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sandbox: Filter "newfstatat" on systems using generic syscalls

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On architectures that use Linux's generic syscall interface the legacy "stat"
and "stat64" calls may not be available; on these systems glibc uses
"newfstatat" instead.  Modify the sandbox implementation to match.

Note that on these architectures as on others glibc 2.33 uses "newfstatat" in a
way the sandbox cannot filter, so preserve in add_noparam_filter() the code
that allows the use of this syscall without restriction when glibc version 2.33
is in use.
This commit is contained in:
Simon South 2021-08-30 12:06:58 -04:00
parent d0297d878d
commit cac7bec130
1 changed files with 51 additions and 3 deletions
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54
src/lib/sandbox/sandbox.c
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@ -125,6 +125,15 @@
#define SYSCALL_NAME_DEBUGGING
#endif
/**
* On newer architectures Linux provides a standardized, generic set of system
* calls (defined in Linux's include/uapi/asm-generic/unistd.h), which omits a
* number of legacy calls used by glibc on other platforms.
*/
#if defined(__aarch64__) || defined(__riscv)
#define ARCH_USES_GENERIC_SYSCALLS
#endif
/**Determines if at least one sandbox is active.*/
static int sandbox_active = 0;
/** Holds the parameter list configuration for the sandbox.*/
@ -259,8 +268,9 @@ static int filter_nopar_gen[] = {
#ifdef __NR_sigreturn
SCMP_SYS(sigreturn),
#endif
#if defined(__NR_stat)
SCMP_SYS(stat),
#if defined(__i386__) && defined(__NR_statx)
#elif defined(__i386__) && defined(__NR_statx)
SCMP_SYS(statx),
#endif
SCMP_SYS(uname),
@ -1377,6 +1387,40 @@ sb_mremap(scmp_filter_ctx ctx, sandbox_cfg_t *filter)
return 0;
}
#ifdef ARCH_USES_GENERIC_SYSCALLS
/**
* Function responsible for setting up the newfstatat syscall for
* the seccomp filter sandbox.
*/
static int
sb_newfstatat(scmp_filter_ctx ctx, sandbox_cfg_t *filter)
{
int rc = 0;
sandbox_cfg_t *elem = NULL;
// for each dynamic parameter filters
for (elem = filter; elem != NULL; elem = elem->next) {
smp_param_t *param = elem->param;
if (param != NULL && param->prot == 1 && (param->syscall == SCMP_SYS(open)
|| param->syscall == PHONY_OPENDIR_SYSCALL
|| param->syscall == SCMP_SYS(newfstatat))) {
rc = seccomp_rule_add_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(newfstatat),
SCMP_CMP_LOWER32_EQ(0, AT_FDCWD),
SCMP_CMP_STR(1, SCMP_CMP_EQ, param->value));
if (rc != 0) {
log_err(LD_BUG,"(Sandbox) failed to add newfstatat syscall, received "
"libseccomp error %d", rc);
return rc;
}
}
}
return 0;
}
#endif /* defined(ARCH_USES_GENERIC_SYSCALLS) */
#ifdef __NR_stat64
/**
* Function responsible for setting up the stat64 syscall for
@ -1465,7 +1509,9 @@ static sandbox_filter_func_t filter_func[] = {
sb_flock,
sb_futex,
sb_mremap,
#ifdef __NR_stat64
#if defined(ARCH_USES_GENERIC_SYSCALLS)
sb_newfstatat,
#elif defined(__NR_stat64)
sb_stat64,
#endif
@ -1743,7 +1789,9 @@ new_element(int syscall, char *value)
#define SCMP_rename SCMP_SYS(renameat2)
#endif
#ifdef __NR_stat64
#if defined(ARCH_USES_GENERIC_SYSCALLS)
#define SCMP_stat SCMP_SYS(newfstatat)
#elif defined(__NR_stat64)
#define SCMP_stat SCMP_SYS(stat64)
#else
#define SCMP_stat SCMP_SYS(stat)