// SPDX-License-Identifier: GPL-2.0/* * Minimal library implementation of AES in CFB mode * * Copyright 2023 Google LLC */ #include <crypto/aes.h>#include <crypto/utils.h>#include <linux/export.h>#include <linux/module.h> /** * aescfb_encrypt - Perform AES-CFB encryption on a block of data * * @key:	The AES-CFB key schedule * @dst:	Pointer to the ciphertext output buffer * @src:	Pointer the plaintext (may equal @dst for encryption in place) * @len:	The size in bytes of the plaintext and ciphertext. * @iv:		The initialization vector (IV) to use for this block of data */void aescfb_encrypt(const struct aes_enckey *key, u8 *dst, const u8 *src,		    int len, const u8 iv[AES_BLOCK_SIZE]){	u8 ks[AES_BLOCK_SIZE];	const u8 *v = iv; 	while (len > 0) {		aes_encrypt(key, ks, v);		crypto_xor_cpy(dst, src, ks, min(len, AES_BLOCK_SIZE));		v = dst; 		dst += AES_BLOCK_SIZE;		src += AES_BLOCK_SIZE;		len -= AES_BLOCK_SIZE;	} 	memzero_explicit(ks, sizeof(ks));}EXPORT_SYMBOL(aescfb_encrypt); /** * aescfb_decrypt - Perform AES-CFB decryption on a block of data * * @key:	The AES-CFB key schedule * @dst:	Pointer to the plaintext output buffer * @src:	Pointer the ciphertext (may equal @dst for decryption in place) * @len:	The size in bytes of the plaintext and ciphertext. * @iv:		The initialization vector (IV) to use for this block of data */void aescfb_decrypt(const struct aes_enckey *key, u8 *dst, const u8 *src,		    int len, const u8 iv[AES_BLOCK_SIZE]){	u8 ks[2][AES_BLOCK_SIZE]; 	aes_encrypt(key, ks[0], iv); 	for (int i = 0; len > 0; i ^= 1) {		if (len > AES_BLOCK_SIZE)			/*			 * Generate the keystream for the next block before			 * performing the XOR, as that may update in place and			 * overwrite the ciphertext.			 */			aes_encrypt(key, ks[!i], src); 		crypto_xor_cpy(dst, src, ks[i], min(len, AES_BLOCK_SIZE)); 		dst += AES_BLOCK_SIZE;		src += AES_BLOCK_SIZE;		len -= AES_BLOCK_SIZE;	} 	memzero_explicit(ks, sizeof(ks));}EXPORT_SYMBOL(aescfb_decrypt); MODULE_DESCRIPTION("Generic AES-CFB library");MODULE_AUTHOR("Ard Biesheuvel <ardb@kernel.org>");MODULE_LICENSE("GPL"); #ifdef CONFIG_CRYPTO_SELFTESTS /* * Test code below. Vectors taken from crypto/testmgr.h */ static struct {	u8	ptext[64] __nonstring;	u8	ctext[64] __nonstring; 	u8	key[AES_MAX_KEY_SIZE] __nonstring;	u8	iv[AES_BLOCK_SIZE] __nonstring; 	int	klen;	int	len;} const aescfb_tv[] __initconst = {	{ /* From NIST SP800-38A */		.key    = "\x2b\x7e\x15\x16\x28\xae\xd2\xa6"			  "\xab\xf7\x15\x88\x09\xcf\x4f\x3c",		.klen	= 16,		.iv	= "\x00\x01\x02\x03\x04\x05\x06\x07"			  "\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f",		.ptext	= "\x6b\xc1\xbe\xe2\x2e\x40\x9f\x96"			  "\xe9\x3d\x7e\x11\x73\x93\x17\x2a"			  "\xae\x2d\x8a\x57\x1e\x03\xac\x9c"			  "\x9e\xb7\x6f\xac\x45\xaf\x8e\x51"			  "\x30\xc8\x1c\x46\xa3\x5c\xe4\x11"			  "\xe5\xfb\xc1\x19\x1a\x0a\x52\xef"			  "\xf6\x9f\x24\x45\xdf\x4f\x9b\x17"			  "\xad\x2b\x41\x7b\xe6\x6c\x37\x10",		.ctext	= "\x3b\x3f\xd9\x2e\xb7\x2d\xad\x20"			  "\x33\x34\x49\xf8\xe8\x3c\xfb\x4a"			  "\xc8\xa6\x45\x37\xa0\xb3\xa9\x3f"			  "\xcd\xe3\xcd\xad\x9f\x1c\xe5\x8b"			  "\x26\x75\x1f\x67\xa3\xcb\xb1\x40"			  "\xb1\x80\x8c\xf1\x87\xa4\xf4\xdf"			  "\xc0\x4b\x05\x35\x7c\x5d\x1c\x0e"			  "\xea\xc4\xc6\x6f\x9f\xf7\xf2\xe6",		.len	= 64,	}, {		.key	= "\x8e\x73\xb0\xf7\xda\x0e\x64\x52"			  "\xc8\x10\xf3\x2b\x80\x90\x79\xe5"			  "\x62\xf8\xea\xd2\x52\x2c\x6b\x7b",		.klen	= 24,		.iv	= "\x00\x01\x02\x03\x04\x05\x06\x07"			  "\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f",		.ptext	= "\x6b\xc1\xbe\xe2\x2e\x40\x9f\x96"			  "\xe9\x3d\x7e\x11\x73\x93\x17\x2a"			  "\xae\x2d\x8a\x57\x1e\x03\xac\x9c"			  "\x9e\xb7\x6f\xac\x45\xaf\x8e\x51"			  "\x30\xc8\x1c\x46\xa3\x5c\xe4\x11"			  "\xe5\xfb\xc1\x19\x1a\x0a\x52\xef"			  "\xf6\x9f\x24\x45\xdf\x4f\x9b\x17"			  "\xad\x2b\x41\x7b\xe6\x6c\x37\x10",		.ctext	= "\xcd\xc8\x0d\x6f\xdd\xf1\x8c\xab"			  "\x34\xc2\x59\x09\xc9\x9a\x41\x74"			  "\x67\xce\x7f\x7f\x81\x17\x36\x21"			  "\x96\x1a\x2b\x70\x17\x1d\x3d\x7a"			  "\x2e\x1e\x8a\x1d\xd5\x9b\x88\xb1"			  "\xc8\xe6\x0f\xed\x1e\xfa\xc4\xc9"			  "\xc0\x5f\x9f\x9c\xa9\x83\x4f\xa0"			  "\x42\xae\x8f\xba\x58\x4b\x09\xff",		.len	= 64,	}, {		.key	= "\x60\x3d\xeb\x10\x15\xca\x71\xbe"			  "\x2b\x73\xae\xf0\x85\x7d\x77\x81"			  "\x1f\x35\x2c\x07\x3b\x61\x08\xd7"			  "\x2d\x98\x10\xa3\x09\x14\xdf\xf4",		.klen	= 32,		.iv	= "\x00\x01\x02\x03\x04\x05\x06\x07"			  "\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f",		.ptext	= "\x6b\xc1\xbe\xe2\x2e\x40\x9f\x96"			  "\xe9\x3d\x7e\x11\x73\x93\x17\x2a"			  "\xae\x2d\x8a\x57\x1e\x03\xac\x9c"			  "\x9e\xb7\x6f\xac\x45\xaf\x8e\x51"			  "\x30\xc8\x1c\x46\xa3\x5c\xe4\x11"			  "\xe5\xfb\xc1\x19\x1a\x0a\x52\xef"			  "\xf6\x9f\x24\x45\xdf\x4f\x9b\x17"			  "\xad\x2b\x41\x7b\xe6\x6c\x37\x10",		.ctext	= "\xdc\x7e\x84\xbf\xda\x79\x16\x4b"			  "\x7e\xcd\x84\x86\x98\x5d\x38\x60"			  "\x39\xff\xed\x14\x3b\x28\xb1\xc8"			  "\x32\x11\x3c\x63\x31\xe5\x40\x7b"			  "\xdf\x10\x13\x24\x15\xe5\x4b\x92"			  "\xa1\x3e\xd0\xa8\x26\x7a\xe2\xf9"			  "\x75\xa3\x85\x74\x1a\xb9\xce\xf8"			  "\x20\x31\x62\x3d\x55\xb1\xe4\x71",		.len	= 64,	}, { /* > 16 bytes, not a multiple of 16 bytes */		.key	= "\x2b\x7e\x15\x16\x28\xae\xd2\xa6"			  "\xab\xf7\x15\x88\x09\xcf\x4f\x3c",		.klen	= 16,		.iv	= "\x00\x01\x02\x03\x04\x05\x06\x07"			  "\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f",		.ptext	= "\x6b\xc1\xbe\xe2\x2e\x40\x9f\x96"			  "\xe9\x3d\x7e\x11\x73\x93\x17\x2a"			  "\xae",		.ctext	= "\x3b\x3f\xd9\x2e\xb7\x2d\xad\x20"			  "\x33\x34\x49\xf8\xe8\x3c\xfb\x4a"			  "\xc8",		.len	= 17,	}, { /* < 16 bytes */		.key	= "\x2b\x7e\x15\x16\x28\xae\xd2\xa6"			  "\xab\xf7\x15\x88\x09\xcf\x4f\x3c",		.klen	= 16,		.iv	= "\x00\x01\x02\x03\x04\x05\x06\x07"			  "\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f",		.ptext	= "\x6b\xc1\xbe\xe2\x2e\x40\x9f",		.ctext	= "\x3b\x3f\xd9\x2e\xb7\x2d\xad",		.len	= 7,	},}; static int __init libaescfb_init(void){	for (int i = 0; i < ARRAY_SIZE(aescfb_tv); i++) {		struct aes_enckey key;		u8 buf[64]; 		if (aes_prepareenckey(&key, aescfb_tv[i].key, aescfb_tv[i].klen)) {			pr_err("aes_prepareenckey() failed on vector %d\n", i);			return -ENODEV;		} 		aescfb_encrypt(&key, buf, aescfb_tv[i].ptext, aescfb_tv[i].len,			       aescfb_tv[i].iv);		if (memcmp(buf, aescfb_tv[i].ctext, aescfb_tv[i].len)) {			pr_err("aescfb_encrypt() #1 failed on vector %d\n", i);			return -ENODEV;		} 		/* decrypt in place */		aescfb_decrypt(&key, buf, buf, aescfb_tv[i].len, aescfb_tv[i].iv);		if (memcmp(buf, aescfb_tv[i].ptext, aescfb_tv[i].len)) {			pr_err("aescfb_decrypt() failed on vector %d\n", i);			return -ENODEV;		} 		/* encrypt in place */		aescfb_encrypt(&key, buf, buf, aescfb_tv[i].len, aescfb_tv[i].iv);		if (memcmp(buf, aescfb_tv[i].ctext, aescfb_tv[i].len)) {			pr_err("aescfb_encrypt() #2 failed on vector %d\n", i); 			return -ENODEV;		} 	}	return 0;}module_init(libaescfb_init); static void __exit libaescfb_exit(void){}module_exit(libaescfb_exit);#endif