This fixes a security issue (CVE-2024-27297) whereby a fixed-output
derivation build process could open a writable file descriptor to its
output, send it to some outside process for instance over an abstract
AF_UNIX socket, which would then allow said process to modify the file
in the store after it has been marked as “valid”.
Vulnerability discovered by puck <https://github.com/puckipedia>.
Nix security advisory:
https://github.com/NixOS/nix/security/advisories/GHSA-2ffj-w4mj-pg37
Nix fix:
244f3eee0b
* nix/libutil/util.cc (readDirectory): Add variants that take a DIR* and
a file descriptor. Rewrite the ‘Path’ variant accordingly.
(copyFile, copyFileRecursively): New functions.
* nix/libutil/util.hh (copyFileRecursively): New declaration.
* nix/libstore/build.cc (DerivationGoal::buildDone): When ‘fixedOutput’
is true, call ‘copyFileRecursively’ followed by ‘rename’ on each output.
Change-Id: I7952d41093eed26e123e38c14a4c1424be1ce1c4
Reported-by: Picnoir <picnoir@alternativebit.fr>, Théophane Hufschmitt <theophane.hufschmitt@tweag.io>
Change-Id: Idb5f2757f35af86b032a9851cecb19b70227bd88
8f4ffb3fae