[PATCH 11/13] Implement security event mapping.

Dr. Greg
2023-07-10T11:03:28Z

The map.c file is responsible for implenting the description of a
security event into a security state coefficient. The following
documentation file provided as a part of the TSEM implementation
contains a description of this mapping process:

Documentation/admin-guide/LSM/tsem.rst

The mapping process takes a security event description, that was
described in the event.c file, and uses that to drive the mapping
process. The allocation and mapping of the event is unified
through the tsem_map_event() function provided in this file.

The function for a security event state coefficient mapping is as
follows:

Sp = HF(HF(EVENT_ID) || TASK_ID || HF(COE) || HF(CELL))

Where HF is the cryptographic hash function that has been
designated for use by a security modeling namespace.

This function is fully described in the previously noted
documentation file.

The TASK_ID is the security state coefficient for the
bprm_creds_for_exec security event hook. It is generated by the
tsem_map_task() function that is implemented in this file.

The TASK_ID mapping function uses the same functional expression
as the security state coefficient mapping but substitutes a
TASK_ID that consists of a buffer of null bytes equal in size to
the digest size of the cryptographic hash function being used in
the model.

Signed-off-by: Greg Wettstein <greg@enjellic.com>
---
security/tsem/map.c | 531 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 531 insertions(+)
create mode 100644 security/tsem/map.c

diff --git a/security/tsem/map.c b/security/tsem/map.c
new file mode 100644
index 000000000000..45f8ee6eca89
--- /dev/null
+++ b/security/tsem/map.c
@@ -0,0 +1,531 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ * Copyright (C) 2023 Enjellic Systems Development, LLC
+ * Author: Dr. Greg Wettstein <greg@enjellic.com>
+ *
+ * This file implements mapping of events into security event points.
+ */
+
+#include "tsem.h"
+
+static int get_COE_mapping(struct tsem_event *ep, u8 *mapping)
+{
+ int retn = 0, size;
+ u8 *p;
+ SHASH_DESC_ON_STACK(shash, tfm);
+
+ shash->tfm = tsem_digest();
+ retn = crypto_shash_init(shash);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->COE.uid;
+ size = sizeof(ep->COE.uid);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->COE.euid;
+ size = sizeof(ep->COE.euid);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->COE.suid;
+ size = sizeof(ep->COE.suid);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->COE.gid;
+ size = sizeof(ep->COE.gid);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->COE.egid;
+ size = sizeof(ep->COE.egid);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->COE.sgid;
+ size = sizeof(ep->COE.sgid);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->COE.fsuid;
+ size = sizeof(ep->COE.fsuid);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->COE.fsgid;
+ size = sizeof(ep->COE.fsgid);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->COE.capeff;
+ size = sizeof(ep->COE.capeff);
+ retn = crypto_shash_finup(shash, p, size, mapping);
+
+ done:
+ return retn;
+}
+
+static int get_cell_mapping(struct tsem_event *ep, u8 *mapping)
+{
+ int retn = 0, size;
+ u8 *p;
+ struct sockaddr_in *ipv4;
+ struct sockaddr_in6 *ipv6;
+ struct tsem_mmap_file_args *mm_args = &ep->CELL.mmap_file;
+ struct tsem_socket_connect_args *scp = &ep->CELL.socket_connect;
+ struct tsem_socket_accept_args *sap = &ep->CELL.socket_accept;
+ SHASH_DESC_ON_STACK(shash, tfm);
+
+ shash->tfm = tsem_digest();
+ retn = crypto_shash_init(shash);
+ if (retn)
+ goto done;
+
+ if (ep->event == TSEM_MMAP_FILE) {
+ p = (u8 *) &mm_args->reqprot;
+ size = sizeof(mm_args->reqprot);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &mm_args->prot;
+ size = sizeof(mm_args->prot);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &mm_args->flags;
+ size = sizeof(mm_args->flags);
+ if (!mm_args->file) {
+ retn = crypto_shash_finup(shash, p, size, mapping);
+ goto done;
+ }
+
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+ }
+
+ switch (ep->event) {
+ case TSEM_FILE_OPEN:
+ case TSEM_MMAP_FILE:
+ case TSEM_BPRM_SET_CREDS:
+ p = (u8 *) &ep->file.flags;
+ size = sizeof(ep->file.flags);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->file.uid;
+ size = sizeof(ep->file.uid);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->file.gid;
+ size = sizeof(ep->file.gid);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->file.mode;
+ size = sizeof(ep->file.mode);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->file.name_length;
+ size = sizeof(ep->file.name_length);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->file.name;
+ size = tsem_digestsize();
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->file.s_magic;
+ size = sizeof(ep->file.s_magic);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->file.s_id;
+ size = sizeof(ep->file.s_id);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->file.s_uuid;
+ size = sizeof(ep->file.s_uuid);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->file.digest;
+ size = tsem_digestsize();
+ retn = crypto_shash_finup(shash, p, size, mapping);
+ break;
+
+ case TSEM_SOCKET_CREATE:
+ p = (u8 *) &ep->CELL.socket_create.family;
+ size = sizeof(ep->CELL.socket_create.family);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->CELL.socket_create.type;
+ size = sizeof(ep->CELL.socket_create.type);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->CELL.socket_create.protocol;
+ size = sizeof(ep->CELL.socket_create.protocol);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->CELL.socket_create.kern;
+ size = sizeof(ep->CELL.socket_create.kern);
+ retn = crypto_shash_finup(shash, p, size, mapping);
+ if (retn)
+ goto done;
+ break;
+
+ case TSEM_SOCKET_CONNECT:
+ case TSEM_SOCKET_BIND:
+ p = (u8 *) &scp->family;
+ size = sizeof(scp->family);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ switch (scp->family) {
+ case AF_INET:
+ ipv4 = (struct sockaddr_in *) &scp->u.ipv4;
+ p = (u8 *) &ipv4->sin_port;
+ size = sizeof(ipv4->sin_port);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ipv4->sin_addr.s_addr;
+ size = sizeof(ipv4->sin_addr.s_addr);
+ retn = crypto_shash_finup(shash, p, size, mapping);
+ break;
+
+ case AF_INET6:
+ ipv6 = (struct sockaddr_in6 *) &scp->u.ipv6;
+ p = (u8 *) &ipv6->sin6_port;
+ size = sizeof(ipv6->sin6_port);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) ipv6->sin6_addr.in6_u.u6_addr8;
+ size = sizeof(ipv6->sin6_addr.in6_u.u6_addr8);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ipv6->sin6_flowinfo;
+ size = sizeof(ipv6->sin6_flowinfo);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ipv6->sin6_scope_id;
+ size = sizeof(ipv6->sin6_scope_id);
+ retn = crypto_shash_finup(shash, p, size, mapping);
+ if (retn)
+ goto done;
+ break;
+
+ case AF_UNIX:
+ p = scp->u.path;
+ size = strlen(scp->u.path);
+ retn = crypto_shash_finup(shash, p, size, mapping);
+ if (retn)
+ goto done;
+ break;
+
+ default:
+ p = (u8 *) scp->u.mapping;
+ size = tsem_digestsize();
+ retn = crypto_shash_finup(shash, p, size, mapping);
+ if (retn)
+ goto done;
+ break;
+ }
+ break;
+
+ case TSEM_SOCKET_ACCEPT:
+ p = (u8 *) &sap->family;
+ size = sizeof(sap->family);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &sap->type;
+ size = sizeof(sap->type);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &sap->port;
+ size = sizeof(sap->port);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ switch (sap->family) {
+ case AF_INET:
+ p = (u8 *) &sap->u.ipv4;
+ size = sizeof(sap->u.ipv4);
+ retn = crypto_shash_finup(shash, p, size, mapping);
+ if (retn)
+ goto done;
+ break;
+
+ case AF_INET6:
+ p = (u8 *) sap->u.ipv6.in6_u.u6_addr8;
+ size = sizeof(sap->u.ipv6.in6_u.u6_addr8);
+ retn = crypto_shash_finup(shash, p, size, mapping);
+ if (retn)
+ goto done;
+ break;
+
+ case AF_UNIX:
+ p = sap->u.path;
+ size = strlen(sap->u.path);
+ retn = crypto_shash_finup(shash, p, size, mapping);
+ if (retn)
+ goto done;
+ break;
+
+ default:
+ p = sap->u.mapping;
+ size = tsem_digestsize();
+ retn = crypto_shash_finup(shash, p, size, mapping);
+ if (retn)
+ goto done;
+ break;
+ }
+ break;
+
+ case TSEM_TASK_KILL:
+ p = (u8 *) &ep->CELL.task_kill.cross_model;
+ size = sizeof(ep->CELL.task_kill.cross_model);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->CELL.task_kill.signal;
+ size = sizeof(ep->CELL.task_kill.signal);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = (u8 *) &ep->CELL.task_kill.target;
+ size = sizeof(ep->CELL.task_kill.target);
+ retn = crypto_shash_finup(shash, p, size, mapping);
+ if (retn)
+ goto done;
+ break;
+
+ case TSEM_GENERIC_EVENT:
+ p = (u8 *) tsem_names[ep->CELL.event_type];
+ size = strlen(tsem_names[ep->CELL.event_type]);
+ retn = crypto_shash_update(shash, p, size);
+ if (retn)
+ goto done;
+
+ p = tsem_context(current)->zero_digest;
+ size = tsem_digestsize();
+ retn = crypto_shash_finup(shash, p, size, mapping);
+ if (retn)
+ goto done;
+ break;
+
+ default:
+ break;
+ }
+
+ done:
+ return retn;
+}
+
+static int get_event_mapping(int event, u8 *task_id, u8 *COE_id, u8 *cell_id,
+ u8 *mapping)
+{
+ int retn = 0;
+ u32 event_id = (u32) event;
+ SHASH_DESC_ON_STACK(shash, tfm);
+
+ shash->tfm = tsem_digest();
+ retn = crypto_shash_init(shash);
+ if (retn)
+ goto done;
+
+ retn = crypto_shash_update(shash, tsem_names[event_id],
+ strlen(tsem_names[event_id]));
+ if (retn)
+ goto done;
+ if (task_id) {
+ retn = crypto_shash_update(shash, task_id, tsem_digestsize());
+ if (retn)
+ goto done;
+ }
+ retn = crypto_shash_update(shash, COE_id, tsem_digestsize());
+ if (retn)
+ goto done;
+ retn = crypto_shash_finup(shash, cell_id, tsem_digestsize(), mapping);
+
+ done:
+ return retn;
+}
+
+static int map_event(enum tsem_event_type event, struct tsem_event *ep,
+ u8 *task_id, u8 *event_mapping)
+{
+ int retn;
+ u8 COE_mapping[HASH_MAX_DIGESTSIZE];
+ u8 cell_mapping[HASH_MAX_DIGESTSIZE];
+
+ retn = get_COE_mapping(ep, COE_mapping);
+ if (retn)
+ goto done;
+
+ retn = get_cell_mapping(ep, cell_mapping);
+ if (retn)
+ goto done;
+
+ retn = get_event_mapping(event, task_id, COE_mapping, cell_mapping,
+ event_mapping);
+ done:
+ return retn;
+}
+
+/**
+ * tsem_map_task() - Create the task identity description structure.
+ * @file: A pointer to the file structure defining the executable.
+ * @task_id: Pointer to the buffer that the task id will be copied to.
+ *
+ * This function creates the security event state point that will be used
+ * as the task identifier for the generation of security state points
+ * that are created by the process that task identifier is assigned to.
+ *
+ * Return: This function returns 0 if the mapping was successfully
+ * created and an error value otherwise.
+ */
+int tsem_map_task(struct file *file, u8 *task_id)
+{
+ int retn = 0;
+ u8 null_taskid[HASH_MAX_DIGESTSIZE];
+ struct tsem_event *ep;
+ struct tsem_event_parameters params;
+
+ params.u.file = file;
+ ep = tsem_event_init(TSEM_BPRM_SET_CREDS, &params, false);
+ if (IS_ERR(ep)) {
+ retn = PTR_ERR(ep);
+ ep = NULL;
+ goto done;
+ }
+
+ memset(null_taskid, '\0', tsem_digestsize());
+ retn = map_event(TSEM_BPRM_SET_CREDS, ep, null_taskid, task_id);
+ tsem_event_put(ep);
+
+ done:
+ return retn;
+}
+
+/**
+ * tsem_map_event() - Create a security event mapping.
+ * @event: The number of the event to be mapped.
+ * @params: A pointer to the structure containing the event description
+ * parameters.
+ *
+ * This function creates a structure to describe a security event
+ * and maps the event into a security state coefficient.
+ *
+ * Return: On success the function returns a pointer to the tsem_event
+ * structure that describes the event. If an error is encountered
+ * an error return value is encoded in the pointer.
+ */
+struct tsem_event *tsem_map_event(enum tsem_event_type event,
+ struct tsem_event_parameters *params)
+{
+ int retn = 0;
+ struct tsem_event *ep;
+ struct tsem_task *task = tsem_task(current);
+
+ ep = tsem_event_init(event, params, false);
+ if (IS_ERR(ep))
+ goto done;
+
+ if (task->context->external)
+ goto done;
+
+ retn = map_event(event, ep, task->task_id, ep->mapping);
+ if (retn) {
+ tsem_event_put(ep);
+ ep = ERR_PTR(retn);
+ }
+
+ done:
+ return ep;
+}
+
+
+/**
+ * tsem_map_event_locked() - Create a security event mapping while atomic.
+ * @event: The number of the event to be mapped.
+ * @params: A pointer to the structure containing the event description
+ * parameters.
+ *
+ * This function creates a structure to describe a security event
+ * and maps the event into a security state coefficient.
+ *
+ * Return: On success the function returns a pointer to the tsem_event
+ * structure that describes the event. If an error is encountered
+ * an error return value is encoded in the pointer.
+ */
+struct tsem_event *tsem_map_event_locked(enum tsem_event_type event,
+ struct tsem_event_parameters *params)
+{
+ int retn = 0;
+ struct tsem_event *ep;
+ struct tsem_task *task = tsem_task(current);
+
+ ep = tsem_event_init(event, params, true);
+ if (IS_ERR(ep))
+ goto done;
+
+ if (task->context->external)
+ goto done;
+
+ retn = map_event(event, ep, task->task_id, ep->mapping);
+ if (retn) {
+ tsem_event_put(ep);
+ ep = ERR_PTR(retn);
+ }
+
+ done:
+ return ep;
+}
--
2.39.1