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Unmarshall update #21721

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Merged
DavidAPierce merged 3 commits into from
Mar 9, 2026
Merged

Unmarshall update #21721

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3a633e8
add quick check for acceptable key types in variables.ts
DavidAPierce Mar 9, 2026
374a39f
refine ignored keys in variables to be a const set.
DavidAPierce Mar 9, 2026
a389c51
Update packages/cli/src/config/extensions/variables.ts
DavidAPierce Mar 9, 2026
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26 changes: 26 additions & 0 deletions packages/cli/src/config/extensions/variables.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -124,4 +124,30 @@ describe('recursivelyHydrateStrings', () => {
const result = recursivelyHydrateStrings(obj, context);
expect(result).toEqual(obj);
});

it('should not allow prototype pollution via __proto__', () => {
const payload = JSON.parse('{"__proto__": {"polluted": "yes"}}');
const result = recursivelyHydrateStrings(payload, context);

expect(result.polluted).toBeUndefined();
expect(Object.prototype.hasOwnProperty.call(result, 'polluted')).toBe(
false,
);
});

it('should not allow prototype pollution via constructor', () => {
const payload = JSON.parse(
'{"constructor": {"prototype": {"polluted": "yes"}}}',
);
const result = recursivelyHydrateStrings(payload, context);

expect(result.polluted).toBeUndefined();
});

it('should not allow prototype pollution via prototype', () => {
const payload = JSON.parse('{"prototype": {"polluted": "yes"}}');
const result = recursivelyHydrateStrings(payload, context);

expect(result.polluted).toBeUndefined();
});
});
15 changes: 14 additions & 1 deletion packages/cli/src/config/extensions/variables.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,16 @@ import * as path from 'node:path';
import { type VariableSchema, VARIABLE_SCHEMA } from './variableSchema.js';
import { GEMINI_DIR } from '@google/gemini-cli-core';

/**
* Respresents a set of keys that will be considered invalid while umarshalling
* JSON in recursivelyHydrateStrings.
*/
const UNMARSHALL_KEY_IGNORE_LIST: Set<string> = new Set<string>([
'__proto__',
'constructor',
'prototype',
]);

export const EXTENSIONS_DIRECTORY_NAME = path.join(GEMINI_DIR, 'extensions');
export const EXTENSIONS_CONFIG_FILENAME = 'gemini-extension.json';
export const INSTALL_METADATA_FILENAME = '.gemini-extension-install.json';
Expand Down Expand Up @@ -65,7 +75,10 @@ export function recursivelyHydrateStrings<T>(
if (typeof obj === 'object' && obj !== null) {
const newObj: Record<string, unknown> = {};
for (const key in obj) {
if (Object.prototype.hasOwnProperty.call(obj, key)) {
if (
!UNMARSHALL_KEY_IGNORE_LIST.has(key) &&
Object.prototype.hasOwnProperty.call(obj, key)
) {
newObj[key] = recursivelyHydrateStrings(
// eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
(obj as Record<string, unknown>)[key],
Expand Down
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