On Fri, Nov 5, 2021 at 12:11 PM Christian Göttsche
<cgzones@xxxxxxxxxxxxxx> wrote:
>
> Add checks for invalid read sizes from a binary policy to guard
> allocations.
>
> The common and class permission counts needs to be limited more strict
> otherwise a too high count of common or class permissions can lead to
> permission values with a too high value, which can lead to overflows
> in shift operations.
>
> In the fuzzer build the value will also be bounded to avoid oom reports.
>
> ==29857== ERROR: libFuzzer: out-of-memory (malloc(17179868160))
> To change the out-of-memory limit use -rss_limit_mb=<N>
>
> #0 0x52dc61 in __sanitizer_print_stack_trace (./out/binpolicy-fuzzer+0x52dc61)
> #1 0x475618 in fuzzer::PrintStackTrace() fuzzer.o
> #2 0x458855 in fuzzer::Fuzzer::HandleMalloc(unsigned long) fuzzer.o
> #3 0x45876a in fuzzer::MallocHook(void const volatile*, unsigned long) fuzzer.o
> #4 0x534557 in __sanitizer::RunMallocHooks(void const*, unsigned long) (./out/binpolicy-fuzzer+0x534557)
> #5 0x4aa7d7 in __asan::Allocator::Allocate(unsigned long, unsigned long, __sanitizer::BufferedStackTrace*, __asan::AllocType, bool) (./out/binpolicy-fuzzer+0x4aa7d7)
> #6 0x4aa143 in __asan::asan_malloc(unsigned long, __sanitizer::BufferedStackTrace*) (./out/binpolicy-fuzzer+0x4aa143)
> #7 0x5259cb in malloc (./out/binpolicy-fuzzer+0x5259cb)
> #8 0x580b5d in mallocarray ./libsepol/src/./private.h:93:9
> #9 0x57c2ed in scope_read ./libsepol/src/policydb.c:4120:7
> #10 0x576b0d in policydb_read ./libsepol/src/policydb.c:4462:9
> #11 0x55a214 in LLVMFuzzerTestOneInput ./libsepol/fuzz/binpolicy-fuzzer.c:26:6
> #12 0x45aed3 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) fuzzer.o
> #13 0x446a12 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) fuzzer.o
> #14 0x44c93b in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) fuzzer.o
> #15 0x475dd2 in main (./out/binpolicy-fuzzer+0x475dd2)
> #16 0x7ffad6e107ec in __libc_start_main csu/../csu/libc-start.c:332:16
> #17 0x423689 in _start (./out/binpolicy-fuzzer+0x423689)
>
> ==19462== ERROR: libFuzzer: out-of-memory (malloc(18253611008))
> To change the out-of-memory limit use -rss_limit_mb=<N>
>
> #0 0x52dc61 in __sanitizer_print_stack_trace (./out/binpolicy-fuzzer+0x52dc61)
> #1 0x475618 in fuzzer::PrintStackTrace() fuzzer.o
> #2 0x458855 in fuzzer::Fuzzer::HandleMalloc(unsigned long) fuzzer.o
> #3 0x45876a in fuzzer::MallocHook(void const volatile*, unsigned long) fuzzer.o
> #4 0x534557 in __sanitizer::RunMallocHooks(void const*, unsigned long) (./out/binpolicy-fuzzer+0x534557)
> #5 0x4aa7d7 in __asan::Allocator::Allocate(unsigned long, unsigned long, __sanitizer::BufferedStackTrace*, __asan::AllocType, bool) (./out/binpolicy-fuzzer+0x4aa7d7)
> #6 0x4aa999 in __asan::asan_calloc(unsigned long, unsigned long, __sanitizer::BufferedStackTrace*) (./out/binpolicy-fuzzer+0x4aa999)
> #7 0x525b63 in __interceptor_calloc (./out/binpolicy-fuzzer+0x525b63)
> #8 0x570938 in policydb_index_others ./libsepol/src/policydb.c:1245:6
> #9 0x5771f3 in policydb_read ./src/policydb.c:4481:6
> #10 0x55a214 in LLVMFuzzerTestOneInput ./libsepol/fuzz/binpolicy-fuzzer.c:26:6
> #11 0x45aed3 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) fuzzer.o
> #12 0x446a12 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) fuzzer.o
> #13 0x44c93b in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) fuzzer.o
> #14 0x475dd2 in main (./out/binpolicy-fuzzer+0x475dd2)
> #15 0x7f4d933157ec in __libc_start_main csu/../csu/libc-start.c:332:16
> #16 0x423689 in _start (./out/binpolicy-fuzzer+0x423689)
>
> Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
> ---
> libsepol/src/policydb.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/libsepol/src/policydb.c b/libsepol/src/policydb.c
> index dcea1807..1408405d 100644
> --- a/libsepol/src/policydb.c
> +++ b/libsepol/src/policydb.c
> @@ -2103,6 +2103,8 @@ static int common_read(policydb_t * p, hashtab_t h, struct policy_file *fp)
> if (symtab_init(&comdatum->permissions, PERM_SYMTAB_SIZE))
> goto bad;
> comdatum->permissions.nprim = le32_to_cpu(buf[2]);
> + if (comdatum->permissions.nprim > 32)
Should use PERM_SYMTAB_SIZE here (like in patch 22).
> + goto bad;
> nel = le32_to_cpu(buf[3]);
>
> key = malloc(len + 1);
> @@ -2251,6 +2253,8 @@ static int class_read(policydb_t * p, hashtab_t h, struct policy_file *fp)
> if (symtab_init(&cladatum->permissions, PERM_SYMTAB_SIZE))
> goto bad;
> cladatum->permissions.nprim = le32_to_cpu(buf[3]);
> + if (cladatum->permissions.nprim > 32)
Same here.
> + goto bad;
> nel = le32_to_cpu(buf[4]);
>
> ncons = le32_to_cpu(buf[5]);
> @@ -3980,6 +3984,8 @@ static int avrule_decl_read(policydb_t * p, avrule_decl_t * decl,
> if (rc < 0)
> return -1;
> nprim = le32_to_cpu(buf[0]);
> + if (is_saturated(nprim))
> + return -1;
> nel = le32_to_cpu(buf[1]);
> for (j = 0; j < nel; j++) {
> if (read_f[i] (p, decl->symtab[i].table, fp)) {
> @@ -4106,7 +4112,7 @@ static int scope_read(policydb_t * p, int symnum, struct policy_file *fp)
> goto cleanup;
> scope->scope = le32_to_cpu(buf[0]);
> scope->decl_ids_len = le32_to_cpu(buf[1]);
> - if (scope->decl_ids_len == 0) {
> + if (zero_or_saturated(scope->decl_ids_len)) {
> ERR(fp->handle, "invalid scope with no declaration");
> goto cleanup;
> }
> @@ -4396,6 +4402,8 @@ int policydb_read(policydb_t * p, struct policy_file *fp, unsigned verbose)
> if (rc < 0)
> goto bad;
> nprim = le32_to_cpu(buf[0]);
> + if (is_saturated(nprim))
> + goto bad;
> nel = le32_to_cpu(buf[1]);
> if (nel && !nprim) {
> ERR(fp->handle, "unexpected items in symbol table with no symbol");
> --
> 2.33.1
>
