1 /** @file 2 Random number generator services that uses RdRand instruction access 3 to provide high-quality random numbers. 4 5 Copyright (c) 2015, Intel Corporation. All rights reserved.<BR> 6 SPDX-License-Identifier: BSD-2-Clause-Patent 7 8 **/ 9 10 #include <Library/BaseLib.h> 11 #include <Library/DebugLib.h> 12 13 // 14 // Bit mask used to determine if RdRand instruction is supported. 15 // 16 #define RDRAND_MASK BIT30 17 18 // 19 // Limited retry number when valid random data is returned. 20 // Uses the recommended value defined in Section 7.3.17 of "Intel 64 and IA-32 21 // Architectures Software Developer's Mannual". 22 // 23 #define RDRAND_RETRY_LIMIT 10 24 25 /** 26 The constructor function checks whether or not RDRAND instruction is supported 27 by the host hardware. 28 29 The constructor function checks whether or not RDRAND instruction is supported. 30 It will ASSERT() if RDRAND instruction is not supported. 31 It will always return RETURN_SUCCESS. 32 33 @retval RETURN_SUCCESS The constructor always returns EFI_SUCCESS. 34 35 **/ 36 RETURN_STATUS 37 EFIAPI BaseRngLibConstructor(VOID)38BaseRngLibConstructor ( 39 VOID 40 ) 41 { 42 UINT32 RegEcx; 43 44 // 45 // Determine RDRAND support by examining bit 30 of the ECX register returned by 46 // CPUID. A value of 1 indicates that processor support RDRAND instruction. 47 // 48 AsmCpuid (1, 0, 0, &RegEcx, 0); 49 ASSERT ((RegEcx & RDRAND_MASK) == RDRAND_MASK); 50 51 return RETURN_SUCCESS; 52 } 53 54 /** 55 Generates a 16-bit random number. 56 57 if Rand is NULL, then ASSERT(). 58 59 @param[out] Rand Buffer pointer to store the 16-bit random value. 60 61 @retval TRUE Random number generated successfully. 62 @retval FALSE Failed to generate the random number. 63 64 **/ 65 BOOLEAN 66 EFIAPI GetRandomNumber16(OUT UINT16 * Rand)67GetRandomNumber16 ( 68 OUT UINT16 *Rand 69 ) 70 { 71 UINT32 Index; 72 73 ASSERT (Rand != NULL); 74 75 // 76 // A loop to fetch a 16 bit random value with a retry count limit. 77 // 78 for (Index = 0; Index < RDRAND_RETRY_LIMIT; Index++) { 79 if (AsmRdRand16 (Rand)) { 80 return TRUE; 81 } 82 } 83 84 return FALSE; 85 } 86 87 /** 88 Generates a 32-bit random number. 89 90 if Rand is NULL, then ASSERT(). 91 92 @param[out] Rand Buffer pointer to store the 32-bit random value. 93 94 @retval TRUE Random number generated successfully. 95 @retval FALSE Failed to generate the random number. 96 97 **/ 98 BOOLEAN 99 EFIAPI GetRandomNumber32(OUT UINT32 * Rand)100GetRandomNumber32 ( 101 OUT UINT32 *Rand 102 ) 103 { 104 UINT32 Index; 105 106 ASSERT (Rand != NULL); 107 108 // 109 // A loop to fetch a 32 bit random value with a retry count limit. 110 // 111 for (Index = 0; Index < RDRAND_RETRY_LIMIT; Index++) { 112 if (AsmRdRand32 (Rand)) { 113 return TRUE; 114 } 115 } 116 117 return FALSE; 118 } 119 120 /** 121 Generates a 64-bit random number. 122 123 if Rand is NULL, then ASSERT(). 124 125 @param[out] Rand Buffer pointer to store the 64-bit random value. 126 127 @retval TRUE Random number generated successfully. 128 @retval FALSE Failed to generate the random number. 129 130 **/ 131 BOOLEAN 132 EFIAPI GetRandomNumber64(OUT UINT64 * Rand)133GetRandomNumber64 ( 134 OUT UINT64 *Rand 135 ) 136 { 137 UINT32 Index; 138 139 ASSERT (Rand != NULL); 140 141 // 142 // A loop to fetch a 64 bit random value with a retry count limit. 143 // 144 for (Index = 0; Index < RDRAND_RETRY_LIMIT; Index++) { 145 if (AsmRdRand64 (Rand)) { 146 return TRUE; 147 } 148 } 149 150 return FALSE; 151 } 152 153 /** 154 Generates a 128-bit random number. 155 156 if Rand is NULL, then ASSERT(). 157 158 @param[out] Rand Buffer pointer to store the 128-bit random value. 159 160 @retval TRUE Random number generated successfully. 161 @retval FALSE Failed to generate the random number. 162 163 **/ 164 BOOLEAN 165 EFIAPI GetRandomNumber128(OUT UINT64 * Rand)166GetRandomNumber128 ( 167 OUT UINT64 *Rand 168 ) 169 { 170 ASSERT (Rand != NULL); 171 172 // 173 // Read first 64 bits 174 // 175 if (!GetRandomNumber64 (Rand)) { 176 return FALSE; 177 } 178 179 // 180 // Read second 64 bits 181 // 182 return GetRandomNumber64 (++Rand); 183 } 184