diff --git a/src/utils/base64.c b/src/utils/base64.c
index 53a92f4..a17d2d3 100644
--- a/src/utils/base64.c
+++ b/src/utils/base64.c
@@ -12,18 +12,16 @@
 #include "os.h"
 #include "base64.h"
 
-static const unsigned char base64_table[65] =
+static const char base64_table[65] =
 	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
-static const unsigned char base64_url_table[65] =
+static const char base64_url_table[65] =
 	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
 
 
-static unsigned char * base64_gen_encode(const unsigned char *src, size_t len,
-					 size_t *out_len,
-					 const unsigned char *table,
-					 int add_pad)
+static char * base64_gen_encode(const unsigned char *src, size_t len,
+				size_t *out_len, const char *table, int add_pad)
 {
-	unsigned char *out, *pos;
+	char *out, *pos;
 	const unsigned char *end, *in;
 	size_t olen;
 	int line_len;
@@ -83,9 +81,8 @@
 }
 
 
-static unsigned char * base64_gen_decode(const unsigned char *src, size_t len,
-					 size_t *out_len,
-					 const unsigned char *table)
+static unsigned char * base64_gen_decode(const char *src, size_t len,
+					 size_t *out_len, const char *table)
 {
 	unsigned char dtable[256], *out, *pos, block[4], tmp;
 	size_t i, count, olen;
@@ -94,12 +91,12 @@
 
 	os_memset(dtable, 0x80, 256);
 	for (i = 0; i < sizeof(base64_table) - 1; i++)
-		dtable[table[i]] = (unsigned char) i;
+		dtable[(unsigned char) table[i]] = (unsigned char) i;
 	dtable['='] = 0;
 
 	count = 0;
 	for (i = 0; i < len; i++) {
-		if (dtable[src[i]] != 0x80)
+		if (dtable[(unsigned char) src[i]] != 0x80)
 			count++;
 	}
 
@@ -165,17 +162,15 @@
  * nul terminated to make it easier to use as a C string. The nul terminator is
  * not included in out_len.
  */
-unsigned char * base64_encode(const unsigned char *src, size_t len,
-			      size_t *out_len)
+char * base64_encode(const void *src, size_t len, size_t *out_len)
 {
 	return base64_gen_encode(src, len, out_len, base64_table, 1);
 }
 
 
-unsigned char * base64_url_encode(const unsigned char *src, size_t len,
-				  size_t *out_len, int add_pad)
+char * base64_url_encode(const void *src, size_t len, size_t *out_len)
 {
-	return base64_gen_encode(src, len, out_len, base64_url_table, add_pad);
+	return base64_gen_encode(src, len, out_len, base64_url_table, 0);
 }
 
 
@@ -189,15 +184,13 @@
  *
  * Caller is responsible for freeing the returned buffer.
  */
-unsigned char * base64_decode(const unsigned char *src, size_t len,
-			      size_t *out_len)
+unsigned char * base64_decode(const char *src, size_t len, size_t *out_len)
 {
 	return base64_gen_decode(src, len, out_len, base64_table);
 }
 
 
-unsigned char * base64_url_decode(const unsigned char *src, size_t len,
-				  size_t *out_len)
+unsigned char * base64_url_decode(const char *src, size_t len, size_t *out_len)
 {
 	return base64_gen_decode(src, len, out_len, base64_url_table);
 }
diff --git a/src/utils/base64.h b/src/utils/base64.h
index 5a72c3e..6216f44 100644
--- a/src/utils/base64.h
+++ b/src/utils/base64.h
@@ -9,13 +9,9 @@
 #ifndef BASE64_H
 #define BASE64_H
 
-unsigned char * base64_encode(const unsigned char *src, size_t len,
-			      size_t *out_len);
-unsigned char * base64_decode(const unsigned char *src, size_t len,
-			      size_t *out_len);
-unsigned char * base64_url_encode(const unsigned char *src, size_t len,
-				  size_t *out_len, int add_pad);
-unsigned char * base64_url_decode(const unsigned char *src, size_t len,
-				  size_t *out_len);
+char * base64_encode(const void *src, size_t len, size_t *out_len);
+unsigned char * base64_decode(const char *src, size_t len, size_t *out_len);
+char * base64_url_encode(const void *src, size_t len, size_t *out_len);
+unsigned char * base64_url_decode(const char *src, size_t len, size_t *out_len);
 
 #endif /* BASE64_H */
diff --git a/src/utils/json.c b/src/utils/json.c
index 3e5e214..5a0edf2 100644
--- a/src/utils/json.c
+++ b/src/utils/json.c
@@ -300,8 +300,10 @@
 				goto fail;
 			if (!curr_token) {
 				token = json_alloc_token(&tokens);
-				if (!token)
+				if (!token) {
+					os_free(str);
 					goto fail;
+				}
 				token->type = JSON_STRING;
 				token->string = str;
 				token->state = JSON_COMPLETED;
@@ -514,8 +516,8 @@
 	token = json_get_member(json, name);
 	if (!token || token->type != JSON_STRING)
 		return NULL;
-	buf = base64_url_decode((const unsigned char *) token->string,
-				os_strlen(token->string), &buflen);
+	buf = base64_url_decode(token->string, os_strlen(token->string),
+				&buflen);
 	if (!buf)
 		return NULL;
 	ret = wpabuf_alloc_ext_data(buf, buflen);
@@ -574,3 +576,79 @@
 	buf[0] = '\0';
 	json_print_token(root, 1, buf, buflen);
 }
+
+
+void json_add_int(struct wpabuf *json, const char *name, int val)
+{
+	wpabuf_printf(json, "\"%s\":%d", name, val);
+}
+
+
+void json_add_string(struct wpabuf *json, const char *name, const char *val)
+{
+	wpabuf_printf(json, "\"%s\":\"%s\"", name, val);
+}
+
+
+int json_add_string_escape(struct wpabuf *json, const char *name,
+			   const void *val, size_t len)
+{
+	char *tmp;
+	size_t tmp_len = 6 * len + 1;
+
+	tmp = os_malloc(tmp_len);
+	if (!tmp)
+		return -1;
+	json_escape_string(tmp, tmp_len, val, len);
+	json_add_string(json, name, tmp);
+	bin_clear_free(tmp, tmp_len);
+	return 0;
+}
+
+
+int json_add_base64url(struct wpabuf *json, const char *name, const void *val,
+		       size_t len)
+{
+	char *b64;
+
+	b64 = base64_url_encode(val, len, NULL);
+	if (!b64)
+		return -1;
+	json_add_string(json, name, b64);
+	os_free(b64);
+	return 0;
+}
+
+
+void json_start_object(struct wpabuf *json, const char *name)
+{
+	if (name)
+		wpabuf_printf(json, "\"%s\":", name);
+	wpabuf_put_u8(json, '{');
+}
+
+
+void json_end_object(struct wpabuf *json)
+{
+	wpabuf_put_u8(json, '}');
+}
+
+
+void json_start_array(struct wpabuf *json, const char *name)
+{
+	if (name)
+		wpabuf_printf(json, "\"%s\":", name);
+	wpabuf_put_u8(json, '[');
+}
+
+
+void json_end_array(struct wpabuf *json)
+{
+	wpabuf_put_u8(json, ']');
+}
+
+
+void json_value_sep(struct wpabuf *json)
+{
+	wpabuf_put_u8(json, ',');
+}
diff --git a/src/utils/json.h b/src/utils/json.h
index 8faa95d..ca4a2e4 100644
--- a/src/utils/json.h
+++ b/src/utils/json.h
@@ -38,5 +38,16 @@
 struct wpabuf * json_get_member_base64url(struct json_token *json,
 					  const char *name);
 void json_print_tree(struct json_token *root, char *buf, size_t buflen);
+void json_add_int(struct wpabuf *json, const char *name, int val);
+void json_add_string(struct wpabuf *json, const char *name, const char *val);
+int json_add_string_escape(struct wpabuf *json, const char *name,
+			   const void *val, size_t len);
+int json_add_base64url(struct wpabuf *json, const char *name, const void *val,
+		       size_t len);
+void json_start_object(struct wpabuf *json, const char *name);
+void json_end_object(struct wpabuf *json);
+void json_start_array(struct wpabuf *json, const char *name);
+void json_end_array(struct wpabuf *json);
+void json_value_sep(struct wpabuf *json);
 
 #endif /* JSON_H */
diff --git a/src/utils/utils_module_tests.c b/src/utils/utils_module_tests.c
index 3af4fcd..b09225d 100644
--- a/src/utils/utils_module_tests.c
+++ b/src/utils/utils_module_tests.c
@@ -296,52 +296,53 @@
 {
 	int errors = 0;
 	unsigned char *res;
+	char *res2;
 	size_t res_len;
 
 	wpa_printf(MSG_INFO, "base64 tests");
 
-	res = base64_encode((const unsigned char *) "", ~0, &res_len);
+	res2 = base64_encode("", ~0, &res_len);
+	if (res2) {
+		errors++;
+		os_free(res2);
+	}
+
+	res2 = base64_encode("=", 1, &res_len);
+	if (!res2 || res_len != 5 || res2[0] != 'P' || res2[1] != 'Q' ||
+	    res2[2] != '=' || res2[3] != '=' || res2[4] != '\n')
+		errors++;
+	os_free(res2);
+
+	res2 = base64_encode("=", 1, NULL);
+	if (!res2 || res2[0] != 'P' || res2[1] != 'Q' ||
+	    res2[2] != '=' || res2[3] != '=' || res2[4] != '\n')
+		errors++;
+	os_free(res2);
+
+	res = base64_decode("", 0, &res_len);
 	if (res) {
 		errors++;
 		os_free(res);
 	}
 
-	res = base64_encode((const unsigned char *) "=", 1, &res_len);
-	if (!res || res_len != 5 || res[0] != 'P' || res[1] != 'Q' ||
-	    res[2] != '=' || res[3] != '=' || res[4] != '\n')
-		errors++;
-	os_free(res);
-
-	res = base64_encode((const unsigned char *) "=", 1, NULL);
-	if (!res || res[0] != 'P' || res[1] != 'Q' ||
-	    res[2] != '=' || res[3] != '=' || res[4] != '\n')
-		errors++;
-	os_free(res);
-
-	res = base64_decode((const unsigned char *) "", 0, &res_len);
+	res = base64_decode("a", 1, &res_len);
 	if (res) {
 		errors++;
 		os_free(res);
 	}
 
-	res = base64_decode((const unsigned char *) "a", 1, &res_len);
+	res = base64_decode("====", 4, &res_len);
 	if (res) {
 		errors++;
 		os_free(res);
 	}
 
-	res = base64_decode((const unsigned char *) "====", 4, &res_len);
-	if (res) {
-		errors++;
-		os_free(res);
-	}
-
-	res = base64_decode((const unsigned char *) "PQ==", 4, &res_len);
+	res = base64_decode("PQ==", 4, &res_len);
 	if (!res || res_len != 1 || res[0] != '=')
 		errors++;
 	os_free(res);
 
-	res = base64_decode((const unsigned char *) "P.Q-=!=*", 8, &res_len);
+	res = base64_decode("P.Q-=!=*", 8, &res_len);
 	if (!res || res_len != 1 || res[0] != '=')
 		errors++;
 	os_free(res);
diff --git a/src/utils/xml_libxml2.c b/src/utils/xml_libxml2.c
index 7b6d276..d73654e 100644
--- a/src/utils/xml_libxml2.c
+++ b/src/utils/xml_libxml2.c
@@ -409,7 +409,7 @@
 	if (txt == NULL)
 		return NULL;
 
-	ret = base64_decode((unsigned char *) txt, strlen(txt), &len);
+	ret = base64_decode(txt, strlen(txt), &len);
 	if (ret_len)
 		*ret_len = len;
 	xml_node_get_text_free(ctx, txt);