// META global=window,worker,shadowrealm
// This test checks that DecompressionStream behaves according to the standard
// when the input is corrupted. To avoid a combinatorial explosion in the
// number of tests, we only mutate one field at a time, and we only test
// "interesting" values.
'use strict';
// The many different cases are summarised in this data structure.
const expectations = [
{
format: 'deflate',
// Decompresses to 'expected output'.
baseInput: [120, 156, 75, 173, 40, 72, 77, 46, 73, 77, 81, 200, 47, 45, 41,
40, 45, 1, 0, 48, 173, 6, 36],
// See RFC1950 for the definition of the various fields used by deflate:
// https://tools.ietf.org/html/rfc1950.
fields: [
{
// The function of this field. This matches the name used in the RFC.
name: 'CMF',
// The offset of the field in bytes from the start of the input.
offset: 0,
// The length of the field in bytes.
length: 1,
cases: [
{
// The value to set the field to. If the field contains multiple
// bytes, all the bytes will be set to this value.
value: 0,
// The expected result. 'success' means the input is decoded
// successfully. 'error' means that the stream will be errored.
result: 'error'
}
]
},
{
name: 'FLG',
offset: 1,
length: 1,
// FLG contains a 4-bit checksum (FCHECK) which is calculated in such a
// way that there are 4 valid values for this field.
cases: [
{
value: 218,
result: 'success'
},
{
value: 1,
result: 'success'
},
{
value: 94,
result: 'success'
},
{
// The remaining 252 values cause an error.
value: 157,
result: 'error'
}
]
},
{
name: 'DATA',
// In general, changing any bit of the data will trigger a checksum
// error. Only the last byte does anything else.
offset: 18,
length: 1,
cases: [
{
value: 4,
result: 'success'
},
{
value: 5,
result: 'error'
}
]
},
{
name: 'ADLER',
offset: -4,
length: 4,
cases: [
{
value: 255,
result: 'error'
}
]
}
]
},
{
format: 'gzip',
// Decompresses to 'expected output'.
baseInput: [31, 139, 8, 0, 0, 0, 0, 0, 0, 3, 75, 173, 40, 72, 77, 46, 73,
77, 81, 200, 47, 45, 41, 40, 45, 1, 0, 176, 1, 57, 179, 15, 0,
0, 0],
// See RFC1952 for the definition of the various fields used by gzip:
// https://tools.ietf.org/html/rfc1952.
fields: [
{
name: 'ID',
offset: 0,
length: 2,
cases: [
{
value: 255,
result: 'error'
}
]
},
{
name: 'CM',
offset: 2,
length: 1,
cases: [
{
value: 0,
result: 'error'
}
]
},
{
name: 'FLG',
offset: 3,
length: 1,
cases: [
{
value: 1, // FTEXT
result: 'success'
},
{
value: 2, // FHCRC
result: 'error'
}
]
},
{
name: 'MTIME',
offset: 4,
length: 4,
cases: [
{
// Any value is valid for this field.
value: 255,
result: 'success'
}
]
},
{
name: 'XFL',
offset: 8,
length: 1,
cases: [
{
// Any value is accepted.
value: 255,
result: 'success'
}
]
},
{
name: 'OS',
offset: 9,
length: 1,
cases: [
{
// Any value is accepted.
value: 128,
result: 'success'
}
]
},
{
name: 'DATA',
// The last byte of the data is the most interesting.
offset: 26,
length: 1,
cases: [
{
value: 3,
result: 'error'
},
{
value: 4,
result: 'success'
}
]
},
{
name: 'CRC',
offset: -8,
length: 4,
cases: [
{
// Any change will error the stream.
value: 0,
result: 'error'
}
]
},
{
name: 'ISIZE',
offset: -4,
length: 4,
cases: [
{
// A mismatch will error the stream.
value: 1,
result: 'error'
}
]
}
]
}
];
async function tryDecompress(input, format) {
const ds = new DecompressionStream(format);
const reader = ds.readable.getReader();
const writer = ds.writable.getWriter();
writer.write(input).catch(() => {});
writer.close().catch(() => {});
let out = [];
while (true) {
try {
const { value, done } = await reader.read();
if (done) {
break;
}
out = out.concat(Array.from(value));
} catch (e) {
if (e instanceof TypeError) {
return { result: 'error' };
} else {
return { result: e.name };
}
}
}
const expectedOutput = 'expected output';
if (out.length !== expectedOutput.length) {
return { result: 'corrupt' };
}
for (let i = 0; i < out.length; ++i) {
if (out[i] !== expectedOutput.charCodeAt(i)) {
return { result: 'corrupt' };
}
}
return { result: 'success' };
}
function corruptInput(input, offset, length, value) {
const output = new Uint8Array(input);
if (offset < 0) {
offset += input.length;
}
for (let i = offset; i < offset + length; ++i) {
output[i] = value;
}
return output;
}
for (const { format, baseInput, fields } of expectations) {
promise_test(async () => {
const { result } = await tryDecompress(new Uint8Array(baseInput), format);
assert_equals(result, 'success', 'decompression should succeed');
}, `the unchanged input for '${format}' should decompress successfully`);
promise_test(async () => {
const truncatedInput = new Uint8Array(baseInput.slice(0, -1));
const { result } = await tryDecompress(truncatedInput, format);
assert_equals(result, 'error', 'decompression should fail');
}, `truncating the input for '${format}' should give an error`);
promise_test(async () => {
const extendedInput = new Uint8Array(baseInput.concat([0]));
const { result } = await tryDecompress(extendedInput, format);
assert_equals(result, 'error', 'decompression should fail');
}, `trailing junk for '${format}' should give an error`);
for (const { name, offset, length, cases } of fields) {
for (const { value, result } of cases) {
promise_test(async () => {
const corruptedInput = corruptInput(baseInput, offset, length, value);
const { result: actual } =
await tryDecompress(corruptedInput, format);
assert_equals(actual, result, 'result should match');
}, `format '${format}' field ${name} should be ${result} for ${value}`);
}
}
}
promise_test(async () => {
// Data generated in Python:
// ```py
// h = b"thequickbrownfoxjumped\x00"
// words = h.split()
// zdict = b''.join(words)
// co = zlib.compressobj(zdict=zdict)
// cd = co.compress(h) + co.flush()
// ```
const { result } = await tryDecompress(new Uint8Array([
0x78, 0xbb, 0x74, 0xee, 0x09, 0x59, 0x2b, 0xc1, 0x2e, 0x0c, 0x00, 0x74, 0xee, 0x09, 0x59
]), 'deflate');
assert_equals(result, 'error', 'Data compressed with a dictionary should throw TypeError');
}, 'the deflate input compressed with dictionary should give an error')
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