On Fri, Apr 5, 2019 at 11:39 AM Joshua Brindle
<joshua.brindle@xxxxxxxxxxxxxxx> wrote:
>
> It seems validatetrans support was never added to libselinux, despite being added to
> selinuxfs in kernel version 4.5
>
> There is a utility to test, however the targeted policy has no validatetrans rules so some must be added:
>
> $ cat validatetrans.cil
> (mlsvalidatetrans db_table (and (or (or (or (eq l1 l2) (and (eq t3 unconfined_t) (domby l1 l2))) (and (eq t3 unconfined_t) (dom l1 l2))) (and (eq t3 unconfined_t) (incomp l1 l2))) (or (or (or (eq l1 h2) (and (eq t3 unconfined_t) (domby h1 h2))) (and (eq t3 unconfined_t) (dom h1 h2))) (and (eq t3 unconfined_t) (incomp h1 h2)))))
>
> $ sudo semodule -i validatetrans.cil
>
> $ ./validatetrans system_u:system_r:kernel_t:s0 system_u:system_r:init_t:s0:c0 db_table system_u:system_r: # invalid context here
> opening /sys/fs/selinux/validatetrans
> security_validatetrans returned -1 errno: Invalid argument
>
> $ ./validatetrans system_u:system_r:kernel_t:s0 system_u:system_r:init_t:s0:c0 db_table system_u:system_r:init_t:s0
> opening /sys/fs/selinux/validatetrans
> security_validatetrans returned -1 errno: Operation not permitted
>
> $ ./validatetrans system_u:system_r:kernel_t:s0 system_u:system_r:init_t:s0:c0 db_table system_u:system_r:unconfined_t:s0
> opening /sys/fs/selinux/validatetrans
> security_validatetrans returned 0 errno: Success
>
> Signed-off-by: Joshua Brindle <joshua.brindle@xxxxxxxxxxxxxxx>
> ---
> libselinux/include/selinux/selinux.h | 13 +++
> libselinux/man/man3/security_compute_av.3 | 13 ++-
> libselinux/man/man3/security_validatetrans.c | 1 +
> .../man/man3/security_validatetrans_raw.c | 1 +
> libselinux/src/selinux_internal.h | 2 +
> libselinux/src/validatetrans.c | 94 +++++++++++++++++++
> libselinux/utils/.gitignore | 1 +
> libselinux/utils/validatetrans.c | 30 ++++++
> 8 files changed, 154 insertions(+), 1 deletion(-)
> create mode 100644 libselinux/man/man3/security_validatetrans.c
> create mode 100644 libselinux/man/man3/security_validatetrans_raw.c
> create mode 100644 libselinux/src/validatetrans.c
> create mode 100644 libselinux/utils/validatetrans.c
>
> diff --git a/libselinux/include/selinux/selinux.h b/libselinux/include/selinux/selinux.h
> index a34d54fc..f54f236b 100644
> --- a/libselinux/include/selinux/selinux.h
> +++ b/libselinux/include/selinux/selinux.h
> @@ -255,6 +255,19 @@ extern int security_compute_user_raw(const char * scon,
> const char *username,
> char *** con);
>
> +/* Validate a transition. This determines whether a transition from scon to newcon
> + using tcon as the target for object class tclass is valid in the loaded policy.
> + This checks against the mlsvalidatetrans and validatetrans constraints in the loaded policy.
> + Returns 0 if allowed and -1 if an error occured with errno set */
> +extern int security_validatetrans(const char *scon,
> + const char *tcon,
> + security_class_t tclass,
> + const char *newcon);
> +extern int security_validatetrans_raw(const char *scon,
> + const char *tcon,
> + security_class_t tclass,
> + const char *newcon);
> +
> /* Load a policy configuration. */
> extern int security_load_policy(void *data, size_t len);
>
> diff --git a/libselinux/man/man3/security_compute_av.3 b/libselinux/man/man3/security_compute_av.3
> index 2aade5fe..a7181bed 100644
> --- a/libselinux/man/man3/security_compute_av.3
> +++ b/libselinux/man/man3/security_compute_av.3
> @@ -1,7 +1,7 @@
> .TH "security_compute_av" "3" "1 January 2004" "russell@xxxxxxxxxxxx" "SELinux API documentation"
> .SH "NAME"
> security_compute_av, security_compute_av_flags, security_compute_create, security_compute_create_name, security_compute_relabel,
> -security_compute_member, security_compute_user, security_get_initial_context \- query
> +security_compute_member, security_compute_user, security_validatetrans, security_get_initial_context \- query
> the SELinux policy database in the kernel
> .
> .SH "SYNOPSIS"
> @@ -35,6 +35,10 @@ the SELinux policy database in the kernel
> .sp
> .BI "int security_compute_user_raw(char *" scon ", const char *" username ", char ***" con );
> .sp
> +.BI "int security_validatetrans(char *" scon ", const char *" tcon ", security_class_t "tclass ", char *" newcon );
> +.sp
> +.BI "int security_validatetrans_raw(char *" scon ", const char *" tcon ", security_class_t "tclass ", char *" newcon );
> +.sp
> .BI "int security_get_initial_context(const char *" name ", char **" con );
> .sp
> .BI "int security_get_initial_context_raw(const char *" name ", char **" con );
> @@ -100,6 +104,12 @@ is used to determine the set of user contexts that can be reached from a
> source context. It is mainly used by
> .BR get_ordered_context_list ().
>
> +.BR security_validatetrans ()
> +is used to determine if a transition from scon to newcon using tcon as the object
> +is valid for object class tclass. This checks against the mlsvalidatetrans and
> +validatetrans constraints in the loaded policy. Returns 0 if allowed, and -1
> +if an error occured with errno set.
> +
> .BR security_get_initial_context ()
> is used to get the context of a kernel initial security identifier specified by
> .I name
> @@ -111,6 +121,7 @@ is used to get the context of a kernel initial security identifier specified by
> .BR \%security_compute_relabel_raw (),
> .BR \%security_compute_member_raw (),
> .BR \%security_compute_user_raw ()
> +.BR \%security_validatetrans_raw ()
> and
> .BR \%security_get_initial_context_raw ()
> behave identically to their non-raw counterparts but do not perform context
> diff --git a/libselinux/man/man3/security_validatetrans.c b/libselinux/man/man3/security_validatetrans.c
> new file mode 100644
> index 00000000..a60bca4d
> --- /dev/null
> +++ b/libselinux/man/man3/security_validatetrans.c
> @@ -0,0 +1 @@
> +.so man3/security_compute_av.3
> diff --git a/libselinux/man/man3/security_validatetrans_raw.c b/libselinux/man/man3/security_validatetrans_raw.c
> new file mode 100644
> index 00000000..a60bca4d
> --- /dev/null
> +++ b/libselinux/man/man3/security_validatetrans_raw.c
> @@ -0,0 +1 @@
> +.so man3/security_compute_av.3
> diff --git a/libselinux/src/selinux_internal.h b/libselinux/src/selinux_internal.h
> index 70b5025d..acd59c7c 100644
> --- a/libselinux/src/selinux_internal.h
> +++ b/libselinux/src/selinux_internal.h
> @@ -29,6 +29,8 @@ hidden_proto(selinux_mkload_policy)
> hidden_proto(security_compute_create_name_raw)
> hidden_proto(security_compute_member_raw)
> hidden_proto(security_compute_relabel_raw)
> + hidden_proto(security_validatetrans)
> + hidden_proto(security_validatetrans_raw)
> hidden_proto(is_selinux_enabled)
> hidden_proto(is_selinux_mls_enabled)
> hidden_proto(freecon)
> diff --git a/libselinux/src/validatetrans.c b/libselinux/src/validatetrans.c
> new file mode 100644
> index 00000000..9e745a91
> --- /dev/null
> +++ b/libselinux/src/validatetrans.c
> @@ -0,0 +1,94 @@
> +#include <unistd.h>
> +#include <sys/types.h>
> +#include <fcntl.h>
> +#include <stdlib.h>
> +#include <stdio.h>
> +#include <errno.h>
> +#include <string.h>
> +#include <limits.h>
> +#include "selinux_internal.h"
> +#include "policy.h"
> +#include "mapping.h"
> +
> +int security_validatetrans_raw(const char *scon,
> + const char *tcon,
> + security_class_t tclass,
> + const char *newcon)
> +{
> + char path[PATH_MAX];
> + char *buf = NULL;
> + int size, bufsz;
> + int fd, ret = -1;
> + errno = ENOENT;
> +
> + if (!selinux_mnt) {
> + return -1;
> + }
> +
> + snprintf(path, sizeof path, "%s/validatetrans", selinux_mnt);
> + fd = open(path, O_WRONLY | O_CLOEXEC);
> + if (fd < 0) {
> + return -1;
> + }
> +
> + errno = EINVAL;
> + size = selinux_page_size;
> + buf = malloc(size);
> + if (!buf) {
> + goto out;
> + }
> +
> + bufsz = snprintf(buf, size, "%s %s %hu %s", scon, tcon, unmap_class(tclass), newcon);
> + if (bufsz >= size) {
I guess this is fine, I don't think the negative return conditions can
exist unless you bork the format
string.
> + // It got truncated
> + goto out;
> + }
> +
> + // clear errno for write()
> + errno = 0;
> + ret = write(fd, buf, strlen(buf));
> + if (ret > 0) {
> + // The kernel returns the bytes written on success, not 0 as noted in the commit message
> + ret = 0;
> + }
> +out:
> + free(buf);
> + close(fd);
> + return ret;
> +}
> +
> +hidden_def(security_validatetrans_raw)
> +
> +int security_validatetrans(const char *scon,
> + const char *tcon,
> + security_class_t tclass,
> + const char *newcon)
> +{
> + int ret = -1;
> + char *rscon = NULL;
> + char *rtcon = NULL;
> + char *rnewcon = NULL;
> +
> + if (selinux_trans_to_raw_context(scon, &rscon)) {
> + goto out;
> + }
> +
> + if (selinux_trans_to_raw_context(tcon, &rtcon)) {
> + goto out;
> + }
> +
> + if (selinux_trans_to_raw_context(newcon, &rnewcon)) {
> + goto out;
> + }
> +
> + ret = security_validatetrans_raw(rscon, rtcon, tclass, rnewcon);
> +
> +out:
> + freecon(rnewcon);
> + freecon(rtcon);
> + freecon(rscon);
> +
> + return ret;
> +}
> +
> +hidden_def(security_validatetrans)
> diff --git a/libselinux/utils/.gitignore b/libselinux/utils/.gitignore
> index 5cd01025..aba18a3c 100644
> --- a/libselinux/utils/.gitignore
> +++ b/libselinux/utils/.gitignore
> @@ -25,3 +25,4 @@ setenforce
> setfilecon
> togglesebool
> selinux_check_access
> +validatetrans
> diff --git a/libselinux/utils/validatetrans.c b/libselinux/utils/validatetrans.c
> new file mode 100644
> index 00000000..1db33e66
> --- /dev/null
> +++ b/libselinux/utils/validatetrans.c
> @@ -0,0 +1,30 @@
> +#include <unistd.h>
> +#include <sys/types.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <errno.h>
> +#include <selinux/selinux.h>
> +
> +int main(int argc, char **argv)
> +{
> + security_class_t tclass;
> + int ret;
> +
> + if (argc != 5) {
> + fprintf(stderr, "usage: %s scontext tcontext tclass newcontext\n",
> + argv[0]);
> + exit(1);
> + }
> +
> + tclass = string_to_security_class(argv[3]);
> + if (!tclass) {
> + fprintf(stderr, "%s: invalid class '%s'\n", argv[0], argv[3]);
> + exit(2);
> + }
> +
> + ret = security_validatetrans(argv[1], argv[2], tclass, argv[4]);
> + printf("security_validatetrans returned %d errno: %s\n", ret, strerror(errno));
> +
> + return ret;
> +}
> --
> 2.17.2
>
ack
