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>
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 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 @@
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 @@
#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)