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v8 error taming should leverage prepareStackTrace #1798

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mhofman opened this issue Sep 30, 2023 · 2 comments
Open

v8 error taming should leverage prepareStackTrace #1798

mhofman opened this issue Sep 30, 2023 · 2 comments
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@mhofman @erights
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enhancement New feature or request

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@mhofman
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mhofman commented Sep 30, 2023

What is the Problem Being Solved?

Error.prepareStackTrace can be used by Node.js to apply source maps to the captured stack trace. However SES sets its own prepareStackTrace during v8 Error taming. Instead of completely discarding it. Maybe instead it should leverage as much as possible the existing prepareStackTrace to prepare its own stack strings?

Furthermore, if the start compartment set a prepareStackTrace after lockdown, it seems the returned value will be used for the .stack property instead of the empty string, even if errorTaming is set to 'safe':

endo/packages/ses/src/error/tame-v8-error-constructor.js

Lines 301 to 304 in 2a85f8a

prepareStackTrace(error, sst) {
weakmapSet(stackInfos, error, { callSites: sst });
return inputPrepareFn(error, safeV8SST(sst));
},

Description of the Design

Use the original prepareStackTrace to generate the stack string.

Alternatively implement source map support in endo itself (maybe once part of the error handling logic has been ejected from SES as a trusted shim?, see #945). While node's prepareStackTrace implementation is not very modular, it should be possible to rebuild it on top of findSourceMap.

Security Considerations

None particularly. The start compartment is already in position to decide how lockdown should tame errors, and can also set prepareStackTrace after lockdown

Scaling Considerations

None

Test Plan

load some minified source which throws errors in Node.js with --use-source-maps and verify stack traces are mapped.

Upgrade Considerations

None particular
@mhofman mhofman added the enhancement New feature or request label Sep 30, 2023
@mhofman mhofman mentioned this issue Sep 30, 2023
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@mhofman mhofman self-assigned this Oct 6, 2023
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@kriskowal kriskowal added the kriskowal-review-2024-01 Issues that kriskowal wants to bring to the attention of the team for review as of January, 2024 label Jan 6, 2024
@aj-agoric aj-agoric removed the kriskowal-review-2024-01 Issues that kriskowal wants to bring to the attention of the team for review as of January, 2024 label Jan 31, 2024
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@erights erights self-assigned this Jul 12, 2024
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erights commented Jul 12, 2024 •
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Hi @mhofman , I've co-assigned myself to this.

@mhofman
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mhofman commented Jul 12, 2024

Use the original prepareStackTrace to generate the stack string.

I believe I explored this, and that didn't work

@mhofman mhofman mentioned this issue Jul 12, 2024
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erights added a commit that referenced this issue Jul 16, 2024
@erights
fix(ses): work around #2348 linenumber bug (#2355)
00f5eab 
Closes: #2348 

Refs: Agoric/agoric-sdk#9711
#1798
#1799
Agoric/agoric-sdk#8662
Agoric/agoric-sdk#9700

## Description

Prior to this PR, when you ran on Ava on Node a test written in
TypeScript, you'd see something like the following in your stack traces.

```
  boot/test/bootstrapTests/stack-linenumbers.test.ts:1:104
```

This is because the TypeScript compiler compiles a TypeScripy file into
one line
of JavaScript with a sourceMap that should map back into original
source positions. Node specifically makes use of that sourceMap
to produce original line-numbers. However, Node does this in a way
that resists virtualization, so the normal SES error taming cannot use
this sourceMap info.

By default, this PR does not change this behavior. However it recognizes
a new `SUPPRESS_NODE_ERROR_TAMING` environment variable.

With the `SUPPRESS_NODE_ERROR_TAMING` environment variable absent
or set to `'disabled'`, you should still see stack traces as shown above

However, if you also set  the `SUPPRESS_NODE_ERROR_TAMING` environment
variable `'enabled'`, for example by doing

```sh
$ export SUPPRESS_NODE_ERROR_TAMING=enabled
```
at a bash shell, then when you run this test you should instead see
something like
```
boot/test/bootstrapTests/stack-linenumbers.test.ts:40:32
```

At Agoric/agoric-sdk#9711 I both 
- turn this PR into an agoric-sdk patch of endo, in order to emulate
this fix until the next endo-release-agoric-sdk-sync cycle, and
- add a test case that emits an error stack trace from an Ava test case
written in TypeScript, to test that it works.

### Security Considerations

This new behavior only applies when `errorTaming: 'unsafe'`, on v8, and
with this new environment variable enabled.

Setting `errorTaming: 'unsafe'` already flags to sacrifice some security
for a better debugging experience. But the loss of security is moderate
enough --- mostly confidentiality rather than integrity --- that some
may chose this setting for some production purposes.

The new behavior is a more severe loss of security that really should be
used ***only during development***, not production, when even a severe
loss of security is usually not an issue.

### Scaling Considerations

none
### Documentation Considerations

The behavior prior to this PR or without this environment variable
enabled is an unpleasant debugging experience. However, developers won't
know how to repair it, or even that it can be repaired, without
explanation. Even then, the difficultly of discovery in a problem.

The names `SUPPRESS_NODE_ERROR_TAMING` and the settings `'enabled'` and
`'disabled'` are by no means clear expressions of what this does.
Reviewers, ***better names would be appreciated!***

### Testing Considerations

The point. As developers write and run tests written in TypeScript, they
need to iterate with problems revealed by the tests, for which they need
good line numbers, including into the test code.

When the environment variable is enabled, the new behavior broke some
SES tests written specifically to test the old behavior. This would not
happen under CI because the environment variable is not set by default,
and so may not have been noticed. But it was revealed in local testing.
To repair this, this PR also sets those tests up to set
`process.env.SUPPRESS_NODE_ERROR_TAMING` to `'disabled'` before
lockdown, protecting those tests from the external environment variable
setting.

Awkwardly, at the moment Agoric/agoric-sdk#9711
serves as the only test of this PR. This is because I failed to figure
out how to configure things so I can run TypeScript tests under Ava,
like Agoric/agoric-sdk#9711 does. I tried cargo
culting the configs that seemed relevant, but it didn't work.

Reviewers, if you let me know how to do this, I'll duplicate the test
case from Agoric/agoric-sdk#9711 here, which
would be good.

### Compatibility Considerations

With the environment variable absent or disabled, there should be zero
difference in behavior, so none.

In a development environment where this environment variable is enabled,
some stack traces will be different. But outside of SES itself, nothing
should depend on the contents of stack traces, so again none.

### Upgrade Considerations

No upgrade considerations.

Nothing BREAKING.

- [x] Update `NEWS.md` for user-facing changes.
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