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 int err; 36 37 if (req->cryptlen < ivsize) 38 return -EINVAL; 39 40 aead_request_set_tfm(subreq, ctx->child); 41 42 info = req->iv; 43 44 if (req->src != req->dst) { 45 SYNC_SKCIPHER_REQUEST_ON_STACK(nreq, ctx->sknull); 46 47 skcipher_request_set_sync_tfm(nreq, ctx->sknull); 48 skcipher_request_set_callback(nreq, req->base.flags, 49 NULL, NULL); 50 skcipher_request_set_crypt(nreq, req->src, req->dst, 51 req->assoclen + req->cryptlen, 52 NULL); 53 54 err = crypto_skcipher_encrypt(nreq); 55 if (err) 56 return err; 57 } 58 59 aead_request_set_callback(subreq, req->base.flags, 60 req->base.complete, req->base.data); 61 aead_request_set_crypt(subreq, req->dst, req->dst, 62 req->cryptlen, info); 63 aead_request_set_ad(subreq, req->assoclen); 64 65 memcpy(&nseqno, info + ivsize - 8, 8); 66 seqno = be64_to_cpu(nseqno); 67 memset(info, 0, ivsize); 68 69 scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1); 70 71 do { 72 u64 a; 73 74 memcpy(&a, ctx->salt + ivsize - 8, 8); 75 76 a |= 1; 77 a *= seqno; 78 79 memcpy(info + ivsize - 8, &a, 8); 80 } while ((ivsize -= 8)); 81 82 return crypto_aead_encrypt(subreq); 83 } 84 85 static int echainiv_decrypt(struct aead_request *req) 86 { 87 struct crypto_aead *geniv = crypto_aead_reqtfm(req); 88 struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv); 89 struct aead_request *subreq = aead_request_ctx(req); 90 crypto_completion_t compl; 91 void *data; 92 unsigned int ivsize = crypto_aead_ivsize(geniv); 93 94 if (req->cryptlen < ivsize) 95 return -EINVAL; 96 97 aead_request_set_tfm(subreq, ctx->child); 98 99 compl = req->base.complete; 100 data = req->base.data; 101 102 aead_request_set_callback(subreq, req->base.flags, compl, data); 103 aead_request_set_crypt(subreq, req->src, req->dst, 104 req->cryptlen - ivsize, req->iv); 105 aead_request_set_ad(subreq, req->assoclen + ivsize); 106 107 scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0); 108 109 return crypto_aead_decrypt(subreq); 110 } 111 112 static int echainiv_aead_create(struct crypto_template *tmpl, 113 struct rtattr **tb) 114 { 115 struct aead_instance *inst; 116 int err; 117 118 inst = aead_geniv_alloc(tmpl, tb, 0, 0); 119 120 if (IS_ERR(inst)) 121 return PTR_ERR(inst); 122 123 err = -EINVAL; 124 if (inst->alg.ivsize & (sizeof(u64) - 1) || !inst->alg.ivsize) 125 goto free_inst; 126 127 inst->alg.encrypt = echainiv_encrypt; 128 inst->alg.decrypt = echainiv_decrypt; 129 130 inst->alg.init = aead_init_geniv; 131 inst->alg.exit = aead_exit_geniv; 132 133 inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx); 134 inst->alg.base.cra_ctxsize += inst->alg.ivsize; 135 136 err = aead_register_instance(tmpl, inst); 137 if (err) { 138 free_inst: 139 inst->free(inst); 140 } 141 return err; 142 } 143 144 static struct crypto_template echainiv_tmpl = { 145 .name = "echainiv", 146 .create = echainiv_aead_create, 147 .module = THIS_MODULE, 148 }; 149 150 static int __init echainiv_module_init(void) 151 { 152 return crypto_register_template(&echainiv_tmpl); 153 } 154 155 static void __exit echainiv_module_exit(void) 156 { 157 crypto_unregister_template(&echainiv_tmpl); 158 } 159 160 subsys_initcall(echainiv_module_init); 161 module_exit(echainiv_module_exit); 162 163 MODULE_LICENSE("GPL"); 164 MODULE_DESCRIPTION("Encrypted Chain IV Generator"); 165 MODULE_ALIAS_CRYPTO("echainiv"); 166