1 /* 2 * echainiv: Encrypted Chain IV Generator 3 * 4 * This generator generates an IV based on a sequence number by xoring it 5 * with a salt and then encrypting it with the same key as used to encrypt 6 * the plain text. This algorithm requires that the block size be equal 7 * to the IV size. It is mainly useful for CBC. 8 * 9 * This generator can only be used by algorithms where authentication 10 * is performed after encryption (i.e., authenc). 11 * 12 * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au> 13 * 14 * This program is free software; you can redistribute it and/or modify it 15 * under the terms of the GNU General Public License as published by the Free 16 * Software Foundation; either version 2 of the License, or (at your option) 17 * any later version. 18 * 19 */ 20 21 #include <crypto/internal/geniv.h> 22 #include <crypto/scatterwalk.h> 23 #include <linux/err.h> 24 #include <linux/init.h> 25 #include <linux/kernel.h> 26 #include <linux/mm.h> 27 #include <linux/module.h> 28 #include <linux/percpu.h> 29 #include <linux/spinlock.h> 30 #include <linux/string.h> 31 32 #define MAX_IV_SIZE 16 33 34 static DEFINE_PER_CPU(u32 [MAX_IV_SIZE / sizeof(u32)], echainiv_iv); 35 36 /* We don't care if we get preempted and read/write IVs from the next CPU. */ 37 static void echainiv_read_iv(u8 *dst, unsigned size) 38 { 39 u32 *a = (u32 *)dst; 40 u32 __percpu *b = echainiv_iv; 41 42 for (; size >= 4; size -= 4) { 43 *a++ = this_cpu_read(*b); 44 b++; 45 } 46 } 47 48 static void echainiv_write_iv(const u8 *src, unsigned size) 49 { 50 const u32 *a = (const u32 *)src; 51 u32 __percpu *b = echainiv_iv; 52 53 for (; size >= 4; size -= 4) { 54 this_cpu_write(*b, *a); 55 a++; 56 b++; 57 } 58 } 59 60 static void echainiv_encrypt_complete2(struct aead_request *req, int err) 61 { 62 struct aead_request *subreq = aead_request_ctx(req); 63 struct crypto_aead *geniv; 64 unsigned int ivsize; 65 66 if (err == -EINPROGRESS) 67 return; 68 69 if (err) 70 goto out; 71 72 geniv = crypto_aead_reqtfm(req); 73 ivsize = crypto_aead_ivsize(geniv); 74 75 echainiv_write_iv(subreq->iv, ivsize); 76 77 if (req->iv != subreq->iv) 78 memcpy(req->iv, subreq->iv, ivsize); 79 80 out: 81 if (req->iv != subreq->iv) 82 kzfree(subreq->iv); 83 } 84 85 static void echainiv_encrypt_complete(struct crypto_async_request *base, 86 int err) 87 { 88 struct aead_request *req = base->data; 89 90 echainiv_encrypt_complete2(req, err); 91 aead_request_complete(req, err); 92 } 93 94 static int echainiv_encrypt(struct aead_request *req) 95 { 96 struct crypto_aead *geniv = crypto_aead_reqtfm(req); 97 struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv); 98 struct aead_request *subreq = aead_request_ctx(req); 99 crypto_completion_t compl; 100 void *data; 101 u8 *info; 102 unsigned int ivsize = crypto_aead_ivsize(geniv); 103 int err; 104 105 if (req->cryptlen < ivsize) 106 return -EINVAL; 107 108 aead_request_set_tfm(subreq, ctx->child); 109 110 compl = echainiv_encrypt_complete; 111 data = req; 112 info = req->iv; 113 114 if (req->src != req->dst) { 115 struct blkcipher_desc desc = { 116 .tfm = ctx->null, 117 }; 118 119 err = crypto_blkcipher_encrypt( 120 &desc, req->dst, req->src, 121 req->assoclen + req->cryptlen); 122 if (err) 123 return err; 124 } 125 126 if (unlikely(!IS_ALIGNED((unsigned long)info, 127 crypto_aead_alignmask(geniv) + 1))) { 128 info = kmalloc(ivsize, req->base.flags & 129 CRYPTO_TFM_REQ_MAY_SLEEP ? GFP_KERNEL: 130 GFP_ATOMIC); 131 if (!info) 132 return -ENOMEM; 133 134 memcpy(info, req->iv, ivsize); 135 } 136 137 aead_request_set_callback(subreq, req->base.flags, compl, data); 138 aead_request_set_crypt(subreq, req->dst, req->dst, 139 req->cryptlen, info); 140 aead_request_set_ad(subreq, req->assoclen); 141 142 crypto_xor(info, ctx->salt, ivsize); 143 scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1); 144 echainiv_read_iv(info, ivsize); 145 146 err = crypto_aead_encrypt(subreq); 147 echainiv_encrypt_complete2(req, err); 148 return err; 149 } 150 151 static int echainiv_decrypt(struct aead_request *req) 152 { 153 struct crypto_aead *geniv = crypto_aead_reqtfm(req); 154 struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv); 155 struct aead_request *subreq = aead_request_ctx(req); 156 crypto_completion_t compl; 157 void *data; 158 unsigned int ivsize = crypto_aead_ivsize(geniv); 159 160 if (req->cryptlen < ivsize) 161 return -EINVAL; 162 163 aead_request_set_tfm(subreq, ctx->child); 164 165 compl = req->base.complete; 166 data = req->base.data; 167 168 aead_request_set_callback(subreq, req->base.flags, compl, data); 169 aead_request_set_crypt(subreq, req->src, req->dst, 170 req->cryptlen - ivsize, req->iv); 171 aead_request_set_ad(subreq, req->assoclen + ivsize); 172 173 scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0); 174 175 return crypto_aead_decrypt(subreq); 176 } 177 178 static int echainiv_aead_create(struct crypto_template *tmpl, 179 struct rtattr **tb) 180 { 181 struct aead_instance *inst; 182 struct crypto_aead_spawn *spawn; 183 struct aead_alg *alg; 184 int err; 185 186 inst = aead_geniv_alloc(tmpl, tb, 0, 0); 187 188 if (IS_ERR(inst)) 189 return PTR_ERR(inst); 190 191 spawn = aead_instance_ctx(inst); 192 alg = crypto_spawn_aead_alg(spawn); 193 194 err = -EINVAL; 195 if (inst->alg.ivsize & (sizeof(u32) - 1) || 196 inst->alg.ivsize > MAX_IV_SIZE) 197 goto free_inst; 198 199 inst->alg.encrypt = echainiv_encrypt; 200 inst->alg.decrypt = echainiv_decrypt; 201 202 inst->alg.init = aead_init_geniv; 203 inst->alg.exit = aead_exit_geniv; 204 205 inst->alg.base.cra_alignmask |= __alignof__(u32) - 1; 206 inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx); 207 inst->alg.base.cra_ctxsize += inst->alg.ivsize; 208 209 inst->free = aead_geniv_free; 210 211 err = aead_register_instance(tmpl, inst); 212 if (err) 213 goto free_inst; 214 215 out: 216 return err; 217 218 free_inst: 219 aead_geniv_free(inst); 220 goto out; 221 } 222 223 static void echainiv_free(struct crypto_instance *inst) 224 { 225 aead_geniv_free(aead_instance(inst)); 226 } 227 228 static struct crypto_template echainiv_tmpl = { 229 .name = "echainiv", 230 .create = echainiv_aead_create, 231 .free = echainiv_free, 232 .module = THIS_MODULE, 233 }; 234 235 static int __init echainiv_module_init(void) 236 { 237 return crypto_register_template(&echainiv_tmpl); 238 } 239 240 static void __exit echainiv_module_exit(void) 241 { 242 crypto_unregister_template(&echainiv_tmpl); 243 } 244 245 module_init(echainiv_module_init); 246 module_exit(echainiv_module_exit); 247 248 MODULE_LICENSE("GPL"); 249 MODULE_DESCRIPTION("Encrypted Chain IV Generator"); 250 MODULE_ALIAS_CRYPTO("echainiv"); 251