Date: Sat, 28 Jun 2008 23:47:09 -0500 From: Dan Nelson <dnelson@allantgroup.com> To: Ivaylo Mateev <mateev@cns-consulting.org> Cc: hackers@freebsd.org Subject: Re: Securelevels Message-ID: <20080629044709.GA76555@dan.emsphone.com> In-Reply-To: <200806290313.21720.mateev@cns-consulting.org> References: <200806290313.21720.mateev@cns-consulting.org>
next in thread | previous in thread | raw e-mail | index | archive | help
In the last episode (Jun 29), Ivaylo Mateev said: > I think I found a bug. > > [strato@darkstar /usr/home/strato]$ sudo sysctl kern.securelevel > kern.securelevel: 2 > [strato@darkstar /usr/home/strato]$ kgdb > kgdb: /dev/mem: Permission denied > [strato@darkstar /usr/home/strato]$ sudo kgdb > [GDB will not be able to debug user-mode threads: /usr/lib/libthread_db.so: > Undefined symbol "ps_pglobal_lookup"] > GNU gdb 6.1.1 [FreeBSD] > > I am running in securelevel 2. That means nithing can have direct access > to /dev/mem, acording to man security: > > 1 Secure mode - the system immutable and system append-only flags may > not be turned off; disks for mounted file systems, /dev/mem and > /dev/kmem may not be opened for writing; /dev/io (if your platform > has it) may not be opened at all; kernel modules (see kld(4)) may > not be loaded or unloaded. > > 2 Highly secure mode - same as secure mode, plus disks may not be > opened for writing (except by mount(2)) whether mounted or not. > This level precludes tampering with file systems by unmounting > them, but also inhibits running newfs(8) while the system is multi- > user. # truss kgdb < /dev/null |& grep /dev/mem open("/dev/mem",O_RDONLY,00) = 4 (0x4) # Read-only opens of /dev/mem are allowed. "kgdb -w" should fail, however. -- Dan Nelson dnelson@allantgroup.com
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20080629044709.GA76555>