Date: Tue, 22 Jul 2025 20:30:59 GMT From: Ed Maste <emaste@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: ce1af6eb54a4 - stable/14 - capsicum.4: Add some more detail from the Capsicum paper Message-ID: <202507222030.56MKUxq0000261@gitrepo.freebsd.org>
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The branch stable/14 has been updated by emaste: URL: https://cgit.FreeBSD.org/src/commit/?id=ce1af6eb54a423af66054e3775bc71bb09c96b41 commit ce1af6eb54a423af66054e3775bc71bb09c96b41 Author: Ed Maste <emaste@FreeBSD.org> AuthorDate: 2025-06-14 17:57:33 +0000 Commit: Ed Maste <emaste@FreeBSD.org> CommitDate: 2025-07-22 20:30:30 +0000 capsicum.4: Add some more detail from the Capsicum paper Adapt some language from "Capsicum: practical capabilities for UNIX" https://www.cl.cam.ac.uk/research/security/capsicum/papers/2010usenix-security-capsicum-website.pdf Reviewed by: markj Discussed with: rwatson Event: Kitchener-Waterloo Hackathon 202506 Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D50855 (cherry picked from commit c54534e60263954fac4db5ebb041ed4597df1195) (cherry picked from commit ce65ff203a4f7ce59c8782f87d90a657f7ccbc46) --- share/man/man4/capsicum.4 | 47 ++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 46 insertions(+), 1 deletion(-) diff --git a/share/man/man4/capsicum.4 b/share/man/man4/capsicum.4 index 6aefae9d6df2..1de8e4531f4f 100644 --- a/share/man/man4/capsicum.4 +++ b/share/man/man4/capsicum.4 @@ -24,7 +24,7 @@ .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" -.Dd June 5, 2025 +.Dd June 17, 2025 .Dt CAPSICUM 4 .Os .Sh NAME @@ -37,6 +37,12 @@ .Nm is a lightweight OS capability and sandbox framework implementing a hybrid capability system model. +.Nm +is designed to blend capabilities with UNIX. +This approach achieves many of the benefits of least-privilege operation, while +preserving existing UNIX APIs and performance, and presents application authors +with an adoption path for capability-oriented design. +.Pp Capabilities are unforgeable tokens of authority that can be delegated and must be presented to perform an action. .Nm @@ -59,6 +65,34 @@ namespaces) is restricted; only explicitly delegated rights, referenced by memory mappings or file descriptors, may be used. Once set, the flag is inherited by future children processes, and may not be cleared. +.Pp +Access to system calls in capability mode is restricted: some system calls +requiring global namespace access are unavailable, while others are +constrained. +For instance, +.Xr sysctl 2 +can be used to query process-local information such as address space layout, +but also to monitor a system’s network connections. +.Xr sysctl 2 +is constrained by explicitly marking \(~~60 of over 15000 parameters as permitted +in capability mode; all others are denied. +.Pp +The system calls which require constraints are +.Xr sysctl 2 , +.Xr shm_open 2 +.Pq which is permitted to create anonymous memory objects but not named ones +and the +.Xr openat 2 +family of system calls. +The +.Xr openat 2 +calls already accept a file descriptor argument as the directory to perform the +.Xr open 2 , +.Xr rename 2 , +etc. relative to; in capability mode the +.Xr openat 2 +family of system calls are constrained so that they can only operate on +objects “under” the provided file descriptor. .It capabilities Limit operations that can be called on file descriptors. For example, a file descriptor returned by @@ -152,3 +186,14 @@ and .An Kris Kennaway Aq Mt kris@FreeBSD.org at Google, Inc., and .An Pawel Jakub Dawidek Aq Mt pawel@dawidek.net . +Portions of this manual page are drawn from +.Rs +.%A Robert N. M. Watson +.%A Jonathan Anderson +.%A Ben Laurie +.%A Kris Kennaway +.%T Capsicum: practical capabilities for UNIX +.%J USENIX Security Symposium +.%D August 2010 +.%O DOI: 10.5555/1929820.1929824 +.Re
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