1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * echainiv: Encrypted Chain IV Generator 4 * 5 * This generator generates an IV based on a sequence number by multiplying 6 * it with a salt and then encrypting it with the same key as used to encrypt 7 * the plain text. This algorithm requires that the block size be equal 8 * to the IV size. It is mainly useful for CBC. 9 * 10 * This generator can only be used by algorithms where authentication 11 * is performed after encryption (i.e., authenc). 12 * 13 * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au> 14 */ 15 16 #include <crypto/internal/geniv.h> 17 #include <crypto/scatterwalk.h> 18 #include <crypto/skcipher.h> 19 #include <linux/err.h> 20 #include <linux/init.h> 21 #include <linux/kernel.h> 22 #include <linux/module.h> 23 #include <linux/slab.h> 24 #include <linux/string.h> 25 26 static int echainiv_encrypt(struct aead_request *req) 27 { 28 struct crypto_aead *geniv = crypto_aead_reqtfm(req); 29 struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv); 30 struct aead_request *subreq = aead_request_ctx(req); 31 __be64 nseqno; 32 u64 seqno; 33 u8 *info; 34 unsigned int ivsize = crypto_aead_ivsize(geniv); 35 36 if (req->cryptlen < ivsize) 37 return -EINVAL; 38 39 aead_request_set_tfm(subreq, ctx->child); 40 41 info = req->iv; 42 43 if (req->src != req->dst) 44 memcpy_sglist(req->dst, req->src, 45 req->assoclen + req->cryptlen); 46 47 aead_request_set_callback(subreq, req->base.flags, 48 req->base.complete, req->base.data); 49 aead_request_set_crypt(subreq, req->dst, req->dst, 50 req->cryptlen, info); 51 aead_request_set_ad(subreq, req->assoclen); 52 53 memcpy(&nseqno, info + ivsize - 8, 8); 54 seqno = be64_to_cpu(nseqno); 55 memset(info, 0, ivsize); 56 57 scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1); 58 59 do { 60 u64 a; 61 62 memcpy(&a, ctx->salt + ivsize - 8, 8); 63 64 a |= 1; 65 a *= seqno; 66 67 memcpy(info + ivsize - 8, &a, 8); 68 } while ((ivsize -= 8)); 69 70 return crypto_aead_encrypt(subreq); 71 } 72 73 static int echainiv_decrypt(struct aead_request *req) 74 { 75 struct crypto_aead *geniv = crypto_aead_reqtfm(req); 76 struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv); 77 struct aead_request *subreq = aead_request_ctx(req); 78 crypto_completion_t compl; 79 void *data; 80 unsigned int ivsize = crypto_aead_ivsize(geniv); 81 82 if (req->cryptlen < ivsize) 83 return -EINVAL; 84 85 aead_request_set_tfm(subreq, ctx->child); 86 87 compl = req->base.complete; 88 data = req->base.data; 89 90 aead_request_set_callback(subreq, req->base.flags, compl, data); 91 aead_request_set_crypt(subreq, req->src, req->dst, 92 req->cryptlen - ivsize, req->iv); 93 aead_request_set_ad(subreq, req->assoclen + ivsize); 94 95 scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0); 96 97 return crypto_aead_decrypt(subreq); 98 } 99 100 static int echainiv_aead_create(struct crypto_template *tmpl, 101 struct rtattr **tb) 102 { 103 struct aead_instance *inst; 104 int err; 105 106 inst = aead_geniv_alloc(tmpl, tb); 107 108 if (IS_ERR(inst)) 109 return PTR_ERR(inst); 110 111 err = -EINVAL; 112 if (inst->alg.ivsize & (sizeof(u64) - 1) || !inst->alg.ivsize) 113 goto free_inst; 114 115 inst->alg.encrypt = echainiv_encrypt; 116 inst->alg.decrypt = echainiv_decrypt; 117 118 inst->alg.init = aead_init_geniv; 119 inst->alg.exit = aead_exit_geniv; 120 121 inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx); 122 inst->alg.base.cra_ctxsize += inst->alg.ivsize; 123 124 err = aead_register_instance(tmpl, inst); 125 if (err) { 126 free_inst: 127 inst->free(inst); 128 } 129 return err; 130 } 131 132 static struct crypto_template echainiv_tmpl = { 133 .name = "echainiv", 134 .create = echainiv_aead_create, 135 .module = THIS_MODULE, 136 }; 137 138 static int __init echainiv_module_init(void) 139 { 140 return crypto_register_template(&echainiv_tmpl); 141 } 142 143 static void __exit echainiv_module_exit(void) 144 { 145 crypto_unregister_template(&echainiv_tmpl); 146 } 147 148 module_init(echainiv_module_init); 149 module_exit(echainiv_module_exit); 150 151 MODULE_LICENSE("GPL"); 152 MODULE_DESCRIPTION("Encrypted Chain IV Generator"); 153 MODULE_ALIAS_CRYPTO("echainiv"); 154