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io_archive: add bounds limit for uname and gname tar header fields 

Modify apk_resolve_[ug]id to take the user/groupname as a blob, so
proper length checking is done and honored.

==31584== Conditional jump or move depends on uninitialised value(s)
==31584==    at 0x5C8CA5: strlen (strlen.c:17)
==31584==    by 0x432575: APK_BLOB_STR (apk_blob.h:79)
==31584==    by 0x4350EB: apk_resolve_uid (io.c:1112)
==31584==    by 0x43696C: apk_tar_parse (io_archive.c:152)
==31584==    by 0x4271BC: apk_pkg_read (package.c:929)
==31584==    by 0x402D75: add_main (app_add.c:163)
==31584==    by 0x40D5FF: main (apk-static.c:516)

Fixes a potential crash (DoS) on a crafted TAR file. CVE-2021-30139.

Reported-by: Sören Tempel <soeren+git@soeren-tempel.net>
Reviewed-by: Ariadne Conill <ariadne@dereferenced.org>
cute-signatures
Timo Teräs 2021-04-11 15:21:42 +03:00
parent 4bcd792194
commit f7143c1766
3 changed files with 11 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
src/apk_io.h
View File

@ -180,7 +180,7 @@ const char *apk_url_local_file(const char *url);
void apk_id_cache_init(struct apk_id_cache *idc, int root_fd);
void apk_id_cache_free(struct apk_id_cache *idc);
void apk_id_cache_reset(struct apk_id_cache *idc);
uid_t apk_resolve_uid(struct apk_id_cache *idc, const char *username, uid_t default_uid);
uid_t apk_resolve_gid(struct apk_id_cache *idc, const char *groupname, uid_t default_gid);
uid_t apk_resolve_uid(struct apk_id_cache *idc, apk_blob_t username, uid_t default_uid);
uid_t apk_resolve_gid(struct apk_id_cache *idc, apk_blob_t groupname, uid_t default_gid);
#endif

12
src/io.c
View File

@ -1114,7 +1114,7 @@ static FILE *fopenat(int dirfd, const char *pathname)
return f;
}
uid_t apk_resolve_uid(struct apk_id_cache *idc, const char *username, uid_t default_uid)
uid_t apk_resolve_uid(struct apk_id_cache *idc, apk_blob_t username, uid_t default_uid)
{
#ifdef HAVE_FGETPWENT_R
char buf[1024];
@ -1124,7 +1124,7 @@ uid_t apk_resolve_uid(struct apk_id_cache *idc, const char *username, uid_t defa
struct passwd *pwd;
FILE *in;
ci = resolve_cache_item(&idc->uid_cache, APK_BLOB_STR(username));
ci = resolve_cache_item(&idc->uid_cache, username);
if (ci == NULL) return default_uid;
if (ci->genid != idc->genid) {
@ -1141,7 +1141,7 @@ uid_t apk_resolve_uid(struct apk_id_cache *idc, const char *username, uid_t defa
#endif
if (pwd == NULL)
break;
if (strcmp(pwd->pw_name, username) == 0) {
if (apk_blob_compare(APK_BLOB_STR(pwd->pw_name), username) == 0) {
ci->uid = pwd->pw_uid;
break;
}
@ -1156,7 +1156,7 @@ uid_t apk_resolve_uid(struct apk_id_cache *idc, const char *username, uid_t defa
return default_uid;
}
uid_t apk_resolve_gid(struct apk_id_cache *idc, const char *groupname, uid_t default_gid)
uid_t apk_resolve_gid(struct apk_id_cache *idc, apk_blob_t groupname, uid_t default_gid)
{
#ifdef HAVE_FGETGRENT_R
char buf[1024];
@ -1166,7 +1166,7 @@ uid_t apk_resolve_gid(struct apk_id_cache *idc, const char *groupname, uid_t def
struct group *grp;
FILE *in;
ci = resolve_cache_item(&idc->gid_cache, APK_BLOB_STR(groupname));
ci = resolve_cache_item(&idc->gid_cache, groupname);
if (ci == NULL) return default_gid;
if (ci->genid != idc->genid) {
@ -1183,7 +1183,7 @@ uid_t apk_resolve_gid(struct apk_id_cache *idc, const char *groupname, uid_t def
#endif
if (grp == NULL)
break;
if (strcmp(grp->gr_name, groupname) == 0) {
if (apk_blob_compare(APK_BLOB_STR(grp->gr_name), groupname) == 0) {
ci->gid = grp->gr_gid;
break;
}

5
src/io_archive.c
View File

@ -49,6 +49,7 @@ struct tar_header {
char padding[12]; /* 500-511 */
};
#define TAR_BLOB(s) APK_BLOB_PTR_LEN(s, strnlen(s, sizeof(s)))
#define GET_OCTAL(s) get_octal(s, sizeof(s))
#define PUT_OCTAL(s,v) put_octal(s, sizeof(s), v)
@ -149,8 +150,8 @@ int apk_tar_parse(struct apk_istream *is, apk_archive_entry_parser parser,
entry = (struct apk_file_info){
.size = GET_OCTAL(buf.size),
.uid = apk_resolve_uid(idc, buf.uname, GET_OCTAL(buf.uid)),
.gid = apk_resolve_gid(idc, buf.gname, GET_OCTAL(buf.gid)),
.uid = apk_resolve_uid(idc, TAR_BLOB(buf.uname), GET_OCTAL(buf.uid)),
.gid = apk_resolve_gid(idc, TAR_BLOB(buf.gname), GET_OCTAL(buf.gid)),
.mode = GET_OCTAL(buf.mode) & 07777,
.mtime = GET_OCTAL(buf.mtime),
.name = entry.name,