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: [EMAIL PROTECTED] ~]$ 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 [EMAIL PROTECTED] ~]$ ssh [EMAIL PROTECTED] [EMAIL PROTECTED]'s password: Last login: Sat Dec 1 10:09:29 2007 from masu.myhome.cx [EMAIL PROTECTED] ~]$ export LANG=C [EMAIL PROTECTED] ~]$ ping 192.168.1.1 ping: icmp open socket: Operation not permitted [EMAIL PROTECTED] ~]$ su Password: pam_cap_bset[6921]: user root does not have 'cap_drop=' property [EMAIL PROTECTED] tak]# cat /proc/self/status | grep ^Cap CapInh: 0000000000000000 CapPrm: 00000000ffffdffe CapEff: 00000000ffffdffe [EMAIL PROTECTED] tak]# # BTW, I replaced the James's address in the Cc: list, # because MTA does not accept it. -- KaiGai Kohei <[EMAIL PROTECTED]> ************************************************************ pam_cap_drop.c ************************************************************ /* * pam_cap_drop.c module -- drop capabilities bounding set * * Copyright: 2007 KaiGai Kohei <[EMAIL PROTECTED]> */ #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-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/