From ba42d6f732d73cc27e10d51b3098ec16a3b4fe80 Mon Sep 17 00:00:00 2001
From: John Safranek <john@wolfssl.com>
Date: Wed, 26 Jan 2022 15:18:16 -0800
Subject: [PATCH] Fix missing pread() and pwrite()

1. configure.ac: Check that the DECLs for `pread()` and `pwrite()` exist
   in unistd.h.
2. port.c: If `pread()` or `pwrite()` aren't available, use the local
   versions that are wrappers around `seek()` and `read()` and
   `write()`.
---
 configure.ac |  1 +
 src/port.c   | 22 +++++++++++++++++++---
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/configure.ac b/configure.ac
index f386e6f5..6470db81 100644
--- a/configure.ac
+++ b/configure.ac
@@ -84,6 +84,7 @@ CPPFLAGS="$CPPFLAGS -I${wcpath}/include"
 
 AC_CHECK_LIB([wolfssl],[wolfCrypt_Init],,[AC_MSG_ERROR([libwolfssl is required for ${PACKAGE}. It can be obtained from https://www.wolfssl.com/download.html/ .])])
 AC_CHECK_FUNCS([gethostbyname getaddrinfo gettimeofday inet_ntoa memset socket wc_ecc_set_rng])
+AC_CHECK_DECLS([[pread],[pwrite]],,[unistd.h])
 
 # DEBUG
 DEBUG_CFLAGS="-g -O0"
diff --git a/src/port.c b/src/port.c
index f21ba153..cdb0463e 100644
--- a/src/port.c
+++ b/src/port.c
@@ -37,6 +37,13 @@
     #include <stdio.h>
 #endif
 
+/*
+Flags:
+  WOLFSSH_LOCAL_PREAD_PWRITE
+    Defined to use local implementations of pread() and pwrite(). Switched
+    on automatically if pread() or pwrite() aren't found by configure.
+*/
+
 
 #if !defined(NO_FILESYSTEM) && !defined(WOLFSSH_USER_FILESYSTEM)
 int wfopen(WFILE** f, const char* filename, const char* mode)
@@ -82,6 +89,16 @@ int wfopen(WFILE** f, const char* filename, const char* mode)
 #endif
 }
 
+
+/* If either pread() or pwrite() are missing, use the local versions. */
+#if (defined(USE_OSE_API) || \
+     !defined(HAVE_DECL_PREAD) || (HAVE_DECL_PREAD == 0) || \
+     !defined(HAVE_DECL_PWRITE) || (HAVE_DECL_PWRITE == 0))
+    #undef WOLFSSH_LOCAL_PREAD_PWRITE
+    #define WOLFSSH_LOCAL_PREAD_PWRITE
+#endif
+
+
 #if (defined(WOLFSSH_SFTP) || defined(WOLFSSH_SCP)) && \
     !defined(NO_WOLFSSH_SERVER)
 
@@ -90,7 +107,7 @@ int wfopen(WFILE** f, const char* filename, const char* mode)
 
         /* This is current inline in the source. */
 
-    #elif defined(USE_OSE_API)
+    #elif defined(WOLFSSH_LOCAL_PREAD_PWRITE)
 
         int wPwrite(WFD fd, unsigned char* buf, unsigned int sz,
                 const unsigned int* shortOffset)
@@ -104,7 +121,6 @@ int wfopen(WFILE** f, const char* filename, const char* mode)
             return ret;
         }
 
-
         int wPread(WFD fd, unsigned char* buf, unsigned int sz,
                 const unsigned int* shortOffset)
         {
@@ -117,7 +133,7 @@ int wfopen(WFILE** f, const char* filename, const char* mode)
             return ret;
         }
 
-    #else /* USE_WINDOWS_API USE_OSE_API */
+    #else /* USE_WINDOWS_API WOLFSSH_LOCAL_PREAD_PWRITE */
 
         int wPwrite(WFD fd, unsigned char* buf, unsigned int sz,
                 const unsigned int* shortOffset)