Add support for strlcpy()

Too many places in xrdp use strncpy() to copy strings to fixed-length
buffers, when this is not the correct function to use.

This PR makes sure strlcpy() from the BSDs is available as a saner
alternative. This function is available by default on Linux and FreeBSD.

common/string_calls.c

@@ -15,6 +15,23 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  *
+ * The strlcpy implementation is taken from OpenBSD and reformatted. The
+ * original has the following notice attached:-
+ * |
+ * |   Copyright (c) 1998, 2015 Todd C. Miller <millert@openbsd.org>
+ * |
+ * |   Permission to use, copy, modify, and distribute this software for any
+ * |   purpose with or without fee is hereby granted, provided that the above
+ * |   copyright notice and this permission notice appear in all copies.
+ * |
+ * |   THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * |   WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * |   MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * |   ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * |   WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * |   ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * |   OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.*
+ *
  * generic string handling calls
  */
 
@@ -448,6 +465,42 @@ g_atoix(const char *str)
     return strtol(str, NULL, base);
 }
 
+/*****************************************************************************/
+#if !defined(HAVE_STRLCPY)
+size_t strlcpy(char *dst, const char *src, size_t dsize)
+{
+    const char *osrc = src;
+    size_t nleft = dsize;
+
+    /* Copy as many bytes as will fit. */
+    if (nleft != 0)
+    {
+        while (--nleft != 0)
+        {
+            if ((*dst++ = *src++) == '\0')
+            {
+                break;
+            }
+        }
+    }
+
+    /* Not enough room in dst, add NUL and traverse rest of src. */
+    if (nleft == 0)
+    {
+        if (dsize != 0)
+        {
+            *dst = '\0';        /* NUL-terminate dst */
+        }
+        while (*src++)
+        {
+            ;
+        }
+    }
+
+    return (src - osrc - 1);      /* count does not include NUL */
+}
+#endif
+
 /*****************************************************************************/
 int
 g_htoi(char *str)

common/string_calls.h

@@ -296,6 +296,11 @@ int      g_strcasecmp(const char *c1, const char *c2);
 int      g_strncasecmp(const char *c1, const char *c2, int len);
 int      g_atoi(const char *str);
 
+/* Non-standard but useful functions */
+#if !defined(HAVE_STRLCPY)
+size_t   strlcpy(char *dst, const char *src, size_t dsize);
+#endif
+
 /**
  * Extends g_atoi(), Converts decimal and hexadecimal number String to integer
  *