| Message ID | 20211105154542.38434-31-cgzones@googlemail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | libsepol: add fuzzer for reading binary policies | expand |
On Fri, Nov 5, 2021 at 12:11 PM Christian Göttsche <cgzones@googlemail.com> wrote: > > 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> > > --- > v2: > also check in base modules > > Signed-off-by: Christian Göttsche <cgzones@googlemail.com> > --- > libsepol/src/policydb_validate.c | 44 ++++++++++++++++++++++++++++++++ > 1 file changed, 44 insertions(+) > > diff --git a/libsepol/src/policydb_validate.c b/libsepol/src/policydb_validate.c > index 57eb2550..96f133c9 100644 > --- a/libsepol/src/policydb_validate.c > +++ b/libsepol/src/policydb_validate.c > @@ -736,6 +736,47 @@ 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; > + > + switch (i) { > + case OCON_FS: > + case OCON_NETIF: > + if (validate_context(&octx->context[1], flavors, p->mls)) > + goto bad; > + break; Should use a default case. The bigger issue, which I didn't catch the first time, is that this doesn't work for a XEN policy. In policydb.c there is an ocontext_read_xen() and an ocontext_read_selinux(), which is called depends on whether p->target_platform is SEPOL_TARGET_SELINUX or SEPOL_TARGET_XEN. Jim > + } > + } > + } > + > + return 0; > + > +bad: > + ERR(handle, "Invalid ocontext"); > + return -1; > +} > + > /* > * Functions to validate a module policydb > */ > @@ -936,6 +977,9 @@ 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; > > -- > 2.33.1 >
diff --git a/libsepol/src/policydb_validate.c b/libsepol/src/policydb_validate.c index 57eb2550..96f133c9 100644 --- a/libsepol/src/policydb_validate.c +++ b/libsepol/src/policydb_validate.c @@ -736,6 +736,47 @@ 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; + + 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 +977,9 @@ 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;
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> --- v2: also check in base modules Signed-off-by: Christian Göttsche <cgzones@googlemail.com> --- libsepol/src/policydb_validate.c | 44 ++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+)