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Title: permission: do not create symlinks if target is relative by tniessen · Pull Request #49156 · nodejs/node · GitHub

Open Graph Title: permission: do not create symlinks if target is relative by tniessen · Pull Request #49156 · nodejs/node

X Title: permission: do not create symlinks if target is relative by tniessen · Pull Request #49156 · nodejs/node

Description: The permission model's security guarantees fall apart in the presence of relative symbolic links. When an application attempts to create a relative symlink, the permission model currently resolves the relative path into an absolute path based on the process's current working directory, checks whether the process has the relevant permissions, and then creates the symlink using the absolute target path. This behavior is plainly incorrect for two reasons: The target path should never be resolved relative to the current working directory. If anything, it should be resolved relative to the symlink's location. (Of course, there is one insane exception to this rule: on Windows, each process has a current working directory per drive, and symlinks can be created with a target path relative to the current working directory of a specific drive. In that case, the relative path will be resolved relative to the current working directory for the respective drive, and the symlink will be created on disk with the resulting absolute path. Other relative symlinks will be stored as-is.) Silently creating an absolute symlink when the user requested a relative symlink is wrong. The user may (or may not) rely on the symlink being relative. For example, npm heavily relies on relative symbolic links such that node_modules directories can be moved around without breaking. Because we don't know the user's intentions, we don't know if creating an absolute symlink instead of a relative symlink is acceptable. This patch prevents the faulty behavior by not (incorrectly) resolving relative symlink targets when the permission model is enabled, and by instead simply refusing the create any relative symlinks. The fs APIs accept Uint8Array objects for paths to be able to handle arbitrary file name charsets, however, checking whether such an object represents a relative part in a reliable and portable manner is tricky. Other parts of the permission model incorrectly convert such objects to strings and then back to an Uint8Array (see 1f64147), however, for now, this bug fix will simply throw on non-string symlink targets when the permission model is enabled. (The permission model already breaks existing applications in various ways, so this shouldn't be too dramatic.)

Open Graph Description: The permission model's security guarantees fall apart in the presence of relative symbolic links. When an application attempts to create a relative symlink, the permission model currently resol...

X Description: The permission model's security guarantees fall apart in the presence of relative symbolic links. When an application attempts to create a relative symlink, the permission model currently r...

Opengraph URL: https://github.com/nodejs/node/pull/49156

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