[tor-commits] [tor/release-0.4.2] Correct how we use libseccomp
teor at torproject.org
teor at torproject.org
Wed Jan 29 21:57:57 UTC 2020
commit 0d64bafcfedd259fb15b3ee85a7b00a840aec73b
Author: Peter Gerber <peter at arbitrary.ch>
Date: Mon Jun 10 14:56:31 2019 +0200
Correct how we use libseccomp
This fixes a startup crash with libseccomp v2.4.0 if Sandbox is
set to 1.
---
changes/bug29819 | 8 ++++++++
src/lib/sandbox/sandbox.c | 40 ++--------------------------------------
2 files changed, 10 insertions(+), 38 deletions(-)
diff --git a/changes/bug29819 b/changes/bug29819
new file mode 100644
index 000000000..d37ac83d6
--- /dev/null
+++ b/changes/bug29819
@@ -0,0 +1,8 @@
+ o Minor bugfixes (linux seccomp sandbox):
+ - Correct how we use libseccomp. Particularly, stop assuming that
+ rules are applied in a particular order or that more rules are
+ processed after the first match. Neither is the case! In libseccomp
+ <2.4.0 this lead to some rules having no effect. Libseccomp 2.4.0
+ changed how rules are generated leading to a different ordering
+ which in turn lead to a fatal crash during startup. Fixes bug
+ 29819; bugfix on 0.2.5.1-alpha. Patch by Peter Gerber.
diff --git a/src/lib/sandbox/sandbox.c b/src/lib/sandbox/sandbox.c
index e2356a172..8f577b066 100644
--- a/src/lib/sandbox/sandbox.c
+++ b/src/lib/sandbox/sandbox.c
@@ -491,24 +491,6 @@ sb_open(scmp_filter_ctx ctx, sandbox_cfg_t *filter)
}
}
- rc = seccomp_rule_add_1(ctx, SCMP_ACT_ERRNO(EACCES), SCMP_SYS(open),
- SCMP_CMP_MASKED(1, O_CLOEXEC|O_NONBLOCK|O_NOCTTY|O_NOFOLLOW,
- O_RDONLY));
- if (rc != 0) {
- log_err(LD_BUG,"(Sandbox) failed to add open syscall, received libseccomp "
- "error %d", rc);
- return rc;
- }
-
- rc = seccomp_rule_add_1(ctx, SCMP_ACT_ERRNO(EACCES), SCMP_SYS(openat),
- SCMP_CMP_MASKED(2, O_CLOEXEC|O_NONBLOCK|O_NOCTTY|O_NOFOLLOW,
- O_RDONLY));
- if (rc != 0) {
- log_err(LD_BUG,"(Sandbox) failed to add openat syscall, received "
- "libseccomp error %d", rc);
- return rc;
- }
-
return 0;
}
@@ -562,23 +544,6 @@ sb_chown(scmp_filter_ctx ctx, sandbox_cfg_t *filter)
return 0;
}
-static int
-sb__sysctl(scmp_filter_ctx ctx, sandbox_cfg_t *filter)
-{
- int rc;
- (void) filter;
- (void) ctx;
-
- rc = seccomp_rule_add_0(ctx, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(_sysctl));
- if (rc != 0) {
- log_err(LD_BUG,"(Sandbox) failed to add _sysctl syscall, "
- "received libseccomp error %d", rc);
- return rc;
- }
-
- return 0;
-}
-
/**
* Function responsible for setting up the rename syscall for
* the seccomp filter sandbox.
@@ -1141,7 +1106,6 @@ static sandbox_filter_func_t filter_func[] = {
sb_chmod,
sb_open,
sb_openat,
- sb__sysctl,
sb_rename,
#ifdef __NR_fcntl64
sb_fcntl64,
@@ -1518,14 +1482,14 @@ install_syscall_filter(sandbox_cfg_t* cfg)
int rc = 0;
scmp_filter_ctx ctx;
- ctx = seccomp_init(SCMP_ACT_TRAP);
+ ctx = seccomp_init(SCMP_ACT_ERRNO(EPERM));
if (ctx == NULL) {
log_err(LD_BUG,"(Sandbox) failed to initialise libseccomp context");
rc = -1;
goto end;
}
- // protectign sandbox parameter strings
+ // protecting sandbox parameter strings
if ((rc = prot_strings(ctx, cfg))) {
goto end;
}
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