cbc.c 5.2 KB

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  1. // SPDX-License-Identifier: GPL-2.0-or-later
  2. /*
  3. * CBC: Cipher Block Chaining mode
  4. *
  5. * Copyright (c) 2006-2016 Herbert Xu <herbert@gondor.apana.org.au>
  6. */
  7. #include <crypto/algapi.h>
  8. #include <crypto/internal/cipher.h>
  9. #include <crypto/internal/skcipher.h>
  10. #include <linux/err.h>
  11. #include <linux/init.h>
  12. #include <linux/kernel.h>
  13. #include <linux/log2.h>
  14. #include <linux/module.h>
  15. static int crypto_cbc_encrypt_segment(struct skcipher_walk *walk,
  16. struct crypto_skcipher *skcipher)
  17. {
  18. unsigned int bsize = crypto_skcipher_blocksize(skcipher);
  19. void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
  20. unsigned int nbytes = walk->nbytes;
  21. u8 *src = walk->src.virt.addr;
  22. u8 *dst = walk->dst.virt.addr;
  23. struct crypto_cipher *cipher;
  24. struct crypto_tfm *tfm;
  25. u8 *iv = walk->iv;
  26. cipher = skcipher_cipher_simple(skcipher);
  27. tfm = crypto_cipher_tfm(cipher);
  28. fn = crypto_cipher_alg(cipher)->cia_encrypt;
  29. do {
  30. crypto_xor(iv, src, bsize);
  31. fn(tfm, dst, iv);
  32. memcpy(iv, dst, bsize);
  33. src += bsize;
  34. dst += bsize;
  35. } while ((nbytes -= bsize) >= bsize);
  36. return nbytes;
  37. }
  38. static int crypto_cbc_encrypt_inplace(struct skcipher_walk *walk,
  39. struct crypto_skcipher *skcipher)
  40. {
  41. unsigned int bsize = crypto_skcipher_blocksize(skcipher);
  42. void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
  43. unsigned int nbytes = walk->nbytes;
  44. u8 *src = walk->src.virt.addr;
  45. struct crypto_cipher *cipher;
  46. struct crypto_tfm *tfm;
  47. u8 *iv = walk->iv;
  48. cipher = skcipher_cipher_simple(skcipher);
  49. tfm = crypto_cipher_tfm(cipher);
  50. fn = crypto_cipher_alg(cipher)->cia_encrypt;
  51. do {
  52. crypto_xor(src, iv, bsize);
  53. fn(tfm, src, src);
  54. iv = src;
  55. src += bsize;
  56. } while ((nbytes -= bsize) >= bsize);
  57. memcpy(walk->iv, iv, bsize);
  58. return nbytes;
  59. }
  60. static int crypto_cbc_encrypt(struct skcipher_request *req)
  61. {
  62. struct crypto_skcipher *skcipher = crypto_skcipher_reqtfm(req);
  63. struct skcipher_walk walk;
  64. int err;
  65. err = skcipher_walk_virt(&walk, req, false);
  66. while (walk.nbytes) {
  67. if (walk.src.virt.addr == walk.dst.virt.addr)
  68. err = crypto_cbc_encrypt_inplace(&walk, skcipher);
  69. else
  70. err = crypto_cbc_encrypt_segment(&walk, skcipher);
  71. err = skcipher_walk_done(&walk, err);
  72. }
  73. return err;
  74. }
  75. static int crypto_cbc_decrypt_segment(struct skcipher_walk *walk,
  76. struct crypto_skcipher *skcipher)
  77. {
  78. unsigned int bsize = crypto_skcipher_blocksize(skcipher);
  79. void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
  80. unsigned int nbytes = walk->nbytes;
  81. u8 *src = walk->src.virt.addr;
  82. u8 *dst = walk->dst.virt.addr;
  83. struct crypto_cipher *cipher;
  84. struct crypto_tfm *tfm;
  85. u8 *iv = walk->iv;
  86. cipher = skcipher_cipher_simple(skcipher);
  87. tfm = crypto_cipher_tfm(cipher);
  88. fn = crypto_cipher_alg(cipher)->cia_decrypt;
  89. do {
  90. fn(tfm, dst, src);
  91. crypto_xor(dst, iv, bsize);
  92. iv = src;
  93. src += bsize;
  94. dst += bsize;
  95. } while ((nbytes -= bsize) >= bsize);
  96. memcpy(walk->iv, iv, bsize);
  97. return nbytes;
  98. }
  99. static int crypto_cbc_decrypt_inplace(struct skcipher_walk *walk,
  100. struct crypto_skcipher *skcipher)
  101. {
  102. unsigned int bsize = crypto_skcipher_blocksize(skcipher);
  103. void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
  104. unsigned int nbytes = walk->nbytes;
  105. u8 *src = walk->src.virt.addr;
  106. u8 last_iv[MAX_CIPHER_BLOCKSIZE];
  107. struct crypto_cipher *cipher;
  108. struct crypto_tfm *tfm;
  109. cipher = skcipher_cipher_simple(skcipher);
  110. tfm = crypto_cipher_tfm(cipher);
  111. fn = crypto_cipher_alg(cipher)->cia_decrypt;
  112. /* Start of the last block. */
  113. src += nbytes - (nbytes & (bsize - 1)) - bsize;
  114. memcpy(last_iv, src, bsize);
  115. for (;;) {
  116. fn(tfm, src, src);
  117. if ((nbytes -= bsize) < bsize)
  118. break;
  119. crypto_xor(src, src - bsize, bsize);
  120. src -= bsize;
  121. }
  122. crypto_xor(src, walk->iv, bsize);
  123. memcpy(walk->iv, last_iv, bsize);
  124. return nbytes;
  125. }
  126. static int crypto_cbc_decrypt(struct skcipher_request *req)
  127. {
  128. struct crypto_skcipher *skcipher = crypto_skcipher_reqtfm(req);
  129. struct skcipher_walk walk;
  130. int err;
  131. err = skcipher_walk_virt(&walk, req, false);
  132. while (walk.nbytes) {
  133. if (walk.src.virt.addr == walk.dst.virt.addr)
  134. err = crypto_cbc_decrypt_inplace(&walk, skcipher);
  135. else
  136. err = crypto_cbc_decrypt_segment(&walk, skcipher);
  137. err = skcipher_walk_done(&walk, err);
  138. }
  139. return err;
  140. }
  141. static int crypto_cbc_create(struct crypto_template *tmpl, struct rtattr **tb)
  142. {
  143. struct skcipher_instance *inst;
  144. struct crypto_alg *alg;
  145. int err;
  146. inst = skcipher_alloc_instance_simple(tmpl, tb);
  147. if (IS_ERR(inst))
  148. return PTR_ERR(inst);
  149. alg = skcipher_ialg_simple(inst);
  150. err = -EINVAL;
  151. if (!is_power_of_2(alg->cra_blocksize))
  152. goto out_free_inst;
  153. inst->alg.encrypt = crypto_cbc_encrypt;
  154. inst->alg.decrypt = crypto_cbc_decrypt;
  155. err = skcipher_register_instance(tmpl, inst);
  156. if (err) {
  157. out_free_inst:
  158. inst->free(inst);
  159. }
  160. return err;
  161. }
  162. static struct crypto_template crypto_cbc_tmpl = {
  163. .name = "cbc",
  164. .create = crypto_cbc_create,
  165. .module = THIS_MODULE,
  166. };
  167. static int __init crypto_cbc_module_init(void)
  168. {
  169. return crypto_register_template(&crypto_cbc_tmpl);
  170. }
  171. static void __exit crypto_cbc_module_exit(void)
  172. {
  173. crypto_unregister_template(&crypto_cbc_tmpl);
  174. }
  175. subsys_initcall(crypto_cbc_module_init);
  176. module_exit(crypto_cbc_module_exit);
  177. MODULE_LICENSE("GPL");
  178. MODULE_DESCRIPTION("CBC block cipher mode of operation");
  179. MODULE_ALIAS_CRYPTO("cbc");