Call cleanup from run_component instead of calling it from each
individual component function.
Clean up after each component rather than before. With the new
structure it makes more sense for each component to leave the place
clean. Run cleanup once at the beginning to start from a clean slate.
Move almost all the code of this script into functions. There is no
intended behavior change. The goal of this commit is to make
subsequent improvements easier to follow.
A very large number of lines have been reintended. To see what's going
on, ignore whitespace differences (e.g. diff -w).
I followed the following rules:
* Minimize the amount of code that gets moved.
* Don't change anything to what gets executed or displayed.
* Almost all the code must end up in a function.
* One function does one thing. For most of the code, that's from one
"cleanup" to the next.
* The test sequence functions (run_XXX) are independent.
The change mostly amounts to putting chunks of code into a function
and calling the functions in order. A few test runs are conditional;
in those cases the conditional is around the function call.
Context: The function `mbedtls_mpi_fill_random()` uses a temporary stack
buffer to hold the random data before reading it into the target MPI.
Problem: This is inefficient both computationally and memory-wise.
Memory-wise, it may lead to a stack overflow on constrained devices with
limited stack.
Fix: This commit introduces the following changes to get rid of the
temporary stack buffer entirely:
1. It modifies the call to the PRNG to output the random data directly
into the target MPI's data buffer.
This alone, however, constitutes a change of observable behaviour:
The previous implementation guaranteed to interpret the bytes emitted by
the PRNG in a big-endian fashion, while rerouting the PRNG output into the
target MPI's limb array leads to an interpretation that depends on the
endianness of the host machine.
As a remedy, the following change is applied, too:
2. Reorder the bytes emitted from the PRNG within the target MPI's
data buffer to ensure big-endian semantics.
Luckily, the byte reordering was already implemented as part of
`mbedtls_mpi_read_binary()`, so:
3. Extract bigendian-to-host byte reordering from
`mbedtls_mpi_read_binary()` to a separate internal function
`mpi_bigendian_to_host()` to be used by `mbedtls_mpi_read_binary()`
and `mbedtls_mpi_fill_random()`.
Clarified and made more coherent the parameter validation feature, it's scope
and what has changed. Added version 2.14.1 to the history which was released on
a branch.
