1 /* This file is distributed under the following terms: 2 3 * Copyright 2005-2014 Colin Percival. All rights reserved. 4 * Copyright 2014 Sean Kelly. All rights reserved. 5 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25 * SUCH DAMAGE. 26 */ 27 28 #ifndef _SHA256_H_ 29 #define _SHA256_H_ 30 31 #include <stddef.h> 32 #include <stdint.h> 33 #include <SHA256.h> 34 35 /* Pointer to memory-zeroing function. */ 36 extern void (* volatile insecure_memzero_ptr)(volatile void *, size_t); 37 38 /** 39 * insecure_memzero(buf, len): 40 * Attempt to zero ${len} bytes at ${buf} in spite of optimizing compilers' 41 * best (standards-compliant) attempts to remove the buffer-zeroing. In 42 * particular, to avoid performing the zeroing, a compiler would need to 43 * use optimistic devirtualization; recognize that non-volatile objects do not 44 * need to be treated as volatile, even if they are accessed via volatile 45 * qualified pointers; and perform link-time optimization; in addition to the 46 * dead-code elimination which often causes buffer-zeroing to be elided. 47 * 48 * Note however that zeroing a buffer does not guarantee that the data held 49 * in the buffer is not stored elsewhere; in particular, there may be copies 50 * held in CPU registers or in anonymous allocations on the stack, even if 51 * every named variable is successfully sanitized. Solving the "wipe data 52 * from the system" problem will require a C language extension which does not 53 * yet exist. 54 * 55 * For more information, see: 56 * http://www.daemonology.net/blog/2014-09-04-how-to-zero-a-buffer.html 57 * http://www.daemonology.net/blog/2014-09-06-zeroing-buffers-is-insufficient.html 58 */ 59 static inline void 60 insecure_memzero(volatile void * buf, size_t len) 61 { 62 63 (insecure_memzero_ptr)(buf, len); 64 } 65 66 /* Context structure for SHA256 operations. */ 67 typedef struct { 68 uint32_t state[8]; 69 uint64_t count; 70 uint8_t buf[64]; 71 } SHA256_CTX; 72 73 /* Context structure for HMAC-SHA256 operations. */ 74 typedef struct { 75 SHA256 ictx; 76 SHA256 octx; 77 } HMAC_SHA256_CTX; 78 79 /** 80 * HMAC_SHA256_Init(ctx, K, Klen): 81 * Initialize the HMAC-SHA256 context ${ctx} with ${Klen} bytes of key from 82 * ${K}. 83 */ 84 void HMAC_SHA256_Init(HMAC_SHA256_CTX *, const void *, size_t); 85 86 /** 87 * HMAC_SHA256_Update(ctx, in, len): 88 * Input ${len} bytes from ${in} into the HMAC-SHA256 context ${ctx}. 89 */ 90 void HMAC_SHA256_Update(HMAC_SHA256_CTX *, const void *, size_t); 91 92 /** 93 * HMAC_SHA256_Final(digest, ctx): 94 * Output the HMAC-SHA256 of the data input to the context ${ctx} into the 95 * buffer ${digest}. 96 */ 97 void HMAC_SHA256_Final(uint8_t[32], HMAC_SHA256_CTX *); 98 99 /** 100 * PBKDF2_SHA256(passwd, passwdlen, salt, saltlen, c, buf, dkLen): 101 * Compute PBKDF2(passwd, salt, c, dkLen) using HMAC-SHA256 as the PRF, and 102 * write the output to buf. The value dkLen must be at most 32 * (2^32 - 1). 103 */ 104 void PBKDF2_SHA256(const uint8_t *, size_t, const uint8_t *, size_t, 105 uint64_t, uint8_t *, size_t); 106 107 #endif /* !_SHA256_H_ */ 108