Fixing map deserialization when header name or value is not a valid UTF8 string

[aqua777]

I used Proxy WASM SDK to write an Envoy plugin to perform some manipulations on requests' headers, for ex. analyzing presence and content of JWT.

Recently the Envoy running with this plugin experienced an outage. Some of the requests received by Envoy contained headers with values which were not valid UTF8 strings. As result, the plugin crashed and rendered corresponding Envoy's worker inaccessible.

The example log trace from such crash can be seen below:

[2023-02-12 19:15:47.296][31][critical][wasm] [source/extensions/common/wasm/context.cc:1179] wasm log: panicked at 'called `Result::unwrap()` on an `Err` value: FromUtf8Error { bytes: [49, 32, 192, 167, 192, 162, 37, 50, 53, 50, 55, 37, 50, 53, 50, 50], error: Utf8Error { valid_up_to: 2, error_len: Some(1) } }', /tmp/.cargo/registry/src/github.com-1ecc6299db9ec823/proxy-wasm-0.2.0/src/hostcalls.rs:1192:17
[2023-02-12 19:15:47.297][31][error][wasm] [source/extensions/common/wasm/wasm_vm.cc:38] Function: proxy_on_request_headers failed: Uncaught RuntimeError: unreachable
Proxy-Wasm plugin in-VM backtrace:
  0:  0x9e0a6 - rust_panic
  1:  0x48e74 - _ZN3std9panicking20rust_panic_with_hook17h2ed774a221e1fba5E
  2:  0x9e803 - _ZN3std9panicking19begin_panic_handler28_$u7b$$u7b$closure$u7d$$u7d$17h52dc4136c22c8436E
  3:  0x9e73c - _ZN3std10sys_common9backtrace26__rust_end_short_backtrace17h01f9905fbe35a014E
  4:  0x3d1fe - rust_begin_unwind
  5:  0x3e43 - _ZN4core9panicking9panic_fmt17h5e87d704dd0e33d8E
  6:  0x3d0f - _ZN4core6result13unwrap_failed17h4087e6a27003bc2eE
  7:  0x5172 - _ZN10proxy_wasm9hostcalls7get_map17h1c32dd056d4a3c34E
  8:  0x1e78d - _ZN79_$LT$...$u20$as$u20$proxy_wasm..traits..HttpContext$GT$23on_http_request_headers17ha2fbc94ade00c1b5E
  9:  0x4e6df - proxy_on_request_headers

The proposed solution is to replace invalid UTF8 keys and values with arbitrary string, for ex. "?".

If there is a better way of handling such situations please let me know.

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Signed-off-by: aqua777 [email protected]

[aqua777]

@PiotrSikora Hi Piotr, would you be able to review my pull request pls?

[jcrugzz]

@aqua777 from experience you are better off using get_header_bytes and using String::from_utf8_lossy() (exact apis lookup as im pulling from memory).

Theres definitely improvements we could do for this potentially but its not quite this simple.