From: Paul Durrant <pdurr...@amazon.com>
Store perms as a GList of strings, check permissions.
Signed-off-by: Paul Durrant <pdurr...@amazon.com>
Signed-off-by: David Woodhouse <d...@amazon.co.uk>
Reviewed-by: Paul Durrant <p...@xen.org>
---
hw/i386/kvm/xen_xenstore.c | 2 +-
hw/i386/kvm/xenstore_impl.c | 259 +++++++++++++++++++++++++++++++++---
hw/i386/kvm/xenstore_impl.h | 8 +-
tests/unit/test-xs-node.c | 27 +++-
4 files changed, 275 insertions(+), 21 deletions(-)
diff --git a/hw/i386/kvm/xen_xenstore.c b/hw/i386/kvm/xen_xenstore.c
index 64d8f1a38f..3b409e3817 100644
--- a/hw/i386/kvm/xen_xenstore.c
+++ b/hw/i386/kvm/xen_xenstore.c
@@ -98,7 +98,7 @@ static void xen_xenstore_realize(DeviceState *dev, Error
**errp)
aio_set_fd_handler(qemu_get_aio_context(), xen_be_evtchn_fd(s->eh), true,
xen_xenstore_event, NULL, NULL, NULL, s);
- s->impl = xs_impl_create();
+ s->impl = xs_impl_create(xen_domid);
}
static bool xen_xenstore_is_needed(void *opaque)
diff --git a/hw/i386/kvm/xenstore_impl.c b/hw/i386/kvm/xenstore_impl.c
index 60f42f61d6..8a2053e243 100644
--- a/hw/i386/kvm/xenstore_impl.c
+++ b/hw/i386/kvm/xenstore_impl.c
@@ -12,6 +12,8 @@
#include "qemu/osdep.h"
#include "qom/object.h"
+#include "hw/xen/xen.h"
+
#include "xen_xenstore.h"
#include "xenstore_impl.h"
@@ -30,6 +32,7 @@
typedef struct XsNode {
uint32_t ref;
GByteArray *content;
+ GList *perms;
GHashTable *children;
uint64_t gencnt;
bool deleted_in_tx;
@@ -133,6 +136,9 @@ static inline void xs_node_unref(XsNode *n)
if (n->content) {
g_byte_array_unref(n->content);
}
+ if (n->perms) {
+ g_list_free_full(n->perms, g_free);
+ }
if (n->children) {
g_hash_table_unref(n->children);
}
@@ -144,8 +150,51 @@ static inline void xs_node_unref(XsNode *n)
g_free(n);
}
+char *xs_perm_as_string(unsigned int perm, unsigned int domid)
+{
+ char letter;
+
+ switch (perm) {
+ case XS_PERM_READ | XS_PERM_WRITE:
+ letter = 'b';
+ break;
+ case XS_PERM_READ:
+ letter = 'r';
+ break;
+ case XS_PERM_WRITE:
+ letter = 'w';
+ break;
+ case XS_PERM_NONE:
+ default:
+ letter = 'n';
+ break;
+ }
+
+ return g_strdup_printf("%c%u", letter, domid);
+}
+
+static gpointer do_perm_copy(gconstpointer src, gpointer user_data)
+{
+ return g_strdup(src);
+}
+
+static XsNode *xs_node_create(const char *name, GList *perms)
+{
+ XsNode *n = xs_node_new();
+
+#ifdef XS_NODE_UNIT_TEST
+ if (name) {
+ n->name = g_strdup(name);
+ }
+#endif
+
+ n->perms = g_list_copy_deep(perms, do_perm_copy, NULL);
+
+ return n;
+}
+
/* For copying from one hash table to another using g_hash_table_foreach() */
-static void do_insert(gpointer key, gpointer value, gpointer user_data)
+static void do_child_insert(gpointer key, gpointer value, gpointer user_data)
{
g_hash_table_insert(user_data, g_strdup(key), xs_node_ref(value));
}
@@ -162,12 +211,16 @@ static XsNode *xs_node_copy(XsNode *old)
}
#endif
+ assert(old);
if (old->children) {
n->children = g_hash_table_new_full(g_str_hash, g_str_equal, g_free,
(GDestroyNotify)xs_node_unref);
- g_hash_table_foreach(old->children, do_insert, n->children);
+ g_hash_table_foreach(old->children, do_child_insert, n->children);
}
- if (old && old->content) {
+ if (old->perms) {
+ n->perms = g_list_copy_deep(old->perms, do_perm_copy, NULL);
+ }
+ if (old->content) {
n->content = g_byte_array_ref(old->content);
}
return n;
@@ -383,6 +436,9 @@ static XsNode *xs_node_copy_deleted(XsNode *old, struct
walk_op *op)
op->op_opaque2 = n->children;
g_hash_table_foreach(old->children, copy_deleted_recurse, op);
}
+ if (old->perms) {
+ n->perms = g_list_copy_deep(old->perms, do_perm_copy, NULL);
+ }
n->deleted_in_tx = true;
/* If it gets resurrected we only fire a watch if it lost its content */
if (old->content) {
@@ -417,6 +473,104 @@ static int xs_node_rm(XsNode **n, struct walk_op *op)
return 0;
}
+static int xs_node_get_perms(XsNode **n, struct walk_op *op)
+{
+ GList **perms = op->op_opaque;
+
+ assert(op->inplace);
+ assert(*n);
+
+ *perms = g_list_copy_deep((*n)->perms, do_perm_copy, NULL);
+ return 0;
+}
+
+static void parse_perm(const char *perm, char *letter, unsigned int *dom_id)
+{
+ unsigned int n = sscanf(perm, "%c%u", letter, dom_id);
+
+ assert(n == 2);
+}
+
+static bool can_access(unsigned int dom_id, GList *perms, const char *letters)
+{
+ unsigned int i, n;
+ char perm_letter;
+ unsigned int perm_dom_id;
+ bool access;
+
+ if (dom_id == 0) {
+ return true;
+ }
+
+ n = g_list_length(perms);
+ assert(n >= 1);
+
+ /*
+ * The dom_id of the first perm is the owner, and the owner always has
+ * read-write access.
+ */
+ parse_perm(g_list_nth_data(perms, 0), &perm_letter, &perm_dom_id);
+ if (dom_id == perm_dom_id) {
+ return true;
+ }
+
+ /*
+ * The letter of the first perm specified the default access for all other
+ * domains.
+ */
+ access = !!strchr(letters, perm_letter);
+ for (i = 1; i < n; i++) {
+ parse_perm(g_list_nth_data(perms, i), &perm_letter, &perm_dom_id);
+ if (dom_id != perm_dom_id) {
+ continue;
+ }
+ access = !!strchr(letters, perm_letter);
+ }
+
+ return access;
+}
+
+static int xs_node_set_perms(XsNode **n, struct walk_op *op)
+{
+ GList *perms = op->op_opaque;
+
+ if (op->dom_id) {
+ unsigned int perm_dom_id;
+ char perm_letter;
+
+ /* A guest may not change permissions on nodes it does not own */
+ if (!can_access(op->dom_id, (*n)->perms, "")) {
+ return EPERM;
+ }
+
+ /* A guest may not change the owner of a node it owns. */
+ parse_perm(perms->data, &perm_letter, &perm_dom_id);
+ if (perm_dom_id != op->dom_id) {
+ return EPERM;
+ }
+
+ if (g_list_length(perms) > XS_MAX_PERMS_PER_NODE) {
+ return ENOSPC;
+ }
+ }
+
+ /* We *are* the node to be written. Either this or a copy. */
+ if (!op->inplace) {
+ XsNode *old = *n;
+ *n = xs_node_copy(old);
+ xs_node_unref(old);
+ }
+
+ if ((*n)->perms) {
+ g_list_free_full((*n)->perms, g_free);
+ }
+ (*n)->perms = g_list_copy_deep(perms, do_perm_copy, NULL);
+ if (op->tx_id != XBT_NULL) {
+ (*n)->modified_in_tx = true;
+ }
+ return 0;
+}
+
/*
* Passed a full reference in *n which it may free if it needs to COW.
*
@@ -458,6 +612,13 @@ static int xs_node_walk(XsNode **n, struct walk_op *op)
}
if (!child_name) {
+ const char *letters = op->mutating ? "wb" : "rb";
+
+ if (!can_access(op->dom_id, old->perms, letters)) {
+ err = EACCES;
+ goto out;
+ }
+
/* This is the actual node on which the operation shall be performed */
err = op->op_fn(n, op);
if (!err) {
@@ -491,12 +652,20 @@ static int xs_node_walk(XsNode **n, struct walk_op *op)
stole_child = true;
}
} else if (op->create_dirs) {
+ assert(op->mutating);
+
+ if (!can_access(op->dom_id, old->perms, "wb")) {
+ err = EACCES;
+ goto out;
+ }
+
if (op->dom_id && op->new_nr_nodes >= XS_MAX_DOMAIN_NODES) {
err = ENOSPC;
goto out;
}
+
+ child = xs_node_create(child_name, old->perms);
op->new_nr_nodes++;
- child = xs_node_new();
/*
* If we're creating a new child, we can clearly modify it (and its
@@ -918,20 +1087,73 @@ int xs_impl_rm(XenstoreImplState *s, unsigned int dom_id,
int xs_impl_get_perms(XenstoreImplState *s, unsigned int dom_id,
xs_transaction_t tx_id, const char *path, GList **perms)
{
- /*
- * The perms are (char *) in the <perm-as-string> wire format to be
- * freed by the caller.
- */
- return ENOSYS;
+ struct walk_op op;
+ XsNode **n;
+ int ret;
+
+ ret = init_walk_op(s, &op, tx_id, dom_id, path, &n);
+ if (ret) {
+ return ret;
+ }
+ op.op_fn = xs_node_get_perms;
+ op.op_opaque = perms;
+ return xs_node_walk(n, &op);
+}
+
+static void is_valid_perm(gpointer data, gpointer user_data)
+{
+ char *perm = data;
+ bool *valid = user_data;
+ char letter;
+ unsigned int dom_id;
+
+ if (!*valid) {
+ return;
+ }
+
+ if (sscanf(perm, "%c%u", &letter, &dom_id) != 2) {
+ *valid = false;
+ return;
+ }
+
+ switch (letter) {
+ case 'n':
+ case 'r':
+ case 'w':
+ case 'b':
+ break;
+
+ default:
+ *valid = false;
+ break;
+ }
}
int xs_impl_set_perms(XenstoreImplState *s, unsigned int dom_id,
xs_transaction_t tx_id, const char *path, GList *perms)
{
- /*
- * The perms are (const char *) in the <perm-as-string> wire format.
- */
- return ENOSYS;
+ struct walk_op op;
+ XsNode **n;
+ bool valid = true;
+ int ret;
+
+ if (!g_list_length(perms)) {
+ return EINVAL;
+ }
+
+ g_list_foreach(perms, is_valid_perm, &valid);
+ if (!valid) {
+ return EINVAL;
+ }
+
+ ret = init_walk_op(s, &op, tx_id, dom_id, path, &n);
+ if (ret) {
+ return ret;
+ }
+ op.op_fn = xs_node_set_perms;
+ op.op_opaque = perms;
+ op.mutating = true;
+ return xs_node_walk(n, &op);
}
int xs_impl_watch(XenstoreImplState *s, unsigned int dom_id, const char *path,
@@ -1122,18 +1344,19 @@ static void xs_tx_free(void *_tx)
g_free(tx);
}
-XenstoreImplState *xs_impl_create(void)
+XenstoreImplState *xs_impl_create(unsigned int dom_id)
{
XenstoreImplState *s = g_new0(XenstoreImplState, 1);
+ GList *perms;
s->watches = g_hash_table_new_full(g_str_hash, g_str_equal, g_free, NULL);
s->transactions = g_hash_table_new_full(g_direct_hash, g_direct_equal,
NULL, xs_tx_free);
+
+ perms = g_list_append(NULL, xs_perm_as_string(XS_PERM_NONE, 0));
+ s->root = xs_node_create("/", perms);
+ g_list_free_full(perms, g_free);
s->nr_nodes = 1;
- s->root = xs_node_new();
-#ifdef XS_NODE_UNIT_TEST
- s->root->name = g_strdup("/");
-#endif
s->root_tx = s->last_tx = 1;
return s;
diff --git a/hw/i386/kvm/xenstore_impl.h b/hw/i386/kvm/xenstore_impl.h
index beb7b29ab8..2f81251b5e 100644
--- a/hw/i386/kvm/xenstore_impl.h
+++ b/hw/i386/kvm/xenstore_impl.h
@@ -16,9 +16,15 @@ typedef uint32_t xs_transaction_t;
#define XBT_NULL 0
+#define XS_PERM_NONE 0x00
+#define XS_PERM_READ 0x01
+#define XS_PERM_WRITE 0x02
+
typedef struct XenstoreImplState XenstoreImplState;
-XenstoreImplState *xs_impl_create(void);
+XenstoreImplState *xs_impl_create(unsigned int dom_id);
+
+char *xs_perm_as_string(unsigned int perm, unsigned int domid);
/*
* These functions return *positive* error numbers. This is a little
diff --git a/tests/unit/test-xs-node.c b/tests/unit/test-xs-node.c
index 02c72baa62..2c0f89c694 100644
--- a/tests/unit/test-xs-node.c
+++ b/tests/unit/test-xs-node.c
@@ -80,8 +80,9 @@ static void watch_cb(void *_str, const char *path, const char
*token)
static XenstoreImplState *setup(void)
{
- XenstoreImplState *s = xs_impl_create();
+ XenstoreImplState *s = xs_impl_create(DOMID_GUEST);
char *abspath;
+ GList *perms;
int err;
abspath = g_strdup_printf("/local/domain/%u", DOMID_GUEST);
@@ -90,6 +91,13 @@ static XenstoreImplState *setup(void)
g_assert(!err);
g_assert(s->nr_nodes == 4);
+ perms = g_list_append(NULL, g_strdup_printf("n%u", DOMID_QEMU));
+ perms = g_list_append(perms, g_strdup_printf("r%u", DOMID_GUEST));
+
+ err = xs_impl_set_perms(s, DOMID_QEMU, XBT_NULL, abspath, perms);
+ g_assert(!err);
+
+ g_list_free_full(perms, g_free);
g_free(abspath);
abspath = g_strdup_printf("/local/domain/%u/some", DOMID_GUEST);
@@ -98,6 +106,12 @@ static XenstoreImplState *setup(void)
g_assert(!err);
g_assert(s->nr_nodes == 5);
+ perms = g_list_append(NULL, g_strdup_printf("n%u", DOMID_GUEST));
+
+ err = xs_impl_set_perms(s, DOMID_QEMU, XBT_NULL, abspath, perms);
+ g_assert(!err);
+
+ g_list_free_full(perms, g_free);
g_free(abspath);
return s;
@@ -166,6 +180,12 @@ static void test_xs_node_simple(void)
/* Keep a copy, to force COW mode */
old_root = xs_node_ref(s->root);
+ /* Write somewhere we aren't allowed, in COW mode */
+ err = write_str(s, DOMID_GUEST, XBT_NULL, "/local/domain/badplace",
+ "moredata");
+ g_assert(err == EACCES);
+ g_assert(s->nr_nodes == 7);
+
/* Write works again */
err = write_str(s, DOMID_GUEST, XBT_NULL,
"/local/domain/1/some/relative/path2",
@@ -226,6 +246,11 @@ static void test_xs_node_simple(void)
g_assert(!err);
g_assert(s->nr_nodes == 8);
+ /* Write somewhere we aren't allowed */
+ err = write_str(s, DOMID_GUEST, XBT_NULL, "/local/domain/badplace",
+ "moredata");
+ g_assert(err == EACCES);
+
g_assert(!strcmp(guest_watches->str,
"/local/domain/1/some/relativewatchrel"));
g_string_truncate(guest_watches, 0);
--
2.39.0
