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added filter protection for string parameter memory

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This commit is contained in:
Cristian Toader 2013-09-10 14:35:11 +03:00
parent 8e003b1c69
commit 79f94e236b
1 changed files with 48 additions and 10 deletions
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58
src/common/sandbox.c
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@ -587,11 +587,6 @@ sb_mprotect(scmp_filter_ctx ctx, sandbox_cfg_t *filter)
if (rc)
return rc;
rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mprotect), 1,
SCMP_CMP(2, SCMP_CMP_EQ, PROT_READ|PROT_WRITE));
if (rc)
return rc;
rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mprotect), 1,
SCMP_CMP(2, SCMP_CMP_EQ, PROT_NONE));
if (rc)
@ -810,7 +805,7 @@ sandbox_intern_string(const char *str)
* mprotect().
*/
static int
prot_strings(sandbox_cfg_t* cfg)
prot_strings(scmp_filter_ctx ctx, sandbox_cfg_t* cfg)
{
int ret = 0;
size_t pr_mem_size = 0, pr_mem_left = 0;
@ -870,6 +865,48 @@ prot_strings(sandbox_cfg_t* cfg)
goto out;
}
/*
* Setting sandbox restrictions so the string memory cannot be tampered with
*/
// no mremap of the protected base address
ret = seccomp_rule_add(ctx, SCMP_ACT_KILL, SCMP_SYS(mremap), 1,
SCMP_CMP(0, SCMP_CMP_EQ, (intptr_t) pr_mem_base));
if (ret) {
log_err(LD_BUG,"(Sandbox) mremap protected memory filter fail!");
return ret;
}
// no munmap of the protected base address
ret = seccomp_rule_add(ctx, SCMP_ACT_KILL, SCMP_SYS(munmap), 1,
SCMP_CMP(0, SCMP_CMP_EQ, (intptr_t) pr_mem_base));
if (ret) {
log_err(LD_BUG,"(Sandbox) munmap protected memory filter fail!");
return ret;
}
/*
* Allow mprotect with PROT_READ|PROT_WRITE because openssl uses it, but
* never over the memory region used by the protected strings.
*
* PROT_READ|PROT_WRITE was originally fully allowed in sb_mprotect(), but
* had to be removed due to limitation of libseccomp regarding intervals.
*/
ret = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mprotect), 2,
SCMP_CMP(0, SCMP_CMP_LT, (intptr_t) pr_mem_base),
SCMP_CMP(2, SCMP_CMP_EQ, PROT_READ|PROT_WRITE));
if (ret) {
log_err(LD_BUG,"(Sandbox) mprotect protected memory filter fail (LT)!");
return ret;
}
ret = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mprotect), 2,
SCMP_CMP(0, SCMP_CMP_GT, (intptr_t) pr_mem_base + pr_mem_size),
SCMP_CMP(2, SCMP_CMP_EQ, PROT_READ|PROT_WRITE));
if (ret) {
log_err(LD_BUG,"(Sandbox) mprotect protected memory filter fail (GT)!");
return ret;
}
out:
return ret;
}
@ -1216,6 +1253,11 @@ install_syscall_filter(sandbox_cfg_t* cfg)
goto end;
}
// protectign sandbox parameter strings
if ((rc = prot_strings(ctx, cfg))) {
goto end;
}
// add parameter filters
if ((rc = add_param_filter(ctx, cfg))) {
log_err(LD_BUG, "(Sandbox) failed to add param filters!");
@ -1362,10 +1404,6 @@ initialise_libseccomp_sandbox(sandbox_cfg_t* cfg)
if (install_sigsys_debugging())
return -1;
if (prot_strings(cfg)) {
return -4;
}
if (install_syscall_filter(cfg))
return -2;