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libsepol: validate ocontexts

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Check the literal contexts in ocontext statements are defined.

    ==91274==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x7f60b0afe8c6 bp 0x7ffd42edc990 sp 0x7ffd42edc148 T0)
    ==91274==The signal is caused by a READ memory access.
    ==91274==Hint: address points to the zero page.
        #0 0x7f60b0afe8c6  string/../sysdeps/x86_64/multiarch/../strlen.S:120
        #1 0x4bd128 in __interceptor_strlen (./out/binpolicy-fuzzer+0x4bd128)
        #2 0x5eb387 in create_str_helper ./libsepol/src/kernel_to_common.c:69:10
        #3 0x5eb11e in create_str ./libsepol/src/kernel_to_common.c:99:8
        #4 0x56ad7b in context_to_str ./libsepol/src/kernel_to_conf.c:2408:9
        #5 0x56a717 in write_sid_context_rules_to_conf ./libsepol/src/kernel_to_conf.c:2441:9
        #6 0x55b26c in write_selinux_isid_rules_to_conf ./libsepol/src/kernel_to_conf.c:2476:9
        #7 0x55b26c in sepol_kernel_policydb_to_conf ./libsepol/src/kernel_to_conf.c:3206:8
        #8 0x55a34f in LLVMFuzzerTestOneInput ./libsepol/fuzz/binpolicy-fuzzer.c:38:9
        #9 0x45aed3 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) fuzzer.o
        #10 0x446a12 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) fuzzer.o
        #11 0x44c93b in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) fuzzer.o
        #12 0x475dd2 in main (./out/binpolicy-fuzzer+0x475dd2)
        #13 0x7f60b0a887ec in __libc_start_main csu/../csu/libc-start.c:332:16
        #14 0x423689 in _start (./out/binpolicy-fuzzer+0x423689)

Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
This commit is contained in:
Christian Göttsche 2021-12-09 17:49:22 +01:00 committed by James Carter
parent 5f81623245
commit 8628133757
1 changed files with 46 additions and 0 deletions
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46
libsepol/src/policydb_validate.c
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@ -736,6 +736,49 @@ static int validate_filename_trans_hashtab(sepol_handle_t *handle, hashtab_t fil
return 0;
}
static int validate_context(context_struct_t *con, validate_t flavors[], int mls)
{
if (validate_value(con->user, &flavors[SYM_USERS]))
return -1;
if (validate_value(con->role, &flavors[SYM_ROLES]))
return -1;
if (validate_value(con->type, &flavors[SYM_TYPES]))
return -1;
if (mls && validate_mls_range(&con->range, &flavors[SYM_LEVELS], &flavors[SYM_CATS]))
return -1;
return 0;
}
static int validate_ocontexts(sepol_handle_t *handle, policydb_t *p, validate_t flavors[])
{
ocontext_t *octx;
unsigned int i;
for (i = 0; i < OCON_NUM; i++) {
for (octx = p->ocontexts[i]; octx; octx = octx->next) {
if (validate_context(&octx->context[0], flavors, p->mls))
goto bad;
if (p->target_platform == SEPOL_TARGET_SELINUX) {
switch (i) {
case OCON_FS:
case OCON_NETIF:
if (validate_context(&octx->context[1], flavors, p->mls))
goto bad;
break;
}
}
}
}
return 0;
bad:
ERR(handle, "Invalid ocontext");
return -1;
}
/*
* Functions to validate a module policydb
*/
@ -936,6 +979,9 @@ int validate_policydb(sepol_handle_t *handle, policydb_t *p)
goto bad;
}
if (validate_ocontexts(handle, p, flavors))
goto bad;
if (validate_scopes(handle, p->scope, p->global))
goto bad;