From 32b1c1d6fff2e138c668810e0fd154e8ab0e9e56 Mon Sep 17 00:00:00 2001
From: Siva Durga Prasad Paladugu <siva.durga.paladugu@xilinx.com>
Date: Fri, 29 Nov 2013 19:01:24 +0530
Subject: [PATCH] image: Added RSA support for zynq

Added RSA support for zynq. This uses the
montogomery multiplications while verifying
the authenticated image.
Modified Makefile to compile rsa-verify.c if
CONFIG_CMD_ZYNQ_RSA was enabled to get rid of
unrequired FDT functionality incase of zynq.

Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
---
 include/rsa.h        |  2 ++
 lib/rsa/Makefile     |  2 ++
 lib/rsa/rsa-verify.c | 47 +++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/include/rsa.h b/include/rsa.h
index add4c789f33..6f07ae368a0 100644
--- a/include/rsa.h
+++ b/include/rsa.h
@@ -89,4 +89,6 @@ static inline int rsa_verify(struct image_sign_info *info,
 }
 #endif
 
+int zynq_pow_mod(uint32_t *keyptr, uint32_t *inout);
+
 #endif
diff --git a/lib/rsa/Makefile b/lib/rsa/Makefile
index decd6e509df..27c3bc3f9cd 100644
--- a/lib/rsa/Makefile
+++ b/lib/rsa/Makefile
@@ -15,6 +15,8 @@ ifdef CONFIG_FIT_SIGNATURE
 COBJS-$(CONFIG_RSA) += rsa-verify.o
 endif
 
+COBJS-$(CONFIG_CMD_ZYNQ_RSA) += rsa-verify.o
+
 COBJS	:= $(sort $(COBJS-y))
 SRCS	:= $(COBJS:.o=.c)
 OBJS	:= $(addprefix $(obj),$(COBJS))
diff --git a/lib/rsa/rsa-verify.c b/lib/rsa/rsa-verify.c
index 02cc4e33530..ccebf27d143 100644
--- a/lib/rsa/rsa-verify.c
+++ b/lib/rsa/rsa-verify.c
@@ -164,7 +164,7 @@ static void montgomery_mul(const struct rsa_public_key *key,
 	for (i = 0; i < key->len; ++i)
 		montgomery_mul_add_step(key, result, a[i], b);
 }
-
+#if IMAGE_ENABLE_VERIFY
 /**
  * pow_mod() - in-place public exponentiation
  *
@@ -370,3 +370,48 @@ int rsa_verify(struct image_sign_info *info,
 
 	return ret;
 }
+#endif
+
+/**
+ * zynq_pow_mod() - in-place public exponentiation
+ *
+ * @keyptr:	RSA key
+ * @inout:	Big-endian word array containing value and result
+ */
+int zynq_pow_mod(uint32_t *keyptr, uint32_t *inout)
+{
+	uint32_t *result, *ptr;
+	uint i;
+	struct rsa_public_key *key;
+
+	key = (struct rsa_public_key *)keyptr;
+
+	/* Sanity check for stack size - key->len is in 32-bit words */
+	if (key->len > RSA_MAX_KEY_BITS / 32) {
+		debug("RSA key words %u exceeds maximum %d\n", key->len,
+		      RSA_MAX_KEY_BITS / 32);
+		return -EINVAL;
+	}
+
+	uint32_t val[key->len], acc[key->len], tmp[key->len];
+	result = tmp;  /* Re-use location. */
+
+	for (i = 0, ptr = inout; i < key->len; i++, ptr++)
+		val[i] = *(ptr);
+
+	montgomery_mul(key, acc, val, key->rr);  /* axx = a * RR / R mod M */
+	for (i = 0; i < 16; i += 2) {
+		montgomery_mul(key, tmp, acc, acc); /* tmp = acc^2 / R mod M */
+		montgomery_mul(key, acc, tmp, tmp); /* acc = tmp^2 / R mod M */
+	}
+	montgomery_mul(key, result, acc, val);  /* result = XX * a / R mod M */
+
+	/* Make sure result < mod; result is at most 1x mod too large. */
+	if (greater_equal_modulus(key, result))
+		subtract_modulus(key, result);
+
+	for (i = 0, ptr = inout; i < key->len; i++, ptr++)
+		*ptr = result[i];
+
+	return 0;
+}
-- 
2.47.3