| Message ID | 20240408150531.63085-1-cgoettsche@seltendoof.de (mailing list archive) |
|---|---|
| State | New |
| Delegated to: | Petr Lautrbach |
| Headers | show |
| Series | libsepol: validate class permissions | expand |
On Mon, Apr 8, 2024 at 11:05 AM Christian Göttsche <cgoettsche@seltendoof.de> wrote: > > From: Christian Göttsche <cgzones@googlemail.com> > > Validate the symbol tables for permissions of security classes and > common classes: > * check their value is valid > * check their values are unique > * check permission values of classes do not reuse values from > inherited permissions > > This simplifies validating permissions of access vectors a lot, since it > is now only a binary and against the valid permission mask of the class. > > Use UINT32_MAX instead of 0 as the special value for validating > constraints signaling a validate-trans rule, since classes with no > permissions are permitted, but they must not have a normal constraint > attached. > > Reported-by: oss-fuzz (issue 67893) > Improves: 8c64e5bb6fe7 ("libsepol: validate access vector permissions") > Signed-off-by: Christian Göttsche <cgzones@googlemail.com> > --- > libsepol/src/policydb_validate.c | 101 ++++++++++++++++++++----------- > 1 file changed, 66 insertions(+), 35 deletions(-) > > diff --git a/libsepol/src/policydb_validate.c b/libsepol/src/policydb_validate.c > index c4f8c300..a5051416 100644 > --- a/libsepol/src/policydb_validate.c > +++ b/libsepol/src/policydb_validate.c > @@ -11,6 +11,7 @@ > > #define bool_xor(a, b) (!(a) != !(b)) > #define bool_xnor(a, b) (!bool_xor(a, b)) > +#define PERMISSION_MASK(nprim) ((nprim) == PERM_SYMTAB_SIZE ? (~UINT32_C(0)) : ((UINT32_C(1) << (nprim)) - 1)) > > typedef struct validate { > uint32_t nprim; > @@ -23,6 +24,12 @@ typedef struct map_arg { > const policydb_t *policy; > } map_arg_t; > > +typedef struct perm_arg { > + uint32_t visited; > + const uint32_t nprim; > + const uint32_t inherited_nprim; > +} perm_arg_t; > + > static int create_gap_ebitmap(char **val_to_name, uint32_t nprim, ebitmap_t *gaps) > { > uint32_t i; > @@ -230,14 +237,17 @@ bad: > static int validate_constraint_nodes(sepol_handle_t *handle, unsigned int nperms, const constraint_node_t *cons, validate_t flavors[]) > { > const constraint_expr_t *cexp; > + const int is_validatetrans = (nperms == UINT32_MAX); > int depth; > > for (; cons; cons = cons->next) { > - if (nperms == 0 && cons->permissions != 0) > + if (is_validatetrans && cons->permissions != 0) > + goto bad; > + if (!is_validatetrans && nperms == 0) This conditional does not need to be in the loop and is_validatetrans will always be false if nperms == 0. The rest of the patch looks good. Thanks, Jim > goto bad; > - if (nperms > 0 && cons->permissions == 0) > + if (!is_validatetrans && cons->permissions == 0) > goto bad; > - if (nperms > 0 && nperms != PERM_SYMTAB_SIZE && cons->permissions >= (UINT32_C(1) << nperms)) > + if (!is_validatetrans && nperms != PERM_SYMTAB_SIZE && cons->permissions >= (UINT32_C(1) << nperms)) > goto bad; > > if (!cons->expr) > @@ -251,7 +261,7 @@ static int validate_constraint_nodes(sepol_handle_t *handle, unsigned int nperms > goto bad; > depth++; > > - if (cexp->attr & CEXPR_XTARGET && nperms != 0) > + if (cexp->attr & CEXPR_XTARGET && !is_validatetrans) > goto bad; > if (!(cexp->attr & CEXPR_TYPE)) { > if (validate_empty_type_set(cexp->type_names)) > @@ -366,11 +376,49 @@ bad: > return -1; > } > > +static int perm_visit(__attribute__((__unused__)) hashtab_key_t k, hashtab_datum_t d, void *args) > +{ > + perm_arg_t *pargs = args; > + const perm_datum_t *perdatum = d; > + > + if (!value_isvalid(perdatum->s.value, pargs->nprim)) > + return -1; > + > + if (pargs->inherited_nprim != 0 && value_isvalid(perdatum->s.value, pargs->inherited_nprim)) > + return -1; > + > + if ((UINT32_C(1) << (perdatum->s.value - 1)) & pargs->visited) > + return -1; > + > + pargs->visited |= (UINT32_C(1) << (perdatum->s.value - 1)); > + return 0; > +} > + > +static int validate_permission_symtab(sepol_handle_t *handle, const symtab_t *permissions, uint32_t inherited_nprim) > +{ > + /* Check each entry has a different valid value and is not overriding an inherited one */ > + > + perm_arg_t pargs = { .visited = 0, .nprim = permissions->nprim, .inherited_nprim = inherited_nprim }; > + > + if (hashtab_map(permissions->table, perm_visit, &pargs)) > + goto bad; > + > + return 0; > + > +bad: > + ERR(handle, "Invalid permission table"); > + return -1; > +} > + > static int validate_common_datum(sepol_handle_t *handle, const common_datum_t *common, validate_t flavors[]) > { > if (validate_value(common->s.value, &flavors[SYM_COMMONS])) > goto bad; > - if (common->permissions.table->nel == 0 || common->permissions.nprim > PERM_SYMTAB_SIZE) > + if (common->permissions.nprim == 0 || common->permissions.nprim > PERM_SYMTAB_SIZE) > + goto bad; > + if (common->permissions.nprim != common->permissions.table->nel) > + goto bad; > + if (validate_permission_symtab(handle, &common->permissions, 0)) > goto bad; > > return 0; > @@ -393,11 +441,17 @@ static int validate_class_datum(sepol_handle_t *handle, const class_datum_t *cla > goto bad; > if (class->comdatum && validate_common_datum(handle, class->comdatum, flavors)) > goto bad; > - if (class->permissions.nprim > PERM_SYMTAB_SIZE) > + /* empty classes are permitted */ > + if (class->permissions.nprim > PERM_SYMTAB_SIZE || class->permissions.table->nel > PERM_SYMTAB_SIZE) > + goto bad; > + if (class->permissions.nprim != > + (class->permissions.table->nel + (class->comdatum ? class->comdatum->permissions.table->nel : 0))) > + goto bad; > + if (validate_permission_symtab(handle, &class->permissions, class->comdatum ? class->comdatum->permissions.nprim : 0)) > goto bad; > if (validate_constraint_nodes(handle, class->permissions.nprim, class->constraints, flavors)) > goto bad; > - if (validate_constraint_nodes(handle, 0, class->validatetrans, flavors)) > + if (validate_constraint_nodes(handle, UINT32_MAX, class->validatetrans, flavors)) > goto bad; > > switch (class->default_user) { > @@ -877,46 +931,23 @@ 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; > - } > - } > - } > + if (!(av & PERMISSION_MASK(cladatum->permissions.nprim))) > + goto bad; > > + return 0; > + > +bad: > 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) > -- > 2.43.0 > >
diff --git a/libsepol/src/policydb_validate.c b/libsepol/src/policydb_validate.c index c4f8c300..a5051416 100644 --- a/libsepol/src/policydb_validate.c +++ b/libsepol/src/policydb_validate.c @@ -11,6 +11,7 @@ #define bool_xor(a, b) (!(a) != !(b)) #define bool_xnor(a, b) (!bool_xor(a, b)) +#define PERMISSION_MASK(nprim) ((nprim) == PERM_SYMTAB_SIZE ? (~UINT32_C(0)) : ((UINT32_C(1) << (nprim)) - 1)) typedef struct validate { uint32_t nprim; @@ -23,6 +24,12 @@ typedef struct map_arg { const policydb_t *policy; } map_arg_t; +typedef struct perm_arg { + uint32_t visited; + const uint32_t nprim; + const uint32_t inherited_nprim; +} perm_arg_t; + static int create_gap_ebitmap(char **val_to_name, uint32_t nprim, ebitmap_t *gaps) { uint32_t i; @@ -230,14 +237,17 @@ bad: static int validate_constraint_nodes(sepol_handle_t *handle, unsigned int nperms, const constraint_node_t *cons, validate_t flavors[]) { const constraint_expr_t *cexp; + const int is_validatetrans = (nperms == UINT32_MAX); int depth; for (; cons; cons = cons->next) { - if (nperms == 0 && cons->permissions != 0) + if (is_validatetrans && cons->permissions != 0) + goto bad; + if (!is_validatetrans && nperms == 0) goto bad; - if (nperms > 0 && cons->permissions == 0) + if (!is_validatetrans && cons->permissions == 0) goto bad; - if (nperms > 0 && nperms != PERM_SYMTAB_SIZE && cons->permissions >= (UINT32_C(1) << nperms)) + if (!is_validatetrans && nperms != PERM_SYMTAB_SIZE && cons->permissions >= (UINT32_C(1) << nperms)) goto bad; if (!cons->expr) @@ -251,7 +261,7 @@ static int validate_constraint_nodes(sepol_handle_t *handle, unsigned int nperms goto bad; depth++; - if (cexp->attr & CEXPR_XTARGET && nperms != 0) + if (cexp->attr & CEXPR_XTARGET && !is_validatetrans) goto bad; if (!(cexp->attr & CEXPR_TYPE)) { if (validate_empty_type_set(cexp->type_names)) @@ -366,11 +376,49 @@ bad: return -1; } +static int perm_visit(__attribute__((__unused__)) hashtab_key_t k, hashtab_datum_t d, void *args) +{ + perm_arg_t *pargs = args; + const perm_datum_t *perdatum = d; + + if (!value_isvalid(perdatum->s.value, pargs->nprim)) + return -1; + + if (pargs->inherited_nprim != 0 && value_isvalid(perdatum->s.value, pargs->inherited_nprim)) + return -1; + + if ((UINT32_C(1) << (perdatum->s.value - 1)) & pargs->visited) + return -1; + + pargs->visited |= (UINT32_C(1) << (perdatum->s.value - 1)); + return 0; +} + +static int validate_permission_symtab(sepol_handle_t *handle, const symtab_t *permissions, uint32_t inherited_nprim) +{ + /* Check each entry has a different valid value and is not overriding an inherited one */ + + perm_arg_t pargs = { .visited = 0, .nprim = permissions->nprim, .inherited_nprim = inherited_nprim }; + + if (hashtab_map(permissions->table, perm_visit, &pargs)) + goto bad; + + return 0; + +bad: + ERR(handle, "Invalid permission table"); + return -1; +} + static int validate_common_datum(sepol_handle_t *handle, const common_datum_t *common, validate_t flavors[]) { if (validate_value(common->s.value, &flavors[SYM_COMMONS])) goto bad; - if (common->permissions.table->nel == 0 || common->permissions.nprim > PERM_SYMTAB_SIZE) + if (common->permissions.nprim == 0 || common->permissions.nprim > PERM_SYMTAB_SIZE) + goto bad; + if (common->permissions.nprim != common->permissions.table->nel) + goto bad; + if (validate_permission_symtab(handle, &common->permissions, 0)) goto bad; return 0; @@ -393,11 +441,17 @@ static int validate_class_datum(sepol_handle_t *handle, const class_datum_t *cla goto bad; if (class->comdatum && validate_common_datum(handle, class->comdatum, flavors)) goto bad; - if (class->permissions.nprim > PERM_SYMTAB_SIZE) + /* empty classes are permitted */ + if (class->permissions.nprim > PERM_SYMTAB_SIZE || class->permissions.table->nel > PERM_SYMTAB_SIZE) + goto bad; + if (class->permissions.nprim != + (class->permissions.table->nel + (class->comdatum ? class->comdatum->permissions.table->nel : 0))) + goto bad; + if (validate_permission_symtab(handle, &class->permissions, class->comdatum ? class->comdatum->permissions.nprim : 0)) goto bad; if (validate_constraint_nodes(handle, class->permissions.nprim, class->constraints, flavors)) goto bad; - if (validate_constraint_nodes(handle, 0, class->validatetrans, flavors)) + if (validate_constraint_nodes(handle, UINT32_MAX, class->validatetrans, flavors)) goto bad; switch (class->default_user) { @@ -877,46 +931,23 @@ 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; - } - } - } + if (!(av & PERMISSION_MASK(cladatum->permissions.nprim))) + goto bad; + return 0; + +bad: 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)