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Merge remote-tracking branch 'tor-gitlab/mr/574'

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This commit is contained in:
Nick Mathewson 2022-05-04 10:34:03 -04:00
commit 853270a871
2 changed files with 117 additions and 16 deletions
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5
changes/aarch64_sandbox Normal file
View File

@ -0,0 +1,5 @@
o Minor bugfixes (sandbox):
- Fix sandbox support on AArch64 systems. More "*at" variants of syscalls
are now supported. Signed 32 bit syscall parameters are checked more
precisely, which should lead to lower likelihood of breakages with future
compiler and libc releases. Fixes bug 40599; bugfix on 0.4.4.3-alpha.

128
src/lib/sandbox/sandbox.c
View File

@ -141,10 +141,12 @@ static sandbox_cfg_t *filter_dynamic = NULL;
* the high bits of the value might get masked out improperly. */
#define SCMP_CMP_MASKED(a,b,c) \
SCMP_CMP4((a), SCMP_CMP_MASKED_EQ, ~(scmp_datum_t)(b), (c))
/* For negative constants, the rule to add depends on the glibc version. */
#define SCMP_CMP_NEG(a,op,b) (libc_negative_constant_needs_cast() ? \
(SCMP_CMP((a), (op), (unsigned int)(b))) : \
(SCMP_CMP_STR((a), (op), (b))))
/* Negative constants aren't consistently sign extended or zero extended.
* Different compilers, libc, and architectures behave differently. For cases
* where the kernel ABI uses a 32 bit integer, this macro can be used to
* mask-compare only the lower 32 bits of the value. */
#define SCMP_CMP_LOWER32_EQ(a,b) \
SCMP_CMP4((a), SCMP_CMP_MASKED_EQ, 0xFFFFFFFF, (unsigned int)(b))
/** Variable used for storing all syscall numbers that will be allowed with the
* stage 1 general Tor sandbox.
@ -513,14 +515,6 @@ libc_uses_openat_for_opendir(void)
(is_libc_at_least(2, 15) && !is_libc_at_least(2, 22));
}
/* Return true if we think we're running with a libc that needs to cast
* negative arguments like AT_FDCWD for seccomp rules. */
static int
libc_negative_constant_needs_cast(void)
{
return is_libc_at_least(2, 27);
}
/** Allow a single file to be opened. If <b>use_openat</b> is true,
* we're using a libc that remaps all the opens into openats. */
static int
@ -528,7 +522,7 @@ allow_file_open(scmp_filter_ctx ctx, int use_openat, const char *file)
{
if (use_openat) {
return seccomp_rule_add_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(openat),
SCMP_CMP_NEG(0, SCMP_CMP_EQ, AT_FDCWD),
SCMP_CMP_LOWER32_EQ(0, AT_FDCWD),
SCMP_CMP_STR(1, SCMP_CMP_EQ, file));
} else {
return seccomp_rule_add_1(ctx, SCMP_ACT_ALLOW, SCMP_SYS(open),
@ -609,6 +603,32 @@ sb_chmod(scmp_filter_ctx ctx, sandbox_cfg_t *filter)
return 0;
}
static int
sb_fchmodat(scmp_filter_ctx ctx, sandbox_cfg_t *filter)
{
int rc;
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(fchmodat)) {
rc = seccomp_rule_add_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(fchmodat),
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 fchmodat syscall, received "
"libseccomp error %d", rc);
return rc;
}
}
}
return 0;
}
#ifdef __i386__
static int
sb_chown32(scmp_filter_ctx ctx, sandbox_cfg_t *filter)
@ -661,6 +681,32 @@ sb_chown(scmp_filter_ctx ctx, sandbox_cfg_t *filter)
}
#endif /* defined(__i386__) */
static int
sb_fchownat(scmp_filter_ctx ctx, sandbox_cfg_t *filter)
{
int rc;
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(fchownat)) {
rc = seccomp_rule_add_2(ctx, SCMP_ACT_ALLOW, SCMP_SYS(fchownat),
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 fchownat syscall, received "
"libseccomp error %d", rc);
return rc;
}
}
}
return 0;
}
/**
* Function responsible for setting up the rename syscall for
* the seccomp filter sandbox.
@ -692,6 +738,39 @@ sb_rename(scmp_filter_ctx ctx, sandbox_cfg_t *filter)
return 0;
}
/**
* Function responsible for setting up the renameat syscall for
* the seccomp filter sandbox.
*/
static int
sb_renameat(scmp_filter_ctx ctx, sandbox_cfg_t *filter)
{
int rc;
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(renameat)) {
rc = seccomp_rule_add_4(ctx, SCMP_ACT_ALLOW, SCMP_SYS(renameat),
SCMP_CMP_LOWER32_EQ(0, AT_FDCWD),
SCMP_CMP_STR(1, SCMP_CMP_EQ, param->value),
SCMP_CMP_LOWER32_EQ(2, AT_FDCWD),
SCMP_CMP_STR(3, SCMP_CMP_EQ, param->value2));
if (rc != 0) {
log_err(LD_BUG,"(Sandbox) failed to add renameat syscall, received "
"libseccomp error %d", rc);
return rc;
}
}
}
return 0;
}
/**
* Function responsible for setting up the openat syscall for
* the seccomp filter sandbox.
@ -709,7 +788,7 @@ sb_openat(scmp_filter_ctx ctx, sandbox_cfg_t *filter)
if (param != NULL && param->prot == 1 && param->syscall
== SCMP_SYS(openat)) {
rc = seccomp_rule_add_3(ctx, SCMP_ACT_ALLOW, SCMP_SYS(openat),
SCMP_CMP_NEG(0, SCMP_CMP_EQ, AT_FDCWD),
SCMP_CMP_LOWER32_EQ(0, AT_FDCWD),
SCMP_CMP_STR(1, SCMP_CMP_EQ, param->value),
SCMP_CMP(2, SCMP_CMP_EQ, O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY|
O_CLOEXEC));
@ -1312,7 +1391,9 @@ static sandbox_filter_func_t filter_func[] = {
#else
sb_chown,
#endif
sb_fchownat,
sb_chmod,
sb_fchmodat,
sb_open,
sb_openat,
sb_opendir,
@ -1320,6 +1401,7 @@ static sandbox_filter_func_t filter_func[] = {
sb_ptrace,
#endif
sb_rename,
sb_renameat,
#ifdef __NR_fcntl64
sb_fcntl64,
#endif
@ -1587,10 +1669,24 @@ new_element(int syscall, char *value)
#ifdef __i386__
#define SCMP_chown SCMP_SYS(chown32)
#elif defined(__aarch64__) && defined(__LP64__)
#define SCMP_chown SCMP_SYS(fchownat)
#else
#define SCMP_chown SCMP_SYS(chown)
#endif
#if defined(__aarch64__) && defined(__LP64__)
#define SCMP_chmod SCMP_SYS(fchmodat)
#else
#define SCMP_chmod SCMP_SYS(chmod)
#endif
#if defined(__aarch64__) && defined(__LP64__)
#define SCMP_rename SCMP_SYS(renameat)
#else
#define SCMP_rename SCMP_SYS(rename)
#endif
#ifdef __NR_stat64
#define SCMP_stat SCMP_SYS(stat64)
#else
@ -1628,7 +1724,7 @@ sandbox_cfg_allow_chmod_filename(sandbox_cfg_t **cfg, char *file)
{
sandbox_cfg_t *elem = NULL;
elem = new_element(SCMP_SYS(chmod), file);
elem = new_element(SCMP_chmod, file);
elem->next = *cfg;
*cfg = elem;
@ -1654,7 +1750,7 @@ sandbox_cfg_allow_rename(sandbox_cfg_t **cfg, char *file1, char *file2)
{
sandbox_cfg_t *elem = NULL;
elem = new_element2(SCMP_SYS(rename), file1, file2);
elem = new_element2(SCMP_rename, file1, file2);
elem->next = *cfg;
*cfg = elem;