Add JSON_ALLOW_NUL decoding flag for enabling NUL byte support

CHANGES

@@ -16,7 +16,8 @@ Released XXXX-XX-XX
     `json_string_setn()` and `json_string_setn_nocheck()`, and a
     function for getting string's length `json_string_length()`.
 
-  - Support ``\u0000`` escapes in the decoder.
+  - Support ``\u0000`` escapes in the decoder. The support can be
+    enabled by using the ``JSON_ALLOW_NUL`` decoding flag.
 
 * Bug fixes:
 

src/jansson.h

@@ -244,6 +244,7 @@ json_t *json_deep_copy(const json_t *value);
 #define JSON_DISABLE_EOF_CHECK  0x2
 #define JSON_DECODE_ANY         0x4
 #define JSON_DECODE_INT_AS_REAL 0x8
+#define JSON_ALLOW_NUL          0x10
 
 typedef size_t (*json_load_callback_t)(void *buffer, size_t buflen, void *data);
 

src/load.c

@@ -802,7 +802,17 @@ static json_t *parse_value(lex_t *lex, size_t flags, json_error_t *error)
 
     switch(lex->token) {
         case TOKEN_STRING: {
-            json = jsonp_stringn_nocheck_own(lex->value.string.val, lex->value.string.len);
+            const char *value = lex->value.string.val;
+            size_t len = lex->value.string.len;
+
+            if(!(flags & JSON_ALLOW_NUL)) {
+                if(memchr(value, '\0', len)) {
+                    error_set(error, lex, "\\u0000 is not allowed without JSON_ALLOW_NUL");
+                    return NULL;
+                }
+            }
+
+            json = jsonp_stringn_nocheck_own(value, len);
             if(json) {
                 lex->value.string.val = NULL;
                 lex->value.string.len = 0;

test/suites/api/test_dump.c

@@ -180,6 +180,20 @@ static void escape_slashes()
     json_decref(json);
 }
 
+static void encode_nul_byte()
+{
+    json_t *json;
+    char *result;
+
+    json = json_stringn("nul byte \0 in string", 20);
+    result = json_dumps(json, JSON_ENCODE_ANY);
+    if(!result || memcmp(result, "\"nul byte \\u0000 in string\"", 27))
+        fail("json_dumps failed to dump an embedded NUL byte");
+
+    free(result);
+    json_decref(json);
+}
+
 static void run_tests()
 {
     encode_null();
@@ -187,4 +201,5 @@ static void run_tests()
     circular_references();
     encode_other_than_array_or_object();
     escape_slashes();
+    encode_nul_byte();
 }

test/suites/api/test_load.c

@@ -115,6 +115,26 @@ static void decode_int_as_real()
 #endif
 }
 
+static void allow_nul()
+{
+    const char *text = "\"nul byte \\u0000 in string\"";
+    const char *expected = "nul byte \0 in string";
+    size_t len = 20;
+    json_t *json;
+
+    json = json_loads(text, JSON_ALLOW_NUL | JSON_DECODE_ANY, NULL);
+    if(!json || !json_is_string(json))
+        fail("unable to decode embedded NUL byte");
+
+    if(json_string_length(json) != len)
+        fail("decoder returned wrong string length");
+
+    if(memcmp(json_string_value(json), expected, len + 1))
+        fail("decoder returned wrong string content");
+
+    json_decref(json);
+}
+
 static void load_wrong_args()
 {
     json_t *json;
@@ -161,6 +181,7 @@ static void run_tests()
     disable_eof_check();
     decode_any();
     decode_int_as_real();
+    allow_nul();
     load_wrong_args();
     position();
 }

test/suites/valid/escaped-null-byte-in-string/input

@@ -1 +0,0 @@
-["null char \u0000 in string"]

test/suites/valid/escaped-null-byte-in-string/output

@@ -1 +0,0 @@
-["null char \u0000 in string"]