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Raise instead of hanging on a truncated frame in Zstd.decompress #143

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Raise instead of hanging on a truncated frame in Zstd.decompress #143

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8 changes: 8 additions & 0 deletions ext/zstdruby/zstdruby.c
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Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,7 @@ static VALUE decode_one_frame(ZSTD_DCtx* dctx, const unsigned char* src, size_t

for (;;) {
ZSTD_outBuffer o = (ZSTD_outBuffer){ buf, cap, 0 };
size_t const in_pos_before = in.pos;
size_t ret = ZSTD_decompressStream(dctx, &o, &in);
if (ZSTD_isError(ret)) {
xfree(buf);
Expand All @@ -62,6 +63,13 @@ static VALUE decode_one_frame(ZSTD_DCtx* dctx, const unsigned char* src, size_t
if (ret == 0) {
break;
}
if (o.pos == 0 && in.pos == in_pos_before) {
/* No progress: the frame is truncated/incomplete. Without this guard the
loop would spin forever calling ZSTD_decompressStream on exhausted
input (see decompress of a header-only frame). */
xfree(buf);
rb_raise(rb_eRuntimeError, "ZSTD_decompressStream failed: truncated or incomplete frame");
}
}
xfree(buf);
return out;
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12 changes: 12 additions & 0 deletions spec/zstd-ruby_spec.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -103,6 +103,18 @@ def to_str
expect { Zstd.decompress(Object.new) }.to raise_error(TypeError)
end

it 'should raise (not hang) on a truncated frame' do
full = Zstd.compress('a' * 2000)
[
"\x28\xB5\x2F\xFD".b, # bare zstd magic, no body
full.byteslice(0, 5),
full.byteslice(0, 6),
full.byteslice(0, full.bytesize / 2),
].each do |truncated|
expect { Zstd.decompress(truncated) }.to raise_error(RuntimeError)
end
end

class DummyForDecompress
def to_str
Zstd.compress('abc')
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