[U-Boot] [PATCH 2/4] rsa: Verify RSA padding programatically
aduda
aduda at meraki.com
Tue Nov 8 19:53:40 CET 2016
From: Andrew Duda <aduda at meraki.com>
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 at meraki.com>
Signed-off-by: aduda <aduda at meraki.com>
---
common/image-sig.c | 9 ++--
include/image.h | 3 +-
include/u-boot/rsa-checksum.h | 4 --
include/u-boot/sha1.h | 3 ++
include/u-boot/sha256.h | 3 ++
lib/rsa/rsa-checksum.c | 121 ------------------------------------------
lib/rsa/rsa-verify.c | 38 ++++++++++++-
lib/sha1.c | 5 ++
lib/sha256.c | 6 +++
9 files changed, 61 insertions(+), 131 deletions(-)
diff --git a/common/image-sig.c b/common/image-sig.c
index 28f7a20..008d2c5 100644
--- a/common/image-sig.c
+++ b/common/image-sig.c
@@ -34,32 +34,35 @@ struct checksum_algo checksum_algos[] = {
{
"sha1",
SHA1_SUM_LEN,
+ SHA1_DER_LEN,
+ sha1_der_prefix,
RSA2048_BYTES,
#if IMAGE_ENABLE_SIGN
EVP_sha1,
#endif
hash_calculate,
- padding_sha1_rsa2048,
},
{
"sha256",
SHA256_SUM_LEN,
+ SHA256_DER_LEN,
+ sha256_der_prefix,
RSA2048_BYTES,
#if IMAGE_ENABLE_SIGN
EVP_sha256,
#endif
hash_calculate,
- padding_sha256_rsa2048,
},
{
"sha256",
SHA256_SUM_LEN,
+ SHA256_DER_LEN,
+ sha256_der_prefix,
RSA4096_BYTES,
#if IMAGE_ENABLE_SIGN
EVP_sha256,
#endif
hash_calculate,
- padding_sha256_rsa4096,
}
};
diff --git a/include/image.h b/include/image.h
index bfe10a0..de73a07 100644
--- a/include/image.h
+++ b/include/image.h
@@ -1070,6 +1070,8 @@ struct image_region {
struct checksum_algo {
const char *name;
const int checksum_len;
+ const int der_len;
+ const uint8_t *der_prefix;
const int key_len;
#if IMAGE_ENABLE_SIGN
const EVP_MD *(*calculate_sign)(void);
@@ -1077,7 +1079,6 @@ struct checksum_algo {
int (*calculate)(const char *name,
const struct image_region region[],
int region_count, uint8_t *checksum);
- const uint8_t *rsa_padding;
};
struct image_sig_algo {
diff --git a/include/u-boot/rsa-checksum.h b/include/u-boot/rsa-checksum.h
index 3c69d85..c240720 100644
--- a/include/u-boot/rsa-checksum.h
+++ b/include/u-boot/rsa-checksum.h
@@ -12,10 +12,6 @@
#include <u-boot/sha1.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
*
diff --git a/include/u-boot/sha1.h b/include/u-boot/sha1.h
index b0d9ce9..2634a29 100644
--- a/include/u-boot/sha1.h
+++ b/include/u-boot/sha1.h
@@ -21,6 +21,9 @@ extern "C" {
#define SHA1_SUM_POS -0x20
#define SHA1_SUM_LEN 20
+#define SHA1_DER_LEN 15
+
+extern const uint8_t sha1_der_prefix[];
/**
* \brief SHA-1 context structure
diff --git a/include/u-boot/sha256.h b/include/u-boot/sha256.h
index beadab3..9aa1251 100644
--- a/include/u-boot/sha256.h
+++ b/include/u-boot/sha256.h
@@ -2,6 +2,9 @@
#define _SHA256_H
#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 */
#define CHUNKSZ_SHA256 (64 * 1024)
diff --git a/lib/rsa/rsa-checksum.c b/lib/rsa/rsa-checksum.c
index db183ff..2bf28e2 100644
--- a/lib/rsa/rsa-checksum.c
+++ b/lib/rsa/rsa-checksum.c
@@ -13,130 +13,9 @@
#include <hash.h>
#else
#include "fdt_host.h"
-#include <u-boot/sha1.h>
-#include <u-boot/sha256.h>
#endif
#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,
const struct image_region region[],
int region_count, uint8_t *checksum)
diff --git a/lib/rsa/rsa-verify.c b/lib/rsa/rsa-verify.c
index 5418f59..ee8988d 100644
--- a/lib/rsa/rsa-verify.c
+++ b/lib/rsa/rsa-verify.c
@@ -25,6 +25,40 @@
#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
*
* Verify a RSA PKCS1.5 signature against an expected hash using
@@ -83,11 +117,11 @@ static int rsa_verify_key(struct key_prop *prop, const uint8_t *sig,
return ret;
}
- padding = algo->rsa_padding;
pad_len = algo->key_len - algo->checksum_len;
/* 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");
return -EINVAL;
}
diff --git a/lib/sha1.c b/lib/sha1.c
index 72c5dea..f54bb5b 100644
--- a/lib/sha1.c
+++ b/lib/sha1.c
@@ -26,6 +26,11 @@
#include <watchdog.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)
*/
diff --git a/lib/sha256.c b/lib/sha256.c
index bb338ba..7f5a361 100644
--- a/lib/sha256.c
+++ b/lib/sha256.c
@@ -15,6 +15,12 @@
#include <watchdog.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)
*/
--
2.10.2
More information about the U-Boot
mailing list