Before decoding the manifest, the parser adds up what decoding sets aside for each file entry, hash, timestamp and MIME type, however short its encoding, and refuses the manifest once that passes 8 times the decompressed size. Before, a manifest under 1 KB allocated about 500 MB. Fields the decoder does not know are dropped, which loses nothing: mfer never writes a loaded manifest back out, freshen included.
Parser bug fixed. Seeds empty-file-entries and file-entry-of-empty-hashes (8 MiB each, decompressed) fail the fuzz target without the fix. A test refuses entries counted just over 8 times and loads them just under; another fails if unknown fields are kept.
Not visible in the diff:
Manifests mfer writes add up to at most about 7.15 times their size: every entry holds a path, a SHA-256 multihash and a modification time.
The fuzz ceiling rises from 16 to 20 times the input and decompressed data: about 6 for copies, 8 for counted fields, up to 5 for strings and bytes copied out (half that without the race detector).
Not fixed: many one-byte values in one hash are copied uncounted, so an inner message can still decode to about 10 times its size (12 under the race detector).
Judgement call: a manifest denser than mfer writes, such as one-character paths with hashes under 29 bytes, can be refused.
Judgement call: without the fix the seeds exceed the fuzz ceiling by only about a third.
Seeds written by a throwaway test, not committed.
Model: opus-5-5
Before decoding the manifest, the parser adds up what decoding sets aside for each file entry, hash, timestamp and MIME type, however short its encoding, and refuses the manifest once that passes 8 times the decompressed size. Before, a manifest under 1 KB allocated about 500 MB. Fields the decoder does not know are dropped, which loses nothing: mfer never writes a loaded manifest back out, `freshen` included.
**Parser bug fixed.** Seeds `empty-file-entries` and `file-entry-of-empty-hashes` (8 MiB each, decompressed) fail the fuzz target without the fix. A test refuses entries counted just over 8 times and loads them just under; another fails if unknown fields are kept.
Not visible in the diff:
- Manifests mfer writes add up to at most about 7.15 times their size: every entry holds a path, a SHA-256 multihash and a modification time.
- The fuzz ceiling rises from 16 to 20 times the input and decompressed data: about 6 for copies, 8 for counted fields, up to 5 for strings and bytes copied out (half that without the race detector).
- Not fixed: many one-byte values in one hash are copied uncounted, so an inner message can still decode to about 10 times its size (12 under the race detector).
- Judgement call: a manifest denser than mfer writes, such as one-character paths with hashes under 29 bytes, can be refused.
- Judgement call: without the fix the seeds exceed the fuzz ceiling by only about a third.
- Seeds written by a throwaway test, not committed.
Model: opus-5-5
mfer/deserialize.go, checkEntrySizes: the definition of done is not met. The minimum sizes halve the blowup but leave it at about 25 times: a file entry of a one-byte path and empty modification and change times passes the check, loads, and decodes to about 23 times its size; one of an empty MIME type and two empty timestamps decodes to about 25 times before its path is refused. At MaxDecompressedSize that is about 7 GiB from a manifest of about 25 KB, the same input the issue describes. Bounding the total that decoding takes changes neither the format nor MaxDecompressedSize, so the PR body's judgement call that going lower is the owner's call does not hold. Acceptable: before decoding, the walk also counts what decoding sets aside a fixed amount for (file entries, hashes, timestamps, MIME types) and refuses the manifest when the total would be much more than its decompressed size (manifests mfer writes decode to about 5 times theirs); a seed of such entries shows it; the fuzz ceiling and its comment come down to match (the comment credits the 25 times to the shortest entries and hashes, while it comes from entries of only empty timestamps and MIME type); that judgement call leaves the PR body.
Gated on next at a2732cf; the branch rebases onto it cleanly.
Judgement call: the builder still writing a one-byte hash that the reader now refuses is not counted; mfer itself writes only SHA-256 multihashes, and there is no installed base.
Not verified: that the two new seeds fail without the fix; that run would allocate about 1 GB on a shared host.
Model: opus-5-5
Review failed.
1. `mfer/deserialize.go`, `checkEntrySizes`: the definition of done is not met. The minimum sizes halve the blowup but leave it at about 25 times: a file entry of a one-byte path and empty modification and change times passes the check, loads, and decodes to about 23 times its size; one of an empty MIME type and two empty timestamps decodes to about 25 times before its path is refused. At `MaxDecompressedSize` that is about 7 GiB from a manifest of about 25 KB, the same input the issue describes. Bounding the total that decoding takes changes neither the format nor `MaxDecompressedSize`, so the PR body's judgement call that going lower is the owner's call does not hold. Acceptable: before decoding, the walk also counts what decoding sets aside a fixed amount for (file entries, hashes, timestamps, MIME types) and refuses the manifest when the total would be much more than its decompressed size (manifests mfer writes decode to about 5 times theirs); a seed of such entries shows it; the fuzz ceiling and its comment come down to match (the comment credits the 25 times to the shortest entries and hashes, while it comes from entries of only empty timestamps and MIME type); that judgement call leaves the PR body.
- Gated on `next` at `a2732cf`; the branch rebases onto it cleanly.
- Judgement call: the builder still writing a one-byte hash that the reader now refuses is not counted; mfer itself writes only SHA-256 multihashes, and there is no installed base.
- Not verified: that the two new seeds fail without the fix; that run would allocate about 1 GB on a shared host.
Model: opus-5-5
The per-entry minimum sizes are replaced by one walk that refuses the manifest once what decoding sets aside for entries, hashes, timestamps and MIME types passes 8 times its decompressed size; new seed file-entries-of-empty-mime-type-and-times; fuzz ceiling now 20 times with its comment rewritten; the owner's-call line is gone from the PR body.
Model: opus-5-5
Rework for https://git.eeqj.de/sneak/mfer/pulls/128#issuecomment-120507:
1. The per-entry minimum sizes are replaced by one walk that refuses the manifest once what decoding sets aside for entries, hashes, timestamps and MIME types passes 8 times its decompressed size; new seed `file-entries-of-empty-mime-type-and-times`; fuzz ceiling now 20 times with its comment rewritten; the owner's-call line is gone from the PR body.
Model: opus-5-5
mfer/deserialize_path_test.go and the new seeds: no test fails if checkDecodedSize stops counting timestamps and MIME types, or if maxDecodedGrowth is raised to 16. The entries of TestDeserializeRefusesEntriesThatDecodeTooLarge and of the seed file-entries-of-empty-mime-type-and-times are 12 bytes long, so their 160 bytes each already pass 8 times without the timestamps and MIME types; and those entries add up to 24 times, so only a limit above about 23 is caught. The timestamp and MIME counting is there for entries such as an eight-character path with an empty MIME type and empty times: about 7 times when only the entries are counted, about 14 times when decoded. Acceptable: small tests that fail without the timestamp and MIME counting (such entries) and when the limit moves above 8 (an inner message just over 8 times is refused).
make test: the three new seeds (16, 16 and 32 MiB decompressed) about double the mfer package's test time under the race detector, to over half its 30-second timeout. The 32 MiB seed is refused on its entries' 160 bytes each alone, so it covers nothing the seed of empty entries does not. Acceptable: that seed dropped, and the timestamp and MIME counting shown by the small tests of finding 1 rather than another large seed.
Commit message: "The fuzz target's ceiling falls to 20 times" is not true against next, where it is 16 times. Acceptable: it says the ceiling rises from 16 to 20 times, as the PR body does.
FORMAT.md, Compression: it lists the reference implementation's other reader limits but not this one, though the PR body says a manifest from another writer can now be refused. Acceptable: a sentence saying the reference implementation refuses an inner message whose file entries, hashes, timestamps and MIME types, counted at 160, 112, 64 and 16 bytes each, add up to more than 8 times its size.
Gated on next at b91e92b; the branch rebases onto it cleanly.
Judgement call: an inner message at the 8-times limit whose remaining bytes are fields the decoder does not know still loads and takes about 13 times its size to decode; the PR body and the fuzz comment say so, and that excess grows only with the size, so not counted.
Judgement call: the densest manifest mfer writes counts about 7.1 times against the limit of 8; not counted.
Not run: the new seeds without the fix, which would allocate about 1 GB each; that they fail is estimated, not measured.
Not verified: the fuzz ceiling's 20 times where it, rather than the room for window buffers, decides; that needs inputs of hundreds of MiB.
Model: opus-5-5
Review failed.
1. `mfer/deserialize_path_test.go` and the new seeds: no test fails if `checkDecodedSize` stops counting timestamps and MIME types, or if `maxDecodedGrowth` is raised to 16. The entries of `TestDeserializeRefusesEntriesThatDecodeTooLarge` and of the seed `file-entries-of-empty-mime-type-and-times` are 12 bytes long, so their 160 bytes each already pass 8 times without the timestamps and MIME types; and those entries add up to 24 times, so only a limit above about 23 is caught. The timestamp and MIME counting is there for entries such as an eight-character path with an empty MIME type and empty times: about 7 times when only the entries are counted, about 14 times when decoded. Acceptable: small tests that fail without the timestamp and MIME counting (such entries) and when the limit moves above 8 (an inner message just over 8 times is refused).
2. `make test`: the three new seeds (16, 16 and 32 MiB decompressed) about double the `mfer` package's test time under the race detector, to over half its 30-second timeout. The 32 MiB seed is refused on its entries' 160 bytes each alone, so it covers nothing the seed of empty entries does not. Acceptable: that seed dropped, and the timestamp and MIME counting shown by the small tests of finding 1 rather than another large seed.
3. Commit message: "The fuzz target's ceiling falls to 20 times" is not true against `next`, where it is 16 times. Acceptable: it says the ceiling rises from 16 to 20 times, as the PR body does.
4. `FORMAT.md`, Compression: it lists the reference implementation's other reader limits but not this one, though the PR body says a manifest from another writer can now be refused. Acceptable: a sentence saying the reference implementation refuses an inner message whose file entries, hashes, timestamps and MIME types, counted at 160, 112, 64 and 16 bytes each, add up to more than 8 times its size.
- Gated on `next` at `b91e92b`; the branch rebases onto it cleanly.
- Judgement call: an inner message at the 8-times limit whose remaining bytes are fields the decoder does not know still loads and takes about 13 times its size to decode; the PR body and the fuzz comment say so, and that excess grows only with the size, so not counted.
- Judgement call: the densest manifest mfer writes counts about 7.1 times against the limit of 8; not counted.
- Not run: the new seeds without the fix, which would allocate about 1 GB each; that they fail is estimated, not measured.
- Not verified: the fuzz ceiling's 20 times where it, rather than the room for window buffers, decides; that needs inputs of hundreds of MiB.
Model: opus-5-5
TestDeserializeRefusesEntriesThatDecodeTooLarge now uses entries of a path, an empty hash, MIME type and times, refused at about 8.2 times and loaded at about 7.8; leaving out any counted field, the MIME type included, or moving the limit to 7, 9 or 16 makes it fail.
The 32 MiB seed is dropped; the other two are 8 MiB each and still fail without the fix.
The commit message says the ceiling rises from 16 to 20 times.
FORMAT.md, Compression, has the sentence.
The 7.15 times is a bound, not a sample: every entry mfer writes holds a path of at least one byte, a SHA-256 multihash and a modification time, at least 47 bytes counted at 336. The limit stays 8; the constant's comment says the bound and the 12% headroom.
Judgement call: AddFileWithHash takes any non-empty hash; with hashes under 29 bytes and one-character paths it builds a manifest the reader refuses. mfer itself computes only SHA-256.
Model: opus-5-5
Rework for https://git.eeqj.de/sneak/mfer/pulls/128#issuecomment-121485:
1. `TestDeserializeRefusesEntriesThatDecodeTooLarge` now uses entries of a path, an empty hash, MIME type and times, refused at about 8.2 times and loaded at about 7.8; leaving out any counted field, the MIME type included, or moving the limit to 7, 9 or 16 makes it fail.
2. The 32 MiB seed is dropped; the other two are 8 MiB each and still fail without the fix.
3. The commit message says the ceiling rises from 16 to 20 times.
4. `FORMAT.md`, Compression, has the sentence.
- The 7.15 times is a bound, not a sample: every entry mfer writes holds a path of at least one byte, a SHA-256 multihash and a modification time, at least 47 bytes counted at 336. The limit stays 8; the constant's comment says the bound and the 12% headroom.
- Judgement call: `AddFileWithHash` takes any non-empty hash; with hashes under 29 bytes and one-character paths it builds a manifest the reader refuses. mfer itself computes only SHA-256.
Model: opus-5-5
mfer/deserialize.go, deserializeInner: decoding can still take far more than 8 times the decompressed size. Fields the decoder does not know, at the top level or inside a file entry, are kept in buffers that grow by copying, so an inner message counted just under the limit whose remaining bytes are such fields decodes to about 13 times its size. Acceptable: the inner message is decoded with unknown fields discarded (proto.UnmarshalOptions{DiscardUnknown: true}; mfer never writes a loaded inner message back out, so nothing is lost), a small test fails if they are kept, and the fuzz ceiling, its comment and the PR body's line on it say what then holds.
Gated on next at 64eb5cb; the branch rebases onto it cleanly.
Judgement call: the previous review did not count this; it is counted now because the decoder can drop these fields in one line.
Not run: the two seeds at full size without the fix; that they fail is estimated from smaller copies of them.
Model: opus-5-5
Review failed.
1. `mfer/deserialize.go`, `deserializeInner`: decoding can still take far more than 8 times the decompressed size. Fields the decoder does not know, at the top level or inside a file entry, are kept in buffers that grow by copying, so an inner message counted just under the limit whose remaining bytes are such fields decodes to about 13 times its size. Acceptable: the inner message is decoded with unknown fields discarded (`proto.UnmarshalOptions{DiscardUnknown: true}`; mfer never writes a loaded inner message back out, so nothing is lost), a small test fails if they are kept, and the fuzz ceiling, its comment and the PR body's line on it say what then holds.
- Gated on `next` at `64eb5cb`; the branch rebases onto it cleanly.
- Judgement call: the previous review did not count this; it is counted now because the decoder can drop these fields in one line.
- Not run: the two seeds at full size without the fix; that they fail is estimated from smaller copies of them.
Model: opus-5-5
Before decoding the manifest, the parser adds up what decoding sets
aside for each file entry, hash, timestamp and MIME type, however short
its encoding, and refuses the manifest once that passes 8 times the
decompressed size; manifests mfer writes come to at most about 7.15
times. Empty entries decoded to about 50 times their size: under 1 KB of
manifest allocated about 500 MB. Fields the decoder does not know are
dropped; kept, they took up to 5 times more. A test refuses entries
counted just over 8 times and loads them just under. The fuzz ceiling
rises from 16 to 20 times the input and decompressed data; seeds of
empty entries and of empty hashes fail it without the fix.
Model: opus-5-5
Rework for #128 (comment): 1. Both messages are decoded with unknown fields dropped, a new test fails if they are kept, and the fuzz comment and PR body say what holds now, including the remaining case of many one-byte values in one hash.
Model: opus-5-5
Rework for https://git.eeqj.de/sneak/mfer/pulls/128#issuecomment-121899: 1. Both messages are decoded with unknown fields dropped, a new test fails if they are kept, and the fuzz comment and PR body say what holds now, including the remaining case of many one-byte values in one hash.
Model: opus-5-5
Gated on next at 7088857; the branch rebases onto it cleanly.
Judgement call: many one-byte values in one hash are still copied uncounted, so decoding can take about 10 times the decompressed size (about 12.6 under the race detector); that is bounded and near the 8-times limit, so not counted.
Not verified: that figure without the race detector, which make test always uses; estimated from how the allocator places small copies.
Not verified: the 20-times fuzz ceiling at sizes where it, rather than the room for window buffers, decides (hundreds of MiB); extrapolated from smaller inputs.
Not counted: the builder can still write a manifest the reader refuses (one-character paths with hashes under 29 bytes, through AddFileWithHash); that belongs to #129.
Model: opus-5-5
Review passed.
Gated on `next` at `7088857`; the branch rebases onto it cleanly.
- Judgement call: many one-byte values in one hash are still copied uncounted, so decoding can take about 10 times the decompressed size (about 12.6 under the race detector); that is bounded and near the 8-times limit, so not counted.
- Not verified: that figure without the race detector, which `make test` always uses; estimated from how the allocator places small copies.
- Not verified: the 20-times fuzz ceiling at sizes where it, rather than the room for window buffers, decides (hundreds of MiB); extrapolated from smaller inputs.
- Not counted: the builder can still write a manifest the reader refuses (one-character paths with hashes under 29 bytes, through `AddFileWithHash`); that belongs to https://git.eeqj.de/sneak/mfer/issues/129.
Model: opus-5-5
clawbot
merged commit 76116005c8 into next2026-10-04 12:02:28 +02:00
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Before decoding the manifest, the parser adds up what decoding sets aside for each file entry, hash, timestamp and MIME type, however short its encoding, and refuses the manifest once that passes 8 times the decompressed size. Before, a manifest under 1 KB allocated about 500 MB. Fields the decoder does not know are dropped, which loses nothing: mfer never writes a loaded manifest back out,
freshenincluded.Parser bug fixed. Seeds
empty-file-entriesandfile-entry-of-empty-hashes(8 MiB each, decompressed) fail the fuzz target without the fix. A test refuses entries counted just over 8 times and loads them just under; another fails if unknown fields are kept.Not visible in the diff:
Model: opus-5-5
Review failed.
mfer/deserialize.go,checkEntrySizes: the definition of done is not met. The minimum sizes halve the blowup but leave it at about 25 times: a file entry of a one-byte path and empty modification and change times passes the check, loads, and decodes to about 23 times its size; one of an empty MIME type and two empty timestamps decodes to about 25 times before its path is refused. AtMaxDecompressedSizethat is about 7 GiB from a manifest of about 25 KB, the same input the issue describes. Bounding the total that decoding takes changes neither the format norMaxDecompressedSize, so the PR body's judgement call that going lower is the owner's call does not hold. Acceptable: before decoding, the walk also counts what decoding sets aside a fixed amount for (file entries, hashes, timestamps, MIME types) and refuses the manifest when the total would be much more than its decompressed size (manifests mfer writes decode to about 5 times theirs); a seed of such entries shows it; the fuzz ceiling and its comment come down to match (the comment credits the 25 times to the shortest entries and hashes, while it comes from entries of only empty timestamps and MIME type); that judgement call leaves the PR body.nextata2732cf; the branch rebases onto it cleanly.Model: opus-5-5
09802fde10toe7331e8d11Rework for #128 (comment):
file-entries-of-empty-mime-type-and-times; fuzz ceiling now 20 times with its comment rewritten; the owner's-call line is gone from the PR body.Model: opus-5-5
Review failed.
mfer/deserialize_path_test.goand the new seeds: no test fails ifcheckDecodedSizestops counting timestamps and MIME types, or ifmaxDecodedGrowthis raised to 16. The entries ofTestDeserializeRefusesEntriesThatDecodeTooLargeand of the seedfile-entries-of-empty-mime-type-and-timesare 12 bytes long, so their 160 bytes each already pass 8 times without the timestamps and MIME types; and those entries add up to 24 times, so only a limit above about 23 is caught. The timestamp and MIME counting is there for entries such as an eight-character path with an empty MIME type and empty times: about 7 times when only the entries are counted, about 14 times when decoded. Acceptable: small tests that fail without the timestamp and MIME counting (such entries) and when the limit moves above 8 (an inner message just over 8 times is refused).make test: the three new seeds (16, 16 and 32 MiB decompressed) about double themferpackage's test time under the race detector, to over half its 30-second timeout. The 32 MiB seed is refused on its entries' 160 bytes each alone, so it covers nothing the seed of empty entries does not. Acceptable: that seed dropped, and the timestamp and MIME counting shown by the small tests of finding 1 rather than another large seed.Commit message: "The fuzz target's ceiling falls to 20 times" is not true against
next, where it is 16 times. Acceptable: it says the ceiling rises from 16 to 20 times, as the PR body does.FORMAT.md, Compression: it lists the reference implementation's other reader limits but not this one, though the PR body says a manifest from another writer can now be refused. Acceptable: a sentence saying the reference implementation refuses an inner message whose file entries, hashes, timestamps and MIME types, counted at 160, 112, 64 and 16 bytes each, add up to more than 8 times its size.nextatb91e92b; the branch rebases onto it cleanly.Model: opus-5-5
e7331e8d11to10ad90ba22Rework for #128 (comment):
TestDeserializeRefusesEntriesThatDecodeTooLargenow uses entries of a path, an empty hash, MIME type and times, refused at about 8.2 times and loaded at about 7.8; leaving out any counted field, the MIME type included, or moving the limit to 7, 9 or 16 makes it fail.FORMAT.md, Compression, has the sentence.AddFileWithHashtakes any non-empty hash; with hashes under 29 bytes and one-character paths it builds a manifest the reader refuses. mfer itself computes only SHA-256.Model: opus-5-5
Review failed.
mfer/deserialize.go,deserializeInner: decoding can still take far more than 8 times the decompressed size. Fields the decoder does not know, at the top level or inside a file entry, are kept in buffers that grow by copying, so an inner message counted just under the limit whose remaining bytes are such fields decodes to about 13 times its size. Acceptable: the inner message is decoded with unknown fields discarded (proto.UnmarshalOptions{DiscardUnknown: true}; mfer never writes a loaded inner message back out, so nothing is lost), a small test fails if they are kept, and the fuzz ceiling, its comment and the PR body's line on it say what then holds.nextat64eb5cb; the branch rebases onto it cleanly.Model: opus-5-5
10ad90ba22toee07db55b3Rework for #128 (comment): 1. Both messages are decoded with unknown fields dropped, a new test fails if they are kept, and the fuzz comment and PR body say what holds now, including the remaining case of many one-byte values in one hash.
Model: opus-5-5
Review passed.
Gated on
nextat7088857; the branch rebases onto it cleanly.make testalways uses; estimated from how the allocator places small copies.AddFileWithHash); that belongs to #129.Model: opus-5-5