From e260535a24a05ccdb9fe6b1f1ad7c4d88f2474ed Mon Sep 17 00:00:00 2001
From: Mark Olsen <git@molsen.co.za>
Date: Mon, 6 Mar 2023 08:46:54 +0000
Subject: [PATCH] Endian fixes for the PKey encryption/decryption.

The PKey crypto code simply treats the data to be encrypted or decrypted as one single BigInt and copies the data into a BigInt verbatim. However, a BigInt simply consists of a number of 32 bit integers in the native endian format, so the data copied to/from the BigInt needs to be byteswapped on big endian systems to yield the same result as on little endian systems.
---
 common/pk.cpp | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/common/pk.cpp b/common/pk.cpp
index 85be286f..281d9d97 100644
--- a/common/pk.cpp
+++ b/common/pk.cpp
@@ -286,9 +286,21 @@ int PKey::Encrypt(void const* source, int slen, void* dest) const
         **	Perform the encryption of the block.
         */
         BigInt temp = 0;
+        unsigned int* tempui = temp;
+        int i;
+
         memmove(&temp, source, Plain_Block_Size());
+
+        for (i = 0; i < (Plain_Block_Size() + 3) / 4; i++) {
+            tempui[i] = htole32(tempui[i]);
+        }
+
         temp = temp.exp_b_mod_c(Exponent, Modulus);
 
+        for (i = 0; i < (Crypt_Block_Size() + 3) / 4; i++) {
+            tempui[i] = le32toh(tempui[i]);
+        }
+
         /*
         **	Move the cypher block to the destination.
         */
@@ -327,6 +339,8 @@ int PKey::Decrypt(void const* source, int slen, void* dest) const
 {
     int total = 0;
     BigInt temp;
+    unsigned int* tempui = temp;
+    int i;
 
     /*
     **	Decrypt the source data in full blocks. Partial blocks are not processed in any way.
@@ -338,8 +352,17 @@ int PKey::Decrypt(void const* source, int slen, void* dest) const
         */
         temp = 0;
         memmove(&temp, source, Crypt_Block_Size());
+
+        for (i = 0; i < (Crypt_Block_Size() + 3) / 4; i++) {
+            tempui[i] = le32toh(tempui[i]);
+        }
+
         temp = temp.exp_b_mod_c(Exponent, Modulus);
 
+        for (i = 0; i < (Plain_Block_Size() + 3) / 4; i++) {
+            tempui[i] = htole32(tempui[i]);
+        }
+
         /*
         **	Move the cypher block to the destination.
         */