iPXE
arc4.c
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1 /*
2  * The ARC4 stream cipher.
3  *
4  * Copyright (c) 2009 Joshua Oreman <oremanj@rwcr.net>.
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License as
8  * published by the Free Software Foundation; either version 2 of the
9  * License, or any later version.
10  *
11  * This program is distributed in the hope that it will be useful, but
12  * WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * General Public License for more details.
15  *
16  * You should have received a copy of the GNU General Public License
17  * along with this program; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
19  * 02110-1301, USA.
20  */
21 
22 FILE_LICENCE ( GPL2_OR_LATER );
23 
24 #include <ipxe/crypto.h>
25 #include <ipxe/arc4.h>
26 
27 #define SWAP( ary, i, j ) \
28  ({ u8 temp = ary[i]; ary[i] = ary[j]; ary[j] = temp; })
29 
30 /**
31  * Set ARC4 key
32  *
33  * @v ctxv ARC4 encryption context
34  * @v keyv Key to set
35  * @v keylen Length of key
36  *
37  * If an initialisation vector is to be used, it should be prepended
38  * to the key; ARC4 does not implement the @c setiv function because
39  * there is no standard length for an initialisation vector in the
40  * cipher.
41  */
42 static int arc4_setkey ( void *ctxv, const void *keyv, size_t keylen )
43 {
44  struct arc4_ctx *ctx = ctxv;
45  const u8 *key = keyv;
46  u8 *S = ctx->state;
47  int i, j;
48 
49  for ( i = 0; i < 256; i++ ) {
50  S[i] = i;
51  }
52 
53  for ( i = j = 0; i < 256; i++ ) {
54  j = ( j + S[i] + key[i % keylen] ) & 0xff;
55  SWAP ( S, i, j );
56  }
57 
58  ctx->i = ctx->j = 0;
59  return 0;
60 }
61 
62 /**
63  * Perform ARC4 encryption or decryption
64  *
65  * @v ctxv ARC4 encryption context
66  * @v srcv Data to encrypt or decrypt
67  * @v dstv Location to store encrypted or decrypted data
68  * @v len Length of data to operate on
69  *
70  * ARC4 is a stream cipher that works by generating a stream of PRNG
71  * data based on the key, and XOR'ing it with the data to be
72  * encrypted. Since XOR is symmetric, encryption and decryption in
73  * ARC4 are the same operation.
74  *
75  * If you pass a @c NULL source or destination pointer, @a len
76  * keystream bytes will be consumed without encrypting any data.
77  */
78 static void arc4_xor ( void *ctxv, const void *srcv, void *dstv,
79  size_t len )
80 {
81  struct arc4_ctx *ctx = ctxv;
82  const u8 *src = srcv;
83  u8 *dst = dstv;
84  u8 *S = ctx->state;
85  int i = ctx->i, j = ctx->j;
86 
87  while ( len-- ) {
88  i = ( i + 1 ) & 0xff;
89  j = ( j + S[i] ) & 0xff;
90  SWAP ( S, i, j );
91  if ( srcv && dstv )
92  *dst++ = *src++ ^ S[(S[i] + S[j]) & 0xff];
93  }
94 
95  ctx->i = i;
96  ctx->j = j;
97 }
98 
99 static void arc4_setiv ( void *ctx __unused, const void *iv __unused )
100 {
101  /* ARC4 does not use a fixed-length IV */
102 }
103 
104 
105 /**
106  * Perform ARC4 encryption or decryption, skipping initial keystream bytes
107  *
108  * @v key ARC4 encryption key
109  * @v keylen Key length
110  * @v skip Number of bytes of keystream to skip
111  * @v src Message to encrypt or decrypt
112  * @v msglen Length of message
113  * @ret dst Encrypted or decrypted message
114  */
115 void arc4_skip ( const void *key, size_t keylen, size_t skip,
116  const void *src, void *dst, size_t msglen )
117 {
118  struct arc4_ctx ctx;
119  arc4_setkey ( &ctx, key, keylen );
120  arc4_xor ( &ctx, NULL, NULL, skip );
121  arc4_xor ( &ctx, src, dst, msglen );
122 }
123 
125  .name = "ARC4",
126  .ctxsize = ARC4_CTX_SIZE,
127  .blocksize = 1,
128  .setkey = arc4_setkey,
129  .setiv = arc4_setiv,
130  .encrypt = arc4_xor,
131  .decrypt = arc4_xor,
132 };
Definition: arc4.h:10
int i
Definition: arc4.h:11
Cryptographic API.
struct golan_eq_context ctx
Definition: CIB_PRM.h:28
u8 iv[16]
Initialization vector.
Definition: wpa.h:60
static u16 S(u16 v)
Perform S-box mapping on a 16-bit value.
Definition: wpa_tkip.c:137
#define SWAP(ary, i, j)
Definition: arc4.c:27
static void arc4_xor(void *ctxv, const void *srcv, void *dstv, size_t len)
Perform ARC4 encryption or decryption.
Definition: arc4.c:78
void arc4_skip(const void *key, size_t keylen, size_t skip, const void *src, void *dst, size_t msglen)
Perform ARC4 encryption or decryption, skipping initial keystream bytes.
Definition: arc4.c:115
static __always_inline void off_t userptr_t src
Definition: efi_uaccess.h:66
int j
Definition: arc4.h:11
static int arc4_setkey(void *ctxv, const void *keyv, size_t keylen)
Set ARC4 key.
Definition: arc4.c:42
struct cipher_algorithm arc4_algorithm
Definition: arc4.c:124
#define __unused
Declare a variable or data structure as unused.
Definition: compiler.h:573
FILE_LICENCE(GPL2_OR_LATER)
uint32_t len
Length.
Definition: ena.h:14
A cipher algorithm.
Definition: crypto.h:48
static void arc4_setiv(void *ctx __unused, const void *iv __unused)
Definition: arc4.c:99
const char * name
Algorithm name.
Definition: crypto.h:50
#define NULL
NULL pointer (VOID *)
Definition: Base.h:362
uint8_t u8
Definition: stdint.h:19
union @375 key
Sense key.
Definition: scsi.h:18
#define ARC4_CTX_SIZE
Definition: arc4.h:15