On 06.02.2020 21:23, Stephen Smalley wrote: > On 2/5/20 12:30 PM, Alexey Budankov wrote: >> >> Introduce CAP_PERFMON capability designed to secure system performance >> monitoring and observability operations so that CAP_PERFMON would assist >> CAP_SYS_ADMIN capability in its governing role for performance monitoring >> and observability subsystems. >> >> CAP_PERFMON hardens system security and integrity during performance >> monitoring and observability operations by decreasing attack surface that >> is available to a CAP_SYS_ADMIN privileged process [2]. Providing the access >> to system performance monitoring and observability operations under CAP_PERFMON >> capability singly, without the rest of CAP_SYS_ADMIN credentials, excludes >> chances to misuse the credentials and makes the operation more secure. >> Thus, CAP_PERFMON implements the principal of least privilege for performance >> monitoring and observability operations (POSIX IEEE 1003.1e: 2.2.2.39 principle >> of least privilege: A security design principle that states that a process >> or program be granted only those privileges (e.g., capabilities) necessary >> to accomplish its legitimate function, and only for the time that such >> privileges are actually required) >> >> CAP_PERFMON meets the demand to secure system performance monitoring and >> observability operations for adoption in security sensitive, restricted, >> multiuser production environments (e.g. HPC clusters, cloud and virtual compute >> environments), where root or CAP_SYS_ADMIN credentials are not available to >> mass users of a system, and securely unblocks accessibility of system performance monitoring and observability operations beyond root and CAP_SYS_ADMIN use cases. >> >> CAP_PERFMON takes over CAP_SYS_ADMIN credentials related to system performance >> monitoring and observability operations and balances amount of CAP_SYS_ADMIN >> credentials following the recommendations in the capabilities man page [1] >> for CAP_SYS_ADMIN: "Note: this capability is overloaded; see Notes to kernel >> developers, below." For backward compatibility reasons access to system >> performance monitoring and observability subsystems of the kernel remains >> open for CAP_SYS_ADMIN privileged processes but CAP_SYS_ADMIN capability >> usage for secure system performance monitoring and observability operations >> is discouraged with respect to the designed CAP_PERFMON capability. >> >> Although the software running under CAP_PERFMON can not ensure avoidance >> of related hardware issues, the software can still mitigate these issues >> following the official hardware issues mitigation procedure [2]. The bugs >> in the software itself can be fixed following the standard kernel development >> process [3] to maintain and harden security of system performance monitoring >> and observability operations. >> >> [1] http://man7.org/linux/man-pages/man7/capabilities.7.html >> [2] https://www.kernel.org/doc/html/latest/process/embargoed-hardware-issues.html >> [3] https://www.kernel.org/doc/html/latest/admin-guide/security-bugs.html >> >> Signed-off-by: Alexey Budankov <alexey.budankov@xxxxxxxxxxxxxxx> > > This will require a small update to the selinux-testsuite to correctly reflect the new capability requirements, but that's easy enough. Is the suite a part of the kernel sources or something else? ~Alexey > > Acked-by: Stephen Smalley <sds@xxxxxxxxxxxxx> > >> --- >> include/linux/capability.h | 4 ++++ >> include/uapi/linux/capability.h | 8 +++++++- >> security/selinux/include/classmap.h | 4 ++-- >> 3 files changed, 13 insertions(+), 3 deletions(-) >> >> diff --git a/include/linux/capability.h b/include/linux/capability.h >> index ecce0f43c73a..027d7e4a853b 100644 >> --- a/include/linux/capability.h >> +++ b/include/linux/capability.h >> @@ -251,6 +251,10 @@ extern bool privileged_wrt_inode_uidgid(struct user_namespace *ns, const struct >> extern bool capable_wrt_inode_uidgid(const struct inode *inode, int cap); >> extern bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap); >> extern bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns); >> +static inline bool perfmon_capable(void) >> +{ >> + return capable(CAP_PERFMON) || capable(CAP_SYS_ADMIN); >> +} >> /* audit system wants to get cap info from files as well */ >> extern int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps); >> diff --git a/include/uapi/linux/capability.h b/include/uapi/linux/capability.h >> index 240fdb9a60f6..8b416e5f3afa 100644 >> --- a/include/uapi/linux/capability.h >> +++ b/include/uapi/linux/capability.h >> @@ -366,8 +366,14 @@ struct vfs_ns_cap_data { >> #define CAP_AUDIT_READ 37 >> +/* >> + * Allow system performance and observability privileged operations >> + * using perf_events, i915_perf and other kernel subsystems >> + */ >> + >> +#define CAP_PERFMON 38 >> -#define CAP_LAST_CAP CAP_AUDIT_READ >> +#define CAP_LAST_CAP CAP_PERFMON >> #define cap_valid(x) ((x) >= 0 && (x) <= CAP_LAST_CAP) >> diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h >> index 7db24855e12d..c599b0c2b0e7 100644 >> --- a/security/selinux/include/classmap.h >> +++ b/security/selinux/include/classmap.h >> @@ -27,9 +27,9 @@ >> "audit_control", "setfcap" >> #define COMMON_CAP2_PERMS "mac_override", "mac_admin", "syslog", \ >> - "wake_alarm", "block_suspend", "audit_read" >> + "wake_alarm", "block_suspend", "audit_read", "perfmon" >> -#if CAP_LAST_CAP > CAP_AUDIT_READ >> +#if CAP_LAST_CAP > CAP_PERFMON >> #error New capability defined, please update COMMON_CAP2_PERMS. >> #endif >> >
