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sftp: confine REALPATH, refuse unsafe roots - #1387
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Fenrir Automated Review — PR #1387
Scan targets checked: wolfssh-src, wolfssh-bugs
Coverage: 5 of 6 in-scope changed file(s) opened by the reviewer; not opened: wolfssh/internal.h
Fenrir result: Approved ✅
No new issues found in the changed files.
Advisory only — this automated result does not count as a GitHub approval.
Review tier: Max
REALPATH now runs its answer through the same confinement check as the other path requests and answers PERMISSION_DENIED for a name outside the root. The check, split out of GetAndCleanPath as SFTP_CheckConfined, compares every byte of the root before testing the boundary. - a start path outside the root, or through a link below it, resolves as the root, so a confined session still opens - prefix compare uses wolfSSH_ConstantCompare; Windows folds ASCII case in a fixed loop - api.c: REALPATH of an escaping path and through an in-jail link Issue: F-10599, F-11669
wolfSSH_SFTP_SetConfinePath returns WS_NOT_COMPILED for any root but "/" where a link below the root cannot be refused: WOLFSSH_NO_SYMLINK_CHECK, WOLFSSH_USER_FILESYSTEM, or POSIX without O_NOFOLLOW. The root is still stored, so a caller that ignores the error keeps the lexical jail. - port.h defines WOLFSSH_NO_SFTP_CONFINE for those builds - OPEN and OPENDIR walk down from the root with O_NOFOLLOW where openat() and O_PATH or O_SEARCH exist; _GNU_SOURCE on Linux for O_PATH - wolfsftp.h states what still acts by name after the check - tests expect the refusal under WOLFSSH_NO_SFTP_CONFINE, swap in a link between check and open, and start a session outside the root Issue: F-8860, F-15661
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REALPATH answers PERMISSION_DENIED outside the confinement root, and the
root compare runs in fixed time. Builds that cannot refuse a link below
the root now refuse confinement itself.
a start path outside the root resolves as the root
user filesystem or the symlink check off, but still stores the root;
OPEN and OPENDIR walk from the root with O_NOFOLLOW
Issue: F-8860, F-10599, F-11669, F-15661