include/crypto/chacha.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * Common values and helper functions for the ChaCha and XChaCha stream ciphers.
   4  *
   5  * XChaCha extends ChaCha's nonce to 192 bits, while provably retaining ChaCha's
   6  * security.  Here they share the same key size, tfm context, and setkey
   7  * function; only their IV size and encrypt/decrypt function differ.
   8  *
   9  * The ChaCha paper specifies 20, 12, and 8-round variants.  In general, it is
  10  * recommended to use the 20-round variant ChaCha20.  However, the other
  11  * variants can be needed in some performance-sensitive scenarios.  The generic
  12  * ChaCha code currently allows only the 20 and 12-round variants.
  13  */
  14
  15 #ifndef _CRYPTO_CHACHA_H
  16 #define _CRYPTO_CHACHA_H
  17
  18 #include <asm/unaligned.h>
  19 #include <linux/types.h>
  20
  21 /* 32-bit stream position, then 96-bit nonce (RFC7539 convention) */
  22 #define CHACHA_IV_SIZE          16
  23
  24 #define CHACHA_KEY_SIZE         32
  25 #define CHACHA_BLOCK_SIZE       64
  26 #define CHACHAPOLY_IV_SIZE      12
  27
  28 #define CHACHA_STATE_WORDS      (CHACHA_BLOCK_SIZE / sizeof(u32))
  29
  30 /* 192-bit nonce, then 64-bit stream position */
  31 #define XCHACHA_IV_SIZE         32
  32
  33 void chacha_block_generic(u32 *state, u8 *stream, int nrounds);
  34 static inline void chacha20_block(u32 *state, u8 *stream)
  35 {
  36         chacha_block_generic(state, stream, 20);
  37 }
  38
  39 void hchacha_block_arch(const u32 *state, u32 *out, int nrounds);
  40 void hchacha_block_generic(const u32 *state, u32 *out, int nrounds);
  41
  42 static inline void hchacha_block(const u32 *state, u32 *out, int nrounds)
  43 {
  44         if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CHACHA))
  45                 hchacha_block_arch(state, out, nrounds);
  46         else
  47                 hchacha_block_generic(state, out, nrounds);
  48 }
  49
  50 void chacha_init_arch(u32 *state, const u32 *key, const u8 *iv);
  51 static inline void chacha_init_generic(u32 *state, const u32 *key, const u8 *iv)
  52 {
  53         state[0]  = 0x61707865; /* "expa" */
  54         state[1]  = 0x3320646e; /* "nd 3" */
  55         state[2]  = 0x79622d32; /* "2-by" */
  56         state[3]  = 0x6b206574; /* "te k" */
  57         state[4]  = key[0];
  58         state[5]  = key[1];
  59         state[6]  = key[2];
  60         state[7]  = key[3];
  61         state[8]  = key[4];
  62         state[9]  = key[5];
  63         state[10] = key[6];
  64         state[11] = key[7];
  65         state[12] = get_unaligned_le32(iv +  0);
  66         state[13] = get_unaligned_le32(iv +  4);
  67         state[14] = get_unaligned_le32(iv +  8);
  68         state[15] = get_unaligned_le32(iv + 12);
  69 }
  70
  71 static inline void chacha_init(u32 *state, const u32 *key, const u8 *iv)
  72 {
  73         if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CHACHA))
  74                 chacha_init_arch(state, key, iv);
  75         else
  76                 chacha_init_generic(state, key, iv);
  77 }
  78
  79 void chacha_crypt_arch(u32 *state, u8 *dst, const u8 *src,
  80                        unsigned int bytes, int nrounds);
  81 void chacha_crypt_generic(u32 *state, u8 *dst, const u8 *src,
  82                           unsigned int bytes, int nrounds);
  83
  84 static inline void chacha_crypt(u32 *state, u8 *dst, const u8 *src,
  85                                 unsigned int bytes, int nrounds)
  86 {
  87         if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CHACHA))
  88                 chacha_crypt_arch(state, dst, src, bytes, nrounds);
  89         else
  90                 chacha_crypt_generic(state, dst, src, bytes, nrounds);
  91 }
  92
  93 static inline void chacha20_crypt(u32 *state, u8 *dst, const u8 *src,
  94                                   unsigned int bytes)
  95 {
  96         chacha_crypt(state, dst, src, bytes, 20);
  97 }
  98
  99 #endif /* _CRYPTO_CHACHA_H */