Security-hardening fix for the read_file device guard, not a new sandbox
boundary. The guard already rejects direct device paths and upstream now
has a resolved-path pass for workspace symlinks to blocked devices, but
its concrete-path helper still compared the expanded path before
normalization. That leaves residual alias cases where the dangerous path
is visible before final terminal-specific resolution, for example:
1. /dev/../dev/zero and /dev/./urandom should match the blocked-device
list as concrete paths, not only after final realpath;
2. /dev/stdin-style aliases can disappear once realpath follows them
to /proc/self/fd/0 and then to a tty path;
3. a user symlink to /dev/../dev/stdin exposes the dangerous
intermediate target before final resolution, but not necessarily
after it.
Normalize expanded paths before matching and inspect each symlink hop
before falling back to realpath. This preserves the existing /proc fd and
/proc pseudo-file guards while enforcing the intended security invariant:
model-supplied read paths must not reach blocking or infinite device
streams through spelling, normalization, or symlink-hop tricks.
Classification: security hardening / residual bypass fix for the
read_file device blocklist. This is defensive code at the file-tool
boundary, but it fixes a concrete denial-of-service class tracked as
security in #10141 and #29158.
Tests:
- normalized /dev/../dev/zero and /dev/./urandom aliases
- symlink to /dev/../dev/stdin blocked before realpath
- existing symlink-to-device and regular-symlink guards still pass
Fixes#10141Fixes#29158
Eugeniusz Gilewski
9078b4bbdf