The array_list_new2 function, which is externally reachable through
json_object_new_array_ext, does not check if specified initial size
actually fits into memory on 32 bit architectures.

It also allows negative values, which could lead to an overflow on these
architectures as well. I have added test cases for these situations.

While at it, also protect array_list_shrink against too large
empty_slots argument. No test added because it takes a huge length
value, therefore a lot of items within the array, to overflow the
calculation. In theory this affects 64 bit sytems as well, but since the
arraylist API is not supposed to be used by external applications
according to its header file, the call is protected due to int
limitation of json_object_array_shrink.

Limit strings at INT_MAX length

Properly format errnos in _json_c_strerror

Prevent signed overflow in get_time_seed

Casting time(2) return value to int and multiplying the result with
such a constant will definitely lead to a signed overflow by this day.

Since signed overflows are undefined behaviour in C, avoid this.

Casting to unsigned is more than enough since the upper bits of a
64 bit time_t value will be removed with the int conversion anyway.

The allocation of printbuf_new might fail. Return NULL to indicate tis
error to the caller. Otherwise later usage of the returned tokener would
lead to null pointer dereference.

Several issues occur if a string is longer than INT_MAX:

- The function json_object_get_string_len returns the length of a string
  as int. If the string is longer than INT_MAX, the result would be
  negative.
- That in turn would lead to possible out of boundary access when
  comparing these strings with memcmp and the returned length as done in
  json_object_equal.
- If json_escape_str is called with such strings, out of boundary
  accesses can occur due to internal int handling (also fixed).
- The string cannot be printed out due to printbuffer limits at
  INT_MAX (which is still true after this commit).

Such huge strings can only be inserted through API calls at this point
because input files are capped at INT_MAX anyway.

Due to huge amount of RAM needed to reproduce these issues I have not
added test cases.

The comment only aligns correctly if tab size is 4. Replaced
spaces with tabs to stay in sync with style of other lines.

The function _json_c_strerror does not properly format unknown errnos.
The int to ascii loop ignores the leading digit if the number can be
divided by 10 and if an errno has been formatted, shorter errnos would
not properly terminate the newly created string, showing the ending
numbers of the previous output.

A test case has been added to show these effects.

Since this function has been introduced for tests, the effect of this on
real life code is basically non-existing. First an environment variable
has to be set to activate this strerror code and second an unknown errno
would have to be encountered.

See also issue #658.

Use GRND_NONBLOCK with getrandom.

The json-c library is used in cryptsetup for LUKS2 header information.
Since cryptsetup can be called very early during boot, the developers
avoid getrandom() calls in their own code base for now. [1]

Introducing a blocking getrandom() call in json-c therefore introduces
this issue for cryptsetup as well. Even though cryptsetup issues do not
have to be json-c issues, here is my proposal:

Let's use a non-blocking call, falling back to other sources if the call
would block. Since getrandom() accesses urandom, it must mean that we
are in an early boot phase -- otherwise the call would not block
according to its manual page.

As stated in manual page of random(4), accessing /dev/urandom won't
block but return weak random numbers, therefore this fallback would work
for json-c.

While at it, fixed the debug message.

[1] https://gitlab.com/cryptsetup/cryptsetup/-/merge_requests/47
    which references to https://lwn.net/Articles/800509/

Fixed warnings

json_parse: Fix read past end of buffer

Resolves https://github.com/json-c/json-c/issues/654

Also, create a _json_object_get_string_len() for internal use when we know
for sure the object we're dealing with is a json_type_string.

Make the documentation build reproducibly

Whilst working on the Reproducible Builds effort [0] I noticed that
json-c could not be built reproducibly.

This is because it used the full, absolute path name as an (sanitised)
input to a filename, resulting in some binary package containing, for
example:

  /usr/share/doc/libjson-c-dev/html/md__build_1st_json-c-0_815_issues_closed_for_0_813.html
                                        ^^^^^^^^^^^^^^^^^^^^^^
or

  /usr/share/doc/libjson-c-dev/html/md__build_2_json-c-0_815_2nd_issues_closed_for_0_813.html
                                        ^^^^^^^^^^^^^^^^^^^^^^^^

These differing values are based on the path in which json-c is built. This was
originally filed in Debian as #966657 [1].

 [0] https://reproducible-builds.org/
 [1] https://bugs.debian.org/966657

Getrandom

Lower overhead than opening & reading from /dev/urandom, and works
in chroots and other situtations where /dev/urandom is not available.
Falls back to existing methods when kernel doesn't support the syscall.

README: fix spelling errors

Signed-off-by: Jakov Smolic <jakov.smolic@sartura.hr>

Fix "may be used uninitialized" Release build failure

Fixes https://github.com/json-c/json-c/issues/647

Example:
mkdir build && cd build
cmake -DOVERRIDE_GET_RANDOM_SEED='do { extern uint32_t getMsTicks(void); int ms = getMsTicks() * 433494437; return ms; } while(0)' ..

Cast to unsigned char instead of int when calling tolower (Fixes #645)

See also PR #639 and issue #621

build: Add a symbol version to all exported symbols

With this version script, newly-linked binaries that depend on the
json-c shared library will refer to its symbols in a versioned form,
preventing their references from being resolved to a symbol of the same
name exported by json-glib or libjansson if those libraries appear in
dependency search order before json-c, which will usually result in
a crash. This is necessary because ELF symbol resolution normally uses
a single flat namespace, not a tree like Windows symbol resolution.
At least one symbol (json_object_iter_next()) is exported by all three
JSON libraries.

Linking with -Bsymbolic is not enough to have this effect in all cases,
because -Bsymbolic only affects symbol lookup within a shared object,
for example when json_object_set_serializer() calls
json_object_set_userdata(). It does not affect calls from external
code into json-c, unless json-c was statically linked into the
external caller.

This change will also not prevent code that depends on json-glib or
libjansson from finding json-c's symbols and crashing; to prevent
that, a corresponding change in json-glib or libjansson would be needed.

Adding a symbol-version is a backwards-compatible change, but once
added, removing or changing the symbol-version on a symbol would be an
incompatible change that requires a SONAME bump.

Resolves: https://github.com/json-c/json-c/issues/621
(when combined with an equivalent change to libjansson).

Signed-off-by: Simon McVittie <smcv@collabora.com>

In practice, the sizes of the signed and unsigned integer types will
almost cetainly be the same, but this is more correct.
Pointed out in issue #638.