From d97c71c3ec62a881b7632db29f15550c9ca374e9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Joachim=20Stro=CC=88mbergson?= <joachim@secworks.se>
Date: Fri, 19 Oct 2018 14:08:35 +0200
Subject: Locked down API write and API digest read access to only be allowed
 when the core is ready and not busy doing processing.

---
 src/rtl/sha512.v | 116 +++++++++++++++++++++++++++----------------------------
 1 file changed, 58 insertions(+), 58 deletions(-)

diff --git a/src/rtl/sha512.v b/src/rtl/sha512.v
index 085783b..6356a8c 100644
--- a/src/rtl/sha512.v
+++ b/src/rtl/sha512.v
@@ -318,84 +318,86 @@ module sha512(
         begin
           if (we)
             begin
-              if ((address >= ADDR_BLOCK0) && (address <= ADDR_BLOCK31))
-                block_we = 1'h1;
+              if (core_ready)
+                begin
+                  if ((address >= ADDR_BLOCK0) && (address <= ADDR_BLOCK31))
+                    block_we = 1'h1;
 
-              case (address)
-                ADDR_CTRL:
-                  begin
-                    init_new        = write_data[CTRL_INIT_BIT];
-                    next_new        = write_data[CTRL_NEXT_BIT];
-                    mode_new        = write_data[CTRL_MODE_HIGH_BIT : CTRL_MODE_LOW_BIT];
-                    mode_we         = 1'h1;
-                    work_factor_new = write_data[CTRL_WORK_FACTOR_BIT];
-                    work_factor_we  = 1'h1;
-                  end
+                  case (address)
+                    ADDR_CTRL:
+                      begin
+                        init_new        = write_data[CTRL_INIT_BIT];
+                        next_new        = write_data[CTRL_NEXT_BIT];
+                        mode_new        = write_data[CTRL_MODE_HIGH_BIT : CTRL_MODE_LOW_BIT];
+                        mode_we         = 1'h1;
+                        work_factor_new = write_data[CTRL_WORK_FACTOR_BIT];
+                        work_factor_we  = 1'h1;
+                      end
 
-                ADDR_WORK_FACTOR_NUM:
-                  begin
-                    work_factor_num_we = 1;
-                  end
+                    ADDR_WORK_FACTOR_NUM:
+                      begin
+                        work_factor_num_we = 1;
+                      end
 
-                ADDR_DIGEST0:
-                  state00_we = 1;
+                    ADDR_DIGEST0:
+                      state00_we = 1;
 
-                ADDR_DIGEST1:
-                  state01_we = 1;
+                    ADDR_DIGEST1:
+                      state01_we = 1;
 
-                ADDR_DIGEST2:
-                  state02_we = 1;
+                    ADDR_DIGEST2:
+                      state02_we = 1;
 
-                ADDR_DIGEST3:
-                  state03_we = 1;
+                    ADDR_DIGEST3:
+                      state03_we = 1;
 
-                ADDR_DIGEST4:
-                  state04_we = 1;
+                    ADDR_DIGEST4:
+                      state04_we = 1;
 
-                ADDR_DIGEST5:
-                  state05_we = 1;
+                    ADDR_DIGEST5:
+                      state05_we = 1;
 
-                ADDR_DIGEST6:
-                  state06_we = 1;
+                    ADDR_DIGEST6:
+                      state06_we = 1;
 
-                ADDR_DIGEST7:
-                  state07_we = 1;
+                    ADDR_DIGEST7:
+                      state07_we = 1;
 
-                ADDR_DIGEST8:
-                  state08_we = 1;
+                    ADDR_DIGEST8:
+                      state08_we = 1;
 
-                ADDR_DIGEST9:
-                  state09_we = 1;
+                    ADDR_DIGEST9:
+                      state09_we = 1;
 
-                ADDR_DIGEST10:
-                  state10_we = 1;
+                    ADDR_DIGEST10:
+                      state10_we = 1;
 
-                ADDR_DIGEST11:
-                  state11_we = 1;
+                    ADDR_DIGEST11:
+                      state11_we = 1;
 
-                ADDR_DIGEST12:
-                  state12_we = 1;
+                    ADDR_DIGEST12:
+                      state12_we = 1;
 
-                ADDR_DIGEST13:
-                  state13_we = 1;
+                    ADDR_DIGEST13:
+                      state13_we = 1;
 
-                ADDR_DIGEST14:
-                  state14_we = 1;
+                    ADDR_DIGEST14:
+                      state14_we = 1;
 
-                ADDR_DIGEST15:
-                  state15_we = 1;
+                    ADDR_DIGEST15:
+                      state15_we = 1;
 
-                default:
-                  begin
-                    tmp_error = 1;
-                  end
-              endcase // case (address)
+                    default:
+                      tmp_error = 1;
+                  endcase // case (address)
+                end // if (core_ready)
             end // if (we)
 
           else
             begin
-              if ((address >= ADDR_DIGEST0) && (address <= ADDR_DIGEST15))
-                tmp_read_data = digest_reg[(15 - (address - ADDR_DIGEST0)) * 32 +: 32];
+              if (core_ready)
+                if ((address >= ADDR_DIGEST0) && (address <= ADDR_DIGEST15))
+                  tmp_read_data = digest_reg[(15 - (address - ADDR_DIGEST0)) * 32 +: 32];
 
               if ((address >= ADDR_BLOCK0) && (address <= ADDR_BLOCK31))
                 tmp_read_data = block_reg[address[4 : 0]];
@@ -420,9 +422,7 @@ module sha512(
                   tmp_read_data = work_factor_num_reg;
 
                 default:
-                  begin
-                    tmp_error = 1;
-                  end
+                  tmp_error = 1;
               endcase // case (address)
             end
         end
-- 
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