src: don't use locale-sensitive strcasecmp()

strcasecmp() is affected by the current locale as configured through
e.g. the LC_ALL environment variable and the setlocale() libc function.

It can result in unpredictable results across systems so replace it with
a function that isn't susceptible to that.

PR-URL: #6582
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

src/node.cc

@@ -69,7 +69,6 @@
 #if defined(_MSC_VER)
 #include <direct.h>
 #include <io.h>
-#define strcasecmp _stricmp
 #define getpid GetCurrentProcessId
 #define umask _umask
 typedef int mode_t;
@@ -1381,27 +1380,27 @@ enum encoding ParseEncoding(const char* encoding,
       break;
   }
 
-  if (strcasecmp(encoding, "utf8") == 0) {
+  if (StringEqualNoCase(encoding, "utf8")) {
     return UTF8;
-  } else if (strcasecmp(encoding, "utf-8") == 0) {
+  } else if (StringEqualNoCase(encoding, "utf-8")) {
     return UTF8;
-  } else if (strcasecmp(encoding, "ascii") == 0) {
+  } else if (StringEqualNoCase(encoding, "ascii")) {
     return ASCII;
-  } else if (strcasecmp(encoding, "base64") == 0) {
+  } else if (StringEqualNoCase(encoding, "base64")) {
     return BASE64;
-  } else if (strcasecmp(encoding, "ucs2") == 0) {
+  } else if (StringEqualNoCase(encoding, "ucs2")) {
     return UCS2;
-  } else if (strcasecmp(encoding, "ucs-2") == 0) {
+  } else if (StringEqualNoCase(encoding, "ucs-2")) {
     return UCS2;
-  } else if (strcasecmp(encoding, "utf16le") == 0) {
+  } else if (StringEqualNoCase(encoding, "utf16le")) {
     return UCS2;
-  } else if (strcasecmp(encoding, "utf-16le") == 0) {
+  } else if (StringEqualNoCase(encoding, "utf-16le")) {
     return UCS2;
-  } else if (strcasecmp(encoding, "binary") == 0) {
+  } else if (StringEqualNoCase(encoding, "binary")) {
     return BINARY;
-  } else if (strcasecmp(encoding, "buffer") == 0) {
+  } else if (StringEqualNoCase(encoding, "buffer")) {
     return BUFFER;
-  } else if (strcasecmp(encoding, "hex") == 0) {
+  } else if (StringEqualNoCase(encoding, "hex")) {
     return HEX;
   } else {
     return default_encoding;

src/node_crypto.cc

@@ -24,10 +24,6 @@
 #include <stdlib.h>
 #include <string.h>
 
-#if defined(_MSC_VER)
-#define strcasecmp _stricmp
-#endif
-
 #define THROW_AND_RETURN_IF_NOT_STRING_OR_BUFFER(val, prefix)                  \
   do {                                                                         \
     if (!Buffer::HasInstance(val) && !val->IsString()) {                       \
@@ -4446,7 +4442,7 @@ void DiffieHellman::DiffieHellmanGroup(
   for (size_t i = 0; i < arraysize(modp_groups); ++i) {
     const modp_group* it = modp_groups + i;
 
-    if (strcasecmp(*group_name, it->name) != 0)
+    if (!StringEqualNoCase(*group_name, it->name))
       continue;
 
     initialized = diffieHellman->Init(it->prime,

src/util-inl.h

@@ -203,7 +203,19 @@ void SwapBytes(uint16_t* dst, const uint16_t* src, size_t buflen) {
     dst[i] = (src[i] << 8) | (src[i] >> 8);
 }
 
+char ToLower(char c) {
+  return c >= 'A' && c <= 'Z' ? c + ('a' - 'A') : c;
+}
 
+bool StringEqualNoCase(const char* a, const char* b) {
+  do {
+    if (*a == '\0')
+      return *b == '\0';
+    if (*b == '\0')
+      return *a == '\0';
+  } while (ToLower(*a++) == ToLower(*b++));
+  return false;
+}
 
 }  // namespace node
 

src/util.h

@@ -178,6 +178,12 @@ inline TypeName* Unwrap(v8::Local<v8::Object> object);
 
 inline void SwapBytes(uint16_t* dst, const uint16_t* src, size_t buflen);
 
+// tolower() is locale-sensitive.  Use ToLower() instead.
+inline char ToLower(char c);
+
+// strcasecmp() is locale-sensitive.  Use StringEqualNoCase() instead.
+inline bool StringEqualNoCase(const char* a, const char* b);
+
 // Allocates an array of member type T. For up to kStackStorageSize items,
 // the stack is used, otherwise malloc().
 template <typename T, size_t kStackStorageSize = 1024>

test/cctest/util.cc

@@ -56,3 +56,21 @@ TEST(UtilTest, ListHead) {
   EXPECT_TRUE(list.IsEmpty());
   EXPECT_FALSE(list.begin() != list.end());
 }
+
+TEST(UtilTest, StringEqualNoCase) {
+  using node::StringEqualNoCase;
+  EXPECT_FALSE(StringEqualNoCase("a", "b"));
+  EXPECT_TRUE(StringEqualNoCase("", ""));
+  EXPECT_TRUE(StringEqualNoCase("equal", "equal"));
+  EXPECT_TRUE(StringEqualNoCase("equal", "EQUAL"));
+  EXPECT_TRUE(StringEqualNoCase("EQUAL", "EQUAL"));
+  EXPECT_FALSE(StringEqualNoCase("equal", "equals"));
+  EXPECT_FALSE(StringEqualNoCase("equals", "equal"));
+}
+
+TEST(UtilTest, ToLower) {
+  using node::ToLower;
+  EXPECT_EQ('0', ToLower('0'));
+  EXPECT_EQ('a', ToLower('a'));
+  EXPECT_EQ('a', ToLower('A'));
+}