Because `builtin_vsnprintf()` returns the length of the (theoretically)
produced string even if the buffer is too small, the `fwrite()` calls
would read past the buffer. While it rarely happens that log messages
are even close to the current buffer size, it might get triggered by an
overlong IKE/EAP identity or similar.
For `vasprintf()`, the allocation for the complete required length is
now correctly handled (capped at `INT_MAX` as that's what
`builtin_vsnprintf()` can technically return).
Also fixed is an incorrect mapping of the return value of `fwrite()` in
case of an error. While the latter returns the elements written so far,
the expected return value from `vfprintf()` is negative.
Fixes: cabe5c0ff4 ("printf-hook-builtin: Add a new "builtin" backend using its own printf() routines")
When precision is given for a string, we must not run unbounded
strlen() as it will read beyond the given length. It might even cause
a crash if the given pointer is near end of heap or mapping.
Fixes numerous valgrind errors such as:
==19215== Invalid read of size 1
==19215== at 0x52D36C6: builtin_vsnprintf (printf_hook_builtin.c:853)
==19215== by 0x52D40A8: builtin_snprintf (printf_hook_builtin.c:1084)
==19215== by 0x52CE464: dntoa (identification.c:337)
==19215== by 0x52CE464: identification_printf_hook (identification.c:837)
==19215== by 0x52D3DAA: builtin_vsnprintf (printf_hook_builtin.c:1010)
==19215== by 0x57040EB: vlog (bus.c:388)
==19215== by 0x570427D: log_ (bus.c:430)
==19215== by 0xA8445D3: load_x509_ca (stroke_cred.c:416)
==19215== by 0xA8445D3: load_certdir (stroke_cred.c:537)
==19215== by 0xA846A95: load_certs (stroke_cred.c:1353)
==19215== by 0xA846A95: stroke_cred_create (stroke_cred.c:1475)
==19215== by 0xA84073E: stroke_socket_create (stroke_socket.c:782)
==19215== by 0xA83F27C: register_stroke (stroke_plugin.c:53)
==19215== by 0x52C3125: load_feature (plugin_loader.c:716)
==19215== by 0x52C3125: load_provided (plugin_loader.c:778)
==19215== by 0x52C3A20: load_features (plugin_loader.c:799)
==19215== by 0x52C3A20: load_plugins (plugin_loader.c:1159)
==19215== Address 0x50cdb42 is 0 bytes after a block of size 2 alloc'd
==19215== at 0x4C919FE: malloc (vg_replace_malloc.c:296)
==19215== by 0x52CD198: chunk_printable (chunk.c:759)
==19215== by 0x52CE442: dntoa (identification.c:334)
==19215== by 0x52CE442: identification_printf_hook (identification.c:837)
==19215== by 0x52D3DAA: builtin_vsnprintf (printf_hook_builtin.c:1010)
==19215== by 0x57040EB: vlog (bus.c:388)
==19215== by 0x570427D: log_ (bus.c:430)
==19215== by 0xA8445D3: load_x509_ca (stroke_cred.c:416)
==19215== by 0xA8445D3: load_certdir (stroke_cred.c:537)
==19215== by 0xA846A95: load_certs (stroke_cred.c:1353)
==19215== by 0xA846A95: stroke_cred_create (stroke_cred.c:1475)
==19215== by 0xA84073E: stroke_socket_create (stroke_socket.c:782)
==19215== by 0xA83F27C: register_stroke (stroke_plugin.c:53)
==19215== by 0x52C3125: load_feature (plugin_loader.c:716)
==19215== by 0x52C3125: load_provided (plugin_loader.c:778)
==19215== by 0x52C3A20: load_features (plugin_loader.c:799)
==19215== by 0x52C3A20: load_plugins (plugin_loader.c:1159)
The hook data counts remaining buffer bytes, not used ones. Counting them
correctly fixes a crash for long hexdumps.
Further, print_in_hook() must return the number of bytes that would have been
written, not the actually written bytes. This is important, as we allocate a
dynamic buffer in bus that relies on the exact byte count. Fixes long hexdumps
that got truncated.
Overloads printf C library functions by a self-contained implementation,
based on klibc. Does not yet feature all the required default formatters,
including those for floating point values.
Tobias Brunner