seccomp: fix decoding of sock_fprog and sock_filter structures
Always print struct sock_fprog.len.
Fix printing of unfetchable elements in sock_filter array.
Fix printing of large sock_filter arrays.
* seccomp.c (decode_fprog): Rewrite into decode_seccomp_fprog and
print_seccomp_fprog.
(print_seccomp_filter): Replace decode_fprog with print_seccomp_fprog.
* tests/prctl-seccomp-filter-v.c (main): Update.
* tests/seccomp-filter-v.c: New file.
* tests/seccomp-filter-v.test: New test.
* tests/.gitignore: Add seccomp-filter-v.
* tests/Makefile.am (check_PROGRAMS): Likewise.
(DECODER_TESTS): Add seccomp-filter-v.test.
diff --git a/seccomp.c b/seccomp.c
index e85666d..e62f99a 100644
--- a/seccomp.c
+++ b/seccomp.c
@@ -162,32 +162,39 @@
#endif
static void
-decode_fprog(struct tcb *tcp, unsigned short len, unsigned long addr)
+decode_seccomp_fprog(struct tcb *tcp, unsigned short len, unsigned long addr)
{
- if (!len || abbrev(tcp)) {
- tprintf("{len = %u, filter = ", len);
- printaddr(addr);
- tprints("}");
- } else {
- unsigned int i = 0;
+ struct bpf_filter filter;
+ const unsigned long start_addr = addr;
+ unsigned int i = 0;
- tprints("[");
- while (i < len && i < BPF_MAXINSNS) {
- struct bpf_filter filter;
-
- if (umove(tcp, addr, &filter) < 0)
+ for (; addr >= start_addr && i < len; ++i, addr += sizeof(filter)) {
+ if (i) {
+ tprints(", ");
+ if (i >= BPF_MAXINSNS) {
+ tprints("...");
break;
- if (i)
- tprints(", ");
- decode_filter(&filter);
-
- addr += sizeof(filter);
- ++i;
+ }
}
- if (i < len)
- tprints("...");
- tprints("]");
+ if (umove_or_printaddr(tcp, addr, &filter))
+ break;
+ if (!i)
+ tprints("[");
+ decode_filter(&filter);
}
+ if (i)
+ tprints("]");
+}
+
+static void
+print_seccomp_fprog(struct tcb *tcp, unsigned short len, unsigned long addr)
+{
+ tprintf("{len=%u, filter=", len);
+ if (abbrev(tcp) || !len)
+ printaddr(addr);
+ else
+ decode_seccomp_fprog(tcp, len, addr);
+ tprints("}");
}
#include "seccomp_fprog.h"
@@ -198,7 +205,7 @@
struct seccomp_fprog fprog;
if (fetch_seccomp_fprog(tcp, addr, &fprog))
- decode_fprog(tcp, fprog.len, fprog.filter);
+ print_seccomp_fprog(tcp, fprog.len, fprog.filter);
}
static void
diff --git a/tests/.gitignore b/tests/.gitignore
index 01b6236..3ed6cee 100644
--- a/tests/.gitignore
+++ b/tests/.gitignore
@@ -128,6 +128,7 @@
sched_xetparam
sched_xetscheduler
scm_rights
+seccomp-filter-v
seccomp-strict
select
sendfile
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 9572015..db33f4d 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -177,6 +177,7 @@
sched_xetparam \
sched_xetscheduler \
scm_rights \
+ seccomp-filter-v \
seccomp-strict \
select \
sendfile \
@@ -375,6 +376,7 @@
sched_xetparam.test \
sched_xetscheduler.test \
scm_rights-fd.test \
+ seccomp-filter-v.test \
seccomp-strict.test \
select.test \
sendfile.test \
diff --git a/tests/prctl-seccomp-filter-v.c b/tests/prctl-seccomp-filter-v.c
index c7fb137..a03f202 100644
--- a/tests/prctl-seccomp-filter-v.c
+++ b/tests/prctl-seccomp-filter-v.c
@@ -91,7 +91,7 @@
};
static const struct sock_fprog prog = {
- .len = sizeof(filter) / sizeof(filter[0]),
+ .len = ARRAY_SIZE(filter),
.filter = (struct sock_filter *) filter,
};
@@ -102,7 +102,8 @@
puts("prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) = 0");
- printf("prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, [");
+ printf("prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, {len=%u, filter=[",
+ prog.len);
printf("BPF_STMT(BPF_LD|BPF_W|BPF_ABS, %#x), ",
(unsigned) offsetof(struct seccomp_data, nr));
@@ -116,7 +117,7 @@
printf("BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_KILL)");
- puts("]) = 0");
+ puts("]}) = 0");
puts("+++ exited with 0 +++");
fflush(stdout);
diff --git a/tests/seccomp-filter-v.c b/tests/seccomp-filter-v.c
new file mode 100644
index 0000000..9a70658
--- /dev/null
+++ b/tests/seccomp-filter-v.c
@@ -0,0 +1,213 @@
+/*
+ * Check verbose decoding of seccomp SECCOMP_SET_MODE_FILTER.
+ *
+ * Copyright (c) 2015-2016 Dmitry V. Levin <ldv@altlinux.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ * derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "tests.h"
+
+#include <errno.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+
+#ifdef HAVE_PRCTL
+# include <sys/prctl.h>
+#endif
+#ifdef HAVE_LINUX_SECCOMP_H
+# include <linux/seccomp.h>
+#endif
+#ifdef HAVE_LINUX_FILTER_H
+# include <linux/filter.h>
+#endif
+
+#if defined __NR_seccomp \
+ && defined PR_SET_NO_NEW_PRIVS \
+ && defined SECCOMP_SET_MODE_FILTER \
+ && defined SECCOMP_RET_ERRNO \
+ && defined BPF_JUMP \
+ && defined BPF_STMT
+
+#define SOCK_FILTER_ALLOW_SYSCALL(nr) \
+ BPF_JUMP(BPF_JMP|BPF_K|BPF_JEQ, __NR_ ## nr, 0, 1), \
+ BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW)
+
+#define SOCK_FILTER_DENY_SYSCALL(nr, err) \
+ BPF_JUMP(BPF_JMP|BPF_K|BPF_JEQ, __NR_ ## nr, 0, 1), \
+ BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ERRNO|(SECCOMP_RET_DATA & (err)))
+
+#define SOCK_FILTER_KILL_PROCESS \
+ BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_KILL)
+
+#define PRINT_ALLOW_SYSCALL(nr) \
+ tprintf("BPF_JUMP(BPF_JMP|BPF_K|BPF_JEQ, %#x, 0, 0x1), " \
+ "BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW), ", \
+ __NR_ ## nr)
+
+#define PRINT_DENY_SYSCALL(nr, err) \
+ tprintf("BPF_JUMP(BPF_JMP|BPF_K|BPF_JEQ, %#x, 0, 0x1), " \
+ "BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ERRNO|%#x), ", \
+ __NR_ ## nr, err)
+
+static const struct sock_filter filter_c[] = {
+ /* load syscall number */
+ BPF_STMT(BPF_LD|BPF_W|BPF_ABS, offsetof(struct seccomp_data, nr)),
+
+ /* allow syscalls */
+ SOCK_FILTER_ALLOW_SYSCALL(close),
+ SOCK_FILTER_ALLOW_SYSCALL(exit),
+ SOCK_FILTER_ALLOW_SYSCALL(exit_group),
+
+ /* deny syscalls */
+ SOCK_FILTER_DENY_SYSCALL(sync, EBUSY),
+ SOCK_FILTER_DENY_SYSCALL(setsid, EPERM),
+
+ /* kill process */
+ SOCK_FILTER_KILL_PROCESS
+};
+
+#ifndef BPF_MAXINSNS
+# define BPF_MAXINSNS 4096
+#endif
+
+int
+main(void)
+{
+ tprintf("%s", "");
+
+ static const char kill_stmt_txt[] =
+ "BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_KILL)";
+ struct sock_filter *const filter =
+ tail_memdup(filter_c, sizeof(filter_c));
+ struct sock_filter *const big_filter =
+ tail_alloc(sizeof(*big_filter) * (BPF_MAXINSNS + 1));
+ struct sock_fprog *const prog = tail_alloc(sizeof(*prog));
+
+ int fds[2];
+ if (pipe(fds))
+ perror_msg_and_fail("pipe");
+ if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0))
+ perror_msg_and_skip("PR_SET_NO_NEW_PRIVS");
+
+ prog->filter = filter + ARRAY_SIZE(filter_c);
+ prog->len = 1;
+ syscall(__NR_seccomp, SECCOMP_SET_MODE_FILTER, 0, prog);
+ tprintf("seccomp(SECCOMP_SET_MODE_FILTER, 0, {len=1, filter=%p})"
+ " = -1 EFAULT (%m)\n", prog->filter);
+
+ prog->filter = filter + ARRAY_SIZE(filter_c) - 1;
+ prog->len = 3;
+ syscall(__NR_seccomp, SECCOMP_SET_MODE_FILTER, 0, prog);
+ tprintf("seccomp(SECCOMP_SET_MODE_FILTER, 0, {len=%u"
+ ", filter=[%s, %p]}) = -1 EFAULT (%m)\n",
+ prog->len, kill_stmt_txt, filter + ARRAY_SIZE(filter_c));
+
+ prog->len = 0;
+ syscall(__NR_seccomp, SECCOMP_SET_MODE_FILTER, 0, prog);
+ tprintf("seccomp(SECCOMP_SET_MODE_FILTER, 0, {len=0, filter=%p})"
+ " = -1 EINVAL (%m)\n", prog->filter);
+
+ unsigned int i;
+ for (i = 0; i <= BPF_MAXINSNS; ++i) {
+ const struct sock_filter stmt =
+ BPF_STMT(BPF_CLASS(i), i << 16);
+ big_filter[i] = stmt;
+ }
+
+ prog->filter = big_filter;
+ prog->len = BPF_MAXINSNS + 1;
+ tprintf("seccomp(SECCOMP_SET_MODE_FILTER, %s, {len=%u, filter=[",
+ "SECCOMP_FILTER_FLAG_TSYNC|0xfffffffe", prog->len);
+ for (i = 0; i < BPF_MAXINSNS; ++i) {
+ if (i)
+ tprintf(", ");
+ switch(BPF_CLASS(i)) {
+ case BPF_LD:
+ tprintf("BPF_STMT(BPF_LD|BPF_W|BPF_IMM, %#x)", i << 16);
+ break;
+ case BPF_LDX:
+ tprintf("BPF_STMT(BPF_LDX|BPF_W|BPF_IMM, %#x)", i << 16);
+ break;
+ case BPF_ST:
+ tprintf("BPF_STMT(BPF_ST, %#x)", i << 16);
+ break;
+ case BPF_STX:
+ tprintf("BPF_STMT(BPF_STX, %#x)", i << 16);
+ break;
+ case BPF_ALU:
+ tprintf("BPF_STMT(BPF_ALU|BPF_K|BPF_ADD, %#x)", i << 16);
+ break;
+ case BPF_JMP:
+ tprintf("BPF_STMT(BPF_JMP|BPF_K|BPF_JA, %#x)", i << 16);
+ break;
+ case BPF_RET:
+ tprintf("BPF_STMT(BPF_RET|BPF_K, %#x"
+ " /* SECCOMP_RET_??? */)", i << 16);
+ break;
+ case BPF_MISC:
+ tprintf("BPF_STMT(BPF_MISC|BPF_TAX, %#x)", i << 16);
+ break;
+ }
+ }
+ tprintf(", ...]})");
+ syscall(__NR_seccomp, SECCOMP_SET_MODE_FILTER, -1, prog);
+ tprintf(" = -1 EINVAL (%m)\n");
+
+ prog->filter = filter;
+ prog->len = ARRAY_SIZE(filter_c);
+
+ tprintf("seccomp(SECCOMP_SET_MODE_FILTER, 0, {len=%u, filter=[",
+ prog->len);
+
+ tprintf("BPF_STMT(BPF_LD|BPF_W|BPF_ABS, %#x), ",
+ (unsigned) offsetof(struct seccomp_data, nr));
+
+ PRINT_ALLOW_SYSCALL(close);
+ PRINT_ALLOW_SYSCALL(exit);
+ PRINT_ALLOW_SYSCALL(exit_group);
+
+ PRINT_DENY_SYSCALL(sync, EBUSY),
+ PRINT_DENY_SYSCALL(setsid, EPERM),
+
+ tprintf("%s]}) = 0\n+++ exited with 0 +++\n", kill_stmt_txt);
+
+ if (syscall(__NR_seccomp, SECCOMP_SET_MODE_FILTER, 0, prog))
+ perror_msg_and_skip("SECCOMP_SET_MODE_FILTER");
+
+ if (close(0) || close(1))
+ _exit(77);
+
+ _exit(0);
+}
+
+#else
+
+SKIP_MAIN_UNDEFINED("__NR_seccomp && PR_SET_NO_NEW_PRIVS"
+ " && SECCOMP_SET_MODE_FILTER && SECCOMP_RET_ERRNO"
+ " && BPF_JUMP && BPF_STMT")
+
+#endif
diff --git a/tests/seccomp-filter-v.test b/tests/seccomp-filter-v.test
new file mode 100755
index 0000000..f873eb6
--- /dev/null
+++ b/tests/seccomp-filter-v.test
@@ -0,0 +1,6 @@
+#!/bin/sh
+
+# Check verbose decoding of seccomp SECCOMP_SET_MODE_FILTER.
+
+. "${srcdir=.}/init.sh"
+run_strace_match_diff -v -e trace=seccomp
