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env: Implement support for encrypting environment

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Add function which allows encrypting the whole environment block with
AES-128-CBC. The key for the environment is retrieved by
env_aes_cbc_get_key() function, which must be implemented on a per-board
basis.

Signed-off-by: Marek Vasut <marex@denx.de>
This commit is contained in:
Marek Vasut 2014-03-05 19:59:51 +01:00 committed by Tom Rini
parent 7ce1526ed2
commit a4223b746d
2 changed files with 73 additions and 1 deletions
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62
common/env_common.c
View file

@ -140,6 +140,52 @@ int set_default_vars(int nvars, char * const vars[])
H_NOCLEAR | H_INTERACTIVE, nvars, vars);
}
#ifdef CONFIG_ENV_AES
#include <aes.h>
/**
* env_aes_cbc_get_key() - Get AES-128-CBC key for the environment
*
* This function shall return 16-byte array containing AES-128 key used
* to encrypt and decrypt the environment. This function must be overriden
* by the implementer as otherwise the environment encryption will not
* work.
*/
__weak uint8_t *env_aes_cbc_get_key(void)
{
return NULL;
}
static int env_aes_cbc_crypt(env_t *env, const int enc)
{
unsigned char *data = env->data;
uint8_t *key;
uint8_t key_exp[AES_EXPAND_KEY_LENGTH];
uint32_t aes_blocks;
key = env_aes_cbc_get_key();
if (!key)
return -EINVAL;
/* First we expand the key. */
aes_expand_key(key, key_exp);
/* Calculate the number of AES blocks to encrypt. */
aes_blocks = ENV_SIZE / AES_KEY_LENGTH;
if (enc)
aes_cbc_encrypt_blocks(key_exp, data, data, aes_blocks);
else
aes_cbc_decrypt_blocks(key_exp, data, data, aes_blocks);
return 0;
}
#else
static inline int env_aes_cbc_crypt(env_t *env, const int enc)
{
return 0;
}
#endif
/*
* Check if CRC is valid and (if yes) import the environment.
* Note that "buf" may or may not be aligned.
@ -147,6 +193,7 @@ int set_default_vars(int nvars, char * const vars[])
int env_import(const char *buf, int check)
{
env_t *ep = (env_t *)buf;
int ret;
if (check) {
uint32_t crc;
@ -159,6 +206,14 @@ int env_import(const char *buf, int check)
}
}
/* Decrypt the env if desired. */
ret = env_aes_cbc_crypt(ep, 0);
if (ret) {
error("Failed to decrypt env!\n");
set_default_env("!import failed");
return ret;
}
if (himport_r(&env_htab, (char *)ep->data, ENV_SIZE, '\0', 0,
0, NULL)) {
gd->flags |= GD_FLG_ENV_READY;
@ -177,6 +232,7 @@ int env_export(env_t *env_out)
{
char *res;
ssize_t len;
int ret;
res = (char *)env_out->data;
len = hexport_r(&env_htab, '\0', 0, &res, ENV_SIZE, 0, NULL);
@ -184,6 +240,12 @@ int env_export(env_t *env_out)
error("Cannot export environment: errno = %d\n", errno);
return 1;
}
/* Encrypt the env if desired. */
ret = env_aes_cbc_crypt(env_out, 1);
if (ret)
return ret;
env_out->crc = crc32(0, env_out->data, ENV_SIZE);
return 0;

12
include/environment.h
View file

@ -146,7 +146,12 @@ extern unsigned long nand_env_oob_offset;
extern char *env_name_spec;
#endif
#ifdef CONFIG_ENV_AES
/* Make sure the payload is multiple of AES block size */
#define ENV_SIZE ((CONFIG_ENV_SIZE - ENV_HEADER_SIZE) & ~(16 - 1))
#else
#define ENV_SIZE (CONFIG_ENV_SIZE - ENV_HEADER_SIZE)
#endif
typedef struct environment_s {
uint32_t crc; /* CRC32 over data bytes */
@ -154,7 +159,12 @@ typedef struct environment_s {
unsigned char flags; /* active/obsolete flags */
#endif
unsigned char data[ENV_SIZE]; /* Environment data */
} env_t;
} env_t
#ifdef CONFIG_ENV_AES
/* Make sure the env is aligned to block size. */
__attribute__((aligned(16)))
#endif
;
#ifdef ENV_IS_EMBEDDED
extern env_t environment;