Messages in this thread | | | Subject | Re: [PATCH v4 2/3] LSM: module hierarchy in /proc/.../attr | From | Casey Schaufler <> | Date | Fri, 24 Jun 2016 13:05:14 -0700 |
| |
On 6/24/2016 12:11 PM, Paul Moore wrote: > On Thu, Jun 23, 2016 at 5:11 PM, Casey Schaufler <casey@schaufler-ca.com> wrote: >> Subject: [PATCH v4 2/3] LSM: module hierarchy in /proc/.../attr >> >> Back in 2007 I made what turned out to be a rather serious >> mistake in the implementation of the Smack security module. >> The SELinux module used an interface in /proc to manipulate >> the security context on processes. Rather than use a similar >> interface, I used the same interface. The AppArmor team did >> likewise. Now /proc/.../attr/current will tell you the >> security "context" of the process, but it will be different >> depending on the security module you're using. That hasn't >> been a problem to date, as you can only have one module >> that supports process attributes at a time. We are coming >> up on a change to that, where multiple modules with process >> attributes can be supported. (Not included here) >> >> This patch provides a subdirectory in /proc/.../attr for >> each of the security modules that use the LSM hooks >> getprocattr() and setprocattr(). Each of the interfaces >> used by a module are presented in the subdirectory. The >> old interfaces remain and work the same as before. >> User space code can begin migrating to the subdirectory >> interfaces in anticipation of the time when what comes >> from /proc/self/attr/current might not be what a runtime >> wants. >> >> The original implementation is by Kees Cook. The code >> has been changed a bit to reflect changes in the direction >> of the multiple concurrent module work, to be independent >> of it, and to bring it up to date with the current tree. >> >> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com> >> >> --- >> Documentation/security/LSM.txt | 26 +++++++++--- >> fs/proc/base.c | 91 +++++++++++++++++++++++++++++++++++++----- >> fs/proc/internal.h | 1 + >> include/linux/security.h | 15 ++++--- >> security/security.c | 31 ++++++++++++-- >> 5 files changed, 140 insertions(+), 24 deletions(-) >> >> diff --git a/Documentation/security/LSM.txt b/Documentation/security/LSM.txt >> index 3db7e67..125c489 100644 >> --- a/Documentation/security/LSM.txt >> +++ b/Documentation/security/LSM.txt >> @@ -16,11 +16,25 @@ MAC extensions, other extensions can be built using the LSM to provide >> specific changes to system operation when these tweaks are not available >> in the core functionality of Linux itself. >> >> -Without a specific LSM built into the kernel, the default LSM will be the >> -Linux capabilities system. Most LSMs choose to extend the capabilities >> -system, building their checks on top of the defined capability hooks. >> -For more details on capabilities, see capabilities(7) in the Linux >> -man-pages project. >> +The Linux capabilities modules will always be included. For more details >> +on capabilities, see capabilities(7) in the Linux man-pages project. >> +This may be followed by any number of "minor" modules and at most one >> +"major" module. >> + >> +A list of the active security modules can be found by reading >> +/sys/kernel/security/lsm. This is a comma separated list, and >> +will always include the capability module. The list reflects the >> +order in which checks are made. The capability module will always >> +be first, followed by any "minor" modules (e.g. Yama) and then >> +the one "major" module (e.g. SELinux) if there is one configured. > I wouldn't respin it just for this, but it seems like the paragraph > above should really be part of patch 1/3, yes?
Yes. I can fix that for v5.
>> +Process attributes associated with "ma >> diff --git a/fs/proc/base.c b/fs/proc/base.c >> index a11eb71..182bc28 100644 >> --- a/fs/proc/base.c >> +++ b/fs/proc/base.c >> @@ -131,9 +131,13 @@ struct pid_entry { >> #define REG(NAME, MODE, fops) \ >> NOD(NAME, (S_IFREG|(MODE)), NULL, &fops, {}) >> #define ONE(NAME, MODE, show) \ >> - NOD(NAME, (S_IFREG|(MODE)), \ >> + NOD(NAME, (S_IFREG|(MODE)), \ >> NULL, &proc_single_file_operations, \ >> { .proc_show = show } ) >> +#define ATTR(LSM, NAME, MODE) \ >> + NOD(NAME, (S_IFREG|(MODE)), \ >> + NULL, &proc_pid_attr_operations, \ >> + { .lsm = LSM }) >> >> /* >> * Count the number of hardlinks for the pid_entry table, excluding the . >> @@ -2433,7 +2437,7 @@ static ssize_t proc_pid_attr_read(struct file * file, char __user * buf, >> if (!task) >> return -ESRCH; >> >> - length = security_getprocattr(task, >> + length = security_getprocattr(task, PROC_I(inode)->op.lsm, >> (char*)file->f_path.dentry->d_name.name, >> &p); >> put_task_struct(task); >> @@ -2473,7 +2477,7 @@ static ssize_t proc_pid_attr_write(struct file * file, const char __user * buf, >> if (length < 0) >> goto out_free; >> >> - length = security_setprocattr(task, >> + length = security_setprocattr(task, PROC_I(inode)->op.lsm, >> (char*)file->f_path.dentry->d_name.name, >> page, count); >> mutex_unlock(&task->signal->cred_guard_mutex); >> @@ -2491,13 +2495,82 @@ static const struct file_operations proc_pid_attr_operations = { >> .llseek = generic_file_llseek, >> }; >> >> +#define LSM_DIR_OPS(LSM) \ >> +static int proc_##LSM##_attr_dir_iterate(struct file *filp, \ >> + struct dir_context *ctx) \ >> +{ \ >> + return proc_pident_readdir(filp, ctx, \ >> + LSM##_attr_dir_stuff, \ >> + ARRAY_SIZE(LSM##_attr_dir_stuff)); \ >> +} \ >> +\ >> +static const struct file_operations proc_##LSM##_attr_dir_ops = { \ >> + .read = generic_read_dir, \ >> + .iterate = proc_##LSM##_attr_dir_iterate, \ >> + .llseek = default_llseek, \ >> +}; \ >> +\ >> +static struct dentry *proc_##LSM##_attr_dir_lookup(struct inode *dir, \ >> + struct dentry *dentry, unsigned int flags) \ >> +{ \ >> + return proc_pident_lookup(dir, dentry, \ >> + LSM##_attr_dir_stuff, \ >> + ARRAY_SIZE(LSM##_attr_dir_stuff)); \ >> +} \ >> +\ >> +static const struct inode_operations proc_##LSM##_attr_dir_inode_ops = { \ >> + .lookup = proc_##LSM##_attr_dir_lookup, \ >> + .getattr = pid_getattr, \ >> + .setattr = proc_setattr, \ >> +} >> + >> +#ifdef CONFIG_SECURITY_SELINUX >> +static const struct pid_entry selinux_attr_dir_stuff[] = { >> + ATTR("selinux", "current", S_IRUGO|S_IWUGO), >> + ATTR("selinux", "prev", S_IRUGO), >> + ATTR("selinux", "exec", S_IRUGO|S_IWUGO), >> + ATTR("selinux", "fscreate", S_IRUGO|S_IWUGO), >> + ATTR("selinux", "keycreate", S_IRUGO|S_IWUGO), >> + ATTR("selinux", "sockcreate", S_IRUGO|S_IWUGO), >> +}; >> +LSM_DIR_OPS(selinux); >> +#endif >> + >> +#ifdef CONFIG_SECURITY_SMACK >> +static const struct pid_entry smack_attr_dir_stuff[] = { >> + ATTR("smack", "current", S_IRUGO|S_IWUGO), >> +}; >> +LSM_DIR_OPS(smack); >> +#endif >> + >> +#ifdef CONFIG_SECURITY_APPARMOR >> +static const struct pid_entry apparmor_attr_dir_stuff[] = { >> + ATTR("apparmor", "current", S_IRUGO|S_IWUGO), >> + ATTR("apparmor", "prev", S_IRUGO), >> + ATTR("apparmor", "exec", S_IRUGO|S_IWUGO), >> +}; >> +LSM_DIR_OPS(apparmor); >> +#endif >> + >> static const struct pid_entry attr_dir_stuff[] = { >> - REG("current", S_IRUGO|S_IWUGO, proc_pid_attr_operations), >> - REG("prev", S_IRUGO, proc_pid_attr_operations), >> - REG("exec", S_IRUGO|S_IWUGO, proc_pid_attr_operations), >> - REG("fscreate", S_IRUGO|S_IWUGO, proc_pid_attr_operations), >> - REG("keycreate", S_IRUGO|S_IWUGO, proc_pid_attr_operations), >> - REG("sockcreate", S_IRUGO|S_IWUGO, proc_pid_attr_operations), >> + ATTR(NULL, "current", S_IRUGO|S_IWUGO), >> + ATTR(NULL, "prev", S_IRUGO), >> + ATTR(NULL, "exec", S_IRUGO|S_IWUGO), >> + ATTR(NULL, "fscreate", S_IRUGO|S_IWUGO), >> + ATTR(NULL, "keycreate", S_IRUGO|S_IWUGO), >> + ATTR(NULL, "sockcreate", S_IRUGO|S_IWUGO), >> +#ifdef CONFIG_SECURITY_SELINUX >> + DIR("selinux", S_IRUGO|S_IXUGO, >> + proc_selinux_attr_dir_inode_ops, proc_selinux_attr_dir_ops), >> +#endif >> +#ifdef CONFIG_SECURITY_SMACK >> + DIR("smack", S_IRUGO|S_IXUGO, >> + proc_smack_attr_dir_inode_ops, proc_smack_attr_dir_ops), >> +#endif >> +#ifdef CONFIG_SECURITY_APPARMOR >> + DIR("apparmor", S_IRUGO|S_IXUGO, >> + proc_apparmor_attr_dir_inode_ops, proc_apparmor_attr_dir_ops), >> +#endif >> }; > With the number of LSMs set to grow, it seems like it might be a lot > cleaner, and easier to maintain, if we moved the various LSM pid_entry > definitions into the LSMs themselves. Granted, I say this without > seriously looking at how one would do that, I'm just mentioning it > here; it may prove to be more hassle than it is worth. > I have looked into doing it that way, but have yet to come up with anything that would work. It seems like a wonderful challenge for a young, nimble brain. Or maybe an old wise one. In neither case, mine.
| |