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Diffstat (limited to 'source/l/libcap')
-rw-r--r-- | source/l/libcap/README.SLACKWARE | 15 | ||||
-rw-r--r-- | source/l/libcap/capfaq-0.2.txt | 264 | ||||
-rw-r--r-- | source/l/libcap/libcap-2.16.tar.bz2.sign | 8 | ||||
-rwxr-xr-x | source/l/libcap/libcap.SlackBuild | 109 | ||||
-rw-r--r-- | source/l/libcap/libcap.capability.h.fix.broken.includes.diff | 11 | ||||
-rw-r--r-- | source/l/libcap/slack-desc | 19 |
6 files changed, 426 insertions, 0 deletions
diff --git a/source/l/libcap/README.SLACKWARE b/source/l/libcap/README.SLACKWARE new file mode 100644 index 00000000..5942189b --- /dev/null +++ b/source/l/libcap/README.SLACKWARE @@ -0,0 +1,15 @@ +This file contains some links to additional sources of documentation +available on libcap usage. + +POSIX 1e and 2c drafts: +http://wt.xpilot.org/publications/posix.1e/download.html + +Olaf Kirch's article: +http://www.lst.de/~okir/blackhats/node125.html + +Serge E. Hallyn' article: +POSIX file capabilities: Parceling the power of root +http://www.ibm.com/developerworks/linux/library/l-posixcap.html?ca=dgr-lnxw06LinuxPOSIX + +Active development of libcap v2 is in filesystem capabilities, see: +http://www.kernel.org/pub/linux/libs/security/linux-privs/README diff --git a/source/l/libcap/capfaq-0.2.txt b/source/l/libcap/capfaq-0.2.txt new file mode 100644 index 00000000..e3e272be --- /dev/null +++ b/source/l/libcap/capfaq-0.2.txt @@ -0,0 +1,264 @@ +This is the Linux kernel capabilities FAQ + +Its history, to the extent that I am able to reconstruct it is that +v2.0 was posted to the Linux kernel list on 1999/04/02 by Boris +Tobotras. Thanks to Denis Ducamp for forwarding me a copy. + +Cheers + +Andrew + +Linux Capabilities FAQ 0.2 +========================== + +1) What is a capability? + +The name "capabilities" as used in the Linux kernel can be confusing. +First there are Capabilities as defined in computer science. A +capability is a token used by a process to prove that it is allowed to +do an operation on an object. The capability identifies the object +and the operations allowed on that object. A file descriptor is a +capability. You create the file descriptor with the "open" call and +request read or write permissions. Later, when doing a read or write +operation, the kernel uses the file descriptor as an index into a +data structure that indicates what operations are allowed. This is an +efficient way to check permissions. The necessary data structures are +created once during the "open" call. Later read and write calls only +have to do a table lookup. Operations on capabilities include copying +capabilities, transferring capabilities between processes, modifying a +capability, and revoking a capability. Modifying a capability can be +something like taking a read-write filedescriptor and making it +read-only. A capability often has a notion of an "owner" which is +able to invalidate all copies and derived versions of a capability. +Entire OSes are based on this "capability" model, with varying degrees +of purity. There are other ways of implementing capabilities than the +file descriptor model - traditionally special hardware has been used, +but modern systems also use the memory management unit of the CPU. + +Then there is something quite different called "POSIX capabilities" +which is what Linux uses. These capabilities are a partitioning of +the all powerful root privilege into a set of distinct privileges (but +look at securelevel emulation to find out that this isn't necessary +the whole truth). Users familiar with VMS or "Trusted" versions of +other UNIX variants will know this under the name "privileges". The +name "capabilities" comes from the now defunct POSIX draft 1003.1e +which used this name. + +2) So what is a "POSIX capability"? + +A process has three sets of bitmaps called the inheritable(I), +permitted(P), and effective(E) capabilities. Each capability is +implemented as a bit in each of these bitmaps which is either set or +unset. When a process tries to do a privileged operation, the +operating system will check the appropriate bit in the effective set +of the process (instead of checking whether the effective uid of the +process i 0 as is normally done). For example, when a process tries +to set the clock, the Linux kernel will check that the process has the +CAP_SYS_TIME bit (which is currently bit 25) set in its effective set. + +The permitted set of the process indicates the capabilities the +process can use. The process can have capabilities set in the +permitted set that are not in the effective set. This indicates that +the process has temporarily disabled this capability. A process is +allowed to set a bit in its effective set only if it is available in +the permitted set. The distinction between effective and permitted +exists so that processes can "bracket" operations that need privilege. + +The inheritable capabilities are the capabilities of the current +process that should be inherited by a program executed by the current +process. The permitted set of a process is masked against the +inheritable set during exec(). Nothing special happens during fork() +or clone(). Child processes and threads are given an exact copy of +the capabilities of the parent process. + +3) What about other entities in the system? Users, Groups, Files? + +Files have capabilities. Conceptually they have the same three +bitmaps that processes have, but to avoid confusion we call them by +other names. Only executable files have capabilities, libraries don't +have capabilities (yet). The three sets are called the allowed set, +the forced set, and the effective set. + +The allowed set indicates what capabilities the executable is allowed +to receive from an execing process. This means that during exec(), +the capabilities of the old process are first masked against a set +which indicates what the process gives away (the inheritable set of +the process), and then they are masked against a set which indicates +what capabilities the new process image is allowed to receive (the +allowed set of the executable). + +The forced set is a set of capabilities created out of thin air and +given to the process after execing the executable. The forced set is +similar in nature to the setuid feature. In fact, the setuid bit from +the filesystem is "read" as a full forced set by the kernel. + +The effective set indicates which bits in the permitted set of the new +process should be transferred to the effective set of the new process. +The effective set is best thought of as a "capability aware" set. It +should consist of only 1s if the executable is capability-dumb, or +only 0s if the executable is capability-smart. Since the effective +set consists of only 0s or only 1s, the filesystem can implement this +set using a single bit. + +NOTE: Filesystem support for capabilities is not part of Linux 2.2. + +Users and Groups don't have associated capabilities from the kernel's +point of view, but it is entirely reasonable to associate users or +groups with capabilities. By letting the "login" program set some +capabilities it is possible to make role users such as a backup user +that will have the CAP_DAC_READ_SEARCH capability and be able to do +backups. This could also be implemented as a PAM module, but nobody +has implemented one yet. + +4) What capabilities exist? + +The capabilities available in Linux are listed and documented in the +file /usr/src/linux/include/linux/capability.h. + +5) Are Linux capabilities hierarchical? + +No, you cannot make a "subcapability" out of a Linux capability as in +capability-based OSes. + +6) How can I use capabilities to make sure Mr. Evil Luser (eluser) +can't exploit my "suid" programs? + +This is the general outline of how this works given filesystem +capability support exists. First, you have a PAM module that sets the +inheritable capabilities of the login-shell of eluser. Then for all +"suid" programs on the system, you decide what capabilities they need +and set the _allowed_ set of the executable to that set of +capabilities. The capability rules + + new permitted = forced | (allowed & inheritable) + +means that you should be careful about setting forced capabilities on +executables. In a few cases, this can be useful though. For example +the login program needs to set the inheritable set of the new user and +therefore needs an almost full permitted set. So if you want eluser +to be able to run login and log in as a different user, you will have +to set some forced bits on that executable. + +7) What about passing capabilities between processes? + +Currently this is done by the system call "setcap" which can set the +capabilities of another process. This requires the CAP_SETPCAP +capability which you really only want to grant a _few_ processes. +CAP_SETPCAP was originally intended as a workaround to be able to +implement filesystem support for capabilities using a daemon outside +the kernel. + +There has been discussions about implementing socket-level capability +passing. This means that you can pass a capability over a socket. No +support for this exists in the official kernel yet. + +8) I see securelevel has been removed from 2.2 and are superceeded by +capabilities. How do I emulate securelevel using capabilities? + +The setcap system call can remove a capability from _all_ processes on +the system in one atomic operation. The setcap utility from the +libcap distribution will do this for you. The utility requires the +CAP_SETPCAP privilege to do this. The CAP_SETPCAP capability is not +enabled by default. + +libcap is available from +ftp://ftp.kernel.org/pub/linux/libs/security/linux-privs/kernel-2.2/ + +9) I noticed that the capability.h file lacks some capabilities that +are needed to fully emulate 2.0 securelevel. Is there a patch for +this? + +Actually yes - funny you should ask :-). The problem with 2.0 +securelevel is that they for example stop root from accessing block +devices. At the same time they restrict the use of iopl. These two +changes are fundamentally different. Blocking access to block devices +means restricting something that usually isn't restricted. +Restricting access to the use of iopl on the other hand means +restricting (blocking) access to something that is already blocked. +Emulating the parts of 2.0 securelevel that restricts things that are +normally not restricted means that the capabilites in the kernel has +to have a set of capabilities that are usually _on_ for a normal +process (note that this breaks the explanation that capabilities are a +partitioning of the root privileges). There is an experimental patch at + +ftp://ftp.guardian.no/pub/free/linux/capabilities/patch-cap-exp-1 + +which implements a set of capabilities with the "CAP_USER" prefix: + +cap_user_sock - allowed to use socket() +cap_user_dev - allowed to open char/block devices +cap_user_fifo - allowed to use pipes + +These should be enough to emulate 2.0 securelevel (tell me if we need +something more). + +10) Seems I need a CAP_SETPCAP capability that I don't have to make use +of capabilities. How do I enable this capability? + +Change the definition of CAP_INIT_EFF_SET and CAP_INIT_INH_SET to the +following in include/linux/capability.h: + +#define CAP_INIT_EFF_SET { ~0 } +#define CAP_INIT_INH_SET { ~0 } + +This will start init with a full capability set and not with +CAP_SETPCAP removed. + +11) How do I start a process with a limited set of capabilities? + +Get the libcap library and use the execcap utility. The following +example starts the update daemon with only the CAP_SYS_ADMIN +capability. + +execcap 'cap_sys_admin=eip' update + +12) How do I start a process with a limited set of capabilities under +another uid? + +Use the sucap utility which changes uid from root without loosing any +capabilities. Normally all capabilities are cleared when changing uid +from root. The sucap utility requires the CAP_SETPCAP capability. +The following example starts updated under uid updated and gid updated +with CAP_SYS_ADMIN raised in the Effective set. + +sucap updated updated execcap 'cap_sys_admin=eip' update + +[ Sucap is currently available from +ftp://ftp.guardian.no/pub/free/linux/capabilities/sucap.c. Put it in +the progs directory of libcap to compile.] + +13) What are the "capability rules" + +The capability rules are the rules used to set the capabilities of the +new process image after an exec. They work like this: + + pI' = pI + (***) pP' = fP | (fI & pI) + pE' = pP' & fE [NB. fE is 0 or ~0] + + I=Inheritable, P=Permitted, E=Effective // p=process, f=file + ' indicates post-exec(). + +Now to make sense of the equations think of fP as the Forced set of +the executable, and fI as the Allowed set of the executable. Notice +how the Inheritable set isn't touched at all during exec(). + +14) What are the laws for setting capability bits in the Inheritable, +Permitted, and Effective sets? + +Bits can be transferred from Permitted to either Effective or +Inheritable set. + +Bits can be removed from all sets. + +15) Where is the standard on which the Linux capabilities are based? + +There used to be a POSIX draft called POSIX.6 and later POSIX 1003.1e. +However after the committee had spent over 10 years, POSIX decided +that enough is enough and dropped the draft. There will therefore not +be a POSIX standard covering security anytime soon. This may lead to +that the POSIX draft is available for free, however. + +-- + Best regards, -- Boris. + diff --git a/source/l/libcap/libcap-2.16.tar.bz2.sign b/source/l/libcap/libcap-2.16.tar.bz2.sign new file mode 100644 index 00000000..d4925d76 --- /dev/null +++ b/source/l/libcap/libcap-2.16.tar.bz2.sign @@ -0,0 +1,8 @@ +-----BEGIN PGP SIGNATURE----- +Version: GnuPG v1.4.9 (GNU/Linux) +Comment: See http://www.kernel.org/signature.html for info + +iD8DBQBJN4JLyGugalF9Dw4RAiqLAJ9L42xfkqkbmmTyQJulpL8VoRjurwCeJkLj +oLAyJMYhVE31Kumb66LU5c8= +=UTrX +-----END PGP SIGNATURE----- diff --git a/source/l/libcap/libcap.SlackBuild b/source/l/libcap/libcap.SlackBuild new file mode 100755 index 00000000..e7603570 --- /dev/null +++ b/source/l/libcap/libcap.SlackBuild @@ -0,0 +1,109 @@ +#!/bin/sh + +# Copyright 2009 Patrick J. Volkerding, Sebeka, MN, USA +# All rights reserved. +# +# Redistribution and use of this script, with or without modification, is +# permitted provided that the following conditions are met: +# +# 1. Redistributions of this script must retain the above copyright +# notice, this list of conditions and the following disclaimer. +# +# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED +# WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF +# MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO +# EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, +# PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; +# OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, +# WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR +# OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF +# ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + +# Originally written by Menno Duursma + + +PRGNAM=libcap +VERSION=${VERSION:-2.16} +ARCH=${ARCH:-x86_64} +BUILD=${BUILD:-2} + +NUMJOBS=${NUMJOBS:-" -j7 "} + +if [ "$ARCH" = "i486" ]; then + SLKCFLAGS="-O2 -march=i486 -mtune=i686" + LIBDIRSUFFIX="" +elif [ "$ARCH" = "i686" ]; then + SLKCFLAGS="-O2 -march=i686 -mtune=i686" + LIBDIRSUFFIX="" +elif [ "$ARCH" = "x86_64" ]; then + SLKCFLAGS="-O2 -fPIC" + LIBDIRSUFFIX="64" +elif [ "$ARCH" = "arm" ]; then + SLKCFLAGS="-O2 -march=armv4 -mtune=xscale" + LIBDIRSUFFIX="" +elif [ "$ARCH" = "armel" ]; then + SLKCFLAGS="-O2 -march=armv4t" + LIBDIRSUFFIX="" +fi + +CWD=$(pwd) +TMP=${TMP:-/tmp} +PKG=$TMP/package-$PRGNAM + +rm -rf $PKG +mkdir -p $TMP $PKG +cd $TMP +rm -rf $PRGNAM-$VERSION +tar xvf $CWD/$PRGNAM-$VERSION.tar.bz2 || exit 1 +cd $PRGNAM-$VERSION || exit 1 + +zcat $CWD/libcap.capability.h.fix.broken.includes.diff.gz | patch -p1 || exit 1 + +chown -R root:root . +find . \ + \( -perm 777 -o -perm 775 -o -perm 711 -o -perm 555 -o -perm 511 \) \ + -exec chmod 755 {} \; -o \ + \( -perm 666 -o -perm 664 -o -perm 600 -o -perm 444 -o -perm 440 -o -perm 400 \) \ + -exec chmod 644 {} \; + +# Set the CFLAGS +sed -i.orig "s/^\(DEBUG =\).*/\1$SLKCFLAGS/" Make.Rules + +make DYNAMIC=yes $NUMJOBS || make DYNAMIC=yes || exit 1 +make install FAKEROOT=$PKG man_prefix=/usr || exit 1 +chmod 755 $PKG/lib/libcap.so* + +find $PKG | xargs file | grep -e "executable" -e "shared object" | grep ELF \ + | cut -f 1 -d : | xargs strip --strip-unneeded 2> /dev/null + +# Add included scripts +( cd contrib || exit 1 + for file in pcaps4convenience pcaps4server pcaps4suid0 ; do + install -m 0755 -D $file $PKG/usr/sbin/$file + done +) + +# glibc already has the capget/capset manpage +rm -rf $PKG/usr/man/man2 + +# Compress the man pages +( cd $PKG/usr/man + find . -type f -exec gzip -9 {} \; + for i in $(find . -type l) ; do ln -s $(readlink $i).gz $i.gz ; rm $i ; done +) + +mkdir -p $PKG/usr/doc/$PRGNAM-$VERSION +cp -a \ + CHANGELOG License README License pgp.keys.asc doc/capability.notes \ + progs/quicktest.sh $CWD/capfaq-0.2.txt $CWD/README.SLACKWARE \ + $PKG/usr/doc/$PRGNAM-$VERSION +chown -R root:root $PKG/usr/doc +find $PKG/usr/doc -type f -exec chmod 644 {} \; + +mkdir -p $PKG/install +cat $CWD/slack-desc > $PKG/install/slack-desc + +cd $PKG +/sbin/makepkg -l y -c n $TMP/$PRGNAM-$VERSION-$ARCH-$BUILD.txz + diff --git a/source/l/libcap/libcap.capability.h.fix.broken.includes.diff b/source/l/libcap/libcap.capability.h.fix.broken.includes.diff new file mode 100644 index 00000000..5a4fcbcf --- /dev/null +++ b/source/l/libcap/libcap.capability.h.fix.broken.includes.diff @@ -0,0 +1,11 @@ +--- ./libcap/include/sys/capability.h.orig 2008-07-10 01:18:40.000000000 -0500 ++++ ./libcap/include/sys/capability.h 2009-04-11 13:19:33.000000000 -0500 +@@ -19,7 +19,7 @@ + * information for the user library. + */ + +-#include <sys/types.h> ++#include <linux/types.h> + #include <stdint.h> + + /* diff --git a/source/l/libcap/slack-desc b/source/l/libcap/slack-desc new file mode 100644 index 00000000..01868635 --- /dev/null +++ b/source/l/libcap/slack-desc @@ -0,0 +1,19 @@ +# HOW TO EDIT THIS FILE: +# The "handy ruler" below makes it easier to edit a package description. Line +# up the first '|' above the ':' following the base package name, and the '|' +# on the right side marks the last column you can put a character in. You must +# make exactly 11 lines for the formatting to be correct. It's also +# customary to leave one space after the ':'. + + |-----handy-ruler------------------------------------------------------| +libcap: libcap (get/set POSIX capabilities) +libcap: +libcap: This is a library for getting and setting POSIX.1e (formerly POSIX 6) +libcap: draft 15 capabilities. +libcap: +libcap: Libcap was written by Andrew G. Morgan; however, it would not +libcap: have been possible without the help of Aleph1, Roland Buresund, +libcap: Andrew Main, and Alexander Kjeldaas. +libcap: +libcap: +libcap: |