The internal Sha1Update() functions only handles buffers up to a size of
UINT32_MAX, due to its usage of the type uint32_t. This causes issues
when processing more than UINT32_MAX bytes, e.g. with a specfile larger
than 4G. 0aa974a4 ("libselinux: limit has buffer size") tried to
address this issue, but failed since the overflow check
if (digest->hashbuf_size + buf_len < digest->hashbuf_size) {
will be done in the widest common type, which is size_t, the type of
`buf_len`.
Revert the type of `hashbuf_size` to size_t and instead process the data
in blocks of supported size.
Reverts: 0aa974a4 ("libselinux: limit has buffer size")
Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
---
UBSAN reports without block processing:
hashbuf_size of uint32_t
label_support.c:158:23: runtime error: implicit conversion from type 'unsigned long' of value 4294968207 (64-bit, unsigned) to type 'uint32_t' (aka 'unsigned int') changed the value to 911 (32-bit, unsigned)
#0 0x4ecdbd in digest_add_specfile /home/christian/Coding/workspaces/selinux_userland/libselinux/src/label_support.c:158:23
#1 0x4e0d83 in selabel_subs_init /home/christian/Coding/workspaces/selinux_userland/libselinux/src/label_file.c:666:6
#2 0x4d5c48 in init /home/christian/Coding/workspaces/selinux_userland/libselinux/src/label_file.c:738:12
#3 0x4d5c48 in selabel_file_init /home/christian/Coding/workspaces/selinux_userland/libselinux/src/label_file.c:1304:9
#4 0x4cfdde in selabel_open /home/christian/Coding/workspaces/selinux_userland/libselinux/src/label.c:228:6
#5 0x4ce76c in main /home/christian/Coding/workspaces/selinux_userland/libselinux/utils/selabel_digest.c:130:8
#6 0x77b65848a1c9 in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16
#7 0x77b65848a277 in __libc_start_main csu/../csu/libc-start.c:409:3
#8 0x41f4c0 in _start (/home/christian/Coding/workspaces/selinux_userland/libselinux/utils/selabel_digest+0x41f4c0)
hashbuf_size of size_t
label_support.c:125:40: runtime error: implicit conversion from type 'size_t' (aka 'unsigned long') of value 4298262406 (64-bit, unsigned) to type 'uint32_t' (aka 'unsigned int') changed the value to 3295110 (32-bit, unsigned)
#0 0x4ec468 in digest_gen_hash /home/christian/Coding/workspaces/selinux_userland/libselinux/src/label_support.c:125:40
#1 0x4d6dd3 in init /home/christian/Coding/workspaces/selinux_userland/libselinux/src/label_file.c:793:2
#2 0x4d6dd3 in selabel_file_init /home/christian/Coding/workspaces/selinux_userland/libselinux/src/label_file.c:1304:9
#3 0x4cfdde in selabel_open /home/christian/Coding/workspaces/selinux_userland/libselinux/src/label.c:228:6
#4 0x4ce76c in main /home/christian/Coding/workspaces/selinux_userland/libselinux/utils/selabel_digest.c:130:8
#5 0x749229c371c9 in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16
#6 0x749229c37277 in __libc_start_main csu/../csu/libc-start.c:409:3
#7 0x41f4c0 in _start (/home/christian/Coding/workspaces/selinux_userland/libselinux/utils/selabel_digest+0x41f4c0)
---
libselinux/src/label_internal.h | 2 +-
libselinux/src/label_support.c | 14 +++++++++++++-
2 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/libselinux/src/label_internal.h b/libselinux/src/label_internal.h
index 82a762f7..782c6aa8 100644
--- a/libselinux/src/label_internal.h
+++ b/libselinux/src/label_internal.h
@@ -57,7 +57,7 @@ int selabel_service_init(struct selabel_handle *rec,
struct selabel_digest {
unsigned char *digest; /* SHA1 digest of specfiles */
unsigned char *hashbuf; /* buffer to hold specfiles */
- uint32_t hashbuf_size; /* buffer size */
+ size_t hashbuf_size; /* buffer size */
size_t specfile_cnt; /* how many specfiles processed */
char **specfile_list; /* and their names */
};
diff --git a/libselinux/src/label_support.c b/libselinux/src/label_support.c
index 94ed6e42..54fd49a5 100644
--- a/libselinux/src/label_support.c
+++ b/libselinux/src/label_support.c
@@ -116,13 +116,25 @@ int read_spec_entries(char *line_buf, const char **errbuf, int num_args, ...)
void digest_gen_hash(struct selabel_digest *digest)
{
Sha1Context context;
+ size_t remaining_size;
+ const unsigned char *ptr;
/* If SELABEL_OPT_DIGEST not set then just return */
if (!digest)
return;
Sha1Initialise(&context);
- Sha1Update(&context, digest->hashbuf, digest->hashbuf_size);
+
+ /* Process in blocks of UINT32_MAX bytes */
+ remaining_size = digest->hashbuf_size;
+ ptr = digest->hashbuf;
+ while (remaining_size > UINT32_MAX) {
+ Sha1Update(&context, ptr, UINT32_MAX);
+ remaining_size -= UINT32_MAX;
+ ptr += UINT32_MAX;
+ }
+ Sha1Update(&context, ptr, remaining_size);
+
Sha1Finalise(&context, (SHA1_HASH *)digest->digest);
free(digest->hashbuf);
digest->hashbuf = NULL;
--
2.35.2
