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Prevent TOCTTOU bugs in C ports

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* libguile/ports-internal.h (scm_port_buffer_can_take):
  (scm_port_buffer_can_put): Add cur/end output arguments so that when a
  caller asks the buffer room, it can be relative to a fixed point in
  the buffer and not whatever point it's at when we go to fill it.
  (scm_port_buffer_did_take, scm_port_buffer_did_put): Similarly,
  require that the caller knows where they took/put data in the buffer.
  Prevents overflow.
  (scm_port_buffer_take_pointer, scm_port_buffer_put_pointer): Likewise,
  require that the caller has already checked and knows a position in
  the buffer and therefore how much data is available.
  (scm_port_buffer_take, scm_port_buffer_put, scm_port_buffer_putback):
  Adapt.
* libguile/ports.h (scm_fill_input): Add cur/avail output arguments.
* libguile/filesys.c:
* libguile/poll.c:
* libguile/ports.c:
* libguile/r6rs-ports.c:
* libguile/read.c:
* libguile/rw.c: Adapt all callers.  Gnarly work!
This commit is contained in:
Andy Wingo 2017-02-08 15:05:03 +01:00
parent 8a4774dec8
commit 09a69dd712
8 changed files with 251 additions and 176 deletions
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3
libguile/rw.c
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@ -232,6 +232,7 @@ SCM_DEFINE (scm_write_string_partial, "write-string/partial", 1, 3, 0,
SCM port = (SCM_UNBNDP (port_or_fdes)?
scm_current_output_port () : port_or_fdes);
SCM write_buf;
size_t end;
SCM_VALIDATE_OPFPORT (2, port);
SCM_VALIDATE_OUTPUT_PORT (2, port);
@ -239,7 +240,7 @@ SCM_DEFINE (scm_write_string_partial, "write-string/partial", 1, 3, 0,
/* Filling the last character in the buffer would require a
flush. */
if (write_len < scm_port_buffer_can_put (write_buf))
if (write_len < scm_port_buffer_can_put (write_buf, &end))
{
scm_c_write (port, src, write_len);
return scm_from_long (write_len);