json: Update parser (jsmn) to verify the length of the input data

This way the string doesn't have to be 0-terminated.

3 files changed, 17 insertions, 7 deletions

diff --git a/src/jplist.c b/src/jplist.c
index fbc963e..889ce30 100644
--- a/src/jplist.c
+++ b/src/jplist.c
@@ -661,7 +661,7 @@ PLIST_API int plist_from_json(const char *json, uint32_t length, plist_t * plist
         }
         tokens = newtokens;
 
-        r = jsmn_parse(&parser, json, tokens, maxtoks);
+        r = jsmn_parse(&parser, json, length, tokens, maxtoks);
         if (r == JSMN_ERROR_NOMEM) {
             maxtoks+=16;
             continue;
diff --git a/src/jsmn.c b/src/jsmn.c
index ff7c818..f190312 100644
--- a/src/jsmn.c
+++ b/src/jsmn.c
@@ -66,7 +66,7 @@ static jsmnerr_t jsmn_parse_primitive(jsmn_parser *parser, const char *js,
 
         start = parser->pos;
 
-        for (; js[parser->pos] != '\0'; parser->pos++) {
+        for (; (parser->end > 0 && parser->pos < parser->end) && js[parser->pos] != '\0'; parser->pos++) {
                 switch (js[parser->pos]) {
 #ifndef JSMN_STRICT
                         /* In strict mode primitive must be followed by "," or "}" or "]" */
@@ -75,6 +75,8 @@ static jsmnerr_t jsmn_parse_primitive(jsmn_parser *parser, const char *js,
                         case '\t' : case '\r' : case '\n' : case ' ' :
                         case ','  : case ']'  : case '}' :
                                 goto found;
+                        default:
+                                break;
                 }
                 if (js[parser->pos] < 32 || js[parser->pos] >= 127) {
                         parser->pos = start;
@@ -102,7 +104,7 @@ found:
 }
 
 /**
- * Filsl next token with JSON string.
+ * Fills next token with JSON string.
  */
 static jsmnerr_t jsmn_parse_string(jsmn_parser *parser, const char *js,
                 jsmntok_t *tokens, int num_tokens) {
@@ -113,7 +115,7 @@ static jsmnerr_t jsmn_parse_string(jsmn_parser *parser, const char *js,
         parser->pos++;
 
         /* Skip starting quote */
-        for (; js[parser->pos] != '\0'; parser->pos++) {
+        for (; (parser->end > 0 && parser->pos < parser->end) && js[parser->pos] != '\0'; parser->pos++) {
                 char c = js[parser->pos];
 
                 /* Quote: end of string */
@@ -133,6 +135,10 @@ static jsmnerr_t jsmn_parse_string(jsmn_parser *parser, const char *js,
                 /* Backslash: Quoted symbol expected */
                 if (c == '\\') {
                         parser->pos++;
+                        if (parser->end > 0 && parser->pos >= parser->end) {
+                                parser->pos = start;
+                                return JSMN_ERROR_INVAL;
+                        }
                         switch (js[parser->pos]) {
                                 /* Allowed escaped symbols */
                                 case '\"': case '/' : case '\\' : case 'b' :
@@ -156,13 +162,15 @@ static jsmnerr_t jsmn_parse_string(jsmn_parser *parser, const char *js,
 /**
  * Parse JSON string and fill tokens.
  */
-jsmnerr_t jsmn_parse(jsmn_parser *parser, const char *js, jsmntok_t *tokens,
+jsmnerr_t jsmn_parse(jsmn_parser *parser, const char *js, unsigned int length, jsmntok_t *tokens,
                 unsigned int num_tokens) {
         jsmnerr_t r;
         int i;
         jsmntok_t *token;
 
-        for (; js[parser->pos] != '\0'; parser->pos++) {
+        parser->end = length;
+
+        for (; (parser->end > 0 && parser->pos < parser->end) && js[parser->pos] != '\0'; parser->pos++) {
                 char c;
                 jsmntype_t type;
 
@@ -274,6 +282,7 @@ jsmnerr_t jsmn_parse(jsmn_parser *parser, const char *js, jsmntok_t *tokens,
  */
 void jsmn_init(jsmn_parser *parser) {
         parser->pos = 0;
+        parser->end = 0;
         parser->toknext = 0;
         parser->toksuper = -1;
 }
diff --git a/src/jsmn.h b/src/jsmn.h
index f12dc5a..380744d 100644
--- a/src/jsmn.h
+++ b/src/jsmn.h
@@ -72,6 +72,7 @@ typedef struct {
  */
 typedef struct {
         unsigned int pos; /* offset in the JSON string */
+        unsigned int end; /* offset after last character of JSON string */
         int toknext; /* next token to allocate */
         int toksuper; /* superior token node, e.g parent object or array */
 } jsmn_parser;
@@ -85,7 +86,7 @@ void jsmn_init(jsmn_parser *parser);
  * Run JSON parser. It parses a JSON data string into and array of tokens, each describing
  * a single JSON object.
  */
-jsmnerr_t jsmn_parse(jsmn_parser *parser, const char *js,
+jsmnerr_t jsmn_parse(jsmn_parser *parser, const char *js, unsigned int length,
                 jsmntok_t *tokens, unsigned int num_tokens);
 
 #endif /* __JSMN_H_ */