Bound decoder work to prevent a pointer fan-out DoS (STF-1570) - #281
Bound decoder work to prevent a pointer fan-out DoS (STF-1570)#281oschwald wants to merge 13 commits into
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Included review availability: Your plan provides up to 4 included reviews per hour; 1 remains after this review. 📝 WalkthroughWalkthroughVersion 1.14.0 adds depth and value limits to the pure PHP decoder. It rejects oversized containers, pointer cycles, excessive pointer expansion, and over-deep data with ChangesDecoder resource limits
Estimated code review effort: 3 (Moderate) | ~20 minutes Merge Risk: 🟡 Moderate · up to The decoder adds work and recursion limits, but the current implementation may allow one level beyond the documented recursion cap, while an oversized-map test may not verify the intended early rejection. These bounded security and validation concerns should be addressed before merge. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
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Inline comments:
In `@src/MaxMind/Db/Reader/Decoder.php`:
- Around line 313-315: Update decodeMap so its budget precheck accounts for both
the key and value decoded for every map entry, charging two child values per
entry. Use a division-based overflow-safe precheck before multiplying, and
preserve InvalidDatabaseException for oversized declarations, including on
32-bit PHP.
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Pull request overview
This PR mitigates a denial-of-service vector in the pure-PHP MaxMind DB decoder where crafted pointer fan-out can cause exponential decode work from a small database, by introducing per-lookup resource limits.
Changes:
- Add per-lookup decode limits (max depth + max value budget) to bound pointer fan-out and over-deep/cyclic structures.
- Add unit tests covering pointer fan-out rejection and cyclic pointer rejection.
- Document the security fix in the changelog (1.14.0).
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.
| File | Description |
|---|---|
| src/MaxMind/Db/Reader/Decoder.php | Introduces depth and per-lookup value budget tracking during decoding to bound work and reject abusive databases. |
| tests/MaxMind/Db/Test/Reader/DecoderTest.php | Adds regression tests for pointer fan-out and pointer cycles throwing InvalidDatabaseException. |
| CHANGELOG.md | Notes the DoS fix and the new InvalidDatabaseException behavior for over-limit/cyclic/over-deep data. |
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Actionable comments posted: 2
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Inline comments:
In `@src/MaxMind/Db/Reader/Decoder.php`:
- Around line 108-114: Update both depth-limit comparisons in the decode logic,
including the check near decodeWithBudget and the corresponding check at the
other reported location, from allowing values greater than MAX_DEPTH to
rejecting values greater than or equal to self::MAX_DEPTH. Preserve the existing
InvalidDatabaseException behavior.
In `@tests/MaxMind/Db/Test/Reader/DecoderTest.php`:
- Around line 463-476: Update testOversizedMapIsBounded to assert the expected
exception message “exceeds the maximum number of values” in addition to
InvalidDatabaseException, confirming Decoder::enterContainer() rejects the
oversized map before decoding entries.
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Pull request overview
Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.
Suppressed comments (3)
src/MaxMind/Db/Reader/Decoder.php:90
decodeWithBudget()is used as a 2-tuple[value, nextOffset], but its phpdoc currently says@return array<mixed>. This makes the internal API contract unclear and can break static analysis.
/**
* @return array<mixed>
*/
private function decodeWithBudget(int $offset, int $depth, int &$budget): array
src/MaxMind/Db/Reader/Decoder.php:112
- The depth limit is described as 512, but using
>means the decoder will still recurse once more at exactlyMAX_DEPTH(effectively allowing depth 513 starting from 0). If the intent is to cap nesting at 512, this should be>=here (and inenterContainer()).
if ($depth > self::MAX_DEPTH) {
throw new InvalidDatabaseException(
"The MaxMind DB file's data section exceeds the maximum depth"
);
}
src/MaxMind/Db/Reader/Decoder.php:220
- Same off-by-one issue as the pointer-follow path:
>makes the effective maximum nesting one deeper thanMAX_DEPTHwhen depth counting starts at 0. Use>=to enforce the stated depth limit consistently.
if ($depth > self::MAX_DEPTH) {
throw new InvalidDatabaseException(
"The MaxMind DB file's data section exceeds the maximum depth"
);
}
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Pull request overview
Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.
Suppressed comments (1)
src/MaxMind/Db/Reader/Decoder.php:90
decodeWithBudget()returns the same 2-tuple asdecode()([value, nextOffset]), but its new phpdoc declares@return array<mixed>, which is misleading for static analysis and IDEs. Update it to a shaped array return type.
/**
* @return array<mixed>
*/
private function decodeWithBudget(int $offset, int $depth, int &$budget): array
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Pull request overview
Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.
Suppressed comments (1)
Previously missed (1) — in code that hasn't changed since the last review.
src/MaxMind/Db/Reader/Decoder.php:89
decodeWithBudget()always returns[value, nextOffset]except in pointer-test-hack mode where pointers return a 1-element array. The new@return array<mixed>PHPDoc is too vague/inaccurate for static analysis and IDE help; it should document the tuple shape (and the pointer-test-hack exception) explicitly.
/**
* @return array<mixed>
*/
private function decodeWithBudget(int $offset, int $depth, int &$budget): array
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🔵 Needs a closer look
It makes substantial security- and correctness-critical changes to the core decoder behavior and resource-limiting logic that warrant final human verification despite targeted test coverage.
Review details
Suppressed comments (6)
tests/MaxMind/Db/Test/ReaderTest.php:329
- This test opens a Reader but does not close it on the exception path. Use try/finally around the get() call so the Reader is always closed.
$this->expectException(InvalidDatabaseException::class);
$this->expectExceptionMessage("The MaxMind DB file's data section exceeds the maximum payload size");
$reader = new Reader('tests/data/test-data/MaxMind-DB-test-payload-amplification-dos-string.mmdb');
$reader->get('1.1.1.1');
}
tests/MaxMind/Db/Test/ReaderTest.php:359
- This test opens a Reader but does not close it when the expected InvalidDatabaseException is thrown. Close the Reader in a finally block to avoid leaking resources.
$this->expectException(InvalidDatabaseException::class);
$this->expectExceptionMessage("The MaxMind DB file's data section exceeds the maximum payload size");
$reader = new Reader('tests/data/test-data/MaxMind-DB-test-decoder-payload-limit-over.mmdb');
$reader->get('1.1.1.1');
}
tests/MaxMind/Db/Test/ReaderTest.php:380
- This test opens a Reader but never closes it if get() throws as expected. Use try/finally to ensure the Reader is closed even on the exception path.
$this->expectException(InvalidDatabaseException::class);
$this->expectExceptionMessage("The MaxMind DB file's data section exceeds the maximum number of values");
$reader = new Reader('tests/data/test-data/MaxMind-DB-test-pointer-decoder-dos.mmdb');
$reader->get('1.1.1.1');
}
tests/MaxMind/Db/Test/ReaderTest.php:390
- This test opens a Reader but does not close it on the exception path. Close the Reader in a finally block so the file handle is released reliably.
$this->expectException(InvalidDatabaseException::class);
$this->expectExceptionMessage("The MaxMind DB file's data section exceeds the maximum number of values");
$reader = new Reader('tests/data/test-data/MaxMind-DB-test-pointer-decoder-dos-ipv6.mmdb');
$reader->get('::1');
}
tests/MaxMind/Db/Test/ReaderTest.php:416
- This test opens a Reader but never closes it when get() throws as expected. Wrap get() in try/finally and close the Reader in finally to prevent leaking file handles.
$this->expectException(InvalidDatabaseException::class);
$this->expectExceptionMessage("The MaxMind DB file's data section exceeds the maximum number of values");
$reader = new Reader('tests/data/test-data/MaxMind-DB-test-decoder-value-limit-over.mmdb');
$reader->get('1.1.1.1');
}
tests/MaxMind/Db/Test/ReaderTest.php:340
- This test opens a Reader but never closes it when the expected exception is thrown. Wrap the lookup in try/finally and close the Reader to avoid leaking file handles.
$this->expectException(InvalidDatabaseException::class);
$this->expectExceptionMessage("The MaxMind DB file's data section exceeds the maximum payload size");
$reader = new Reader('tests/data/test-data/MaxMind-DB-test-payload-amplification-dos-worst-case.mmdb');
$reader->get('1.1.1.1');
}
- Files reviewed: 10/10 changed files
- Comments generated: 1
- Review effort level: Lite
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🟡 Changes recommended
ExtensionDosTest currently asserts an exact exception message substring via expectExceptionMessage(), but the extension prefixes libmaxminddb error text, making these tests brittle/incorrect and likely to fail.
Once you've addressed the issues Copilot identified, you can request another Copilot review.
Review details
Suppressed comments (5)
tests/MaxMind/Db/Test/Reader/ExtensionDosTest.php:83
expectExceptionMessage()asserts an exact match, but the extension prefixes the libmaxminddb error text (see ext/maxminddb.c formatting like"Error while looking up data for %s. %s"). This should match the substring instead to avoid brittle failures.
$this->expectExceptionMessage(self::LIMIT_MESSAGE);
tests/MaxMind/Db/Test/Reader/ExtensionDosTest.php:95
expectExceptionMessage()requires the full exception message to equalLIMIT_MESSAGE, but the extension'sInvalidDatabaseExceptionmessage includes additional context (IP address + prefix). Match the decoder-limit text as a substring/regex instead.
$this->expectExceptionMessage(self::LIMIT_MESSAGE);
tests/MaxMind/Db/Test/Reader/ExtensionDosTest.php:103
- The maxminddb extension's exception message is not just the raw libmaxminddb error text; it is wrapped with a prefix (e.g.,
Error while looking up data for ...).expectExceptionMessage()will fail unless the full message matches exactly, so prefer a regex match onLIMIT_MESSAGE.
$this->expectExceptionMessage(self::LIMIT_MESSAGE);
tests/MaxMind/Db/Test/Reader/ExtensionDosTest.php:111
expectExceptionMessage()checks exact equality, but the extension wraps the libmaxminddb message with additional text. UseexpectExceptionMessageMatches()(or build the full expected string) so the test asserts the intended condition.
$this->expectExceptionMessage(self::LIMIT_MESSAGE);
tests/MaxMind/Db/Test/Reader/ExtensionDosTest.php:119
- This uses
expectExceptionMessage()with the raw limit substring, but the extension prepends context to the message. Matching viaexpectExceptionMessageMatches()avoids false failures while still asserting the limit was hit.
$this->expectExceptionMessage(self::LIMIT_MESSAGE);
- Files reviewed: 11/11 changed files
- Comments generated: 1
- Review effort level: Lite
A crafted data section could nest pointers to shared targets so that decoding one record cost exponential time and memory from a small file (GHSA-hj94-g986-h9r7). The pure PHP decoder now limits the number of values it decodes for a single record and rejects a database that exceeds the limit with an InvalidDatabaseException. The limit is 65,536, far above the few hundred values the largest real records decode. The count follows the flat rule from the MaxMind DB specification: the root is one value, each array and map charges its declared children before it reads any of them, and a pointer costs nothing beyond the value it resolves to. Pointer cycles and over-deep data are rejected by a depth limit of 512 rather than exhausting the stack, which PHP cannot recover from. Both limits are the ones the specification recommends. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
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Pointers to a shared string or bytes value can amplify copied payload without exceeding the decoded-value limit. Bound each decode to 2 MiB of string and bytes payload. Charge each occurrence before reading it, including map keys and values reached through pointers. Reject scalar declarations above 16 bytes before reading their payload. Both checks throw InvalidDatabaseException. The budgets are passed by reference within one decode call. Update the shared fixtures and test amplification, payload boundaries, and metadata rejection through both the PHP reader and the extension. Assert each implementation's error text and the full boundary result. Probe the extension with a small over-limit record before larger DoS fixtures. Skip libraries older than 1.14.0 without the fix, accept working backports, and fail if 1.14.0 or later does not enforce the limit. Unexpected probe errors propagate. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Run the shared IPv4 and IPv6 pointer fan-out fixtures through both reader implementations and assert InvalidDatabaseException with the expected limit message. Assert all 65,535 array elements at the 65,536-value boundary, including on a second lookup with the same reader. Also accept the depth-15 pointer fan-out with 65,535 values and reject the fixture one value over the limit. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Update the bundled library from 1.13.3 to 1.14.0 and match its reported version. The new library bounds MMDB_get_entry_data_list() to 65,536 values and 2 MiB of payload per call. The extension already converts MMDB_DECODER_LIMIT_ERROR into InvalidDatabaseException. The shared ReaderTest limit checks now run against bundled builds instead of skipping. A failed probe on 1.14.0 or later fails the tests automatically. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
The value and payload budgets were passed by reference through every recursive decode call. On GeoLite2-City lookups that cost about 3.5% per lookup against main, most of the total cost of the resource limits. Keep both budgets as decoder properties instead and reset them at the start of each decode() call, so every call still starts with the full allowance. No other lookup can observe them mid-decode: PHP runs one request per thread, and the decoder never yields while it decodes. The same GeoLite2-City benchmark then runs within about 1% of main. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Every read seeked first and then called ftell() to check the length. fseek() discards PHP's read buffer, so each small read of a control byte, a size, or a scalar became its own system call. Most of a record is laid out in order, so nearly all of those seeks landed where the stream already was. Give the decoder its own read method that tracks the stream position and seeks only when a read does not continue from the previous one, which is a pointer follow or the first read of a call. The position is reset at the start of each decode() call because the search tree walk moves the stream between calls. Util::read, which the tree walk still uses, checks the length with strlen() instead of ftell(); string length is stored, so the comment claiming ftell() was faster no longer holds. On GeoLite2-City, 60,000 lookups per process over five alternating runs, main takes 172.5 to 173.4 us per lookup and this branch 105.2 to 106.0, about 40% faster, with identical results. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
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Nice. Claude had a few comments as usual...
| // The value at the pointer's position was charged by its containing | ||
| // array or map, so the target costs nothing more. Only the depth | ||
| // grows. | ||
| [$result] = $this->decodeWithBudget($pointer, $depth + 1); |
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Pointer-to-pointer is not rejected, so a 198 KB file still costs 9.8 s per lookup.
The spec says it is illegal (MaxMind-DB-spec.md:310, "It is illegal for a pointer to point to another pointer"), and libmaxminddb enforces it at src/maxminddb.c:1819-1821. Here a pointer follow charges only depth, never the value or byte budget, so chains are free.
That lets an attacker multiply the maximum array width by the maximum chain length: an array of 65,535 pointers, each aimed at one shared 508-long pointer chain. I built it and ran it against this branch:
| Input | Result |
|---|---|
| 198,135-byte crafted data section | decodes successfully in 9.82 s |
| normal GeoIP2-City lookup | 99.7 µs |
About 98,000x, and it stays inside all three new limits. This is bounded and linear rather than exponential, so the PR meets its stated goal, but 9.8 s of CPU from a 198 KB file is still usable as a denial of service.
Rejecting pointer-to-pointer removes the chain multiplier and costs nothing for valid data. I instrumented the decoder and counted pointer-to-pointer follows across 57,600 lookups on all 40 valid test fixtures: zero. The depth tests added in this PR use pointer-to-array (DecoderTest.php:539-551), so they keep passing.
Also worth noting that the pure PHP reader and the bundled extension currently disagree on this input.
🤖 Comment by Claude (Claude Code) on behalf of Will.
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Fixed in 3241a02. The decoder rejects a pointer as soon as its target's control byte identifies another pointer, without an extra stream read. New tests cover a direct chain and a cycle through a container. The existing pointer-to-container depth tests still pass.
Codex, responding on behalf of the author.
| * | ||
| * @param int<0, max> $numberOfBytes | ||
| */ | ||
| private function read(int $offset, int $numberOfBytes): string |
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The position cache turns re-entrancy into a silently wrong record.
$this->position is a claim about a handle Decoder does not own. Reader::readNode() moves the same handle through Util::read() (Reader.php:261, :273, :290), which knows nothing about the cache. Today the only thing holding this together is that nothing runs between decode()'s reset and its last read. That invariant is unenforced and breakable.
The comment at Decoder.php:127-129 says it cannot happen:
No other lookup can observe them mid-decode: PHP runs one request per thread, and the decoder never yields while it decodes.
fread() on a userland stream wrapper runs PHP code, and Reader::__construct opens an arbitrary path string, so a proto:// path reaches a registered wrapper. I re-entered Reader::get() from stream_read() against the stock MaxMind-DB-test-decoder.mmdb, sweeping 60 different re-entry points:
| correct | threw | silently wrong | |
|---|---|---|---|
main |
0 | 60 | 0 |
| this branch | 47 | 10 | 3 |
A wrong record, no exception, nothing to grep for. Reachability is low, but the failure mode moved from loud to silent, and that is the part worth fixing.
A guard inside decode() alone does not close it: in my proof of concept the desync started in findAddressInTree() -> Util::read(), before the inner decode() ran. Put a busy flag on Reader::getWithPrefixLen(), or give Decoder its own fopen() handle so nothing else can move it.
🤖 Comment by Claude (Claude Code) on behalf of Will.
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If the user is wrapping a stream and doing weird things in that wrapper, this kind of feels like their issue. However, I guess we can guard against it even though the guard does come at a small cost.
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Fixed in bca4e14. The guard runs in getWithPrefixLen() before the tree walk, and finally clears it after success or failure. Tests cover a stream callback that propagates the rejection, one that catches it, and another lookup on the same reader afterward.
I reran the benchmark against the previous PR head, 5658655, using the full 65 MB GeoLite2-City database. Ten alternating pairs of fresh PHP 8.5.5 processes, pinned to one CPU, used 5,000 warmup lookups per process. The timed totals were:
| Workload | Lookups per version | Previous median µs | Current median µs | Change |
|---|---|---|---|---|
| Full City database | 500,000 | 99.369 | 100.129 | +0.76% |
| Small-record fixture | 2,500,000 | 7.207 | 7.263 | +0.77% |
This measures both the pointer validation and the reentrancy guard. Records and network prefixes matched for all sampled addresses. Peak allocated PHP memory was 2 MiB in both versions. CLI OPcache was disabled.
Codex, responding on behalf of the author.
| // much slower. | ||
| if ($value !== false && ftell($stream) - $offset === $numberOfBytes) { | ||
| // Check that the number of bytes read is the number asked for. | ||
| if ($value !== false && \strlen($value) === $numberOfBytes) { |
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This change also removed an accidental re-entrancy detector.
The old ftell($stream) - $offset === $numberOfBytes check failed whenever something else moved the handle between the fseek and the ftell. That is why main throws on every re-entrant lookup instead of returning bad data. strlen() is the correct check for the short-read case and is faster, so this is the right change on its own, but it is the second half of the silent-corruption path described on Decoder::read().
Worth a comment here noting that nothing now detects a moved handle.
🤖 Comment by Claude (Claude Code) on behalf of Will.
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The Reader guard in bca4e14 now prevents a nested lookup from moving the shared stream. Its comments document that invariant at the guard and at decoder entry. The strlen() short-read check can stay without relying on ftell() to detect reentrancy.
Codex, responding on behalf of the author.
| // Compare with a division rather than multiplying the declared size, so | ||
| // an oversized declaration cannot overflow the integer on 32-bit builds | ||
| // before the budget check runs. | ||
| if ($size > intdiv($this->budget, $valuesPerEntry)) { |
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The overflow rationale in the comment above is not true.
Two independent reasons:
- The overflow is unreachable.
$sizecomes fromsizeFromCtrlByte(), whose largest output is0xFFFFFF + 65821= 16,843,036.$valuesPerEntryis only ever 1 or 2, so the product tops out at 33,686,072, well underPHP_INT_MAXon a 32-bit build (2,147,483,647). - PHP does not wrap on integer overflow. It promotes to float, so
$size * $valuesPerEntry > $this->budgetwould still compare correctly even if the product did overflow.
The two forms are equivalent for positive integers, so intdiv() is a fine style choice. The problem is the comment presents it as a safety requirement. Someone will either refuse to simplify it, or copy the "division guards overflow" pattern somewhere it does not hold. Drop the justification, or state the real intent.
🤖 Comment by Claude (Claude Code) on behalf of Will.
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Removed the overflow rationale in 87b1147. The division check still expresses the remaining entry allowance, but the comment no longer presents it as necessary for integer safety.
Codex, responding on behalf of the author.
| // reject it before the read, so the error is the payload limit and not | ||
| // the short read that would otherwise follow. 0x5f is a string with | ||
| // size code 31, then three size bytes for | ||
| // 2,097,153 - 65,821 = 2,031,332 (0x1eff64). |
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The hex is wrong, so this is not the boundary test it says it is.
The subtraction is right, the conversion is not: 2,031,332 is 0x1EFEE4, not 0x1EFF64.
The fixture written on the next line is "\x5f\x1e\xff\x64", so the declared size is 0x1EFF64 + 65,821 = 2,097,281, which is 129 bytes past the limit rather than one.
The test passes either way, but it is presented as an off-by-one boundary and it is not one, and no decoder-level test covers 2,097,152 (allowed) against 2,097,153 (rejected). Either change the bytes to "\x5f\x1e\xfe\xe4" and keep the comment, or correct the comment to 2,097,281.
🤖 Comment by Claude (Claude Code) on behalf of Will.
| * the previous one ended. Most values in a record are laid out in order, and | ||
| * fseek() discards PHP's read buffer, so seeking before every read turned | ||
| * each small read into a system call. Skipping the seek makes a City lookup | ||
| * about 40% faster. |
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A hard percentage in a permanent comment will rot.
There is no benchmark in the repo, no PHP version and no workload definition beyond "a City lookup", so nothing will re-verify this. CHANGELOG.md already carries the number, and changelog entries are dated and versioned in a way code comments are not. Keep the mechanism here and drop the figure.
Same at Decoder.php:126, "costs a few percent per lookup".
While I am here: the mechanism as stated is a little strong. php_stream_seek() has a fast path for a forward SEEK_SET inside the buffered region, so fseek() does not unconditionally discard the buffer. The reason the change helps is narrower and more interesting: that fast path is gated on offset > stream->position, so a seek to the position the stream is already at, the dominant case in sequential decoding, misses it and takes the full invalidate-and-syscall path.
🤖 Comment by Claude (Claude Code) on behalf of Will.
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Removed both performance percentages and the unconditional buffer-invalidation claim in 87b1147. The read comment now states only that consecutive reads avoid seeking. Benchmark results are recorded in the PR description and the reentrancy reply.
Codex, responding on behalf of the author.
| // pointers to one large string or bytes value keeps the value count low | ||
| // while forcing the reader to copy the target once per pointer. This | ||
| // second, independent limit bounds the total string and bytes payload | ||
| // copied for one lookup to 2 MiB, matching libmaxminddb and the Go reader. |
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Citing sibling implementations rather than the spec.
The libmaxminddb half is true today: MAXIMUM_DATA_STRUCTURE_BYTES (1U << 21) at src/maxminddb.c:74, with depth 512 and values 1U << 16 matching too. But there they are #ifndef-overridable at build time while these constants are hard-coded, so "matching" already holds only for the C defaults. The Go claim cannot be checked from this repo at all.
The spec's Reader Resource Limits section is the stable reference, and libmaxminddb's own comments cite it rather than us. The CHANGELOG already names it.
🤖 Comment by Claude (Claude Code) on behalf of Will.
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Removed the comparisons with Go and libmaxminddb in 87b1147. The comment explains why each visit to a shared target charges its payload again. The PR description also makes clear that the specification leaves the payload strategy to each reader, rather than requiring 2 MiB.
Codex, responding on behalf of the author.
| /** | ||
| * Applies the per-lookup limits when entering a container. The depth limit | ||
| * stops cycles and over-deep data (checked here and at pointer follows, | ||
| * the only places depth grows). The value budget is charged per declared |
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enterContainer() is not where depth grows.
It checks the container's own depth. Growth happens at the three $depth + 1 sites: Decoder.php:170 for a pointer follow, :359 for array elements, and :445-446 for map keys and values.
The parenthetical also omits the consequence that matters: the depth guard never runs on the scalar path, because decodeByType's scalar branch has no check. That is correct behaviour under the spec, where a scalar does not add a level, and it is why testPointerChainAtMaximumDepthDecodes passes. It is just not what this sentence says.
🤖 Comment by Claude (Claude Code) on behalf of Will.
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Removed the inaccurate parenthetical in 87b1147. The shorter comment explains charging declared children and revisiting shared containers. The depth-boundary tests still cover the allowed scalar leaf at maximum depth.
Codex, responding on behalf of the author.
| private function decodeMap(int $size, int $offset): array | ||
| private function decodeMap(int $size, int $offset, int $depth): array | ||
| { | ||
| // A map entry decodes a key and a value, so it costs two values. |
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Third statement of the same fact.
The value-charging rule is already spelled out at Decoder.php:76-81 and again at :322-323. Comments are 46% of the added lines in this file. Most of that is earned, since the security invariants here are genuinely invisible in the code, but this one and a couple of others restate what the line below already says.
The strongest comment in the diff, for contrast, is at :216-220: it states that the payload charge is per-decode rather than per-distinct-target, which is the entire reason the limit works and is nowhere visible in the three lines beneath it.
🤖 Comment by Claude (Claude Code) on behalf of Will.
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Shortened the repeated explanations in decode() and enterContainer() in 87b1147. Kept the brief map comment because it explains the literal 2 at the call site, and retained the explanation of charging payload on every decode.
Codex, responding on behalf of the author.
| * The bundled libmaxminddb used by `--with-maxminddb-bundled` builds of the | ||
| extension now applies the same decoder limits. The extension throws an | ||
| `InvalidDatabaseException` when a lookup exceeds them. | ||
| * The pure PHP reader is about 40% faster on City lookups. It no longer seeks |
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The 40% figure is conservative, if you want to claim more.
I benchmarked both branches on GeoIP2-City-Test, 40,000 lookups after a 2,000-lookup warmup, three alternating runs:
| µs per lookup | |
|---|---|
main |
182.4 / 191.4 / 182.9 |
| this branch | 89.9 / 90.7 / 89.9 |
About 51% faster on this machine, against the 39% in the PR description's table. Different hardware, so the number is not directly comparable, but the claim holds comfortably.
🤖 Comment by Claude (Claude Code) on behalf of Will.
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Keeping the conservative 40% figure in the changelog. The measurements vary with the workload and machine, so the higher result does not justify a broader claim.
Codex, responding on behalf of the author.
Enforce the format rule before following a second pointer. This removes the chain multiplier from repeated pointer decoding without adding stream reads. Keep pointers inside target containers valid, with the depth limit still bounding container cycles.
A PHP stream wrapper can call back into the reader during a read. Reject the nested lookup before it moves the shared stream or resets the decoder budgets, and clear the guard when the outer lookup returns or throws. Cover callbacks that propagate or catch the rejection, and verify that the same reader can perform another lookup afterward.
Correct the encoded size to 2,097,153 bytes. The previous header declared 2,097,281 bytes, so it did not test the boundary described by the comment.
Reuse the same decoder after a partially charged value or payload budget fails, then decode a record at the corresponding limit. Also move the stream between calls to verify that the cached position is discarded.
The decoder applies the same limits to metadata and lookup records. Remove the data-section label so metadata failures describe the correct scope without adding context to the decode path.
The shared decoder-limit probe uses str_contains() on supported PHP 7 versions. Require its polyfill in require-dev instead of depending on the formatter to install it.
Keep the budget counting and sequential-read rules. Remove repeated explanations, benchmark percentages, and unsupported claims about buffer invalidation, integer overflow, and record sizes.
Fixes STF-1570. Crafted databases can make a decoder repeatedly expand shared pointer targets, consuming excessive CPU or memory during one lookup.
The pure PHP decoder now limits each lookup to:
The value and depth limits follow the MaxMind DB specification. The specification leaves the payload strategy to each reader. Oversized fixed-width scalars and pointers that directly target other pointers are also rejected. Limit failures throw
InvalidDatabaseException, including during metadata decoding.The bundled libmaxminddb pin includes its decoder resource limits. Shared
ReaderTestcases exercise the PHP reader and the extension. A safe probe skips limit tests for older libraries, but fails if libmaxminddb reports version 1.14.0 or newer without enforcing the limits. No environment flag is needed.Regression tests cover amplification, limit boundaries, rejection before payload reads, decoder recovery after failures, and stream movement between calls. The PHP reader also rejects nested lookups on the same instance before a stream wrapper can move its shared stream. Tests cover both caught and propagated reentrancy errors.
The decoder avoids seeks between consecutive reads and checks read lengths with
strlen(). Budgets and the cached stream position reset for each decode call.The final pointer and reentrancy fixes were benchmarked against the reviewed commit
5658655on a full 65 MB GeoLite2-City database. Five alternating runs of 30,000 timed lookups per version produced identical result checksums:The follow-up fixes add about 0.9% to lookup time in this workload.
Validation: PHPUnit with pure PHP, the patched extension, and libmaxminddb 1.13.3, plus PHPStan, PHP CS Fixer, and PHP_CodeSniffer. Local tests have three existing incomplete cases because GMP is unavailable. Extension runs skip the two stream-wrapper tests, and the older library also skips eight resource-limit tests.
Minor version bump to 1.14.0.
Updated by Codex on behalf of the author.
Summary by CodeRabbit