request: json_init_library

[dorssel]

Many libraries allow overriding malloc, realloc, and free by (optionally) calling an initialization function. One of the use cases is to securely zeroize sensitive buffers. Currently, json-c uses platform malloc and free, which leaves all kinds of data (think: passwords) on the heap.

I suggest to use new functions json_malloc etc. throughout the library, which default to malloc etc., but which can be set to user provided functions (only upon initialization). Currently, json-c also uses strdup, which could be replaced by an internal function that implements it using the new json_malloc.

[hawicz]

If we're going to go through the trouble of changing every memory allocation, it would be worthwhile to also use a type-specific slab allocators for the struct json_object's, struct array_list's, struct lh_table's, etc... Then again, that's a rather more significant change.

As for zeroizing sensitive buffers, if you're worried about that then it seems that merely changing the allocator used by json-c would be insufficient, as you'd be likely to have other allocations in your program that might have worthwhile-to-be-wiped content, in which case you should just replace malloc, free, etc... for the entire process.

In short, I'm not actually convinced that overriding library-specific memory allocation in this way is worthwhile.

[dota17]

@hawicz As you said, slab allocator is suitable for the fixed-size struct/object which is scheduled frequently indeed. It is a good optimization direction. I will try to implement this function 0.0.
Using malloc/free will casue sensitive data leak. And malloc is not good func which also brings memory leak. In short, rewrite malloc/free is complicated and we shouldconsider it carefully.

[hawicz]

@dota17, before implementing anything a change like that is worth discussing in more detail. If you have some ideas about an existing allocator to bring in to json-c, please mention it on the json-c Google group, or in a separate github issue.

[dota17]

@hawicz ok, I got it!

[hawicz]

I don't think there's anything to be done for this, so I'm closing it.