On Tue, Dec 12, 2023 at 10:11 AM James Carter <jwcart2@xxxxxxxxx> wrote:
>
> In the internal function sepol_av_to_string(), use a dynamically
> allocated buffer for the permission names of an access vector instead
> of a fixed static buffer to support very long permission names.
>
> Update the internal users of sepol_av_to_string() to free the buffer.
>
> The exported function sepol_perm_to_string() is just a wrapper to
> the internal function. To avoid changing the behavior of this function,
> use a static buffer and copy the resulting string from the internal
> function. If the string is too long for the buffer or there was an
> error in creating the string, return a string indicating the error.
>
> All of the changes to the internal function and users was the work
> of Christian Göttsche <cgzones@xxxxxxxxxxxxxx>.
>
> Reported-by: oss-fuzz (issue 64832, 64933)
> Suggested-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
> Signed-off-by: James Carter <jwcart2@xxxxxxxxx>
This patch has been merged.
Jim
> ---
> v2: In sepol_av_perm_to_string():
> - Use "sizeof(avbuf)" instead of 1024
> - Added "free(avstr)"
> In sepol_av_to_string():
> - Added "*p = '\0';" to ensure buffer is initialized
>
> checkpolicy/test/dismod.c | 11 +++---
> checkpolicy/test/dispol.c | 7 ++--
> libsepol/include/sepol/policydb/util.h | 2 +-
> libsepol/src/assertion.c | 16 ++++++---
> libsepol/src/hierarchy.c | 7 ++--
> libsepol/src/kernel_to_cil.c | 7 ++++
> libsepol/src/kernel_to_conf.c | 15 +++++---
> libsepol/src/module_to_cil.c | 7 ++++
> libsepol/src/services.c | 26 ++++++++++++--
> libsepol/src/util.c | 50 +++++++++++++++-----------
> 10 files changed, 103 insertions(+), 45 deletions(-)
>
> diff --git a/checkpolicy/test/dismod.c b/checkpolicy/test/dismod.c
> index ac2d61d2..bd45c95e 100644
> --- a/checkpolicy/test/dismod.c
> +++ b/checkpolicy/test/dismod.c
> @@ -118,12 +118,11 @@ static __attribute__((__noreturn__)) void usage(const char *progname)
> static void render_access_mask(uint32_t mask, uint32_t class, policydb_t * p,
> FILE * fp)
> {
> - char *perm;
> + char *perm = sepol_av_to_string(p, class, mask);
> fprintf(fp, "{");
> - perm = sepol_av_to_string(p, class, mask);
> - if (perm)
> - fprintf(fp, "%s ", perm);
> + fprintf(fp, "%s ", perm ?: "<format-failure>");
> fprintf(fp, "}");
> + free(perm);
> }
>
> static void render_access_bitmap(ebitmap_t * map, uint32_t class,
> @@ -135,8 +134,8 @@ static void render_access_bitmap(ebitmap_t * map, uint32_t class,
> for (i = ebitmap_startbit(map); i < ebitmap_length(map); i++) {
> if (ebitmap_get_bit(map, i)) {
> perm = sepol_av_to_string(p, class, UINT32_C(1) << i);
> - if (perm)
> - fprintf(fp, "%s", perm);
> + fprintf(fp, "%s", perm ?: "<format-failure>");
> + free(perm);
> }
> }
> fprintf(fp, " }");
> diff --git a/checkpolicy/test/dispol.c b/checkpolicy/test/dispol.c
> index 944ef7ec..2662048e 100644
> --- a/checkpolicy/test/dispol.c
> +++ b/checkpolicy/test/dispol.c
> @@ -93,12 +93,11 @@ static __attribute__((__noreturn__)) void usage(const char *progname)
> static int render_access_mask(uint32_t mask, avtab_key_t * key, policydb_t * p,
> FILE * fp)
> {
> - char *perm;
> + char *perm = sepol_av_to_string(p, key->target_class, mask);
> fprintf(fp, "{");
> - perm = sepol_av_to_string(p, key->target_class, mask);
> - if (perm)
> - fprintf(fp, "%s ", perm);
> + fprintf(fp, "%s ", perm ?: "<format-failure>");
> fprintf(fp, "}");
> + free(perm);
> return 0;
> }
>
> diff --git a/libsepol/include/sepol/policydb/util.h b/libsepol/include/sepol/policydb/util.h
> index db8da213..70c531d3 100644
> --- a/libsepol/include/sepol/policydb/util.h
> +++ b/libsepol/include/sepol/policydb/util.h
> @@ -31,7 +31,7 @@ extern "C" {
>
> extern int add_i_to_a(uint32_t i, uint32_t * cnt, uint32_t ** a);
>
> -extern char *sepol_av_to_string(policydb_t * policydbp, uint32_t tclass,
> +extern char *sepol_av_to_string(const policydb_t *policydbp, sepol_security_class_t tclass,
> sepol_access_vector_t av);
>
> char *sepol_extended_perms_to_string(avtab_extended_perms_t *xperms);
> diff --git a/libsepol/src/assertion.c b/libsepol/src/assertion.c
> index 6de7d031..3076babe 100644
> --- a/libsepol/src/assertion.c
> +++ b/libsepol/src/assertion.c
> @@ -48,26 +48,30 @@ static void report_failure(sepol_handle_t *handle, policydb_t *p, const avrule_t
> unsigned int stype, unsigned int ttype,
> const class_perm_node_t *curperm, uint32_t perms)
> {
> + char *permstr = sepol_av_to_string(p, curperm->tclass, perms);
> +
> if (avrule->source_filename) {
> ERR(handle, "neverallow on line %lu of %s (or line %lu of %s) violated by allow %s %s:%s {%s };",
> avrule->source_line, avrule->source_filename, avrule->line, policy_name(p),
> p->p_type_val_to_name[stype],
> p->p_type_val_to_name[ttype],
> p->p_class_val_to_name[curperm->tclass - 1],
> - sepol_av_to_string(p, curperm->tclass, perms));
> + permstr ?: "<format-failure>");
> } else if (avrule->line) {
> ERR(handle, "neverallow on line %lu violated by allow %s %s:%s {%s };",
> avrule->line, p->p_type_val_to_name[stype],
> p->p_type_val_to_name[ttype],
> p->p_class_val_to_name[curperm->tclass - 1],
> - sepol_av_to_string(p, curperm->tclass, perms));
> + permstr ?: "<format-failure>");
> } else {
> ERR(handle, "neverallow violated by allow %s %s:%s {%s };",
> p->p_type_val_to_name[stype],
> p->p_type_val_to_name[ttype],
> p->p_class_val_to_name[curperm->tclass - 1],
> - sepol_av_to_string(p, curperm->tclass, perms));
> + permstr ?: "<format-failure>");
> }
> +
> + free(permstr);
> }
>
> static int match_any_class_permissions(class_perm_node_t *cp, uint32_t class, uint32_t data)
> @@ -200,13 +204,17 @@ static int report_assertion_extended_permissions(sepol_handle_t *handle,
>
> /* failure on the regular permissions */
> if (!found_xperm) {
> + char *permstr = sepol_av_to_string(p, curperm->tclass, perms);
> +
> ERR(handle, "neverallowxperm on line %lu of %s (or line %lu of %s) violated by\n"
> "allow %s %s:%s {%s };",
> avrule->source_line, avrule->source_filename, avrule->line, policy_name(p),
> p->p_type_val_to_name[stype],
> p->p_type_val_to_name[ttype],
> p->p_class_val_to_name[curperm->tclass - 1],
> - sepol_av_to_string(p, curperm->tclass, perms));
> + permstr ?: "<format-failure>");
> +
> + free(permstr);
> errors++;
>
> }
> diff --git a/libsepol/src/hierarchy.c b/libsepol/src/hierarchy.c
> index 350443a8..06e05310 100644
> --- a/libsepol/src/hierarchy.c
> +++ b/libsepol/src/hierarchy.c
> @@ -443,12 +443,15 @@ static void bounds_report(sepol_handle_t *handle, policydb_t *p, uint32_t child,
> p->p_type_val_to_name[child - 1],
> p->p_type_val_to_name[parent - 1]);
> for (; cur; cur = cur->next) {
> + char *permstr = sepol_av_to_string(p, cur->key.target_class, cur->datum.data);
> +
> ERR(handle, " %s %s : %s { %s }",
> p->p_type_val_to_name[cur->key.source_type - 1],
> p->p_type_val_to_name[cur->key.target_type - 1],
> p->p_class_val_to_name[cur->key.target_class - 1],
> - sepol_av_to_string(p, cur->key.target_class,
> - cur->datum.data));
> + permstr ?: "<format-failure>");
> +
> + free(permstr);
> }
> }
>
> diff --git a/libsepol/src/kernel_to_cil.c b/libsepol/src/kernel_to_cil.c
> index bcb58eee..634826d5 100644
> --- a/libsepol/src/kernel_to_cil.c
> +++ b/libsepol/src/kernel_to_cil.c
> @@ -297,6 +297,11 @@ static int class_constraint_rules_to_strs(struct policydb *pdb, char *classkey,
> }
>
> perms = sepol_av_to_string(pdb, class->s.value, curr->permissions);
> + if (!perms) {
> + ERR(NULL, "Failed to generate permission string");
> + rc = -1;
> + goto exit;
> + }
>
> if (is_mls) {
> key_word = "mlsconstrain";
> @@ -307,6 +312,7 @@ static int class_constraint_rules_to_strs(struct policydb *pdb, char *classkey,
> }
>
> rc = strs_create_and_add(strs, "(%s (%s (%s)) %s)", key_word, classkey, perms+1, expr);
> + free(perms);
> free(expr);
> if (rc != 0) {
> goto exit;
> @@ -1772,6 +1778,7 @@ static char *avtab_node_to_str(struct policydb *pdb, avtab_key_t *key, avtab_dat
> }
> rule = create_str("(%s %s %s (%s (%s)))",
> flavor, src, tgt, class, perms+1);
> + free(perms);
> } else if (key->specified & AVTAB_XPERMS) {
> perms = xperms_to_str(datum->xperms);
> if (perms == NULL) {
> diff --git a/libsepol/src/kernel_to_conf.c b/libsepol/src/kernel_to_conf.c
> index 83f46e0f..de1d9e09 100644
> --- a/libsepol/src/kernel_to_conf.c
> +++ b/libsepol/src/kernel_to_conf.c
> @@ -292,6 +292,11 @@ static int class_constraint_rules_to_strs(struct policydb *pdb, char *classkey,
> }
>
> perms = sepol_av_to_string(pdb, class->s.value, curr->permissions);
> + if (!perms) {
> + ERR(NULL, "Failed to generate permission string");
> + rc = -1;
> + goto exit;
> + }
> if (strchr(perms, ' ')) {
> perm_prefix = "{ ";
> perm_suffix = " }";
> @@ -311,6 +316,7 @@ static int class_constraint_rules_to_strs(struct policydb *pdb, char *classkey,
> flavor, classkey,
> perm_prefix, perms+1, perm_suffix,
> expr);
> + free(perms);
> free(expr);
> if (rc != 0) {
> goto exit;
> @@ -1682,7 +1688,7 @@ static char *avtab_node_to_str(struct policydb *pdb, avtab_key_t *key, avtab_dat
> {
> uint32_t data = datum->data;
> type_datum_t *type;
> - const char *flavor, *src, *tgt, *class, *perms, *new;
> + const char *flavor, *src, *tgt, *class, *new;
> char *rule = NULL, *permstring;
>
> switch (0xFFF & key->specified) {
> @@ -1730,13 +1736,14 @@ static char *avtab_node_to_str(struct policydb *pdb, avtab_key_t *key, avtab_dat
> class = pdb->p_class_val_to_name[key->target_class - 1];
>
> if (key->specified & AVTAB_AV) {
> - perms = sepol_av_to_string(pdb, key->target_class, data);
> - if (perms == NULL) {
> + permstring = sepol_av_to_string(pdb, key->target_class, data);
> + if (permstring == NULL) {
> ERR(NULL, "Failed to generate permission string");
> goto exit;
> }
> rule = create_str("%s %s %s:%s { %s };",
> - flavor, src, tgt, class, perms+1);
> + flavor, src, tgt, class, permstring+1);
> + free(permstring);
> } else if (key->specified & AVTAB_XPERMS) {
> permstring = sepol_extended_perms_to_string(datum->xperms);
> if (permstring == NULL) {
> diff --git a/libsepol/src/module_to_cil.c b/libsepol/src/module_to_cil.c
> index ee22dbbd..2ec66292 100644
> --- a/libsepol/src/module_to_cil.c
> +++ b/libsepol/src/module_to_cil.c
> @@ -597,6 +597,7 @@ static int avrule_to_cil(int indent, struct policydb *pdb, uint32_t type, const
> rule, src, tgt,
> pdb->p_class_val_to_name[classperm->tclass - 1],
> perms + 1);
> + free(perms);
> } else {
> cil_println(indent, "(%s %s %s %s %s)",
> rule, src, tgt,
> @@ -1967,7 +1968,13 @@ static int constraints_to_cil(int indent, struct policydb *pdb, char *classkey,
>
> if (is_constraint) {
> perms = sepol_av_to_string(pdb, class->s.value, node->permissions);
> + if (perms == NULL) {
> + ERR(NULL, "Failed to generate permission string");
> + rc = -1;
> + goto exit;
> + }
> cil_println(indent, "(%sconstrain (%s (%s)) %s)", mls, classkey, perms + 1, expr);
> + free(perms);
> } else {
> cil_println(indent, "(%svalidatetrans %s %s)", mls, classkey, expr);
> }
> diff --git a/libsepol/src/services.c b/libsepol/src/services.c
> index 0eeee7ec..36e2368f 100644
> --- a/libsepol/src/services.c
> +++ b/libsepol/src/services.c
> @@ -347,9 +347,11 @@ static char *get_class_info(sepol_security_class_t tclass,
> p += len;
> buf_used += len;
> if (state_num < 2) {
> + char *permstr = sepol_av_to_string(policydb, tclass, constraint->permissions);
> +
> len = snprintf(p, class_buf_len - buf_used, "{%s } (",
> - sepol_av_to_string(policydb, tclass,
> - constraint->permissions));
> + permstr ?: "<format-failure>");
> + free(permstr);
> } else {
> len = snprintf(p, class_buf_len - buf_used, "(");
> }
> @@ -1237,7 +1239,25 @@ out:
> const char *sepol_av_perm_to_string(sepol_security_class_t tclass,
> sepol_access_vector_t av)
> {
> - return sepol_av_to_string(policydb, tclass, av);
> + static char avbuf[1024];
> + char *avstr = sepol_av_to_string(policydb, tclass, av);
> + size_t len;
> +
> + memset(avbuf, 0, sizeof(avbuf));
> +
> + if (avstr) {
> + len = strlen(avstr);
> + if (len < sizeof(avbuf)) {
> + strcpy(avbuf, avstr);
> + } else {
> + sprintf(avbuf, "<access-vector overflowed buffer>");
> + }
> + free(avstr);
> + } else {
> + sprintf(avbuf, "<format-failure>");
> + }
> +
> + return avbuf;
> }
>
> /*
> diff --git a/libsepol/src/util.c b/libsepol/src/util.c
> index 2f877920..dcbdccf1 100644
> --- a/libsepol/src/util.c
> +++ b/libsepol/src/util.c
> @@ -32,7 +32,7 @@
>
> struct val_to_name {
> unsigned int val;
> - char *name;
> + const char *name;
> };
>
> /* Add an unsigned integer to a dynamically reallocated array. *cnt
> @@ -82,20 +82,27 @@ static int perm_name(hashtab_key_t key, hashtab_datum_t datum, void *data)
> return 0;
> }
>
> -char *sepol_av_to_string(policydb_t * policydbp, uint32_t tclass,
> +char *sepol_av_to_string(const policydb_t *policydbp, sepol_security_class_t tclass,
> sepol_access_vector_t av)
> {
> struct val_to_name v;
> - static char avbuf[1024];
> - class_datum_t *cladatum;
> - char *perm = NULL, *p;
> - unsigned int i;
> + const class_datum_t *cladatum = policydbp->class_val_to_struct[tclass - 1];
> + uint32_t i;
> int rc;
> - int avlen = 0, len;
> + char *buffer = NULL, *p;
> + int len;
> + size_t remaining, size = 64;
> +
> +retry:
> + if (__builtin_mul_overflow(size, 2, &size))
> + goto err;
> + p = realloc(buffer, size);
> + if (!p)
> + goto err;
> + *p = '\0'; /* Just in case there are no permissions */
> + buffer = p;
> + remaining = size;
>
> - memset(avbuf, 0, sizeof avbuf);
> - cladatum = policydbp->class_val_to_struct[tclass - 1];
> - p = avbuf;
> for (i = 0; i < cladatum->permissions.nprim; i++) {
> if (av & (UINT32_C(1) << i)) {
> v.val = i + 1;
> @@ -106,22 +113,23 @@ char *sepol_av_to_string(policydb_t * policydbp, uint32_t tclass,
> permissions.table, perm_name,
> &v);
> }
> - if (rc)
> - perm = v.name;
> - if (perm) {
> - len =
> - snprintf(p, sizeof(avbuf) - avlen, " %s",
> - perm);
> - if (len < 0
> - || (size_t) len >= (sizeof(avbuf) - avlen))
> - return NULL;
> + if (rc == 1) {
> + len = snprintf(p, remaining, " %s", v.name);
> + if (len < 0)
> + goto err;
> + if ((size_t) len >= remaining)
> + goto retry;
> p += len;
> - avlen += len;
> + remaining -= len;
> }
> }
> }
>
> - return avbuf;
> + return buffer;
> +
> +err:
> + free(buffer);
> + return NULL;
> }
>
> #define next_bit_in_range(i, p) (((i) + 1 < sizeof(p)*8) && xperm_test(((i) + 1), p))
> --
> 2.43.0
>
