1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Minimal library implementation of AES in CFB mode 4 * 5 * Copyright 2023 Google LLC 6 */ 7 8 #include <crypto/aes.h> 9 #include <crypto/utils.h> 10 #include <linux/export.h> 11 #include <linux/module.h> 12 13 /** 14 * aescfb_encrypt - Perform AES-CFB encryption on a block of data 15 * 16 * @key: The AES-CFB key schedule 17 * @dst: Pointer to the ciphertext output buffer 18 * @src: Pointer the plaintext (may equal @dst for encryption in place) 19 * @len: The size in bytes of the plaintext and ciphertext. 20 * @iv: The initialization vector (IV) to use for this block of data 21 */ 22 void aescfb_encrypt(const struct aes_enckey *key, u8 *dst, const u8 *src, 23 int len, const u8 iv[AES_BLOCK_SIZE]) 24 { 25 u8 ks[AES_BLOCK_SIZE]; 26 const u8 *v = iv; 27 28 while (len > 0) { 29 aes_encrypt(key, ks, v); 30 crypto_xor_cpy(dst, src, ks, min(len, AES_BLOCK_SIZE)); 31 v = dst; 32 33 dst += AES_BLOCK_SIZE; 34 src += AES_BLOCK_SIZE; 35 len -= AES_BLOCK_SIZE; 36 } 37 38 memzero_explicit(ks, sizeof(ks)); 39 } 40 EXPORT_SYMBOL(aescfb_encrypt); 41 42 /** 43 * aescfb_decrypt - Perform AES-CFB decryption on a block of data 44 * 45 * @key: The AES-CFB key schedule 46 * @dst: Pointer to the plaintext output buffer 47 * @src: Pointer the ciphertext (may equal @dst for decryption in place) 48 * @len: The size in bytes of the plaintext and ciphertext. 49 * @iv: The initialization vector (IV) to use for this block of data 50 */ 51 void aescfb_decrypt(const struct aes_enckey *key, u8 *dst, const u8 *src, 52 int len, const u8 iv[AES_BLOCK_SIZE]) 53 { 54 u8 ks[2][AES_BLOCK_SIZE]; 55 56 aes_encrypt(key, ks[0], iv); 57 58 for (int i = 0; len > 0; i ^= 1) { 59 if (len > AES_BLOCK_SIZE) 60 /* 61 * Generate the keystream for the next block before 62 * performing the XOR, as that may update in place and 63 * overwrite the ciphertext. 64 */ 65 aes_encrypt(key, ks[!i], src); 66 67 crypto_xor_cpy(dst, src, ks[i], min(len, AES_BLOCK_SIZE)); 68 69 dst += AES_BLOCK_SIZE; 70 src += AES_BLOCK_SIZE; 71 len -= AES_BLOCK_SIZE; 72 } 73 74 memzero_explicit(ks, sizeof(ks)); 75 } 76 EXPORT_SYMBOL(aescfb_decrypt); 77 78 MODULE_DESCRIPTION("Generic AES-CFB library"); 79 MODULE_AUTHOR("Ard Biesheuvel <ardb@kernel.org>"); 80 MODULE_LICENSE("GPL"); 81 82 #ifdef CONFIG_CRYPTO_SELFTESTS 83 84 /* 85 * Test code below. Vectors taken from crypto/testmgr.h 86 */ 87 88 static struct { 89 u8 ptext[64] __nonstring; 90 u8 ctext[64] __nonstring; 91 92 u8 key[AES_MAX_KEY_SIZE] __nonstring; 93 u8 iv[AES_BLOCK_SIZE] __nonstring; 94 95 int klen; 96 int len; 97 } const aescfb_tv[] __initconst = { 98 { /* From NIST SP800-38A */ 99 .key = "\x2b\x7e\x15\x16\x28\xae\xd2\xa6" 100 "\xab\xf7\x15\x88\x09\xcf\x4f\x3c", 101 .klen = 16, 102 .iv = "\x00\x01\x02\x03\x04\x05\x06\x07" 103 "\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f", 104 .ptext = "\x6b\xc1\xbe\xe2\x2e\x40\x9f\x96" 105 "\xe9\x3d\x7e\x11\x73\x93\x17\x2a" 106 "\xae\x2d\x8a\x57\x1e\x03\xac\x9c" 107 "\x9e\xb7\x6f\xac\x45\xaf\x8e\x51" 108 "\x30\xc8\x1c\x46\xa3\x5c\xe4\x11" 109 "\xe5\xfb\xc1\x19\x1a\x0a\x52\xef" 110 "\xf6\x9f\x24\x45\xdf\x4f\x9b\x17" 111 "\xad\x2b\x41\x7b\xe6\x6c\x37\x10", 112 .ctext = "\x3b\x3f\xd9\x2e\xb7\x2d\xad\x20" 113 "\x33\x34\x49\xf8\xe8\x3c\xfb\x4a" 114 "\xc8\xa6\x45\x37\xa0\xb3\xa9\x3f" 115 "\xcd\xe3\xcd\xad\x9f\x1c\xe5\x8b" 116 "\x26\x75\x1f\x67\xa3\xcb\xb1\x40" 117 "\xb1\x80\x8c\xf1\x87\xa4\xf4\xdf" 118 "\xc0\x4b\x05\x35\x7c\x5d\x1c\x0e" 119 "\xea\xc4\xc6\x6f\x9f\xf7\xf2\xe6", 120 .len = 64, 121 }, { 122 .key = "\x8e\x73\xb0\xf7\xda\x0e\x64\x52" 123 "\xc8\x10\xf3\x2b\x80\x90\x79\xe5" 124 "\x62\xf8\xea\xd2\x52\x2c\x6b\x7b", 125 .klen = 24, 126 .iv = "\x00\x01\x02\x03\x04\x05\x06\x07" 127 "\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f", 128 .ptext = "\x6b\xc1\xbe\xe2\x2e\x40\x9f\x96" 129 "\xe9\x3d\x7e\x11\x73\x93\x17\x2a" 130 "\xae\x2d\x8a\x57\x1e\x03\xac\x9c" 131 "\x9e\xb7\x6f\xac\x45\xaf\x8e\x51" 132 "\x30\xc8\x1c\x46\xa3\x5c\xe4\x11" 133 "\xe5\xfb\xc1\x19\x1a\x0a\x52\xef" 134 "\xf6\x9f\x24\x45\xdf\x4f\x9b\x17" 135 "\xad\x2b\x41\x7b\xe6\x6c\x37\x10", 136 .ctext = "\xcd\xc8\x0d\x6f\xdd\xf1\x8c\xab" 137 "\x34\xc2\x59\x09\xc9\x9a\x41\x74" 138 "\x67\xce\x7f\x7f\x81\x17\x36\x21" 139 "\x96\x1a\x2b\x70\x17\x1d\x3d\x7a" 140 "\x2e\x1e\x8a\x1d\xd5\x9b\x88\xb1" 141 "\xc8\xe6\x0f\xed\x1e\xfa\xc4\xc9" 142 "\xc0\x5f\x9f\x9c\xa9\x83\x4f\xa0" 143 "\x42\xae\x8f\xba\x58\x4b\x09\xff", 144 .len = 64, 145 }, { 146 .key = "\x60\x3d\xeb\x10\x15\xca\x71\xbe" 147 "\x2b\x73\xae\xf0\x85\x7d\x77\x81" 148 "\x1f\x35\x2c\x07\x3b\x61\x08\xd7" 149 "\x2d\x98\x10\xa3\x09\x14\xdf\xf4", 150 .klen = 32, 151 .iv = "\x00\x01\x02\x03\x04\x05\x06\x07" 152 "\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f", 153 .ptext = "\x6b\xc1\xbe\xe2\x2e\x40\x9f\x96" 154 "\xe9\x3d\x7e\x11\x73\x93\x17\x2a" 155 "\xae\x2d\x8a\x57\x1e\x03\xac\x9c" 156 "\x9e\xb7\x6f\xac\x45\xaf\x8e\x51" 157 "\x30\xc8\x1c\x46\xa3\x5c\xe4\x11" 158 "\xe5\xfb\xc1\x19\x1a\x0a\x52\xef" 159 "\xf6\x9f\x24\x45\xdf\x4f\x9b\x17" 160 "\xad\x2b\x41\x7b\xe6\x6c\x37\x10", 161 .ctext = "\xdc\x7e\x84\xbf\xda\x79\x16\x4b" 162 "\x7e\xcd\x84\x86\x98\x5d\x38\x60" 163 "\x39\xff\xed\x14\x3b\x28\xb1\xc8" 164 "\x32\x11\x3c\x63\x31\xe5\x40\x7b" 165 "\xdf\x10\x13\x24\x15\xe5\x4b\x92" 166 "\xa1\x3e\xd0\xa8\x26\x7a\xe2\xf9" 167 "\x75\xa3\x85\x74\x1a\xb9\xce\xf8" 168 "\x20\x31\x62\x3d\x55\xb1\xe4\x71", 169 .len = 64, 170 }, { /* > 16 bytes, not a multiple of 16 bytes */ 171 .key = "\x2b\x7e\x15\x16\x28\xae\xd2\xa6" 172 "\xab\xf7\x15\x88\x09\xcf\x4f\x3c", 173 .klen = 16, 174 .iv = "\x00\x01\x02\x03\x04\x05\x06\x07" 175 "\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f", 176 .ptext = "\x6b\xc1\xbe\xe2\x2e\x40\x9f\x96" 177 "\xe9\x3d\x7e\x11\x73\x93\x17\x2a" 178 "\xae", 179 .ctext = "\x3b\x3f\xd9\x2e\xb7\x2d\xad\x20" 180 "\x33\x34\x49\xf8\xe8\x3c\xfb\x4a" 181 "\xc8", 182 .len = 17, 183 }, { /* < 16 bytes */ 184 .key = "\x2b\x7e\x15\x16\x28\xae\xd2\xa6" 185 "\xab\xf7\x15\x88\x09\xcf\x4f\x3c", 186 .klen = 16, 187 .iv = "\x00\x01\x02\x03\x04\x05\x06\x07" 188 "\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f", 189 .ptext = "\x6b\xc1\xbe\xe2\x2e\x40\x9f", 190 .ctext = "\x3b\x3f\xd9\x2e\xb7\x2d\xad", 191 .len = 7, 192 }, 193 }; 194 195 static int __init libaescfb_init(void) 196 { 197 for (int i = 0; i < ARRAY_SIZE(aescfb_tv); i++) { 198 struct aes_enckey key; 199 u8 buf[64]; 200 201 if (aes_prepareenckey(&key, aescfb_tv[i].key, aescfb_tv[i].klen)) { 202 pr_err("aes_prepareenckey() failed on vector %d\n", i); 203 return -ENODEV; 204 } 205 206 aescfb_encrypt(&key, buf, aescfb_tv[i].ptext, aescfb_tv[i].len, 207 aescfb_tv[i].iv); 208 if (memcmp(buf, aescfb_tv[i].ctext, aescfb_tv[i].len)) { 209 pr_err("aescfb_encrypt() #1 failed on vector %d\n", i); 210 return -ENODEV; 211 } 212 213 /* decrypt in place */ 214 aescfb_decrypt(&key, buf, buf, aescfb_tv[i].len, aescfb_tv[i].iv); 215 if (memcmp(buf, aescfb_tv[i].ptext, aescfb_tv[i].len)) { 216 pr_err("aescfb_decrypt() failed on vector %d\n", i); 217 return -ENODEV; 218 } 219 220 /* encrypt in place */ 221 aescfb_encrypt(&key, buf, buf, aescfb_tv[i].len, aescfb_tv[i].iv); 222 if (memcmp(buf, aescfb_tv[i].ctext, aescfb_tv[i].len)) { 223 pr_err("aescfb_encrypt() #2 failed on vector %d\n", i); 224 225 return -ENODEV; 226 } 227 228 } 229 return 0; 230 } 231 module_init(libaescfb_init); 232 233 static void __exit libaescfb_exit(void) 234 { 235 } 236 module_exit(libaescfb_exit); 237 #endif 238