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libselinux: correctly hash specfiles larger than 4G

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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.

Acked-by: James Carter <jwcart2@gmail.com>
Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
Reverts: 0aa974a4 ("libselinux: limit has buffer size")
This commit is contained in:
Christian Göttsche 2022-04-13 17:56:33 +02:00 committed by James Carter
parent b9a4d13a30
commit e17619792f
2 changed files with 14 additions and 2 deletions
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2
libselinux/src/label_internal.h
View File

@ -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 */
};

14
libselinux/src/label_support.c
View File

@ -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;