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/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)
*/