From: Michal Sojka <sojkam1@fel.cvut.cz>
Date: Sun, 24 Sep 2017 14:38:21 +0000 (+0200)
Subject: utrace: Support non-contiguous syscall numbers
X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=1c48104ffc7f8d2c27dd8660a03a7728540fa946;p=oweals%2Fprocd.git
utrace: Support non-contiguous syscall numbers
ARM architecture does not have its system call numbers contiguous. So
far, utrace ignored the non-contiguous system calls, but it makes it
difficult to setup seccomp whitelists. This patch adds support for
these extra out-of-range syscalls.
It extends the generated file syscall_names.h to include a few
functions. Now, for ARM this file looks like:
#include <asm/unistd.h>
static const char *__syscall_names[] = {
[280] = "waitid",
[148] = "fdatasync",
...
[252] = "epoll_wait",
[74] = "sethostname",
};
static inline const char *syscall_name(unsigned i) {
if (i < ARRAY_SIZE(__syscall_names))
return __syscall_names[i];
switch (i) {
case 0x0f0001: return "breakpoint";
case 0x0f0003: return "usr26";
case 0x0f0004: return "usr32";
case 0x0f0005: return "set_tls";
case 0x0f0002: return "cacheflush";
default: return (void*)0;
}
}
static inline int syscall_index(unsigned i) {
if (i < ARRAY_SIZE(__syscall_names))
return i;
switch (i) {
case 0x0f0001: return ARRAY_SIZE(__syscall_names) + 0;
case 0x0f0003: return ARRAY_SIZE(__syscall_names) + 1;
case 0x0f0004: return ARRAY_SIZE(__syscall_names) + 2;
case 0x0f0005: return ARRAY_SIZE(__syscall_names) + 3;
case 0x0f0002: return ARRAY_SIZE(__syscall_names) + 4;
default: return -1;
}
}
static inline int syscall_index_to_number(unsigned i) {
if (i < ARRAY_SIZE(__syscall_names))
return i;
switch (i) {
case ARRAY_SIZE(__syscall_names) + 0: return 0x0f0001;
case ARRAY_SIZE(__syscall_names) + 1: return 0x0f0003;
case ARRAY_SIZE(__syscall_names) + 2: return 0x0f0004;
case ARRAY_SIZE(__syscall_names) + 3: return 0x0f0005;
case ARRAY_SIZE(__syscall_names) + 4: return 0x0f0002;
default: return -1;
}
}
#define SYSCALL_COUNT (ARRAY_SIZE(__syscall_names) + 5)
For x86, which does not have extra syscalls, the file looks this way:
#include <asm/unistd.h>
static const char *__syscall_names[] = {
[247] = "waitid",
[75] = "fdatasync",
...
[232] = "epoll_wait",
[170] = "sethostname",
};
static inline const char *syscall_name(unsigned i) {
if (i < ARRAY_SIZE(__syscall_names))
return __syscall_names[i];
switch (i) {
default: return (void*)0;
}
}
static inline int syscall_index(unsigned i) {
if (i < ARRAY_SIZE(__syscall_names))
return i;
switch (i) {
default: return -1;
}
}
static inline int syscall_index_to_number(unsigned i) {
if (i < ARRAY_SIZE(__syscall_names))
return i;
switch (i) {
default: return -1;
}
}
#define SYSCALL_COUNT (ARRAY_SIZE(__syscall_names) + 0)
Signed-off-by: Michal Sojka <sojkam1@fel.cvut.cz>
---
diff --git a/jail/seccomp.c b/jail/seccomp.c
index 27bf3ce..eeb5781 100644
--- a/jail/seccomp.c
+++ b/jail/seccomp.c
@@ -22,15 +22,15 @@
#include "seccomp.h"
#include "../syscall-names.h"
-static int max_syscall = ARRAY_SIZE(syscall_names);
-
static int find_syscall(const char *name)
{
int i;
- for (i = 0; i < max_syscall; i++)
- if (syscall_names[i] && !strcmp(syscall_names[i], name))
- return i;
+ for (i = 0; i < SYSCALL_COUNT; i++) {
+ int sc = syscall_index_to_number(i);
+ if (syscall_name(sc) && !strcmp(syscall_name(sc), name))
+ return sc;
+ }
return -1;
}
diff --git a/make_syscall_h.sh b/make_syscall_h.sh
index 3363bc7..18d9131 100755
--- a/make_syscall_h.sh
+++ b/make_syscall_h.sh
@@ -12,7 +12,53 @@ CC=$1
[ -n "$TARGET_CC_NOCACHE" ] && CC=$TARGET_CC_NOCACHE
echo "#include <asm/unistd.h>"
-echo "static const char *syscall_names[] = {"
+echo "static const char *__syscall_names[] = {"
echo "#include <sys/syscall.h>" | ${CC} -E -dM - | grep '^#define __NR_' | \
LC_ALL=C sed -r -n -e 's/^\#define[ \t]+__NR_([a-z0-9_]+)[ \t]+([ ()+0-9a-zNR_Linux]+)(.*)/ [\2] = "\1",/p'
echo "};"
+
+extra_syscalls="$(echo "#include <sys/syscall.h>" | ${CC} -E -dM - | sed -n -e '/^#define __ARM_NR_/ s///p')"
+
+cat <<EOF
+static inline const char *syscall_name(unsigned i) {
+ if (i < ARRAY_SIZE(__syscall_names))
+ return __syscall_names[i];
+ switch (i) {
+EOF
+echo "$extra_syscalls" | \
+ LC_ALL=C sed -r -n -e 's/^([a-z0-9_]+)[ \t]+([ ()+0-9a-zNR_Linux]+)(.*)/ case \2: return "\1";/p'
+cat <<EOF
+ default: return (void*)0;
+ }
+}
+EOF
+
+cat <<EOF
+static inline int syscall_index(unsigned i) {
+ if (i < ARRAY_SIZE(__syscall_names))
+ return i;
+ switch (i) {
+EOF
+echo "$extra_syscalls" | \
+ LC_ALL=C perl -ne 'print " case $2: return ARRAY_SIZE(__syscall_names) + ", $. - 1, ";\n" if /^([a-z0-9_]+)[ \t]+([ ()+0-9a-zNR_Linux]+)(.*)/;'
+cat <<EOF
+ default: return -1;
+ }
+}
+EOF
+
+cat <<EOF
+static inline int syscall_index_to_number(unsigned i) {
+ if (i < ARRAY_SIZE(__syscall_names))
+ return i;
+ switch (i) {
+EOF
+echo "$extra_syscalls" | \
+ LC_ALL=C perl -ne 'print " case ARRAY_SIZE(__syscall_names) + ", $. - 1, ": return $2;\n" if /^([a-z0-9_]+)[ \t]+([ ()+0-9a-zNR_Linux]+)(.*)/;'
+cat <<EOF
+ default: return -1;
+ }
+}
+EOF
+
+echo "#define SYSCALL_COUNT (ARRAY_SIZE(__syscall_names) + $({ test -n "$extra_syscalls" && echo "$extra_syscalls"; } | wc -l))"
diff --git a/trace/trace.c b/trace/trace.c
index d878a65..e7b7610 100644
--- a/trace/trace.c
+++ b/trace/trace.c
@@ -87,25 +87,24 @@ struct tracee {
};
static struct tracee tracer;
-static int *syscall_count;
+static int syscall_count[SYSCALL_COUNT];
static int violation_count;
static struct blob_buf b;
-static int syscall_max;
static int debug;
char *json = NULL;
int ptrace_restart;
-static int max_syscall = ARRAY_SIZE(syscall_names);
-
static void set_syscall(const char *name, int val)
{
int i;
- for (i = 0; i < max_syscall; i++)
- if (syscall_names[i] && !strcmp(syscall_names[i], name)) {
+ for (i = 0; i < SYSCALL_COUNT; i++) {
+ int sc = syscall_index_to_number(i);
+ if (syscall_name(sc) && !strcmp(syscall_name(sc), name)) {
syscall_count[i] = val;
return;
}
+ }
}
struct syscall {
@@ -131,27 +130,27 @@ static void print_syscalls(int policy, const char *json)
set_syscall("exit", 1);
}
- struct syscall sorted[ARRAY_SIZE(syscall_names)];
+ struct syscall sorted[SYSCALL_COUNT];
- for (i = 0; i < ARRAY_SIZE(syscall_names); i++) {
- sorted[i].syscall = i;
+ for (i = 0; i < SYSCALL_COUNT; i++) {
+ sorted[i].syscall = syscall_index_to_number(i);
sorted[i].count = syscall_count[i];
}
- qsort(sorted, ARRAY_SIZE(syscall_names), sizeof(sorted[0]), cmp_count);
+ qsort(sorted, SYSCALL_COUNT, sizeof(sorted[0]), cmp_count);
blob_buf_init(&b, 0);
c = blobmsg_open_array(&b, "whitelist");
- for (i = 0; i < ARRAY_SIZE(syscall_names); i++) {
+ for (i = 0; i < SYSCALL_COUNT; i++) {
int sc = sorted[i].syscall;
if (!sorted[i].count)
break;
- if (syscall_names[sc]) {
+ if (syscall_name(sc)) {
if (debug)
printf("syscall %d (%s) was called %d times\n",
- sc, syscall_names[sc], sorted[i].count);
- blobmsg_add_string(&b, NULL, syscall_names[sc]);
+ sc, syscall_name(sc), sorted[i].count);
+ blobmsg_add_string(&b, NULL, syscall_name(sc));
} else {
ERROR("no name found for syscall(%d)\n", sc);
}
@@ -188,10 +187,11 @@ static void report_seccomp_vialation(pid_t pid, unsigned syscall)
if (violation_count < INT_MAX)
violation_count++;
- if (syscall < ARRAY_SIZE(syscall_names)) {
- syscall_count[syscall]++;
+ int i = syscall_index(syscall);
+ if (i >= 0) {
+ syscall_count[i]++;
LOGERR("%s[%u] tried to call non-whitelisted syscall: %s (see %s)\n",
- buf, pid, syscall_names[syscall], json);
+ buf, pid, syscall_name(syscall), json);
} else {
LOGERR("%s[%u] tried to call non-whitelisted syscall: %d (see %s)\n",
buf, pid, syscall, json);
@@ -210,11 +210,11 @@ static void tracer_cb(struct uloop_process *c, int ret)
if (WSTOPSIG(ret) & 0x80) {
if (!tracee->in_syscall) {
int syscall = ptrace(PTRACE_PEEKUSER, c->pid, reg_syscall_nr);
-
- if (syscall < syscall_max) {
- syscall_count[syscall]++;
+ int i = syscall_index(syscall);
+ if (i >= 0) {
+ syscall_count[i]++;
if (debug)
- fprintf(stderr, "%s()\n", syscall_names[syscall]);
+ fprintf(stderr, "%s()\n", syscall_name(syscall));
} else if (debug) {
fprintf(stderr, "syscal(%d)\n", syscall);
}
@@ -351,8 +351,6 @@ int main(int argc, char **argv, char **envp)
if (child < 0)
return -1;
- syscall_max = ARRAY_SIZE(syscall_names);
- syscall_count = calloc(syscall_max, sizeof(int));
waitpid(child, &status, WUNTRACED);
if (!WIFSTOPPED(status)) {
ERROR("failed to start %s\n", *argv);