fs/smb/common/cifs_arc4.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Cryptographic API
   4  *
   5  * ARC4 Cipher Algorithm
   6  *
   7  * Jon Oberheide <jon@oberheide.org>
   8  */
   9
  10 #include <linux/module.h>
  11 #include "arc4.h"
  12
  13 MODULE_DESCRIPTION("ARC4 Cipher Algorithm");
  14 MODULE_LICENSE("GPL");
  15
  16 int cifs_arc4_setkey(struct arc4_ctx *ctx, const u8 *in_key, unsigned int key_len)
  17 {
  18         int i, j = 0, k = 0;
  19
  20         ctx->x = 1;
  21         ctx->y = 0;
  22
  23         for (i = 0; i < 256; i++)
  24                 ctx->S[i] = i;
  25
  26         for (i = 0; i < 256; i++) {
  27                 u32 a = ctx->S[i];
  28
  29                 j = (j + in_key[k] + a) & 0xff;
  30                 ctx->S[i] = ctx->S[j];
  31                 ctx->S[j] = a;
  32                 if (++k >= key_len)
  33                         k = 0;
  34         }
  35
  36         return 0;
  37 }
  38 EXPORT_SYMBOL_GPL(cifs_arc4_setkey);
  39
  40 void cifs_arc4_crypt(struct arc4_ctx *ctx, u8 *out, const u8 *in, unsigned int len)
  41 {
  42         u32 *const S = ctx->S;
  43         u32 x, y, a, b;
  44         u32 ty, ta, tb;
  45
  46         if (len == 0)
  47                 return;
  48
  49         x = ctx->x;
  50         y = ctx->y;
  51
  52         a = S[x];
  53         y = (y + a) & 0xff;
  54         b = S[y];
  55
  56         do {
  57                 S[y] = a;
  58                 a = (a + b) & 0xff;
  59                 S[x] = b;
  60                 x = (x + 1) & 0xff;
  61                 ta = S[x];
  62                 ty = (y + ta) & 0xff;
  63                 tb = S[ty];
  64                 *out++ = *in++ ^ S[a];
  65                 if (--len == 0)
  66                         break;
  67                 y = ty;
  68                 a = ta;
  69                 b = tb;
  70         } while (true);
  71
  72         ctx->x = x;
  73         ctx->y = y;
  74 }
  75 EXPORT_SYMBOL_GPL(cifs_arc4_crypt);