/* Common capabilities, needed by capability.o and root_plug.o * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * */ #include <linux/capability.h>#include <linux/module.h>#include <linux/init.h>#include <linux/kernel.h>#include <linux/security.h>#include <linux/file.h>#include <linux/mm.h>#include <linux/mman.h>#include <linux/pagemap.h>#include <linux/swap.h>#include <linux/skbuff.h>#include <linux/netlink.h>#include <linux/ptrace.h>#include <linux/xattr.h>#include <linux/hugetlb.h>#include <linux/mount.h>#include <linux/sched.h>#include <linux/prctl.h>#include <linux/securebits.h> int cap_netlink_send(struct sock *sk, struct sk_buff *skb){ NETLINK_CB(skb).eff_cap = current->cap_effective; return 0;} int cap_netlink_recv(struct sk_buff *skb, int cap){ if (!cap_raised(NETLINK_CB(skb).eff_cap, cap)) return -EPERM; return 0;} EXPORT_SYMBOL(cap_netlink_recv); /* * NOTE WELL: cap_capable() cannot be used like the kernel's capable() * function. That is, it has the reverse semantics: cap_capable() * returns 0 when a task has a capability, but the kernel's capable() * returns 1 for this case. */int cap_capable (struct task_struct *tsk, int cap){ /* Derived from include/linux/sched.h:capable. */ if (cap_raised(tsk->cap_effective, cap)) return 0; return -EPERM;} int cap_settime(struct timespec *ts, struct timezone *tz){ if (!capable(CAP_SYS_TIME)) return -EPERM; return 0;} int cap_ptrace (struct task_struct *parent, struct task_struct *child){ /* Derived from arch/i386/kernel/ptrace.c:sys_ptrace. */ if (!cap_issubset(child->cap_permitted, parent->cap_permitted) && !__capable(parent, CAP_SYS_PTRACE)) return -EPERM; return 0;} int cap_capget (struct task_struct *target, kernel_cap_t *effective, kernel_cap_t *inheritable, kernel_cap_t *permitted){ /* Derived from kernel/capability.c:sys_capget. */ *effective = target->cap_effective; *inheritable = target->cap_inheritable; *permitted = target->cap_permitted; return 0;} #ifdef CONFIG_SECURITY_FILE_CAPABILITIES static inline int cap_block_setpcap(struct task_struct *target){ /* * No support for remote process capability manipulation with * filesystem capability support. */ return (target != current);} static inline int cap_inh_is_capped(void){ /* * Return 1 if changes to the inheritable set are limited * to the old permitted set. That is, if the current task * does *not* possess the CAP_SETPCAP capability. */ return (cap_capable(current, CAP_SETPCAP) != 0);} static inline int cap_limit_ptraced_target(void) { return 1; } #else /* ie., ndef CONFIG_SECURITY_FILE_CAPABILITIES */ static inline int cap_block_setpcap(struct task_struct *t) { return 0; }static inline int cap_inh_is_capped(void) { return 1; }static inline int cap_limit_ptraced_target(void){ return !capable(CAP_SETPCAP);} #endif /* def CONFIG_SECURITY_FILE_CAPABILITIES */ int cap_capset_check (struct task_struct *target, kernel_cap_t *effective, kernel_cap_t *inheritable, kernel_cap_t *permitted){ if (cap_block_setpcap(target)) { return -EPERM; } if (cap_inh_is_capped() && !cap_issubset(*inheritable, cap_combine(target->cap_inheritable, current->cap_permitted))) { /* incapable of using this inheritable set */ return -EPERM; } if (!cap_issubset(*inheritable, cap_combine(target->cap_inheritable, current->cap_bset))) { /* no new pI capabilities outside bounding set */ return -EPERM; } /* verify restrictions on target's new Permitted set */ if (!cap_issubset (*permitted, cap_combine (target->cap_permitted, current->cap_permitted))) { return -EPERM; } /* verify the _new_Effective_ is a subset of the _new_Permitted_ */ if (!cap_issubset (*effective, *permitted)) { return -EPERM; } return 0;} void cap_capset_set (struct task_struct *target, kernel_cap_t *effective, kernel_cap_t *inheritable, kernel_cap_t *permitted){ target->cap_effective = *effective; target->cap_inheritable = *inheritable; target->cap_permitted = *permitted;} static inline void bprm_clear_caps(struct linux_binprm *bprm){ cap_clear(bprm->cap_inheritable); cap_clear(bprm->cap_permitted); bprm->cap_effective = false;} #ifdef CONFIG_SECURITY_FILE_CAPABILITIES int cap_inode_need_killpriv(struct dentry *dentry){ struct inode *inode = dentry->d_inode; int error; if (!inode->i_op || !inode->i_op->getxattr) return 0; error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0); if (error <= 0) return 0; return 1;} int cap_inode_killpriv(struct dentry *dentry){ struct inode *inode = dentry->d_inode; if (!inode->i_op || !inode->i_op->removexattr) return 0; return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS);} static inline int cap_from_disk(struct vfs_cap_data *caps, struct linux_binprm *bprm, unsigned size){ __u32 magic_etc; unsigned tocopy, i; if (size < sizeof(magic_etc)) return -EINVAL; magic_etc = le32_to_cpu(caps->magic_etc); switch ((magic_etc & VFS_CAP_REVISION_MASK)) { case VFS_CAP_REVISION_1: if (size != XATTR_CAPS_SZ_1) return -EINVAL; tocopy = VFS_CAP_U32_1; break; case VFS_CAP_REVISION_2: if (size != XATTR_CAPS_SZ_2) return -EINVAL; tocopy = VFS_CAP_U32_2; break; default: return -EINVAL; } if (magic_etc & VFS_CAP_FLAGS_EFFECTIVE) { bprm->cap_effective = true; } else { bprm->cap_effective = false; } for (i = 0; i < tocopy; ++i) { bprm->cap_permitted.cap[i] = le32_to_cpu(caps->data[i].permitted); bprm->cap_inheritable.cap[i] = le32_to_cpu(caps->data[i].inheritable); } while (i < VFS_CAP_U32) { bprm->cap_permitted.cap[i] = 0; bprm->cap_inheritable.cap[i] = 0; i++; } return 0;} /* Locate any VFS capabilities: */static int get_file_caps(struct linux_binprm *bprm){ struct dentry *dentry; int rc = 0; struct vfs_cap_data vcaps; struct inode *inode; if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID) { bprm_clear_caps(bprm); return 0; } dentry = dget(bprm->file->f_dentry); inode = dentry->d_inode; if (!inode->i_op || !inode->i_op->getxattr) goto out; rc = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, &vcaps, XATTR_CAPS_SZ); if (rc == -ENODATA || rc == -EOPNOTSUPP) { /* no data, that's ok */ rc = 0; goto out; } if (rc < 0) goto out; rc = cap_from_disk(&vcaps, bprm, rc); if (rc) printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n", __func__, rc, bprm->filename); out: dput(dentry); if (rc) bprm_clear_caps(bprm); return rc;} #elseint cap_inode_need_killpriv(struct dentry *dentry){ return 0;} int cap_inode_killpriv(struct dentry *dentry){ return 0;} static inline int get_file_caps(struct linux_binprm *bprm){ bprm_clear_caps(bprm); return 0;}#endif int cap_bprm_set_security (struct linux_binprm *bprm){ int ret; ret = get_file_caps(bprm); if (ret) printk(KERN_NOTICE "%s: get_file_caps returned %d for %s\n", __func__, ret, bprm->filename); /* To support inheritance of root-permissions and suid-root * executables under compatibility mode, we raise all three * capability sets for the file. * * If only the real uid is 0, we only raise the inheritable * and permitted sets of the executable file. */ if (!issecure (SECURE_NOROOT)) { if (bprm->e_uid == 0 || current->uid == 0) { cap_set_full (bprm->cap_inheritable); cap_set_full (bprm->cap_permitted); } if (bprm->e_uid == 0) bprm->cap_effective = true; } return ret;} void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe){ /* Derived from fs/exec.c:compute_creds. */ kernel_cap_t new_permitted, working; new_permitted = cap_intersect(bprm->cap_permitted, current->cap_bset); working = cap_intersect(bprm->cap_inheritable, current->cap_inheritable); new_permitted = cap_combine(new_permitted, working); if (bprm->e_uid != current->uid || bprm->e_gid != current->gid || !cap_issubset (new_permitted, current->cap_permitted)) { set_dumpable(current->mm, suid_dumpable); current->pdeath_signal = 0; if (unsafe & ~LSM_UNSAFE_PTRACE_CAP) { if (!capable(CAP_SETUID)) { bprm->e_uid = current->uid; bprm->e_gid = current->gid; } if (cap_limit_ptraced_target()) { new_permitted = cap_intersect(new_permitted, current->cap_permitted); } } } current->suid = current->euid = current->fsuid = bprm->e_uid; current->sgid = current->egid = current->fsgid = bprm->e_gid; /* For init, we want to retain the capabilities set * in the init_task struct. Thus we skip the usual * capability rules */ if (!is_global_init(current)) { current->cap_permitted = new_permitted; if (bprm->cap_effective) current->cap_effective = new_permitted; else cap_clear(current->cap_effective); } /* AUD: Audit candidate if current->cap_effective is set */ current->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);} int cap_bprm_secureexec (struct linux_binprm *bprm){ if (current->uid != 0) { if (bprm->cap_effective) return 1; if (!cap_isclear(bprm->cap_permitted)) return 1; if (!cap_isclear(bprm->cap_inheritable)) return 1; } return (current->euid != current->uid || current->egid != current->gid);} int cap_inode_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags){ if (!strcmp(name, XATTR_NAME_CAPS)) { if (!capable(CAP_SETFCAP)) return -EPERM; return 0; } else if (!strncmp(name, XATTR_SECURITY_PREFIX, sizeof(XATTR_SECURITY_PREFIX) - 1) && !capable(CAP_SYS_ADMIN)) return -EPERM; return 0;} int cap_inode_removexattr(struct dentry *dentry, const char *name){ if (!strcmp(name, XATTR_NAME_CAPS)) { if (!capable(CAP_SETFCAP)) return -EPERM; return 0; } else if (!strncmp(name, XATTR_SECURITY_PREFIX, sizeof(XATTR_SECURITY_PREFIX) - 1) && !capable(CAP_SYS_ADMIN)) return -EPERM; return 0;} /* moved from kernel/sys.c. *//* * cap_emulate_setxuid() fixes the effective / permitted capabilities of * a process after a call to setuid, setreuid, or setresuid. * * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of * {r,e,s}uid != 0, the permitted and effective capabilities are * cleared. * * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective * capabilities of the process are cleared. * * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective * capabilities are set to the permitted capabilities. * * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should * never happen. * * -astor * * cevans - New behaviour, Oct '99 * A process may, via prctl(), elect to keep its capabilities when it * calls setuid() and switches away from uid==0. Both permitted and * effective sets will be retained. * Without this change, it was impossible for a daemon to drop only some * of its privilege. The call to setuid(!=0) would drop all privileges! * Keeping uid 0 is not an option because uid 0 owns too many vital * files.. * Thanks to Olaf Kirch and Peter Benie for spotting this. */static inline void cap_emulate_setxuid (int old_ruid, int old_euid, int old_suid){ if ((old_ruid == 0 || old_euid == 0 || old_suid == 0) && (current->uid != 0 && current->euid != 0 && current->suid != 0) && !issecure(SECURE_KEEP_CAPS)) { cap_clear (current->cap_permitted); cap_clear (current->cap_effective); } if (old_euid == 0 && current->euid != 0) { cap_clear (current->cap_effective); } if (old_euid != 0 && current->euid == 0) { current->cap_effective = current->cap_permitted; }} int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid, int flags){ switch (flags) { case LSM_SETID_RE: case LSM_SETID_ID: case LSM_SETID_RES: /* Copied from kernel/sys.c:setreuid/setuid/setresuid. */ if (!issecure (SECURE_NO_SETUID_FIXUP)) { cap_emulate_setxuid (old_ruid, old_euid, old_suid); } break; case LSM_SETID_FS: { uid_t old_fsuid = old_ruid; /* Copied from kernel/sys.c:setfsuid. */ /* * FIXME - is fsuser used for all CAP_FS_MASK capabilities? * if not, we might be a bit too harsh here. */ if (!issecure (SECURE_NO_SETUID_FIXUP)) { if (old_fsuid == 0 && current->fsuid != 0) { current->cap_effective = cap_drop_fs_set( current->cap_effective); } if (old_fsuid != 0 && current->fsuid == 0) { current->cap_effective = cap_raise_fs_set( current->cap_effective, current->cap_permitted);Lines 1–500 of 691. 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/* Common capabilities, needed by capability.o and root_plug.o * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * */ #include <linux/capability.h> #include <linux/module.h> #include <linux/init.h> #include <linux/kernel.h> #include <linux/security.h> #include <linux/file.h> #include <linux/mm.h> #include <linux/mman.h> #include <linux/pagemap.h> #include <linux/swap.h> #include <linux/skbuff.h> #include <linux/netlink.h> #include <linux/ptrace.h> #include <linux/xattr.h> #include <linux/hugetlb.h> #include <linux/mount.h> #include <linux/sched.h> #include <linux/prctl.h> #include <linux/securebits.h> int cap_netlink_send(struct sock *sk, struct sk_buff *skb) { NETLINK_CB(skb).eff_cap = current->cap_effective; return 0; } int cap_netlink_recv(struct sk_buff *skb, int cap) { if (!cap_raised(NETLINK_CB(skb).eff_cap, cap)) return -EPERM; return 0; } EXPORT_SYMBOL(cap_netlink_recv); /* * NOTE WELL: cap_capable() cannot be used like the kernel's capable() * function. That is, it has the reverse semantics: cap_capable() * returns 0 when a task has a capability, but the kernel's capable() * returns 1 for this case. */ int cap_capable (struct task_struct *tsk, int cap) { /* Derived from include/linux/sched.h:capable. */ if (cap_raised(tsk->cap_effective, cap)) return 0; return -EPERM; } int cap_settime(struct timespec *ts, struct timezone *tz) { if (!capable(CAP_SYS_TIME)) return -EPERM; return 0; } int cap_ptrace (struct task_struct *parent, struct task_struct *child) { /* Derived from arch/i386/kernel/ptrace.c:sys_ptrace. */ if (!cap_issubset(child->cap_permitted, parent->cap_permitted) && !__capable(parent, CAP_SYS_PTRACE)) return -EPERM; return 0; } int cap_capget (struct task_struct *target, kernel_cap_t *effective, kernel_cap_t *inheritable, kernel_cap_t *permitted) { /* Derived from kernel/capability.c:sys_capget. */ *effective = target->cap_effective; *inheritable = target->cap_inheritable; *permitted = target->cap_permitted; return 0; } #ifdef CONFIG_SECURITY_FILE_CAPABILITIES static inline int cap_block_setpcap(struct task_struct *target) { /* * No support for remote process capability manipulation with * filesystem capability support. */ return (target != current); } static inline int cap_inh_is_capped(void) { /* * Return 1 if changes to the inheritable set are limited * to the old permitted set. That is, if the current task * does *not* possess the CAP_SETPCAP capability. */ return (cap_capable(current, CAP_SETPCAP) != 0); } static inline int cap_limit_ptraced_target(void) { return 1; } #else /* ie., ndef CONFIG_SECURITY_FILE_CAPABILITIES */ static inline int cap_block_setpcap(struct task_struct *t) { return 0; } static inline int cap_inh_is_capped(void) { return 1; } static inline int cap_limit_ptraced_target(void) { return !capable(CAP_SETPCAP); } #endif /* def CONFIG_SECURITY_FILE_CAPABILITIES */ int cap_capset_check (struct task_struct *target, kernel_cap_t *effective, kernel_cap_t *inheritable, kernel_cap_t *permitted) { if (cap_block_setpcap(target)) { return -EPERM; } if (cap_inh_is_capped() && !cap_issubset(*inheritable, cap_combine(target->cap_inheritable, current->cap_permitted))) { /* incapable of using this inheritable set */ return -EPERM; } if (!cap_issubset(*inheritable, cap_combine(target->cap_inheritable, current->cap_bset))) { /* no new pI capabilities outside bounding set */ return -EPERM; } /* verify restrictions on target's new Permitted set */ if (!cap_issubset (*permitted, cap_combine (target->cap_permitted, current->cap_permitted))) { return -EPERM; } /* verify the _new_Effective_ is a subset of the _new_Permitted_ */ if (!cap_issubset (*effective, *permitted)) { return -EPERM; } return 0; } void cap_capset_set (struct task_struct *target, kernel_cap_t *effective, kernel_cap_t *inheritable, kernel_cap_t *permitted) { target->cap_effective = *effective; target->cap_inheritable = *inheritable; target->cap_permitted = *permitted; } static inline void bprm_clear_caps(struct linux_binprm *bprm) { cap_clear(bprm->cap_inheritable); cap_clear(bprm->cap_permitted); bprm->cap_effective = false; } #ifdef CONFIG_SECURITY_FILE_CAPABILITIES int cap_inode_need_killpriv(struct dentry *dentry) { struct inode *inode = dentry->d_inode; int error; if (!inode->i_op || !inode->i_op->getxattr) return 0; error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0); if (error <= 0) return 0; return 1; } int cap_inode_killpriv(struct dentry *dentry) { struct inode *inode = dentry->d_inode; if (!inode->i_op || !inode->i_op->removexattr) return 0; return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS); } static inline int cap_from_disk(struct vfs_cap_data *caps, struct linux_binprm *bprm, unsigned size) { __u32 magic_etc; unsigned tocopy, i; if (size < sizeof(magic_etc)) return -EINVAL; magic_etc = le32_to_cpu(caps->magic_etc); switch ((magic_etc & VFS_CAP_REVISION_MASK)) { case VFS_CAP_REVISION_1: if (size != XATTR_CAPS_SZ_1) return -EINVAL; tocopy = VFS_CAP_U32_1; break; case VFS_CAP_REVISION_2: if (size != XATTR_CAPS_SZ_2) return -EINVAL; tocopy = VFS_CAP_U32_2; break; default: return -EINVAL; } if (magic_etc & VFS_CAP_FLAGS_EFFECTIVE) { bprm->cap_effective = true; } else { bprm->cap_effective = false; } for (i = 0; i < tocopy; ++i) { bprm->cap_permitted.cap[i] = le32_to_cpu(caps->data[i].permitted); bprm->cap_inheritable.cap[i] = le32_to_cpu(caps->data[i].inheritable); } while (i < VFS_CAP_U32) { bprm->cap_permitted.cap[i] = 0; bprm->cap_inheritable.cap[i] = 0; i++; } return 0; } /* Locate any VFS capabilities: */ static int get_file_caps(struct linux_binprm *bprm) { struct dentry *dentry; int rc = 0; struct vfs_cap_data vcaps; struct inode *inode; if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID) { bprm_clear_caps(bprm); return 0; } dentry = dget(bprm->file->f_dentry); inode = dentry->d_inode; if (!inode->i_op || !inode->i_op->getxattr) goto out; rc = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, &vcaps, XATTR_CAPS_SZ); if (rc == -ENODATA || rc == -EOPNOTSUPP) { /* no data, that's ok */ rc = 0; goto out; } if (rc < 0) goto out; rc = cap_from_disk(&vcaps, bprm, rc); if (rc) printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n", __func__, rc, bprm->filename); out: dput(dentry); if (rc) bprm_clear_caps(bprm); return rc; } #else int cap_inode_need_killpriv(struct dentry *dentry) { return 0; } int cap_inode_killpriv(struct dentry *dentry) { return 0; } static inline int get_file_caps(struct linux_binprm *bprm) { bprm_clear_caps(bprm); return 0; } #endif int cap_bprm_set_security (struct linux_binprm *bprm) { int ret; ret = get_file_caps(bprm); if (ret) printk(KERN_NOTICE "%s: get_file_caps returned %d for %s\n", __func__, ret, bprm->filename); /* To support inheritance of root-permissions and suid-root * executables under compatibility mode, we raise all three * capability sets for the file. * * If only the real uid is 0, we only raise the inheritable * and permitted sets of the executable file. */ if (!issecure (SECURE_NOROOT)) { if (bprm->e_uid == 0 || current->uid == 0) { cap_set_full (bprm->cap_inheritable); cap_set_full (bprm->cap_permitted); } if (bprm->e_uid == 0) bprm->cap_effective = true; } return ret; } void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe) { /* Derived from fs/exec.c:compute_creds. */ kernel_cap_t new_permitted, working; new_permitted = cap_intersect(bprm->cap_permitted, current->cap_bset); working = cap_intersect(bprm->cap_inheritable, current->cap_inheritable); new_permitted = cap_combine(new_permitted, working); if (bprm->e_uid != current->uid || bprm->e_gid != current->gid || !cap_issubset (new_permitted, current->cap_permitted)) { set_dumpable(current->mm, suid_dumpable); current->pdeath_signal = 0; if (unsafe & ~LSM_UNSAFE_PTRACE_CAP) { if (!capable(CAP_SETUID)) { bprm->e_uid = current->uid; bprm->e_gid = current->gid; } if (cap_limit_ptraced_target()) { new_permitted = cap_intersect(new_permitted, current->cap_permitted); } } } current->suid = current->euid = current->fsuid = bprm->e_uid; current->sgid = current->egid = current->fsgid = bprm->e_gid; /* For init, we want to retain the capabilities set * in the init_task struct. Thus we skip the usual * capability rules */ if (!is_global_init(current)) { current->cap_permitted = new_permitted; if (bprm->cap_effective) current->cap_effective = new_permitted; else cap_clear(current->cap_effective); } /* AUD: Audit candidate if current->cap_effective is set */ current->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); } int cap_bprm_secureexec (struct linux_binprm *bprm) { if (current->uid != 0) { if (bprm->cap_effective) return 1; if (!cap_isclear(bprm->cap_permitted)) return 1; if (!cap_isclear(bprm->cap_inheritable)) return 1; } return (current->euid != current->uid || current->egid != current->gid); } int cap_inode_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags) { if (!strcmp(name, XATTR_NAME_CAPS)) { if (!capable(CAP_SETFCAP)) return -EPERM; return 0; } else if (!strncmp(name, XATTR_SECURITY_PREFIX, sizeof(XATTR_SECURITY_PREFIX) - 1) && !capable(CAP_SYS_ADMIN)) return -EPERM; return 0; } int cap_inode_removexattr(struct dentry *dentry, const char *name) { if (!strcmp(name, XATTR_NAME_CAPS)) { if (!capable(CAP_SETFCAP)) return -EPERM; return 0; } else if (!strncmp(name, XATTR_SECURITY_PREFIX, sizeof(XATTR_SECURITY_PREFIX) - 1) && !capable(CAP_SYS_ADMIN)) return -EPERM; return 0; } /* moved from kernel/sys.c. */ /* * cap_emulate_setxuid() fixes the effective / permitted capabilities of * a process after a call to setuid, setreuid, or setresuid. * * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of * {r,e,s}uid != 0, the permitted and effective capabilities are * cleared. * * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective * capabilities of the process are cleared. * * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective * capabilities are set to the permitted capabilities. * * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should * never happen. * * -astor * * cevans - New behaviour, Oct '99 * A process may, via prctl(), elect to keep its capabilities when it * calls setuid() and switches away from uid==0. Both permitted and * effective sets will be retained. * Without this change, it was impossible for a daemon to drop only some * of its privilege. The call to setuid(!=0) would drop all privileges! * Keeping uid 0 is not an option because uid 0 owns too many vital * files.. * Thanks to Olaf Kirch and Peter Benie for spotting this. */ static inline void cap_emulate_setxuid (int old_ruid, int old_euid, int old_suid) { if ((old_ruid == 0 || old_euid == 0 || old_suid == 0) && (current->uid != 0 && current->euid != 0 && current->suid != 0) && !issecure(SECURE_KEEP_CAPS)) { cap_clear (current->cap_permitted); cap_clear (current->cap_effective); } if (old_euid == 0 && current->euid != 0) { cap_clear (current->cap_effective); } if (old_euid != 0 && current->euid == 0) { current->cap_effective = current->cap_permitted; } } int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid, int flags) { switch (flags) { case LSM_SETID_RE: case LSM_SETID_ID: case LSM_SETID_RES: /* Copied from kernel/sys.c:setreuid/setuid/setresuid. */ if (!issecure (SECURE_NO_SETUID_FIXUP)) { cap_emulate_setxuid (old_ruid, old_euid, old_suid); } break; case LSM_SETID_FS: { uid_t old_fsuid = old_ruid; /* Copied from kernel/sys.c:setfsuid. */ /* * FIXME - is fsuser used for all CAP_FS_MASK capabilities? * if not, we might be a bit too harsh here. */ if (!issecure (SECURE_NO_SETUID_FIXUP)) { if (old_fsuid == 0 && current->fsuid != 0) { current->cap_effective = cap_drop_fs_set( current->cap_effective); } if (old_fsuid != 0 && current->fsuid == 0) { current->cap_effective = cap_raise_fs_set( current->cap_effective, current->cap_permitted);