Added hextobin xlat.

It's useful for creating binary nonsense

src/modules/rlm_expr/rlm_expr.c

@@ -691,6 +691,27 @@ EVP_MD_XLAT(sha256);
 EVP_MD_XLAT(sha512);
 #endif
 
+/**
+ * @brief Encode string or attribute from hex to binary
+ *
+ * Example: "%{hextobin:0x616161}" == "aaa"
+ */
+static ssize_t hex_to_bin_xlat(UNUSED void *instance, UNUSED REQUEST *request,
+			   char const *fmt, char *out, size_t outlen)
+{
+	ssize_t inlen;
+	uint8_t const *p;
+
+	inlen = xlat_fmt_to_ref(&p, request, fmt);
+	if (inlen < 0) {
+		return -1;
+	}
+
+	if ((p[0] != '0') && (p[1] != 'x')) return -1;
+
+	return fr_hex2bin((uint8_t *) out, (char *) p + 2, outlen);
+}
+
 /**
  * @brief Encode string or attribute as base64
  *
@@ -789,6 +810,7 @@ static int mod_instantiate(CONF_SECTION *conf, void *instance)
 #endif
 	xlat_register("base64", base64_xlat, NULL, inst);
 	xlat_register("base64tohex", base64_to_hex_xlat, NULL, inst);
+	xlat_register("hextobin", hex_to_bin_xlat, NULL, inst);
 
 	/*
 	 *	Initialize various paircompare functions