Messages in this thread | | | Date | Fri, 30 Nov 2007 21:58:24 -0600 | From | serge@hallyn ... | Subject | Re: [PATCH] capabilities: introduce per-process capability bounding set (v10) |
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Quoting KaiGai Kohei (kaigai@kaigai.gr.jp): > Serge E. Hallyn wrote: > > The capability bounding set is a set beyond which capabilities > > cannot grow. Currently cap_bset is per-system. It can be > > manipulated through sysctl, but only init can add capabilities. > > Root can remove capabilities. By default it includes all caps > > except CAP_SETPCAP. > > Serge, > > This feature makes me being interested in. > I think you intend to apply this feature for the primary process > of security container. > However, it is also worthwhile to apply when a session is starting up. > > The following PAM module enables to drop capability bounding bit > specified by the fifth field in /etc/passwd entry. > This code is just an example now, but considerable feature. > > build and install: > # gcc -Wall -c pam_cap_drop.c > # gcc -Wall -shared -Xlinker -x -o pam_cap_drop.so pam_cap_drop.o -lpam > # cp pam_cap_drop.so /lib/security > > modify /etc/passwd as follows: > > tak:x:1004:100:cap_drop=cap_net_raw,cap_chown:/home/tak:/bin/bash > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > example: > [kaigai@masu ~]$ ping 192.168.1.1 > PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data. > 64 bytes from 192.168.1.1: icmp_seq=1 ttl=64 time=1.23 ms > 64 bytes from 192.168.1.1: icmp_seq=2 ttl=64 time=1.02 ms > > --- 192.168.1.1 ping statistics --- > 2 packets transmitted, 2 received, 0% packet loss, time 999ms > rtt min/avg/max/mdev = 1.023/1.130/1.237/0.107 ms > > [kaigai@masu ~]$ ssh tak@localhost > tak@localhost's password: > Last login: Sat Dec 1 10:09:29 2007 from masu.myhome.cx > [tak@masu ~]$ export LANG=C > [tak@masu ~]$ ping 192.168.1.1 > ping: icmp open socket: Operation not permitted > > [tak@masu ~]$ su > Password: > pam_cap_bset[6921]: user root does not have 'cap_drop=' property > [root@masu tak]# cat /proc/self/status | grep ^Cap > CapInh: 0000000000000000 > CapPrm: 00000000ffffdffe > CapEff: 00000000ffffdffe > [root@masu tak]#
Neat. A bigger-stick version of not adding the account to group wheel. I'll use that.
Is there any reason not to have a separate /etc/login.capbounds config file, though, so the account can still have a full name? Did you only use that for convenience of proof of concept, or is there another reason?
> # BTW, I replaced the James's address in the Cc: list, > # because MTA does not accept it.
Thanks! I don't know what happened to my alias for him...
thanks, -serge
> -- > KaiGai Kohei <kaigai@kaigai.gr.jp> > > ************************************************************ > pam_cap_drop.c > ************************************************************ > > /* > * pam_cap_drop.c module -- drop capabilities bounding set > * > * Copyright: 2007 KaiGai Kohei <kaigai@kaigai.gr.jp> > */ > > #include <errno.h> > #include <pwd.h> > #include <stdlib.h> > #include <stdio.h> > #include <string.h> > #include <syslog.h> > #include <sys/prctl.h> > #include <sys/types.h> > > #include <security/pam_modules.h> > > #ifndef PR_CAPBSET_DROP > #define PR_CAPBSET_DROP 24 > #endif > > static char *captable[] = { > "cap_chown", > "cap_dac_override", > "cap_dac_read_search", > "cap_fowner", > "cap_fsetid", > "cap_kill", > "cap_setgid", > "cap_setuid", > "cap_setpcap", > "cap_linux_immutable", > "cap_net_bind_service", > "cap_net_broadcast", > "cap_net_admin", > "cap_net_raw", > "cap_ipc_lock", > "cap_ipc_owner", > "cap_sys_module", > "cap_sys_rawio", > "cap_sys_chroot", > "cap_sys_ptrace", > "cap_sys_pacct", > "cap_sys_admin", > "cap_sys_boot", > "cap_sys_nice", > "cap_sys_resource", > "cap_sys_time", > "cap_sys_tty_config", > "cap_mknod", > "cap_lease", > "cap_audit_write", > "cap_audit_control", > "cap_setfcap", > NULL, > }; > > > PAM_EXTERN int > pam_sm_open_session(pam_handle_t *pamh, int flags, > int argc, const char **argv) > { > struct passwd *pwd; > char *pos, *buf; > char *username = NULL; > > /* open system logger */ > openlog("pam_cap_bset", LOG_PERROR | LOG_PID, LOG_AUTHPRIV); > > /* get the unix username */ > if (pam_get_item(pamh, PAM_USER, (void *) &username) != PAM_SUCCESS || !username) > return PAM_USER_UNKNOWN; > > /* get the passwd entry */ > pwd = getpwnam(username); > if (!pwd) > return PAM_USER_UNKNOWN; > > /* Is there "cap_drop=" ? */ > pos = strstr(pwd->pw_gecos, "cap_drop="); > if (pos) { > buf = strdup(pos + sizeof("cap_drop=") - 1); > if (!buf) > return PAM_SESSION_ERR; > pos = strtok(buf, ","); > while (pos) { > int rc, i; > > for (i=0; captable[i]; i++) { > if (!strcmp(pos, captable[i])) { > rc = prctl(PR_CAPBSET_DROP, i); > if (rc < 0) { > syslog(LOG_NOTICE, "user %s could not drop %s (%s)", > username, captable[i], strerror(errno)); > break; > } > syslog(LOG_NOTICE, "user %s drops %s\n", username, captable[i]); > goto next; > } > } > break; > next: > pos = strtok(NULL, ","); > } > free(buf); > } else { > syslog(LOG_NOTICE, "user %s does not have 'cap_drop=' property", username); > } > return PAM_SUCCESS; > } > > PAM_EXTERN int > pam_sm_close_session(pam_handle_t *pamh, int flags, > int argc, const char **argv) > { > /* do nothing */ > return PAM_SUCCESS; > } > > ************************************************************ > - > To unsubscribe from this list: send the line "unsubscribe linux-security-module" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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