Bruno Haible <br...@clisp.org> writes:
> Here's the relevant output on macOS 13:
>
> empty1d...
> Running command: 'basenc --base64 -d 'empty1d.1' > empty1d.O 2> empty1d.E'
> sh: line 1: 79138 Segmentation fault: 11 basenc --base64 -d 'empty1d.1' >
> empty1d.O 2> empty1d.E
> basenc.pl: test empty1d failed: exit status mismatch: expected 0, got 139
> creating file 'empty2d.1' with contents ''
> creating file 'empty2d.2' with contents ''
> creating file 'empty2d.3' with contents ''
Thanks.
Looks like it was caused by this commit:
commit 4141ae3e4970dbc206b56366b0581f04fa87dfc1
Author: Pádraig Brady <p...@draigbrady.com>
AuthorDate: Mon Sep 8 17:40:00 2025 +0100
Commit: Pádraig Brady <p...@draigbrady.com>
CommitDate: Wed Sep 10 23:24:46 2025 +0100
maint: basenc: refactor all encodings to use finalize
Finalize was required for base58, but it's a more general mechanism
which simplifies the logic for all encodings
* src/basenc.c (do_decode): Always call base_decode_ctx_finalize(),
rather than the awkward double loop at end of buffer.
* tests/basenc/basenc.pl: Add basenc finalization tests.1
Focusing on this change:
- ok = base_decode_ctx (&ctx, inbuf, sum, outbuf, &n);
+ if (sum)
+ ok = base_decode_ctx (&ctx, inbuf, sum, outbuf, &n);
+ else
+ ok = base_decode_ctx_finalize (&ctx, &outbuf, &n);
For an empty file 'sum' would be zero and base_decode_ctx is never
called. For --base32 here is what that function pointer calls:
static bool
base32_decode_ctx_wrapper (struct base_decode_context *ctx,
char const *restrict in, idx_t inlen,
char *restrict out, idx_t *outlen)
{
bool b = base32_decode_ctx (&ctx->ctx.base32, in, inlen, out, outlen);
ctx->i = ctx->ctx.base32.i;
return b;
}
If that is never called, using ctx->i is undefined behavior. Therefore,
the padding can cause a crash:
static bool
base32_ctx_has_padding (struct base_decode_context *ctx)
{
return ctx->i && ctx->ctx.base32.buf[ctx->i - 1] == '=';
}
On the other systems we probably get lucky and ctx->i is set to zero.
That is my hypothesis at least, will need to write a patch to test it.
Collin
