From 8c64e5bb6fe76ac72a7f31fadb5258af577c66aa Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Christian=20G=C3=B6ttsche?= Date: Tue, 2 Apr 2024 17:29:22 +0200 Subject: [PATCH] libsepol: validate access vector permissions MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Since commit c205b924e280 ("libsepol: Fix buffer overflow when using sepol_av_to_string()") writing an access vector with no valid permission results in an error instead of an empty string being written. Validate that at least one permission of an access vector is valid. There might be invalid bits set, e.g. by previous versions of checkpolicy setting all bits for the wildcard (*) permission. Reported-by: oss-fuzz (issue 67730) Signed-off-by: Christian Göttsche Acked-by: James Carter --- libsepol/src/policydb_validate.c | 62 ++++++++++++++++++++++++++++++++ 1 file changed, 62 insertions(+) diff --git a/libsepol/src/policydb_validate.c b/libsepol/src/policydb_validate.c index e987d8da..c4f8c300 100644 --- a/libsepol/src/policydb_validate.c +++ b/libsepol/src/policydb_validate.c @@ -876,6 +876,49 @@ static int validate_xperms(const avtab_extended_perms_t *xperms) bad: return -1; } + +static int perm_match(__attribute__ ((unused)) hashtab_key_t key, hashtab_datum_t datum, void *data) +{ + const uint32_t *v = data; + const perm_datum_t *perdatum = datum; + + return *v == perdatum->s.value; +} + +static int validate_access_vector(sepol_handle_t *handle, const policydb_t *p, sepol_security_class_t tclass, + sepol_access_vector_t av) +{ + const class_datum_t *cladatum = p->class_val_to_struct[tclass - 1]; + uint32_t i; + + /* + * Check that at least one permission bit is valid. + * Older compilers might set invalid bits for the wildcard permission. + */ + for (i = 0; i < cladatum->permissions.nprim; i++) { + if (av & (UINT32_C(1) << i)) { + uint32_t v = i + 1; + int rc; + + rc = hashtab_map(cladatum->permissions.table, perm_match, &v); + if (rc == 1) + goto good; + + if (cladatum->comdatum) { + rc = hashtab_map(cladatum->comdatum->permissions.table, perm_match, &v); + if (rc == 1) + goto good; + } + } + } + + ERR(handle, "Invalid access vector"); + return -1; + +good: + return 0; +} + static int validate_avtab_key_and_datum(avtab_key_t *k, avtab_datum_t *d, void *args) { map_arg_t *margs = args; @@ -883,6 +926,16 @@ static int validate_avtab_key_and_datum(avtab_key_t *k, avtab_datum_t *d, void * if (validate_avtab_key(k, 0, margs->policy, margs->flavors)) return -1; + if (k->specified & AVTAB_AV) { + uint32_t data = d->data; + + if ((0xFFF & k->specified) == AVTAB_AUDITDENY) + data = ~data; + + if (validate_access_vector(margs->handle, margs->policy, k->target_class, data)) + return -1; + } + if ((k->specified & AVTAB_TYPE) && validate_simpletype(d->data, margs->policy, margs->flavors)) return -1; @@ -915,6 +968,15 @@ static int validate_cond_av_list(sepol_handle_t *handle, const cond_av_list_t *c if (validate_avtab_key(key, 1, p, flavors)) goto bad; + if (key->specified & AVTAB_AV) { + uint32_t data = datum->data; + + if ((0xFFF & key->specified) == AVTAB_AUDITDENY) + data = ~data; + + if (validate_access_vector(handle, p, key->target_class, data)) + goto bad; + } if ((key->specified & AVTAB_TYPE) && validate_simpletype(datum->data, p, flavors)) goto bad; }