From 006ebb40d3d65338bd74abb03b945f8d60e362bd Mon Sep 17 00:00:00 2001 From: Stephen Smalley Date: Mon, 19 May 2008 08:32:49 -0400 Subject: Security: split proc ptrace checking into read vs. attach Enable security modules to distinguish reading of process state via proc from full ptrace access by renaming ptrace_may_attach to ptrace_may_access and adding a mode argument indicating whether only read access or full attach access is requested. This allows security modules to permit access to reading process state without granting full ptrace access. The base DAC/capability checking remains unchanged. Read access to /proc/pid/mem continues to apply a full ptrace attach check since check_mem_permission() already requires the current task to already be ptracing the target. The other ptrace checks within proc for elements like environ, maps, and fds are changed to pass the read mode instead of attach. In the SELinux case, we model such reading of process state as a reading of a proc file labeled with the target process' label. This enables SELinux policy to permit such reading of process state without permitting control or manipulation of the target process, as there are a number of cases where programs probe for such information via proc but do not need to be able to control the target (e.g. procps, lsof, PolicyKit, ConsoleKit). At present we have to choose between allowing full ptrace in policy (more permissive than required/desired) or breaking functionality (or in some cases just silencing the denials via dontaudit rules but this can hide genuine attacks). This version of the patch incorporates comments from Casey Schaufler (change/replace existing ptrace_may_attach interface, pass access mode), and Chris Wright (provide greater consistency in the checking). Note that like their predecessors __ptrace_may_attach and ptrace_may_attach, the __ptrace_may_access and ptrace_may_access interfaces use different return value conventions from each other (0 or -errno vs. 1 or 0). I retained this difference to avoid any changes to the caller logic but made the difference clearer by changing the latter interface to return a bool rather than an int and by adding a comment about it to ptrace.h for any future callers. Signed-off-by: Stephen Smalley Acked-by: Chris Wright Signed-off-by: James Morris --- kernel/ptrace.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) (limited to 'kernel/ptrace.c') diff --git a/kernel/ptrace.c b/kernel/ptrace.c index 6c19e94fd0a..e337390fce0 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -121,7 +121,7 @@ int ptrace_check_attach(struct task_struct *child, int kill) return ret; } -int __ptrace_may_attach(struct task_struct *task) +int __ptrace_may_access(struct task_struct *task, unsigned int mode) { /* May we inspect the given task? * This check is used both for attaching with ptrace @@ -148,16 +148,16 @@ int __ptrace_may_attach(struct task_struct *task) if (!dumpable && !capable(CAP_SYS_PTRACE)) return -EPERM; - return security_ptrace(current, task); + return security_ptrace(current, task, mode); } -int ptrace_may_attach(struct task_struct *task) +bool ptrace_may_access(struct task_struct *task, unsigned int mode) { int err; task_lock(task); - err = __ptrace_may_attach(task); + err = __ptrace_may_access(task, mode); task_unlock(task); - return !err; + return (!err ? true : false); } int ptrace_attach(struct task_struct *task) @@ -195,7 +195,7 @@ repeat: /* the same process cannot be attached many times */ if (task->ptrace & PT_PTRACED) goto bad; - retval = __ptrace_may_attach(task); + retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH); if (retval) goto bad; @@ -494,7 +494,8 @@ int ptrace_traceme(void) */ task_lock(current); if (!(current->ptrace & PT_PTRACED)) { - ret = security_ptrace(current->parent, current); + ret = security_ptrace(current->parent, current, + PTRACE_MODE_ATTACH); /* * Set the ptrace bit in the process ptrace flags. */ -- cgit v1.2.3