| 1 | |
| 2 | *
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| 3 | * This program is free software; you can redistribute it and/or modify
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| 4 | * it under the terms of the GNU General Public License as published by
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| 5 | * the Free Software Foundation; either version 2 of the License, or
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| 6 | * (at your option) any later version.
|
| 7 | *
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| 8 |
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| 9 |
|
| 10 | #include <linux/capability.h>
|
| 11 | #include <linux/audit.h>
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| 12 | #include <linux/module.h>
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| 13 | #include <linux/init.h>
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| 14 | #include <linux/kernel.h>
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| 15 | #include <linux/lsm_hooks.h>
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| 16 | #include <linux/file.h>
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| 17 | #include <linux/mm.h>
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| 18 | #include <linux/mman.h>
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| 19 | #include <linux/pagemap.h>
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| 20 | #include <linux/swap.h>
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| 21 | #include <linux/skbuff.h>
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| 22 | #include <linux/netlink.h>
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| 23 | #include <linux/ptrace.h>
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| 24 | #include <linux/xattr.h>
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| 25 | #include <linux/hugetlb.h>
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| 26 | #include <linux/mount.h>
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| 27 | #include <linux/sched.h>
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| 28 | #include <linux/prctl.h>
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| 29 | #include <linux/securebits.h>
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| 30 | #include <linux/user_namespace.h>
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| 31 | #include <linux/binfmts.h>
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| 32 | #include <linux/personality.h>
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| 33 |
|
| 34 | |
| 35 | * If a non-root user executes a setuid-root binary in
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| 36 | * !secure(SECURE_NOROOT) mode, then we raise capabilities.
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| 37 | * However if fE is also set, then the intent is for only
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| 38 | * the file capabilities to be applied, and the setuid-root
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| 39 | * bit is left on either to change the uid (plausible) or
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| 40 | * to get full privilege on a kernel without file capabilities
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| 41 | * support. So in that case we do not raise capabilities.
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| 42 | *
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| 43 | * Warn if that happens, once per boot.
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| 44 |
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| 45 | static void warn_setuid_and_fcaps_mixed(const char *fname)
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| 46 | {
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| 47 | static int warned;
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| 48 | if (!warned) {
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| 49 | printk(KERN_INFO "warning: `%s' has both setuid-root and"
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| 50 | " effective capabilities. Therefore not raising all"
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| 51 | " capabilities.\n", fname);
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| 52 | warned = 1;
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| 53 | }
|
| 54 | }
|
| 55 |
|
| 56 | |
| 57 | * cap_capable - Determine whether a task has a particular effective capability
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| 58 | * @cred: The credentials to use
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| 59 | * @ns: The user namespace in which we need the capability
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| 60 | * @cap: The capability to check for
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| 61 | * @audit: Whether to write an audit message or not
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| 62 | *
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| 63 | * Determine whether the nominated task has the specified capability amongst
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| 64 | * its effective set, returning 0 if it does, -ve if it does not.
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| 65 | *
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| 66 | * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
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| 67 | * and has_capability() functions. That is, it has the reverse semantics:
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| 68 | * cap_has_capability() returns 0 when a task has a capability, but the
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| 69 | * kernel's capable() and has_capability() returns 1 for this case.
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| 70 |
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| 71 | int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
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| 72 | int cap, int audit)
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| 73 | {
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| 74 | struct user_namespace *ns = targ_ns;
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| 75 |
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| 76 | |
| 77 | * by examining the target user namespace and all of the target
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| 78 | * user namespace's parents.
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| 79 |
|
| 80 | for (;;) {
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| 81 |
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| 82 | if (ns == cred->user_ns)
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| 83 | return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
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| 84 |
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| 85 |
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| 86 | if (ns == &init_user_ns)
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| 87 | return -EPERM;
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| 88 |
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| 89 | |
| 90 | * The owner of the user namespace in the parent of the
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| 91 | * user namespace has all caps.
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| 92 |
|
| 93 | if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid))
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| 94 | return 0;
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| 95 |
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| 96 | |
| 97 | * If you have a capability in a parent user ns, then you have
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| 98 | * it over all children user namespaces as well.
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| 99 |
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| 100 | ns = ns->parent;
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| 101 | }
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| 102 |
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| 103 |
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| 104 | }
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| 105 |
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| 106 | |
| 107 | * cap_settime - Determine whether the current process may set the system clock
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| 108 | * @ts: The time to set
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| 109 | * @tz: The timezone to set
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| 110 | *
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| 111 | * Determine whether the current process may set the system clock and timezone
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| 112 | * information, returning 0 if permission granted, -ve if denied.
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| 113 |
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| 114 | int cap_settime(const struct timespec *ts, const struct timezone *tz)
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| 115 | {
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| 116 | if (!capable(CAP_SYS_TIME))
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| 117 | return -EPERM;
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| 118 | return 0;
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| 119 | }
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| 120 |
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| 121 | |
| 122 | * cap_ptrace_access_check - Determine whether the current process may access
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| 123 | * another
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| 124 | * @child: The process to be accessed
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| 125 | * @mode: The mode of attachment.
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| 126 | *
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| 127 | * If we are in the same or an ancestor user_ns and have all the target
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| 128 | * task's capabilities, then ptrace access is allowed.
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| 129 | * If we have the ptrace capability to the target user_ns, then ptrace
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| 130 | * access is allowed.
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| 131 | * Else denied.
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| 132 | *
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| 133 | * Determine whether a process may access another, returning 0 if permission
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| 134 | * granted, -ve if denied.
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| 135 |
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| 136 | int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
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| 137 | {
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| 138 | int ret = 0;
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| 139 | const struct cred *cred, *child_cred;
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| 140 |
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| 141 | rcu_read_lock();
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| 142 | cred = current_cred();
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| 143 | child_cred = __task_cred(child);
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| 144 | if (cred->user_ns == child_cred->user_ns &&
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| 145 | cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
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| 146 | goto out;
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| 147 | if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE))
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| 148 | goto out;
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| 149 | ret = -EPERM;
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| 150 | out:
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| 151 | rcu_read_unlock();
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| 152 | return ret;
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| 153 | }
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| 154 |
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| 155 | |
| 156 | * cap_ptrace_traceme - Determine whether another process may trace the current
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| 157 | * @parent: The task proposed to be the tracer
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| 158 | *
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| 159 | * If parent is in the same or an ancestor user_ns and has all current's
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| 160 | * capabilities, then ptrace access is allowed.
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| 161 | * If parent has the ptrace capability to current's user_ns, then ptrace
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| 162 | * access is allowed.
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| 163 | * Else denied.
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| 164 | *
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| 165 | * Determine whether the nominated task is permitted to trace the current
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| 166 | * process, returning 0 if permission is granted, -ve if denied.
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| 167 |
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| 168 | int cap_ptrace_traceme(struct task_struct *parent)
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| 169 | {
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| 170 | int ret = 0;
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| 171 | const struct cred *cred, *child_cred;
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| 172 |
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| 173 | rcu_read_lock();
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| 174 | cred = __task_cred(parent);
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| 175 | child_cred = current_cred();
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| 176 | if (cred->user_ns == child_cred->user_ns &&
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| 177 | cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
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| 178 | goto out;
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| 179 | if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE))
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| 180 | goto out;
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| 181 | ret = -EPERM;
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| 182 | out:
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| 183 | rcu_read_unlock();
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| 184 | return ret;
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| 185 | }
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| 186 |
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| 187 | |
| 188 | * cap_capget - Retrieve a task's capability sets
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| 189 | * @target: The task from which to retrieve the capability sets
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| 190 | * @effective: The place to record the effective set
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| 191 | * @inheritable: The place to record the inheritable set
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| 192 | * @permitted: The place to record the permitted set
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| 193 | *
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| 194 | * This function retrieves the capabilities of the nominated task and returns
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| 195 | * them to the caller.
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| 196 |
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| 197 | int cap_capget(struct task_struct *target, kernel_cap_t *effective,
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| 198 | kernel_cap_t *inheritable, kernel_cap_t *permitted)
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| 199 | {
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| 200 | const struct cred *cred;
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| 201 |
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| 202 |
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| 203 | rcu_read_lock();
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| 204 | cred = __task_cred(target);
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| 205 | *effective = cred->cap_effective;
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| 206 | *inheritable = cred->cap_inheritable;
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| 207 | *permitted = cred->cap_permitted;
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| 208 | rcu_read_unlock();
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| 209 | return 0;
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| 210 | }
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| 211 |
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| 212 | |
| 213 | * Determine whether the inheritable capabilities are limited to the old
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| 214 | * permitted set. Returns 1 if they are limited, 0 if they are not.
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| 215 |
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| 216 | static inline int cap_inh_is_capped(void)
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| 217 | {
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| 218 |
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| 219 | |
| 220 | * capability
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| 221 |
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| 222 | if (cap_capable(current_cred(), current_cred()->user_ns,
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| 223 | CAP_SETPCAP, SECURITY_CAP_AUDIT) == 0)
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| 224 | return 0;
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| 225 | return 1;
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| 226 | }
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| 227 |
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| 228 | |
| 229 | * cap_capset - Validate and apply proposed changes to current's capabilities
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| 230 | * @new: The proposed new credentials; alterations should be made here
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| 231 | * @old: The current task's current credentials
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| 232 | * @effective: A pointer to the proposed new effective capabilities set
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| 233 | * @inheritable: A pointer to the proposed new inheritable capabilities set
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| 234 | * @permitted: A pointer to the proposed new permitted capabilities set
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| 235 | *
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| 236 | * This function validates and applies a proposed mass change to the current
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| 237 | * process's capability sets. The changes are made to the proposed new
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| 238 | * credentials, and assuming no error, will be committed by the caller of LSM.
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| 239 |
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| 240 | int cap_capset(struct cred *new,
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| 241 | const struct cred *old,
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| 242 | const kernel_cap_t *effective,
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| 243 | const kernel_cap_t *inheritable,
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| 244 | const kernel_cap_t *permitted)
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| 245 | {
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| 246 | if (cap_inh_is_capped() &&
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| 247 | !cap_issubset(*inheritable,
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| 248 | cap_combine(old->cap_inheritable,
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| 249 | old->cap_permitted)))
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| 250 |
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| 251 | return -EPERM;
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| 252 |
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| 253 | if (!cap_issubset(*inheritable,
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| 254 | cap_combine(old->cap_inheritable,
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| 255 | old->cap_bset)))
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| 256 |
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| 257 | return -EPERM;
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| 258 |
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| 259 |
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| 260 | if (!cap_issubset(*permitted, old->cap_permitted))
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| 261 | return -EPERM;
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| 262 |
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| 263 |
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| 264 | if (!cap_issubset(*effective, *permitted))
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| 265 | return -EPERM;
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| 266 |
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| 267 | new->cap_effective = *effective;
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| 268 | new->cap_inheritable = *inheritable;
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| 269 | new->cap_permitted = *permitted;
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| 270 | return 0;
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| 271 | }
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| 272 |
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| 273 | |
| 274 | * Clear proposed capability sets for execve().
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| 275 |
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| 276 | static inline void bprm_clear_caps(struct linux_binprm *bprm)
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| 277 | {
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| 278 | cap_clear(bprm->cred->cap_permitted);
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| 279 | bprm->cap_effective = false;
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| 280 | }
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| 281 |
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| 282 | |
| 283 | * cap_inode_need_killpriv - Determine if inode change affects privileges
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| 284 | * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
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| 285 | *
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| 286 | * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
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| 287 | * affects the security markings on that inode, and if it is, should
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| 288 | * inode_killpriv() be invoked or the change rejected?
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| 289 | *
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| 290 | * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and
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| 291 | * -ve to deny the change.
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| 292 |
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| 293 | int cap_inode_need_killpriv(struct dentry *dentry)
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| 294 | {
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| 295 | struct inode *inode = d_backing_inode(dentry);
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| 296 | int error;
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| 297 |
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| 298 | if (!inode->i_op->getxattr)
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| 299 | return 0;
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| 300 |
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| 301 | error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0);
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| 302 | if (error <= 0)
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| 303 | return 0;
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| 304 | return 1;
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| 305 | }
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| 306 |
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| 307 | |
| 308 | * cap_inode_killpriv - Erase the security markings on an inode
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| 309 | * @dentry: The inode/dentry to alter
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| 310 | *
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| 311 | * Erase the privilege-enhancing security markings on an inode.
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| 312 | *
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| 313 | * Returns 0 if successful, -ve on error.
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| 314 |
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| 315 | int cap_inode_killpriv(struct dentry *dentry)
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| 316 | {
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| 317 | struct inode *inode = d_backing_inode(dentry);
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| 318 |
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| 319 | if (!inode->i_op->removexattr)
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| 320 | return 0;
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| 321 |
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| 322 | return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS);
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| 323 | }
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| 324 |
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| 325 | |
| 326 | * Calculate the new process capability sets from the capability sets attached
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| 327 | * to a file.
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| 328 |
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| 329 | static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
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| 330 | struct linux_binprm *bprm,
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| 331 | bool *effective,
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| 332 | bool *has_cap)
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| 333 | {
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| 334 | struct cred *new = bprm->cred;
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| 335 | unsigned i;
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| 336 | int ret = 0;
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| 337 |
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| 338 | if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
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| 339 | *effective = true;
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| 340 |
|
| 341 | if (caps->magic_etc & VFS_CAP_REVISION_MASK)
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| 342 | *has_cap = true;
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| 343 |
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| 344 | CAP_FOR_EACH_U32(i) {
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| 345 | __u32 permitted = caps->permitted.cap[i];
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| 346 | __u32 inheritable = caps->inheritable.cap[i];
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| 347 |
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| 348 | |
| 349 | * pP' = (X & fP) | (pI & fI)
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| 350 |
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| 351 | new->cap_permitted.cap[i] =
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| 352 | (new->cap_bset.cap[i] & permitted) |
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| 353 | (new->cap_inheritable.cap[i] & inheritable);
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| 354 |
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| 355 | if (permitted & ~new->cap_permitted.cap[i])
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| 356 |
|
| 357 | ret = -EPERM;
|
| 358 | }
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| 359 |
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| 360 | |
| 361 | * For legacy apps, with no internal support for recognizing they
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| 362 | * do not have enough capabilities, we return an error if they are
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| 363 | * missing some "forced" (aka file-permitted) capabilities.
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| 364 |
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| 365 | return *effective ? ret : 0;
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| 366 | }
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| 367 |
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| 368 | |
| 369 | * Extract the on-exec-apply capability sets for an executable file.
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| 370 |
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| 371 | int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps)
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| 372 | {
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| 373 | struct inode *inode = d_backing_inode(dentry);
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| 374 | __u32 magic_etc;
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| 375 | unsigned tocopy, i;
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| 376 | int size;
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| 377 | struct vfs_cap_data caps;
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| 378 |
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| 379 | memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
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| 380 |
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| 381 | if (!inode || !inode->i_op->getxattr)
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| 382 | return -ENODATA;
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| 383 |
|
| 384 | size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps,
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| 385 | XATTR_CAPS_SZ);
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| 386 | if (size == -ENODATA || size == -EOPNOTSUPP)
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| 387 |
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| 388 | return -ENODATA;
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| 389 | if (size < 0)
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| 390 | return size;
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| 391 |
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| 392 | if (size < sizeof(magic_etc))
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| 393 | return -EINVAL;
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| 394 |
|
| 395 | cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc);
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| 396 |
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| 397 | switch (magic_etc & VFS_CAP_REVISION_MASK) {
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| 398 | case VFS_CAP_REVISION_1:
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| 399 | if (size != XATTR_CAPS_SZ_1)
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| 400 | return -EINVAL;
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| 401 | tocopy = VFS_CAP_U32_1;
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| 402 | break;
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| 403 | case VFS_CAP_REVISION_2:
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| 404 | if (size != XATTR_CAPS_SZ_2)
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| 405 | return -EINVAL;
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| 406 | tocopy = VFS_CAP_U32_2;
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| 407 | break;
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| 408 | default:
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| 409 | return -EINVAL;
|
| 410 | }
|
| 411 |
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| 412 | CAP_FOR_EACH_U32(i) {
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| 413 | if (i >= tocopy)
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| 414 | break;
|
| 415 | cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted);
|
| 416 | cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable);
|
| 417 | }
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| 418 |
|
| 419 | cpu_caps->permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
|
| 420 | cpu_caps->inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
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| 421 |
|
| 422 | return 0;
|
| 423 | }
|
| 424 |
|
| 425 | |
| 426 | * Attempt to get the on-exec apply capability sets for an executable file from
|
| 427 | * its xattrs and, if present, apply them to the proposed credentials being
|
| 428 | * constructed by execve().
|
| 429 |
|
| 430 | static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap)
|
| 431 | {
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| 432 | int rc = 0;
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| 433 | struct cpu_vfs_cap_data vcaps;
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| 434 |
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| 435 | bprm_clear_caps(bprm);
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| 436 |
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| 437 | if (!file_caps_enabled)
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| 438 | return 0;
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| 439 |
|
| 440 | if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)
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| 441 | return 0;
|
| 442 |
|
| 443 | rc = get_vfs_caps_from_disk(bprm->file->f_path.dentry, &vcaps);
|
| 444 | if (rc < 0) {
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| 445 | if (rc == -EINVAL)
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| 446 | printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n",
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| 447 | __func__, rc, bprm->filename);
|
| 448 | else if (rc == -ENODATA)
|
| 449 | rc = 0;
|
| 450 | goto out;
|
| 451 | }
|
| 452 |
|
| 453 | rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap);
|
| 454 | if (rc == -EINVAL)
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| 455 | printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n",
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| 456 | __func__, rc, bprm->filename);
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| 457 |
|
| 458 | out:
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| 459 | if (rc)
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| 460 | bprm_clear_caps(bprm);
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| 461 |
|
| 462 | return rc;
|
| 463 | }
|
| 464 |
|
| 465 | |
| 466 | * cap_bprm_set_creds - Set up the proposed credentials for execve().
|
| 467 | * @bprm: The execution parameters, including the proposed creds
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| 468 | *
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| 469 | * Set up the proposed credentials for a new execution context being
|
| 470 | * constructed by execve(). The proposed creds in @bprm->cred is altered,
|
| 471 | * which won't take effect immediately. Returns 0 if successful, -ve on error.
|
| 472 |
|
| 473 | int cap_bprm_set_creds(struct linux_binprm *bprm)
|
| 474 | {
|
| 475 | const struct cred *old = current_cred();
|
| 476 | struct cred *new = bprm->cred;
|
| 477 | bool effective, has_cap = false;
|
| 478 | int ret;
|
| 479 | kuid_t root_uid;
|
| 480 |
|
| 481 | effective = false;
|
| 482 | ret = get_file_caps(bprm, &effective, &has_cap);
|
| 483 | if (ret < 0)
|
| 484 | return ret;
|
| 485 |
|
| 486 | root_uid = make_kuid(new->user_ns, 0);
|
| 487 |
|
| 488 | if (!issecure(SECURE_NOROOT)) {
|
| 489 | |
| 490 | * If the legacy file capability is set, then don't set privs
|
| 491 | * for a setuid root binary run by a non-root user. Do set it
|
| 492 | * for a root user just to cause least surprise to an admin.
|
| 493 |
|
| 494 | if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) {
|
| 495 | warn_setuid_and_fcaps_mixed(bprm->filename);
|
| 496 | goto skip;
|
| 497 | }
|
| 498 | |
| 499 | * To support inheritance of root-permissions and suid-root
|
| 500 | * executables under compatibility mode, we override the
|
| 501 | * capability sets for the file.
|
| 502 | *
|
| 503 | * If only the real uid is 0, we do not set the effective bit.
|
| 504 |
|
| 505 | if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) {
|
| 506 |
|
| 507 | new->cap_permitted = cap_combine(old->cap_bset,
|
| 508 | old->cap_inheritable);
|
| 509 | }
|
| 510 | if (uid_eq(new->euid, root_uid))
|
| 511 | effective = true;
|
| 512 | }
|
| 513 | skip:
|
| 514 |
|
| 515 |
|
| 516 | if (!cap_issubset(new->cap_permitted, old->cap_permitted))
|
| 517 | bprm->per_clear |= PER_CLEAR_ON_SETID;
|
| 518 |
|
| 519 |
|
| 520 | |
| 521 | * credentials unless they have the appropriate permit.
|
| 522 | *
|
| 523 | * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
|
| 524 |
|
| 525 | if ((!uid_eq(new->euid, old->uid) ||
|
| 526 | !gid_eq(new->egid, old->gid) ||
|
| 527 | !cap_issubset(new->cap_permitted, old->cap_permitted)) &&
|
| 528 | bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
|
| 529 |
|
| 530 | if (!capable(CAP_SETUID) ||
|
| 531 | (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {
|
| 532 | new->euid = new->uid;
|
| 533 | new->egid = new->gid;
|
| 534 | }
|
| 535 | new->cap_permitted = cap_intersect(new->cap_permitted,
|
| 536 | old->cap_permitted);
|
| 537 | }
|
| 538 |
|
| 539 | new->suid = new->fsuid = new->euid;
|
| 540 | new->sgid = new->fsgid = new->egid;
|
| 541 |
|
| 542 | if (effective)
|
| 543 | new->cap_effective = new->cap_permitted;
|
| 544 | else
|
| 545 | cap_clear(new->cap_effective);
|
| 546 | bprm->cap_effective = effective;
|
| 547 |
|
| 548 | |
| 549 | * Audit candidate if current->cap_effective is set
|
| 550 | *
|
| 551 | * We do not bother to audit if 3 things are true:
|
| 552 | * 1) cap_effective has all caps
|
| 553 | * 2) we are root
|
| 554 | * 3) root is supposed to have all caps (SECURE_NOROOT)
|
| 555 | * Since this is just a normal root execing a process.
|
| 556 | *
|
| 557 | * Number 1 above might fail if you don't have a full bset, but I think
|
| 558 | * that is interesting information to audit.
|
| 559 |
|
| 560 | if (!cap_isclear(new->cap_effective)) {
|
| 561 | if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||
|
| 562 | !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) ||
|
| 563 | issecure(SECURE_NOROOT)) {
|
| 564 | ret = audit_log_bprm_fcaps(bprm, new, old);
|
| 565 | if (ret < 0)
|
| 566 | return ret;
|
| 567 | }
|
| 568 | }
|
| 569 |
|
| 570 | new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
|
| 571 | return 0;
|
| 572 | }
|
| 573 |
|
| 574 | |
| 575 | * cap_bprm_secureexec - Determine whether a secure execution is required
|
| 576 | * @bprm: The execution parameters
|
| 577 | *
|
| 578 | * Determine whether a secure execution is required, return 1 if it is, and 0
|
| 579 | * if it is not.
|
| 580 | *
|
| 581 | * The credentials have been committed by this point, and so are no longer
|
| 582 | * available through @bprm->cred.
|
| 583 |
|
| 584 | int cap_bprm_secureexec(struct linux_binprm *bprm)
|
| 585 | {
|
| 586 | const struct cred *cred = current_cred();
|
| 587 | kuid_t root_uid = make_kuid(cred->user_ns, 0);
|
| 588 |
|
| 589 | if (!uid_eq(cred->uid, root_uid)) {
|
| 590 | if (bprm->cap_effective)
|
| 591 | return 1;
|
| 592 | if (!cap_isclear(cred->cap_permitted))
|
| 593 | return 1;
|
| 594 | }
|
| 595 |
|
| 596 | return (!uid_eq(cred->euid, cred->uid) ||
|
| 597 | !gid_eq(cred->egid, cred->gid));
|
| 598 | }
|
| 599 |
|
| 600 | |
| 601 | * cap_inode_setxattr - Determine whether an xattr may be altered
|
| 602 | * @dentry: The inode/dentry being altered
|
| 603 | * @name: The name of the xattr to be changed
|
| 604 | * @value: The value that the xattr will be changed to
|
| 605 | * @size: The size of value
|
| 606 | * @flags: The replacement flag
|
| 607 | *
|
| 608 | * Determine whether an xattr may be altered or set on an inode, returning 0 if
|
| 609 | * permission is granted, -ve if denied.
|
| 610 | *
|
| 611 | * This is used to make sure security xattrs don't get updated or set by those
|
| 612 | * who aren't privileged to do so.
|
| 613 |
|
| 614 | int cap_inode_setxattr(struct dentry *dentry, const char *name,
|
| 615 | const void *value, size_t size, int flags)
|
| 616 | {
|
| 617 | if (!strcmp(name, XATTR_NAME_CAPS)) {
|
| 618 | if (!capable(CAP_SETFCAP))
|
| 619 | return -EPERM;
|
| 620 | return 0;
|
| 621 | }
|
| 622 |
|
| 623 | if (!strncmp(name, XATTR_SECURITY_PREFIX,
|
| 624 | sizeof(XATTR_SECURITY_PREFIX) - 1) &&
|
| 625 | !capable(CAP_SYS_ADMIN))
|
| 626 | return -EPERM;
|
| 627 | return 0;
|
| 628 | }
|
| 629 |
|
| 630 | |
| 631 | * cap_inode_removexattr - Determine whether an xattr may be removed
|
| 632 | * @dentry: The inode/dentry being altered
|
| 633 | * @name: The name of the xattr to be changed
|
| 634 | *
|
| 635 | * Determine whether an xattr may be removed from an inode, returning 0 if
|
| 636 | * permission is granted, -ve if denied.
|
| 637 | *
|
| 638 | * This is used to make sure security xattrs don't get removed by those who
|
| 639 | * aren't privileged to remove them.
|
| 640 |
|
| 641 | int cap_inode_removexattr(struct dentry *dentry, const char *name)
|
| 642 | {
|
| 643 | if (!strcmp(name, XATTR_NAME_CAPS)) {
|
| 644 | if (!capable(CAP_SETFCAP))
|
| 645 | return -EPERM;
|
| 646 | return 0;
|
| 647 | }
|
| 648 |
|
| 649 | if (!strncmp(name, XATTR_SECURITY_PREFIX,
|
| 650 | sizeof(XATTR_SECURITY_PREFIX) - 1) &&
|
| 651 | !capable(CAP_SYS_ADMIN))
|
| 652 | return -EPERM;
|
| 653 | return 0;
|
| 654 | }
|
| 655 |
|
| 656 | |
| 657 | * cap_emulate_setxuid() fixes the effective / permitted capabilities of
|
| 658 | * a process after a call to setuid, setreuid, or setresuid.
|
| 659 | *
|
| 660 | * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
|
| 661 | * {r,e,s}uid != 0, the permitted and effective capabilities are
|
| 662 | * cleared.
|
| 663 | *
|
| 664 | * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
|
| 665 | * capabilities of the process are cleared.
|
| 666 | *
|
| 667 | * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
|
| 668 | * capabilities are set to the permitted capabilities.
|
| 669 | *
|
| 670 | * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
|
| 671 | * never happen.
|
| 672 | *
|
| 673 | * -astor
|
| 674 | *
|
| 675 | * cevans - New behaviour, Oct '99
|
| 676 | * A process may, via prctl(), elect to keep its capabilities when it
|
| 677 | * calls setuid() and switches away from uid==0. Both permitted and
|
| 678 | * effective sets will be retained.
|
| 679 | * Without this change, it was impossible for a daemon to drop only some
|
| 680 | * of its privilege. The call to setuid(!=0) would drop all privileges!
|
| 681 | * Keeping uid 0 is not an option because uid 0 owns too many vital
|
| 682 | * files..
|
| 683 | * Thanks to Olaf Kirch and Peter Benie for spotting this.
|
| 684 |
|
| 685 | static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
|
| 686 | {
|
| 687 | kuid_t root_uid = make_kuid(old->user_ns, 0);
|
| 688 |
|
| 689 | if ((uid_eq(old->uid, root_uid) ||
|
| 690 | uid_eq(old->euid, root_uid) ||
|
| 691 | uid_eq(old->suid, root_uid)) &&
|
| 692 | (!uid_eq(new->uid, root_uid) &&
|
| 693 | !uid_eq(new->euid, root_uid) &&
|
| 694 | !uid_eq(new->suid, root_uid)) &&
|
| 695 | !issecure(SECURE_KEEP_CAPS)) {
|
| 696 | cap_clear(new->cap_permitted);
|
| 697 | cap_clear(new->cap_effective);
|
| 698 | }
|
| 699 | if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))
|
| 700 | cap_clear(new->cap_effective);
|
| 701 | if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))
|
| 702 | new->cap_effective = new->cap_permitted;
|
| 703 | }
|
| 704 |
|
| 705 | |
| 706 | * cap_task_fix_setuid - Fix up the results of setuid() call
|
| 707 | * @new: The proposed credentials
|
| 708 | * @old: The current task's current credentials
|
| 709 | * @flags: Indications of what has changed
|
| 710 | *
|
| 711 | * Fix up the results of setuid() call before the credential changes are
|
| 712 | * actually applied, returning 0 to grant the changes, -ve to deny them.
|
| 713 |
|
| 714 | int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
|
| 715 | {
|
| 716 | switch (flags) {
|
| 717 | case LSM_SETID_RE:
|
| 718 | case LSM_SETID_ID:
|
| 719 | case LSM_SETID_RES:
|
| 720 | |
| 721 | * otherwise suppressed
|
| 722 | if (!issecure(SECURE_NO_SETUID_FIXUP))
|
| 723 | cap_emulate_setxuid(new, old);
|
| 724 | break;
|
| 725 |
|
| 726 | case LSM_SETID_FS:
|
| 727 | |
| 728 | * otherwise suppressed
|
| 729 | *
|
| 730 | * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
|
| 731 | * if not, we might be a bit too harsh here.
|
| 732 |
|
| 733 | if (!issecure(SECURE_NO_SETUID_FIXUP)) {
|
| 734 | kuid_t root_uid = make_kuid(old->user_ns, 0);
|
| 735 | if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))
|
| 736 | new->cap_effective =
|
| 737 | cap_drop_fs_set(new->cap_effective);
|
| 738 |
|
| 739 | if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))
|
| 740 | new->cap_effective =
|
| 741 | cap_raise_fs_set(new->cap_effective,
|
| 742 | new->cap_permitted);
|
| 743 | }
|
| 744 | break;
|
| 745 |
|
| 746 | default:
|
| 747 | return -EINVAL;
|
| 748 | }
|
| 749 |
|
| 750 | return 0;
|
| 751 | }
|
| 752 |
|
| 753 | |
| 754 | * Rationale: code calling task_setscheduler, task_setioprio, and
|
| 755 | * task_setnice, assumes that
|
| 756 | * . if capable(cap_sys_nice), then those actions should be allowed
|
| 757 | * . if not capable(cap_sys_nice), but acting on your own processes,
|
| 758 | * then those actions should be allowed
|
| 759 | * This is insufficient now since you can call code without suid, but
|
| 760 | * yet with increased caps.
|
| 761 | * So we check for increased caps on the target process.
|
| 762 |
|
| 763 | static int cap_safe_nice(struct task_struct *p)
|
| 764 | {
|
| 765 | int is_subset, ret = 0;
|
| 766 |
|
| 767 | rcu_read_lock();
|
| 768 | is_subset = cap_issubset(__task_cred(p)->cap_permitted,
|
| 769 | current_cred()->cap_permitted);
|
| 770 | if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
|
| 771 | ret = -EPERM;
|
| 772 | rcu_read_unlock();
|
| 773 |
|
| 774 | return ret;
|
| 775 | }
|
| 776 |
|
| 777 | |
| 778 | * cap_task_setscheduler - Detemine if scheduler policy change is permitted
|
| 779 | * @p: The task to affect
|
| 780 | *
|
| 781 | * Detemine if the requested scheduler policy change is permitted for the
|
| 782 | * specified task, returning 0 if permission is granted, -ve if denied.
|
| 783 |
|
| 784 | int cap_task_setscheduler(struct task_struct *p)
|
| 785 | {
|
| 786 | return cap_safe_nice(p);
|
| 787 | }
|
| 788 |
|
| 789 | |
| 790 | * cap_task_ioprio - Detemine if I/O priority change is permitted
|
| 791 | * @p: The task to affect
|
| 792 | * @ioprio: The I/O priority to set
|
| 793 | *
|
| 794 | * Detemine if the requested I/O priority change is permitted for the specified
|
| 795 | * task, returning 0 if permission is granted, -ve if denied.
|
| 796 |
|
| 797 | int cap_task_setioprio(struct task_struct *p, int ioprio)
|
| 798 | {
|
| 799 | return cap_safe_nice(p);
|
| 800 | }
|
| 801 |
|
| 802 | |
| 803 | * cap_task_ioprio - Detemine if task priority change is permitted
|
| 804 | * @p: The task to affect
|
| 805 | * @nice: The nice value to set
|
| 806 | *
|
| 807 | * Detemine if the requested task priority change is permitted for the
|
| 808 | * specified task, returning 0 if permission is granted, -ve if denied.
|
| 809 |
|
| 810 | int cap_task_setnice(struct task_struct *p, int nice)
|
| 811 | {
|
| 812 | return cap_safe_nice(p);
|
| 813 | }
|
| 814 |
|
| 815 | |
| 816 | * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
|
| 817 | * the current task's bounding set. Returns 0 on success, -ve on error.
|
| 818 |
|
| 819 | static int cap_prctl_drop(unsigned long cap)
|
| 820 | {
|
| 821 | struct cred *new;
|
| 822 |
|
| 823 | if (!ns_capable(current_user_ns(), CAP_SETPCAP))
|
| 824 | return -EPERM;
|
| 825 | if (!cap_valid(cap))
|
| 826 | return -EINVAL;
|
| 827 |
|
| 828 | new = prepare_creds();
|
| 829 | if (!new)
|
| 830 | return -ENOMEM;
|
| 831 | cap_lower(new->cap_bset, cap);
|
| 832 | return commit_creds(new);
|
| 833 | }
|
| 834 |
|
| 835 | |
| 836 | * cap_task_prctl - Implement process control functions for this security module
|
| 837 | * @option: The process control function requested
|
| 838 | * @arg2, @arg3, @arg4, @arg5: The argument data for this function
|
| 839 | *
|
| 840 | * Allow process control functions (sys_prctl()) to alter capabilities; may
|
| 841 | * also deny access to other functions not otherwise implemented here.
|
| 842 | *
|
| 843 | * Returns 0 or +ve on success, -ENOSYS if this function is not implemented
|
| 844 | * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
|
| 845 | * modules will consider performing the function.
|
| 846 |
|
| 847 | int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
|
| 848 | unsigned long arg4, unsigned long arg5)
|
| 849 | {
|
| 850 | const struct cred *old = current_cred();
|
| 851 | struct cred *new;
|
| 852 |
|
| 853 | switch (option) {
|
| 854 | case PR_CAPBSET_READ:
|
| 855 | if (!cap_valid(arg2))
|
| 856 | return -EINVAL;
|
| 857 | return !!cap_raised(old->cap_bset, arg2);
|
| 858 |
|
| 859 | case PR_CAPBSET_DROP:
|
| 860 | return cap_prctl_drop(arg2);
|
| 861 |
|
| 862 | |
| 863 | * The next four prctl's remain to assist with transitioning a
|
| 864 | * system from legacy UID=0 based privilege (when filesystem
|
| 865 | * capabilities are not in use) to a system using filesystem
|
| 866 | * capabilities only - as the POSIX.1e draft intended.
|
| 867 | *
|
| 868 | * Note:
|
| 869 | *
|
| 870 | * PR_SET_SECUREBITS =
|
| 871 | * issecure_mask(SECURE_KEEP_CAPS_LOCKED)
|
| 872 | * | issecure_mask(SECURE_NOROOT)
|
| 873 | * | issecure_mask(SECURE_NOROOT_LOCKED)
|
| 874 | * | issecure_mask(SECURE_NO_SETUID_FIXUP)
|
| 875 | * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
|
| 876 | *
|
| 877 | * will ensure that the current process and all of its
|
| 878 | * children will be locked into a pure
|
| 879 | * capability-based-privilege environment.
|
| 880 |
|
| 881 | case PR_SET_SECUREBITS:
|
| 882 | if ((((old->securebits & SECURE_ALL_LOCKS) >> 1)
|
| 883 | & (old->securebits ^ arg2))
|
| 884 | || ((old->securebits & SECURE_ALL_LOCKS & ~arg2))
|
| 885 | || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS))
|
| 886 | || (cap_capable(current_cred(),
|
| 887 | current_cred()->user_ns, CAP_SETPCAP,
|
| 888 | SECURITY_CAP_AUDIT) != 0)
|
| 889 | |
| 890 | * [1] no changing of bits that are locked
|
| 891 | * [2] no unlocking of locks
|
| 892 | * [3] no setting of unsupported bits
|
| 893 | * [4] doing anything requires privilege (go read about
|
| 894 | * the "sendmail capabilities bug")
|
| 895 |
|
| 896 | )
|
| 897 |
|
| 898 | return -EPERM;
|
| 899 |
|
| 900 | new = prepare_creds();
|
| 901 | if (!new)
|
| 902 | return -ENOMEM;
|
| 903 | new->securebits = arg2;
|
| 904 | return commit_creds(new);
|
| 905 |
|
| 906 | case PR_GET_SECUREBITS:
|
| 907 | return old->securebits;
|
| 908 |
|
| 909 | case PR_GET_KEEPCAPS:
|
| 910 | return !!issecure(SECURE_KEEP_CAPS);
|
| 911 |
|
| 912 | case PR_SET_KEEPCAPS:
|
| 913 | if (arg2 > 1)
|
| 914 | return -EINVAL;
|
| 915 | if (issecure(SECURE_KEEP_CAPS_LOCKED))
|
| 916 | return -EPERM;
|
| 917 |
|
| 918 | new = prepare_creds();
|
| 919 | if (!new)
|
| 920 | return -ENOMEM;
|
| 921 | if (arg2)
|
| 922 | new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
|
| 923 | else
|
| 924 | new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
|
| 925 | return commit_creds(new);
|
| 926 |
|
| 927 | default:
|
| 928 |
|
| 929 | return -ENOSYS;
|
| 930 | }
|
| 931 | }
|
| 932 |
|
| 933 | |
| 934 | * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
|
| 935 | * @mm: The VM space in which the new mapping is to be made
|
| 936 | * @pages: The size of the mapping
|
| 937 | *
|
| 938 | * Determine whether the allocation of a new virtual mapping by the current
|
| 939 | * task is permitted, returning 1 if permission is granted, 0 if not.
|
| 940 |
|
| 941 | int cap_vm_enough_memory(struct mm_struct *mm, long pages)
|
| 942 | {
|
| 943 | int cap_sys_admin = 0;
|
| 944 |
|
| 945 | if (cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN,
|
| 946 | SECURITY_CAP_NOAUDIT) == 0)
|
| 947 | cap_sys_admin = 1;
|
| 948 | return cap_sys_admin;
|
| 949 | }
|
| 950 |
|
| 951 | |
| 952 | * cap_mmap_addr - check if able to map given addr
|
| 953 | * @addr: address attempting to be mapped
|
| 954 | *
|
| 955 | * If the process is attempting to map memory below dac_mmap_min_addr they need
|
| 956 | * CAP_SYS_RAWIO. The other parameters to this function are unused by the
|
| 957 | * capability security module. Returns 0 if this mapping should be allowed
|
| 958 | * -EPERM if not.
|
| 959 |
|
| 960 | int cap_mmap_addr(unsigned long addr)
|
| 961 | {
|
| 962 | int ret = 0;
|
| 963 |
|
| 964 | if (addr < dac_mmap_min_addr) {
|
| 965 | ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
|
| 966 | SECURITY_CAP_AUDIT);
|
| 967 |
|
| 968 | if (ret == 0)
|
| 969 | current->flags |= PF_SUPERPRIV;
|
| 970 | }
|
| 971 | return ret;
|
| 972 | }
|
| 973 |
|
| 974 | int cap_mmap_file(struct file *file, unsigned long reqprot,
|
| 975 | unsigned long prot, unsigned long flags)
|
| 976 | {
|
| 977 | return 0;
|
| 978 | }
|
| 979 |
|
| 980 | #ifdef CONFIG_SECURITY
|
| 981 |
|
| 982 | struct security_hook_list capability_hooks[] = {
|
| 983 | LSM_HOOK_INIT(capable, cap_capable),
|
| 984 | LSM_HOOK_INIT(settime, cap_settime),
|
| 985 | LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check),
|
| 986 | LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme),
|
| 987 | LSM_HOOK_INIT(capget, cap_capget),
|
| 988 | LSM_HOOK_INIT(capset, cap_capset),
|
| 989 | LSM_HOOK_INIT(bprm_set_creds, cap_bprm_set_creds),
|
| 990 | LSM_HOOK_INIT(bprm_secureexec, cap_bprm_secureexec),
|
| 991 | LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv),
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| 992 | LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv),
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| 993 | LSM_HOOK_INIT(mmap_addr, cap_mmap_addr),
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| 994 | LSM_HOOK_INIT(mmap_file, cap_mmap_file),
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| 995 | LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid),
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| 996 | LSM_HOOK_INIT(task_prctl, cap_task_prctl),
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| 997 | LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler),
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| 998 | LSM_HOOK_INIT(task_setioprio, cap_task_setioprio),
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| 999 | LSM_HOOK_INIT(task_setnice, cap_task_setnice),
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| 1000 | LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory),
|
| 1001 | };
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| 1002 |
|
| 1003 | void __init capability_add_hooks(void)
|
| 1004 | {
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| 1005 | security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks));
|
| 1006 | }
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| 1007 |
|
| 1008 | #endif
|