Be more careful calling wcstombs

The function is not guaranteed to NUL-terminate its output.  It
*is*, however, guaranteed not to generate more than two bytes per
multibyte character (plus terminating nul), so the general approach
I'm taking is to try to allocate enough space, AND to manually add a
NUL at the end of each buffer just in case I screwed up the "enough
space" thing.

Fixes bug 5909.

6 files changed, 30 insertions, 12 deletions

diff --git a/changes/bug5909 b/changes/bug5909
new file mode 100644
index 0000000000..61990faefa
--- /dev/null
+++ b/changes/bug5909
@@ -0,0 +1,5 @@
+  o Major bugfixes:
+    - When building Tor on Windows with -DUNICODE (not default),
+      ensure that error messages, filenames, and DNS server names are
+      always NUL-terminated when we convert them to a single-byte
+      encoding.  Fixes bug 5909; bugfix on 0.2.2.16-alpha.
diff --git a/src/common/compat.c b/src/common/compat.c
index 334ea1b8b4..db2187b836 100644
--- a/src/common/compat.c
+++ b/src/common/compat.c
@@ -3046,28 +3046,37 @@ format_win32_error(DWORD err)
 {
   TCHAR *str = NULL;
   char *result;
+  DWORD n;
 
   /* Somebody once decided that this interface was better than strerror(). */
-  FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER |
+  n = FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER |
                  FORMAT_MESSAGE_FROM_SYSTEM |
                  FORMAT_MESSAGE_IGNORE_INSERTS,
                  NULL, err,
                  MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
-                (LPVOID)&str,
+                 (LPVOID)&str,
                  0, NULL);
 
-  if (str) {
+  if (str && n) {
 #ifdef UNICODE
-    char abuf[1024] = {0};
-    wcstombs(abuf,str,1024);
-    result = tor_strdup(abuf);
+    size_t len;
+    if (n > 128*1024)
+      len = (128 * 1024) * 2 + 1; /* This shouldn't be possible, but let's
+                                   * make sure. */
+    else
+      len = n * 2 + 1;
+    result = tor_malloc(len);
+    wcstombs(result,str,len);
+    result[len-1] = '\0';
 #else
     result = tor_strdup(str);
 #endif
-    LocalFree(str); /* LocalFree != free() */
   } else {
     result = tor_strdup("<unformattable error>");
   }
+  if (str) {
+    LocalFree(str); /* LocalFree != free() */
+  }
   return result;
 }
 #endif
diff --git a/src/common/util.c b/src/common/util.c
index 4c086e86fc..dc8f8b7995 100644
--- a/src/common/util.c
+++ b/src/common/util.c
@@ -2855,7 +2855,7 @@ tor_listdir(const char *dirname)
 #ifdef _WIN32
   char *pattern=NULL;
   TCHAR tpattern[MAX_PATH] = {0};
-  char name[MAX_PATH] = {0};
+  char name[MAX_PATH*2+1] = {0};
   HANDLE handle;
   WIN32_FIND_DATA findData;
   tor_asprintf(&pattern, "%s\\*", dirname);
@@ -2872,6 +2872,7 @@ tor_listdir(const char *dirname)
   while (1) {
 #ifdef UNICODE
     wcstombs(name,findData.cFileName,MAX_PATH);
+    name[sizeof(name)-1] = '\0';
 #else
     strlcpy(name,findData.cFileName,sizeof(name));
 #endif
diff --git a/src/or/config.c b/src/or/config.c
index 090d96c155..2e3ce6429d 100644
--- a/src/or/config.c
+++ b/src/or/config.c
@@ -4302,7 +4302,7 @@ static char *
 get_windows_conf_root(void)
 {
   static int is_set = 0;
-  static char path[MAX_PATH+1];
+  static char path[MAX_PATH*2+1];
   TCHAR tpath[MAX_PATH] = {0};
 
   LPITEMIDLIST idl;
@@ -4332,7 +4332,8 @@ get_windows_conf_root(void)
   /* Convert the path from an "ID List" (whatever that is!) to a path. */
   result = SHGetPathFromIDList(idl, tpath);
 #ifdef UNICODE
-  wcstombs(path,tpath,MAX_PATH);
+  wcstombs(path,tpath,sizeof(path));
+  path[sizeof(path)-1] = '\0';
 #else
   strlcpy(path,tpath,sizeof(path));
 #endif
diff --git a/src/or/eventdns.c b/src/or/eventdns.c
index 61a28361ab..768693aba6 100644
--- a/src/or/eventdns.c
+++ b/src/or/eventdns.c
@@ -3213,7 +3213,7 @@ static int
 config_nameserver_from_reg_key(HKEY key, const TCHAR *subkey)
 {
 	char *buf;
-  char ansibuf[MAX_PATH] = {0};
+	char ansibuf[MAX_PATH] = {0};
 	DWORD bufsz = 0, type = 0;
 	int status = 0;
 
@@ -3226,6 +3226,7 @@ config_nameserver_from_reg_key(HKEY key, const TCHAR *subkey)
 	if (RegQueryValueEx(key, subkey, 0, &type, (LPBYTE)buf, &bufsz)
 		== ERROR_SUCCESS && bufsz > 1) {
 		wcstombs(ansibuf,(wchar_t*)buf,MAX_PATH);/*XXXX UNICODE */
+		abuf[MAX_PATH-1] = '\0';
 		status = evdns_nameserver_ip_add_line(ansibuf);
 	}
 
diff --git a/src/or/ntmain.c b/src/or/ntmain.c
index 01244c4c08..d001f7be13 100644
--- a/src/or/ntmain.c
+++ b/src/or/ntmain.c
@@ -455,7 +455,7 @@ static char *
 nt_service_command_line(int *using_default_torrc)
 {
   TCHAR tor_exe[MAX_PATH+1];
-  char tor_exe_ascii[MAX_PATH+1];
+  char tor_exe_ascii[MAX_PATH*2+1];
   char *command=NULL, *options=NULL;
   smartlist_t *sl;
   int i;
@@ -483,6 +483,7 @@ nt_service_command_line(int *using_default_torrc)
 
 #ifdef UNICODE
   wcstombs(tor_exe_ascii, tor_exe, sizeof(tor_exe_ascii));
+  tor_exe_ascii[sizeof(tor_exe_ascii)-1] = '\0';
 #else
   strlcpy(tor_exe_ascii, tor_exe, sizeof(tor_exe_ascii));
 #endif