| Message ID | 20171110053747.21093-1-mahesh@bandewar.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Quoting Mahesh Bandewar (mahesh@bandewar.net): > From: Mahesh Bandewar <maheshb@google.com> > > Add a sysctl variable kernel.controlled_userns_caps_whitelist. This > takes input as capability mask expressed as two comma separated hex > u32 words. The mask, however, is stored in kernel as kernel_cap_t type. > > Any capabilities that are not part of this mask will be controlled and > will not be allowed to processes in controlled user-ns. > > Signed-off-by: Mahesh Bandewar <maheshb@google.com> Acked-by: Serge Hallyn <serge@hallyn.com> > --- > v2: > Rebase > v1: > Initial submission > > Documentation/sysctl/kernel.txt | 21 ++++++++++++++++++ > include/linux/capability.h | 3 +++ > kernel/capability.c | 47 +++++++++++++++++++++++++++++++++++++++++ > kernel/sysctl.c | 5 +++++ > 4 files changed, 76 insertions(+) > > diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt > index 694968c7523c..a1d39dbae847 100644 > --- a/Documentation/sysctl/kernel.txt > +++ b/Documentation/sysctl/kernel.txt > @@ -25,6 +25,7 @@ show up in /proc/sys/kernel: > - bootloader_version [ X86 only ] > - callhome [ S390 only ] > - cap_last_cap > +- controlled_userns_caps_whitelist > - core_pattern > - core_pipe_limit > - core_uses_pid > @@ -187,6 +188,26 @@ CAP_LAST_CAP from the kernel. > > ============================================================== > > +controlled_userns_caps_whitelist > + > +Capability mask that is whitelisted for "controlled" user namespaces. > +Any capability that is missing from this mask will not be allowed to > +any process that is attached to a controlled-userns. e.g. if CAP_NET_RAW > +is not part of this mask, then processes running inside any controlled > +userns's will not be allowed to perform action that needs CAP_NET_RAW > +capability. However, processes that are attached to a parent user-ns > +hierarchy that is *not* controlled and has CAP_NET_RAW can continue > +performing those actions. User-namespaces are marked "controlled" at > +the time of their creation based on the capabilities of the creator. > +A process that does not have CAP_SYS_ADMIN will create user-namespaces > +that are controlled. > + > +The value is expressed as two comma separated hex words (u32). This > +sysctl is avaialble in init-ns and users with CAP_SYS_ADMIN in init-ns > +are allowed to make changes. > + > +============================================================== > + > core_pattern: > > core_pattern is used to specify a core dumpfile pattern name. > diff --git a/include/linux/capability.h b/include/linux/capability.h > index f640dcbc880c..7d79a4689625 100644 > --- a/include/linux/capability.h > +++ b/include/linux/capability.h > @@ -14,6 +14,7 @@ > #define _LINUX_CAPABILITY_H > > #include <uapi/linux/capability.h> > +#include <linux/sysctl.h> > > > #define _KERNEL_CAPABILITY_VERSION _LINUX_CAPABILITY_VERSION_3 > @@ -248,6 +249,8 @@ extern bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns); > > /* audit system wants to get cap info from files as well */ > extern int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps); > +int proc_douserns_caps_whitelist(struct ctl_table *table, int write, > + void __user *buff, size_t *lenp, loff_t *ppos); > > extern int cap_convert_nscap(struct dentry *dentry, void **ivalue, size_t size); > > diff --git a/kernel/capability.c b/kernel/capability.c > index 1e1c0236f55b..4a859b7d4902 100644 > --- a/kernel/capability.c > +++ b/kernel/capability.c > @@ -29,6 +29,8 @@ EXPORT_SYMBOL(__cap_empty_set); > > int file_caps_enabled = 1; > > +kernel_cap_t controlled_userns_caps_whitelist = CAP_FULL_SET; > + > static int __init file_caps_disable(char *str) > { > file_caps_enabled = 0; > @@ -507,3 +509,48 @@ bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns) > rcu_read_unlock(); > return (ret == 0); > } > + > +/* Controlled-userns capabilities routines */ > +#ifdef CONFIG_SYSCTL > +int proc_douserns_caps_whitelist(struct ctl_table *table, int write, > + void __user *buff, size_t *lenp, loff_t *ppos) > +{ > + DECLARE_BITMAP(caps_bitmap, CAP_LAST_CAP); > + struct ctl_table caps_table; > + char tbuf[NAME_MAX]; > + int ret; > + > + ret = bitmap_from_u32array(caps_bitmap, CAP_LAST_CAP, > + controlled_userns_caps_whitelist.cap, > + _KERNEL_CAPABILITY_U32S); > + if (ret != CAP_LAST_CAP) > + return -1; > + > + scnprintf(tbuf, NAME_MAX, "%*pb", CAP_LAST_CAP, caps_bitmap); > + > + caps_table.data = tbuf; > + caps_table.maxlen = NAME_MAX; > + caps_table.mode = table->mode; > + ret = proc_dostring(&caps_table, write, buff, lenp, ppos); > + if (ret) > + return ret; > + if (write) { > + kernel_cap_t tmp; > + > + if (!capable(CAP_SYS_ADMIN)) > + return -EPERM; > + > + ret = bitmap_parse_user(buff, *lenp, caps_bitmap, CAP_LAST_CAP); > + if (ret) > + return ret; > + > + ret = bitmap_to_u32array(tmp.cap, _KERNEL_CAPABILITY_U32S, > + caps_bitmap, CAP_LAST_CAP); > + if (ret != CAP_LAST_CAP) > + return -1; > + > + controlled_userns_caps_whitelist = tmp; > + } > + return 0; > +} > +#endif /* CONFIG_SYSCTL */ > diff --git a/kernel/sysctl.c b/kernel/sysctl.c > index d9c31bc2eaea..25c3f7b76ece 100644 > --- a/kernel/sysctl.c > +++ b/kernel/sysctl.c > @@ -1226,6 +1226,11 @@ static struct ctl_table kern_table[] = { > .extra2 = &one, > }, > #endif > + { > + .procname = "controlled_userns_caps_whitelist", > + .mode = 0644, > + .proc_handler = proc_douserns_caps_whitelist, > + }, > { } > }; > > -- > 2.15.0.448.gf294e3d99a-goog
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt index 694968c7523c..a1d39dbae847 100644 --- a/Documentation/sysctl/kernel.txt +++ b/Documentation/sysctl/kernel.txt @@ -25,6 +25,7 @@ show up in /proc/sys/kernel: - bootloader_version [ X86 only ] - callhome [ S390 only ] - cap_last_cap +- controlled_userns_caps_whitelist - core_pattern - core_pipe_limit - core_uses_pid @@ -187,6 +188,26 @@ CAP_LAST_CAP from the kernel. ============================================================== +controlled_userns_caps_whitelist + +Capability mask that is whitelisted for "controlled" user namespaces. +Any capability that is missing from this mask will not be allowed to +any process that is attached to a controlled-userns. e.g. if CAP_NET_RAW +is not part of this mask, then processes running inside any controlled +userns's will not be allowed to perform action that needs CAP_NET_RAW +capability. However, processes that are attached to a parent user-ns +hierarchy that is *not* controlled and has CAP_NET_RAW can continue +performing those actions. User-namespaces are marked "controlled" at +the time of their creation based on the capabilities of the creator. +A process that does not have CAP_SYS_ADMIN will create user-namespaces +that are controlled. + +The value is expressed as two comma separated hex words (u32). This +sysctl is avaialble in init-ns and users with CAP_SYS_ADMIN in init-ns +are allowed to make changes. + +============================================================== + core_pattern: core_pattern is used to specify a core dumpfile pattern name. diff --git a/include/linux/capability.h b/include/linux/capability.h index f640dcbc880c..7d79a4689625 100644 --- a/include/linux/capability.h +++ b/include/linux/capability.h @@ -14,6 +14,7 @@ #define _LINUX_CAPABILITY_H #include <uapi/linux/capability.h> +#include <linux/sysctl.h> #define _KERNEL_CAPABILITY_VERSION _LINUX_CAPABILITY_VERSION_3 @@ -248,6 +249,8 @@ extern bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns); /* audit system wants to get cap info from files as well */ extern int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps); +int proc_douserns_caps_whitelist(struct ctl_table *table, int write, + void __user *buff, size_t *lenp, loff_t *ppos); extern int cap_convert_nscap(struct dentry *dentry, void **ivalue, size_t size); diff --git a/kernel/capability.c b/kernel/capability.c index 1e1c0236f55b..4a859b7d4902 100644 --- a/kernel/capability.c +++ b/kernel/capability.c @@ -29,6 +29,8 @@ EXPORT_SYMBOL(__cap_empty_set); int file_caps_enabled = 1; +kernel_cap_t controlled_userns_caps_whitelist = CAP_FULL_SET; + static int __init file_caps_disable(char *str) { file_caps_enabled = 0; @@ -507,3 +509,48 @@ bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns) rcu_read_unlock(); return (ret == 0); } + +/* Controlled-userns capabilities routines */ +#ifdef CONFIG_SYSCTL +int proc_douserns_caps_whitelist(struct ctl_table *table, int write, + void __user *buff, size_t *lenp, loff_t *ppos) +{ + DECLARE_BITMAP(caps_bitmap, CAP_LAST_CAP); + struct ctl_table caps_table; + char tbuf[NAME_MAX]; + int ret; + + ret = bitmap_from_u32array(caps_bitmap, CAP_LAST_CAP, + controlled_userns_caps_whitelist.cap, + _KERNEL_CAPABILITY_U32S); + if (ret != CAP_LAST_CAP) + return -1; + + scnprintf(tbuf, NAME_MAX, "%*pb", CAP_LAST_CAP, caps_bitmap); + + caps_table.data = tbuf; + caps_table.maxlen = NAME_MAX; + caps_table.mode = table->mode; + ret = proc_dostring(&caps_table, write, buff, lenp, ppos); + if (ret) + return ret; + if (write) { + kernel_cap_t tmp; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + ret = bitmap_parse_user(buff, *lenp, caps_bitmap, CAP_LAST_CAP); + if (ret) + return ret; + + ret = bitmap_to_u32array(tmp.cap, _KERNEL_CAPABILITY_U32S, + caps_bitmap, CAP_LAST_CAP); + if (ret != CAP_LAST_CAP) + return -1; + + controlled_userns_caps_whitelist = tmp; + } + return 0; +} +#endif /* CONFIG_SYSCTL */ diff --git a/kernel/sysctl.c b/kernel/sysctl.c index d9c31bc2eaea..25c3f7b76ece 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1226,6 +1226,11 @@ static struct ctl_table kern_table[] = { .extra2 = &one, }, #endif + { + .procname = "controlled_userns_caps_whitelist", + .mode = 0644, + .proc_handler = proc_douserns_caps_whitelist, + }, { } };