILY) |
20 | | /* |
21 | | * According to Intel, RDRAND is guaranteed to generate a random |
22 | | * number within 10 retries on a working CPU |
23 | | */ |
24 | | const size_t HWRNG_RETRIES = 10; |
25 | | |
26 | | #elif defined(BOTAN_TARGET_CPU_IS_PPC_FAMILY) |
27 | | /** |
28 | | * PowerISA 3.0 p.78: |
29 | | * When the error value is obtained, software is expected to repeat the |
30 | | * operation. [...] The recommended number of attempts may be |
31 | | * implementation specific. In the absence of other guidance, ten attempts |
32 | | * should be adequate. |
33 | | */ |
34 | | const size_t HWRNG_RETRIES = 10; |
35 | | |
36 | | #else |
37 | | /* |
38 | | * Lacking specific guidance we give the CPU quite a bit of leeway |
39 | | */ |
40 | | const size_t HWRNG_RETRIES = 512; |
41 | | #endif |
42 | | |
43 | | #if defined(BOTAN_TARGET_ARCH_IS_X86_32) |
44 | | typedef uint32_t hwrng_output; |
45 | | #else |
46 | | typedef uint64_t hwrng_output; |
47 | | #endif |
48 | | |
49 | | hwrng_output read_hwrng(bool& success) |
50 | 0 | { |
51 | 0 | hwrng_output output = 0; |
52 | 0 | success = false; |
53 | |
|
54 | 0 | #if defined(BOTAN_TARGET_CPU_IS_X86_FAMILY) |
55 | 0 | int cf = 0; |
56 | 0 | #if defined(BOTAN_USE_GCC_INLINE_ASM) |
57 | | // same asm seq works for 32 and 64 bit |
58 | 0 | asm volatile("rdrand %0; adcl $0,%1" : |
59 | 0 | "=r" (output), "=r" (cf) : "0" (output), "1" (cf) : "cc"); |
60 | | #elif defined(BOTAN_TARGET_ARCH_IS_X86_32) |
61 | | cf = _rdrand32_step(&output); |
62 | | #else |
63 | | cf = _rdrand64_step(&output); |
64 | | #endif |
65 | 0 | success = (1 == cf); |
66 | |
|
67 | | #elif defined(BOTAN_TARGET_CPU_IS_PPC_FAMILY) |
68 | | |
69 | | /* |
70 | | DARN indicates error by returning 0xFF..FF, ie is biased. Which is crazy. |
71 | | Avoid the bias by invoking it twice and, assuming both succeed, returning the |
72 | | XOR of the two results, which should unbias the output. |
73 | | */ |
74 | | uint64_t output2 = 0; |
75 | | // DARN codes are 0: 32-bit conditioned, 1: 64-bit conditioned, 2: 64-bit raw (ala RDSEED) |
76 | | asm volatile("darn %0, 1" : "=r" (output)); |
77 | | asm volatile("darn %0, 1" : "=r" (output2)); |
78 | | |
79 | | if((~output) != 0 && (~output2) != 0) |
80 | | { |
81 | | output ^= output2; |
82 | | success = true; |
83 | | } |
84 | | |
85 | | #endif |
86 | |
|
87 | 0 | if(success) |
88 | 0 | return output; |
89 | | |
90 | 0 | return 0; |
91 | 0 | } |
92 | | |
93 | | hwrng_output read_hwrng() |
94 | 0 | { |
95 | 0 | for(size_t i = 0; i < HWRNG_RETRIES; ++i) |
96 | 0 | { |
97 | 0 | bool success = false; |
98 | 0 | hwrng_output output = read_hwrng(success); |
99 | |
|
100 | 0 | if(success) |
101 | 0 | return output; |
102 | 0 | } |
103 | | |
104 | 0 | throw PRNG_Unseeded("Processor RNG instruction failed to produce output within expected iterations"); |
105 | 0 | } |
106 | | |
107 | | } |
108 | | |
109 | | //static |
110 | | bool Processor_RNG::available() |
111 | 0 | { |
112 | 0 | #if defined(BOTAN_TARGET_CPU_IS_X86_FAMILY) |
113 | 0 | return CPUID::has_rdrand(); |
114 | | #elif defined(BOTAN_TARGET_CPU_IS_PPC_FAMILY) |
115 | | return CPUID::has_darn_rng(); |
116 | | #else |
117 | | return false; |
118 | | #endif |
119 | 0 | } |
120 | | |
121 | | std::string Processor_RNG::name() const |
122 | 0 | { |
123 | 0 | #if defined(BOTAN_TARGET_CPU_IS_X86_FAMILY) |
124 | 0 | return "rdrand"; |
125 | | #elif defined(BOTAN_TARGET_CPU_IS_PPC_FAMILY) |
126 | | return "darn"; |
127 | | #else |
128 | | return "hwrng"; |
129 | | #endif |
130 | 0 | } |
131 | | |
132 | | void Processor_RNG::randomize(uint8_t out[], size_t out_len) |
133 | 0 | { |
134 | 0 | while(out_len >= sizeof(hwrng_output)) |
135 | 0 | { |
136 | 0 | const hwrng_output r = read_hwrng(); |
137 | 0 | store_le(r, out); |
138 | 0 | out += sizeof(hwrng_output); |
139 | 0 | out_len -= sizeof(hwrng_output); |
140 | 0 | } |
141 | |
|
142 | 0 | if(out_len > 0) // at most sizeof(hwrng_output)-1 |
143 | 0 | { |
144 | 0 | const hwrng_output r = read_hwrng(); |
145 | 0 | uint8_t hwrng_bytes[sizeof(hwrng_output)]; |
146 | 0 | store_le(r, hwrng_bytes); |
147 | |
|
148 | 0 | for(size_t i = 0; i != out_len; ++i) |
149 | 0 | out[i] = hwrng_bytes[i]; |
150 | 0 | } |
151 | 0 | } |
152 | | |
153 | | Processor_RNG::Processor_RNG() |
154 | 0 | { |
155 | 0 | if(!Processor_RNG::available()) |
156 | 0 | throw Invalid_State("Current CPU does not support RNG instruction"); |
157 | 0 | } |
158 | | |
159 | | void Processor_RNG::add_entropy(const uint8_t /*input*/[], size_t /*length*/) |
160 | 0 | { |
161 | | /* no way to add entropy */ |
162 | 0 | } |
163 | | |
164 | | size_t Processor_RNG::reseed(Entropy_Sources& /*srcs*/, size_t /*poll_bits*/, std::chrono::milliseconds /*poll_timeout*/) |
165 | 0 | { |
166 | | /* no way to add entropy */ |
167 | 0 | return 0; |
168 | 0 | } |
169 | | |
170 | | } |