Bundle libseccomp 2.3.1

[linux-seccomp.git] / libseccomp / src / system.c

diff --git a/libseccomp/src/system.c b/libseccomp/src/system.c
new file mode 100644 (file)
index 0000000..c0a1adc
--- /dev/null
+++ b/libseccomp/src/system.c
@@ -0,0 +1,163 @@
+/**
+ * Seccomp System Interfaces
+ *
+ * Copyright (c) 2014 Red Hat <pmoore@redhat.com>
+ * Author: Paul Moore <paul@paul-moore.com>
+ */
+
+/*
+ * This library is free software; you can redistribute it and/or modify it
+ * under the terms of version 2.1 of the GNU Lesser General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This library is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library; if not, see <http://www.gnu.org/licenses>.
+ */
+
+#include <stdlib.h>
+#include <errno.h>
+#include <sys/prctl.h>
+
+#define _GNU_SOURCE
+#include <unistd.h>
+
+#include <seccomp.h>
+
+#include "arch.h"
+#include "db.h"
+#include "gen_bpf.h"
+#include "system.h"
+
+/* NOTE: the seccomp syscall whitelist is currently disabled for testing
+ *       purposes, but unless we can verify all of the supported ABIs before
+ *       our next release we may have to enable the whitelist */
+#define SYSCALL_WHITELIST_ENABLE       0
+
+static int _nr_seccomp = -1;
+static int _support_seccomp_syscall = -1;
+
+/**
+ * Check to see if the seccomp() syscall is supported
+ *
+ * This function attempts to see if the system supports the seccomp() syscall.
+ * Unfortunately, there are a few reasons why this check may fail, including
+ * a previously loaded seccomp filter, so it is hard to say for certain.
+ * Return one if the syscall is supported, zero otherwise.
+ *
+ */
+int sys_chk_seccomp_syscall(void)
+{
+       int rc;
+       int nr_seccomp;
+
+       /* NOTE: it is reasonably safe to assume that we should be able to call
+        *       seccomp() when the caller first starts, but we can't rely on
+        *       it later so we need to cache our findings for use later */
+       if (_support_seccomp_syscall >= 0)
+               return _support_seccomp_syscall;
+
+#if SYSCALL_WHITELIST_ENABLE
+       /* architecture whitelist */
+       switch (arch_def_native->token) {
+       case SCMP_ARCH_X86_64:
+       case SCMP_ARCH_ARM:
+       case SCMP_ARCH_AARCH64:
+       case SCMP_ARCH_PPC64:
+       case SCMP_ARCH_PPC64LE:
+       case SCMP_ARCH_S390:
+       case SCMP_ARCH_S390X:
+               break;
+       default:
+               goto unsupported;
+       }
+#endif
+
+       nr_seccomp = arch_syscall_resolve_name(arch_def_native, "seccomp");
+       if (nr_seccomp < 0)
+               goto unsupported;
+
+       /* this is an invalid call because the second argument is non-zero, but
+        * depending on the errno value of ENOSYS or EINVAL we can guess if the
+        * seccomp() syscal is supported or not */
+       rc = syscall(nr_seccomp, SECCOMP_SET_MODE_STRICT, 1, NULL);
+       if (rc < 0 && errno == EINVAL)
+               goto supported;
+
+unsupported:
+       _support_seccomp_syscall = 0;
+       return 0;
+supported:
+       _nr_seccomp = nr_seccomp;
+       _support_seccomp_syscall = 1;
+       return 1;
+}
+
+/**
+ * Check to see if a seccomp() flag is supported
+ * @param flag the seccomp() flag
+ *
+ * This function checks to see if a seccomp() flag is supported by the system.
+ * If the flag is supported one is returned, zero if unsupported, negative
+ * values on error.
+ *
+ */
+int sys_chk_seccomp_flag(int flag)
+{
+       switch (flag) {
+       case SECCOMP_FILTER_FLAG_TSYNC:
+               return sys_chk_seccomp_syscall();
+       }
+
+       return -EOPNOTSUPP;
+}
+
+/**
+ * Loads the filter into the kernel
+ * @param col the filter collection
+ *
+ * This function loads the given seccomp filter context into the kernel.  If
+ * the filter was loaded correctly, the kernel will be enforcing the filter
+ * when this function returns.  Returns zero on success, negative values on
+ * error.
+ *
+ */
+int sys_filter_load(const struct db_filter_col *col)
+{
+       int rc;
+       struct bpf_program *prgm = NULL;
+
+       prgm = gen_bpf_generate(col);
+       if (prgm == NULL)
+               return -ENOMEM;
+
+       /* attempt to set NO_NEW_PRIVS */
+       if (col->attr.nnp_enable) {
+               rc = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+               if (rc < 0)
+                       goto filter_load_out;
+       }
+
+       /* load the filter into the kernel */
+       if (sys_chk_seccomp_syscall() == 1) {
+               int flgs = 0;
+               if (col->attr.tsync_enable)
+                       flgs = SECCOMP_FILTER_FLAG_TSYNC;
+               rc = syscall(_nr_seccomp, SECCOMP_SET_MODE_FILTER, flgs, prgm);
+               if (rc > 0 && col->attr.tsync_enable)
+                       /* always return -ESRCH if we fail to sync threads */
+                       errno = ESRCH;
+       } else
+               rc = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, prgm);
+
+filter_load_out:
+       /* cleanup and return */
+       gen_bpf_release(prgm);
+       if (rc < 0)
+               return -errno;
+       return 0;
+}