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rsa: Verify RSA padding programatically 

Padding verification was done against static SHA/RSA pair arrays which
take up a lot of static memory, are mostly 0xff, and cannot be reused
for additional SHA/RSA pairings. The padding can be easily computed
according to PKCS#1v2.1 as:

  EM = 0x00 || 0x01 || PS || 0x00 || T

where PS is (emLen - tLen - 3) octets of 0xff and T is DER encoding
of the hash.

Store DER prefix in checksum_algo and create rsa_verify_padding
function to handle verification of a message for any SHA/RSA pairing.

Signed-off-by: Andrew Duda <aduda@meraki.com>
Signed-off-by: aduda <aduda@meraki.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
This commit is contained in:
Andrew Duda 2016-11-08 18:53:40 +00:00 committed by Tom Rini
parent 5300a4f933
commit da29f2991d
9 changed files with 61 additions and 131 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
common/image-sig.c
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@ -34,32 +34,35 @@ struct checksum_algo checksum_algos[] = {
{ {
"sha1", "sha1",
SHA1_SUM_LEN, SHA1_SUM_LEN,
SHA1_DER_LEN,
sha1_der_prefix,
RSA2048_BYTES, RSA2048_BYTES,
#if IMAGE_ENABLE_SIGN #if IMAGE_ENABLE_SIGN
EVP_sha1, EVP_sha1,
#endif #endif
hash_calculate, hash_calculate,
padding_sha1_rsa2048,
}, },
{ {
"sha256", "sha256",
SHA256_SUM_LEN, SHA256_SUM_LEN,
SHA256_DER_LEN,
sha256_der_prefix,
RSA2048_BYTES, RSA2048_BYTES,
#if IMAGE_ENABLE_SIGN #if IMAGE_ENABLE_SIGN
EVP_sha256, EVP_sha256,
#endif #endif
hash_calculate, hash_calculate,
padding_sha256_rsa2048,
}, },
{ {
"sha256", "sha256",
SHA256_SUM_LEN, SHA256_SUM_LEN,
SHA256_DER_LEN,
sha256_der_prefix,
RSA4096_BYTES, RSA4096_BYTES,
#if IMAGE_ENABLE_SIGN #if IMAGE_ENABLE_SIGN
EVP_sha256, EVP_sha256,
#endif #endif
hash_calculate, hash_calculate,
padding_sha256_rsa4096,
} }
}; };

3
include/image.h
View File

@ -1070,6 +1070,8 @@ struct image_region {
struct checksum_algo { struct checksum_algo {
const char *name; const char *name;
const int checksum_len; const int checksum_len;
const int der_len;
const uint8_t *der_prefix;
const int key_len; const int key_len;
#if IMAGE_ENABLE_SIGN #if IMAGE_ENABLE_SIGN
const EVP_MD *(*calculate_sign)(void); const EVP_MD *(*calculate_sign)(void);
@ -1077,7 +1079,6 @@ struct checksum_algo {
int (*calculate)(const char *name, int (*calculate)(const char *name,
const struct image_region region[], const struct image_region region[],
int region_count, uint8_t *checksum); int region_count, uint8_t *checksum);
const uint8_t *rsa_padding;
}; };
struct image_sig_algo { struct image_sig_algo {

4
include/u-boot/rsa-checksum.h
View File

@ -12,10 +12,6 @@
#include <u-boot/sha1.h> #include <u-boot/sha1.h>
#include <u-boot/sha256.h> #include <u-boot/sha256.h>
extern const uint8_t padding_sha256_rsa4096[];
extern const uint8_t padding_sha256_rsa2048[];
extern const uint8_t padding_sha1_rsa2048[];
/** /**
* hash_calculate() - Calculate hash over the data * hash_calculate() - Calculate hash over the data
* *

3
include/u-boot/sha1.h
View File

@ -21,6 +21,9 @@ extern "C" {
#define SHA1_SUM_POS -0x20 #define SHA1_SUM_POS -0x20
#define SHA1_SUM_LEN 20 #define SHA1_SUM_LEN 20
#define SHA1_DER_LEN 15
extern const uint8_t sha1_der_prefix[];
/** /**
* \brief SHA-1 context structure * \brief SHA-1 context structure

3
include/u-boot/sha256.h
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@ -2,6 +2,9 @@
#define _SHA256_H #define _SHA256_H
#define SHA256_SUM_LEN 32 #define SHA256_SUM_LEN 32
#define SHA256_DER_LEN 19
extern const uint8_t sha256_der_prefix[];
/* Reset watchdog each time we process this many bytes */ /* Reset watchdog each time we process this many bytes */
#define CHUNKSZ_SHA256 (64 * 1024) #define CHUNKSZ_SHA256 (64 * 1024)

121
lib/rsa/rsa-checksum.c
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@ -13,130 +13,9 @@
#include <hash.h> #include <hash.h>
#else #else
#include "fdt_host.h" #include "fdt_host.h"
#include <u-boot/sha1.h>
#include <u-boot/sha256.h>
#endif #endif
#include <u-boot/rsa.h> #include <u-boot/rsa.h>
/* PKCS 1.5 paddings as described in the RSA PKCS#1 v2.1 standard. */
const uint8_t padding_sha256_rsa2048[RSA2048_BYTES - SHA256_SUM_LEN] = {
0x00, 0x01, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00, 0x30, 0x31, 0x30,
0x0d, 0x06, 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, 0x05,
0x00, 0x04, 0x20
};
const uint8_t padding_sha1_rsa2048[RSA2048_BYTES - SHA1_SUM_LEN] = {
0x00, 0x01, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0x00, 0x30, 0x21, 0x30,
0x09, 0x06, 0x05, 0x2b, 0x0e, 0x03, 0x02, 0x1a,
0x05, 0x00, 0x04, 0x14
};
const uint8_t padding_sha256_rsa4096[RSA4096_BYTES - SHA256_SUM_LEN] = {
0x00, 0x01, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0x00, 0x30, 0x31, 0x30,
0x0d, 0x06, 0x09, 0x60, 0x86, 0x48, 0x01, 0x65,
0x03, 0x04, 0x02, 0x01, 0x05, 0x00, 0x04, 0x20
};
int hash_calculate(const char *name, int hash_calculate(const char *name,
const struct image_region region[], const struct image_region region[],
int region_count, uint8_t *checksum) int region_count, uint8_t *checksum)

38
lib/rsa/rsa-verify.c
View File

@ -24,6 +24,40 @@
/* Default public exponent for backward compatibility */ /* Default public exponent for backward compatibility */
#define RSA_DEFAULT_PUBEXP 65537 #define RSA_DEFAULT_PUBEXP 65537
/**
* rsa_verify_padding() - Verify RSA message padding is valid
*
* Verify a RSA message's padding is consistent with PKCS1.5
* padding as described in the RSA PKCS#1 v2.1 standard.
*
* @msg: Padded message
* @pad_len: Number of expected padding bytes
* @algo: Checksum algo structure having information on DER encoding etc.
* @return 0 on success, != 0 on failure
*/
static int rsa_verify_padding(const uint8_t *msg, const int pad_len,
struct checksum_algo *algo)
{
int ff_len;
int ret;
/* first byte must be 0x00 */
ret = *msg++;
/* second byte must be 0x01 */
ret |= *msg++ ^ 0x01;
/* next ff_len bytes must be 0xff */
ff_len = pad_len - algo->der_len - 3;
ret |= *msg ^ 0xff;
ret |= memcmp(msg, msg+1, ff_len-1);
msg += ff_len;
/* next byte must be 0x00 */
ret |= *msg++;
/* next der_len bytes must match der_prefix */
ret |= memcmp(msg, algo->der_prefix, algo->der_len);
return ret;
}
/** /**
* rsa_verify_key() - Verify a signature against some data using RSA Key * rsa_verify_key() - Verify a signature against some data using RSA Key
* *
@ -83,11 +117,11 @@ static int rsa_verify_key(struct key_prop *prop, const uint8_t *sig,
return ret; return ret;
} }
padding = algo->rsa_padding;
pad_len = algo->key_len - algo->checksum_len; pad_len = algo->key_len - algo->checksum_len;
/* Check pkcs1.5 padding bytes. */ /* Check pkcs1.5 padding bytes. */
if (memcmp(buf, padding, pad_len)) { ret = rsa_verify_padding(buf, pad_len, algo);
if (ret) {
debug("In RSAVerify(): Padding check failed!\n"); debug("In RSAVerify(): Padding check failed!\n");
return -EINVAL; return -EINVAL;
} }

5
lib/sha1.c
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@ -26,6 +26,11 @@
#include <watchdog.h> #include <watchdog.h>
#include <u-boot/sha1.h> #include <u-boot/sha1.h>
const uint8_t sha1_der_prefix[SHA1_DER_LEN] = {
0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b, 0x0e,
0x03, 0x02, 0x1a, 0x05, 0x00, 0x04, 0x14
};
/* /*
* 32-bit integer manipulation macros (big endian) * 32-bit integer manipulation macros (big endian)
*/ */

6
lib/sha256.c
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@ -15,6 +15,12 @@
#include <watchdog.h> #include <watchdog.h>
#include <u-boot/sha256.h> #include <u-boot/sha256.h>
const uint8_t sha256_der_prefix[SHA256_DER_LEN] = {
0x30, 0x31, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86,
0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, 0x05,
0x00, 0x04, 0x20
};
/* /*
* 32-bit integer manipulation macros (big endian) * 32-bit integer manipulation macros (big endian)
*/ */