MSVC SDL compliance: avoid calls to strcpy and wcsncpy

src/agent/ConsoleFont.cc

@@ -383,7 +383,7 @@ static bool setFontVista(
     infoex.cbSize = sizeof(AGENT_CONSOLE_FONT_INFOEX);
     infoex.dwFontSize.Y = pxSize;
     infoex.FontWeight = 400;
-    wcsncpy(infoex.FaceName, faceName, COUNT_OF(infoex.FaceName));
+    winpty_wcsncpy_nul(infoex.FaceName, faceName);
     dumpFontInfoEx(infoex, "setFontVista: setting font to: ");
     if (!api.SetCurrentConsoleFontEx()(conout, FALSE, &infoex)) {
         trace("setFontVista: SetCurrentConsoleFontEx call failed");

src/shared/DebugClient.cc

@@ -22,8 +22,10 @@
 
 #include <windows.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 
+#include <algorithm>
 #include <string>
 
 #include "winpty_snprintf.h"
@@ -82,11 +84,14 @@ static const char *getDebugConfig()
     if (g_debugConfig == NULL) {
         const int bufSize = 256;
         char buf[bufSize];
-        DWORD actualSize = GetEnvironmentVariableA("WINPTY_DEBUG", buf, bufSize);
-        if (actualSize == 0 || actualSize >= (DWORD)bufSize)
+        DWORD actualSize =
+            GetEnvironmentVariableA("WINPTY_DEBUG", buf, bufSize);
+        if (actualSize == 0 || actualSize >= static_cast<DWORD>(bufSize)) {
             buf[0] = '\0';
-        char *newConfig = new char[strlen(buf) + 1];
-        strcpy(newConfig, buf);
+        }
+        const size_t len = strlen(buf) + 1;
+        char *newConfig = new char[len];
+        std::copy(buf, buf + len, newConfig);
         void *oldValue = InterlockedCompareExchangePointer(
             &g_debugConfig, newConfig, NULL);
         if (oldValue != NULL) {

src/shared/StringUtil.h

@@ -22,10 +22,15 @@
 #define STRING_UTIL_H
 
 #include <stdlib.h>
+#include <string.h>
+#include <wchar.h>
 
+#include <algorithm>
 #include <string>
 #include <vector>
 
+#include "WinptyAssert.h"
+
 size_t winpty_wcsnlen(const wchar_t *s, size_t maxlen);
 std::string utf8FromWide(const std::wstring &input);
 
@@ -46,4 +51,30 @@ std::vector<T> vectorWithNulFromString(const std::basic_string<T> &str) {
     return ret;
 }
 
+// A safer(?) version of wcsncpy that is accepted by MSVC's /SDL mode.
+template <size_t N>
+wchar_t *winpty_wcsncpy(wchar_t (&d)[N], const wchar_t *s) {
+    ASSERT(s != nullptr);
+    size_t i = 0;
+    for (; i < N; ++i) {
+        if (s[i] == L'\0') {
+            break;
+        }
+        d[i] = s[i];
+    }
+    for (; i < N; ++i) {
+        d[i] = L'\0';
+    }
+    return d;
+}
+
+// Like wcsncpy, but ensure that the destination buffer is NUL-terminated.
+template <size_t N>
+wchar_t *winpty_wcsncpy_nul(wchar_t (&d)[N], const wchar_t *s) {
+    static_assert(N > 0, "array cannot be 0-size");
+    winpty_wcsncpy(d, s);
+    d[N - 1] = L'\0';
+    return d;
+}
+
 #endif // STRING_UTIL_H