Avoid send empty body to ext_proc server if decodeData() never called #28672

yanjunxiang-google · 2023-07-27T23:38:49Z

If decodeData() is not called, currently ext_proc filter is still possible to send an empty body to ext_proc server with

envoy/source/extensions/filters/http/ext_proc/ext_proc.cc

Line 480 in b8853df

    
           sendBufferedData(state, ProcessorState::CallbackState::BufferedBodyCallback, true);

and

envoy/source/extensions/filters/http/ext_proc/ext_proc.cc

Line 565 in b8853df

sendBodyChunk(state, data, new_state, end_stream);

After body mutation from ext_proc server is received by ext_proc filter, it will modify the decoding buffer, which leads to an ASSERT() in filter manager
common/http/filter_manager.cc:426] assert failure: parent_.state_.latest_data_decoding_filter_ == this

The condition to trigger this ASSERT is ext_proc filter is configured to send body, but client only sends headers and trailers.

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Additional Description:
Risk Level:
Testing:
Docs Changes:
Release Notes:
Platform Specific Features:
[Optional Runtime guard:]
[Optional Fixes #Issue]
[Optional Fixes commit #PR or SHA]
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Signed-off-by: Yanjun Xiang <[email protected]>

repokitteh-read-only · 2023-07-27T23:38:58Z

CC @envoyproxy/api-shepherds: Your approval is needed for changes made to (api/envoy/|docs/root/api-docs/).
envoyproxy/api-shepherds assignee is @mattklein123
CC @envoyproxy/api-watchers: FYI only for changes made to (api/envoy/|docs/root/api-docs/).

🐱

Caused by: #28672 was opened by yanjunxiang-google.

see: more, trace.

yanjunxiang-google · 2023-07-27T23:46:38Z

The solution is to add a bufferedData() check before sending body to ext_proc server. bufferedData() will only become valid pointer if decodeData() is every called.

If no data received, and decodeData() is never called, it will be nullptr.

Signed-off-by: Yanjun Xiang <[email protected]>

yanjunxiang-google · 2023-07-28T12:24:18Z

/retest

yanjunxiang-google · 2023-07-28T13:40:29Z

/assign @tyxia @yanavlasov

…_body_add Signed-off-by: Yanjun Xiang <[email protected]>

yanjunxiang-google · 2023-07-29T13:12:14Z

/assign @stevenzzzz

yanjunxiang-google · 2023-07-29T13:16:45Z

source/extensions/filters/http/ext_proc/ext_proc.cc

@@ -463,7 +463,7 @@ FilterTrailersStatus Filter::onTrailers(ProcessorState& state, Http::HeaderMap&
    return FilterTrailersStatus::StopIteration;
  }

-  if (!body_delivered && state.bodyMode() == ProcessingMode::BUFFERED) {
+  if (!body_delivered && state.bufferedData() && state.bodyMode() == ProcessingMode::BUFFERED) {


The other utility function hasBufferedData() can not be used here since it not only check bufferedData() not nullptr, also checks the data->length >0. Using hasBufferedData() here will break the decodeData() with an empty chunk case.

QQ: I am wondering when do we need to decodeData() with an empty chunk case? What are the use cases for this?

bufferedData()!=nullptr

yanjunxiang-google · 2023-07-29T13:28:30Z

This is the crash log and crash traceback decode:

test_ext_proc copy.odt

yanjunxiang-google · 2023-07-29T13:37:11Z

The root cause of the issue is this:

If ext_proc filter is configured to send body, and if only headers and trailers are received, no body is received by the ext_proc filter, it will send an empty boy to the ext_proc server.
The ext_proc server will mutate the body, and send back a body response. The body response will modify the decoding buffer, which trigger the ASSERT there:

envoy/source/common/http/filter_manager.cc

Line 426 in 522f991

ASSERT(parent_.state_.latest_data_decoding_filter_ == this);

So, filter_manager carefully maintain state_.latest_data_decoding_filter_ during decodeData():

envoy/source/common/http/filter_manager.cc

Line 658 in 522f991

    
           recordLatestDataFilter(entry, state_.latest_data_decoding_filter_, decoder_filters_);

In this case, decodeData() is never called due to client is not sending data, and data is constructed by ext_proc filter itself. That leads to latest_data_decoding_filter_ is an empty pointer not pointing the ext_proc filter

Thus the ASSERT failed, and crashed there.

Overall, the ext_proc filter should not send data based on the ext_proc filter configuration. It should only send data if the data presents. Concept wise, this issue is similar to sending trailer when trailer is not present case : #28592

yanjunxiang-google · 2023-07-29T13:49:45Z

/assign @mattklein123

yanjunxiang-google · 2023-08-01T14:11:37Z

Kind Ping

tyxia

Nice work!

tyxia · 2023-08-01T15:00:21Z

source/extensions/filters/http/ext_proc/ext_proc.cc

@@ -463,7 +463,7 @@ FilterTrailersStatus Filter::onTrailers(ProcessorState& state, Http::HeaderMap&
    return FilterTrailersStatus::StopIteration;
  }

-  if (!body_delivered && state.bodyMode() == ProcessingMode::BUFFERED) {
+  if (!body_delivered && state.bufferedData() && state.bodyMode() == ProcessingMode::BUFFERED) {


QQ: I am wondering when do we need to decodeData() with an empty chunk case? What are the use cases for this?

source/extensions/filters/http/ext_proc/ext_proc.cc

tyxia

LGTM, Thanks!

stevenzzzz

The "skipping body" approach in this PR feels like a behavior change that we can avoid by calling de/encodeData(dataMutations, false); on receiving the data mutation response from ext_server.

But no strong feelings.

stevenzzzz · 2023-08-01T18:46:25Z

source/extensions/filters/http/ext_proc/ext_proc.cc

@@ -463,7 +463,7 @@ FilterTrailersStatus Filter::onTrailers(ProcessorState& state, Http::HeaderMap&
    return FilterTrailersStatus::StopIteration;
  }

-  if (!body_delivered && state.bodyMode() == ProcessingMode::BUFFERED) {
+  if (!body_delivered && state.bufferedData() && state.bodyMode() == ProcessingMode::BUFFERED) {


bufferedData()!=nullptr

source/extensions/filters/http/ext_proc/processor_state.cc

yanjunxiang-google · 2023-08-01T20:15:58Z

The "skipping body" approach in this PR feels like a behavior change that we can avoid by calling de/encodeData(dataMutations, false); on receiving the data mutation response from ext_server.

But no strong feelings.

Thanks for the comments!

The ext_proc behavior is now changed into "if configured as such, deliver body/trailer to the ext_proc server if they are present".

yanjunxiang-google · 2023-08-02T12:35:24Z

@envoyproxy/api-shepherds PTAL

yanavlasov · 2023-08-03T13:30:08Z

API change is comment only.

Avoid send empty body to ext_proc server if decodeData() not called

eed0899

Signed-off-by: Yanjun Xiang <[email protected]>

yanjunxiang-google requested a review from mattklein123 as a code owner July 27, 2023 23:38

repokitteh-read-only bot added the api label Jul 27, 2023

repokitteh-read-only bot assigned mattklein123 Jul 27, 2023

yanjunxiang-google marked this pull request as draft July 27, 2023 23:45

yanjunxiang-google added 2 commits July 27, 2023 23:53

fixing test

cdd12f3

Signed-off-by: Yanjun Xiang <[email protected]>

adding a body send test

63619af

Signed-off-by: Yanjun Xiang <[email protected]>

yanjunxiang-google marked this pull request as ready for review July 28, 2023 13:40

Merge branch 'main' of https://github.com/envoyproxy/envoy into empty…

f68d230

…_body_add Signed-off-by: Yanjun Xiang <[email protected]>

mattklein123 assigned yanavlasov and tyxia and unassigned mattklein123 Jul 28, 2023

repokitteh-read-only bot assigned stevenzzzz Jul 29, 2023

yanjunxiang-google changed the title ~~Avoid send empty body to ext_proc server if decodeData() not called~~ Avoid send empty body to ext_proc server if decodeData() never called Jul 29, 2023

yanjunxiang-google commented Jul 29, 2023

View reviewed changes

repokitteh-read-only bot assigned mattklein123 Jul 29, 2023

mattklein123 removed their assignment Jul 30, 2023

yanavlasov approved these changes Aug 1, 2023

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tyxia reviewed Aug 1, 2023

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tyxia approved these changes Aug 1, 2023

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stevenzzzz approved these changes Aug 1, 2023

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yanavlasov merged commit 5e4f350 into envoyproxy:main Aug 3, 2023
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tyxia mentioned this pull request Jan 25, 2024

ext_proc: Update the proto comment #32031

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Avoid send empty body to ext_proc server if decodeData() never called #28672

Avoid send empty body to ext_proc server if decodeData() never called #28672

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Avoid send empty body to ext_proc server if decodeData() never called #28672

Avoid send empty body to ext_proc server if decodeData() never called #28672

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