AppArmor: policy routines for loading and unpacking policy

AppArmor policy is loaded in a platform independent flattened binary
stream.  Verify and unpack the data converting it to the internal
format needed for enforcement.

Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: James Morris <jmorris@namei.org>

2 files changed, 723 insertions, 0 deletions

diff --git a/security/apparmor/include/policy_unpack.h b/security/apparmor/include/policy_unpack.h
new file mode 100644
index 000000000000..a2dcccac45aa
--- /dev/null
+++ b/security/apparmor/include/policy_unpack.h
@@ -0,0 +1,20 @@
+/*
+ * AppArmor security module
+ *
+ * This file contains AppArmor policy loading interface function definitions.
+ *
+ * Copyright (C) 1998-2008 Novell/SUSE
+ * Copyright 2009-2010 Canonical Ltd.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation, version 2 of the
+ * License.
+ */
+
+#ifndef __POLICY_INTERFACE_H
+#define __POLICY_INTERFACE_H
+
+struct aa_profile *aa_unpack(void *udata, size_t size, const char **ns);
+
+#endif /* __POLICY_INTERFACE_H */
diff --git a/security/apparmor/policy_unpack.c b/security/apparmor/policy_unpack.c
new file mode 100644
index 000000000000..eb3700e9fd37
--- /dev/null
+++ b/security/apparmor/policy_unpack.c
@@ -0,0 +1,703 @@
+/*
+ * AppArmor security module
+ *
+ * This file contains AppArmor functions for unpacking policy loaded from
+ * userspace.
+ *
+ * Copyright (C) 1998-2008 Novell/SUSE
+ * Copyright 2009-2010 Canonical Ltd.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation, version 2 of the
+ * License.
+ *
+ * AppArmor uses a serialized binary format for loading policy.
+ * To find policy format documentation look in Documentation/apparmor.txt
+ * All policy is validated before it is used.
+ */
+
+#include <asm/unaligned.h>
+#include <linux/ctype.h>
+#include <linux/errno.h>
+
+#include "include/apparmor.h"
+#include "include/audit.h"
+#include "include/context.h"
+#include "include/match.h"
+#include "include/policy.h"
+#include "include/policy_unpack.h"
+#include "include/sid.h"
+
+/*
+ * The AppArmor interface treats data as a type byte followed by the
+ * actual data.  The interface has the notion of a a named entry
+ * which has a name (AA_NAME typecode followed by name string) followed by
+ * the entries typecode and data.  Named types allow for optional
+ * elements and extensions to be added and tested for without breaking
+ * backwards compatibility.
+ */
+
+enum aa_code {
+        AA_U8,
+        AA_U16,
+        AA_U32,
+        AA_U64,
+        AA_NAME,                /* same as string except it is items name */
+        AA_STRING,
+        AA_BLOB,
+        AA_STRUCT,
+        AA_STRUCTEND,
+        AA_LIST,
+        AA_LISTEND,
+        AA_ARRAY,
+        AA_ARRAYEND,
+};
+
+/*
+ * aa_ext is the read of the buffer containing the serialized profile.  The
+ * data is copied into a kernel buffer in apparmorfs and then handed off to
+ * the unpack routines.
+ */
+struct aa_ext {
+        void *start;
+        void *end;
+        void *pos;              /* pointer to current position in the buffer */
+        u32 version;
+};
+
+/* audit callback for unpack fields */
+static void audit_cb(struct audit_buffer *ab, void *va)
+{
+        struct common_audit_data *sa = va;
+        if (sa->aad.iface.target) {
+                struct aa_profile *name = sa->aad.iface.target;
+                audit_log_format(ab, " name=");
+                audit_log_untrustedstring(ab, name->base.hname);
+        }
+        if (sa->aad.iface.pos)
+                audit_log_format(ab, " offset=%ld", sa->aad.iface.pos);
+}
+
+/**
+ * audit_iface - do audit message for policy unpacking/load/replace/remove
+ * @new: profile if it has been allocated (MAYBE NULL)
+ * @name: name of the profile being manipulated (MAYBE NULL)
+ * @info: any extra info about the failure (MAYBE NULL)
+ * @e: buffer position info (NOT NULL)
+ * @error: error code
+ *
+ * Returns: %0 or error
+ */
+static int audit_iface(struct aa_profile *new, const char *name,
+                       const char *info, struct aa_ext *e, int error)
+{
+        struct aa_profile *profile = __aa_current_profile();
+        struct common_audit_data sa;
+        COMMON_AUDIT_DATA_INIT(&sa, NONE);
+        sa.aad.iface.pos = e->pos - e->start;
+        sa.aad.iface.target = new;
+        sa.aad.name = name;
+        sa.aad.info = info;
+        sa.aad.error = error;
+
+        return aa_audit(AUDIT_APPARMOR_STATUS, profile, GFP_KERNEL, &sa,
+                        audit_cb);
+}
+
+/* test if read will be in packed data bounds */
+static bool inbounds(struct aa_ext *e, size_t size)
+{
+        return (size <= e->end - e->pos);
+}
+
+/**
+ * aa_u16_chunck - test and do bounds checking for a u16 size based chunk
+ * @e: serialized data read head (NOT NULL)
+ * @chunk: start address for chunk of data (NOT NULL)
+ *
+ * Returns: the size of chunk found with the read head at the end of the chunk.
+ */
+static size_t unpack_u16_chunk(struct aa_ext *e, char **chunk)
+{
+        size_t size = 0;
+
+        if (!inbounds(e, sizeof(u16)))
+                return 0;
+        size = le16_to_cpu(get_unaligned((u16 *) e->pos));
+        e->pos += sizeof(u16);
+        if (!inbounds(e, size))
+                return 0;
+        *chunk = e->pos;
+        e->pos += size;
+        return size;
+}
+
+/* unpack control byte */
+static bool unpack_X(struct aa_ext *e, enum aa_code code)
+{
+        if (!inbounds(e, 1))
+                return 0;
+        if (*(u8 *) e->pos != code)
+                return 0;
+        e->pos++;
+        return 1;
+}
+
+/**
+ * unpack_nameX - check is the next element is of type X with a name of @name
+ * @e: serialized data extent information  (NOT NULL)
+ * @code: type code
+ * @name: name to match to the serialized element.  (MAYBE NULL)
+ *
+ * check that the next serialized data element is of type X and has a tag
+ * name @name.  If @name is specified then there must be a matching
+ * name element in the stream.  If @name is NULL any name element will be
+ * skipped and only the typecode will be tested.
+ *
+ * Returns 1 on success (both type code and name tests match) and the read
+ * head is advanced past the headers
+ *
+ * Returns: 0 if either match fails, the read head does not move
+ */
+static bool unpack_nameX(struct aa_ext *e, enum aa_code code, const char *name)
+{
+        /*
+         * May need to reset pos if name or type doesn't match
+         */
+        void *pos = e->pos;
+        /*
+         * Check for presence of a tagname, and if present name size
+         * AA_NAME tag value is a u16.
+         */
+        if (unpack_X(e, AA_NAME)) {
+                char *tag = NULL;
+                size_t size = unpack_u16_chunk(e, &tag);
+                /* if a name is specified it must match. otherwise skip tag */
+                if (name && (!size || strcmp(name, tag)))
+                        goto fail;
+        } else if (name) {
+                /* if a name is specified and there is no name tag fail */
+                goto fail;
+        }
+
+        /* now check if type code matches */
+        if (unpack_X(e, code))
+                return 1;
+
+fail:
+        e->pos = pos;
+        return 0;
+}
+
+static bool unpack_u32(struct aa_ext *e, u32 *data, const char *name)
+{
+        if (unpack_nameX(e, AA_U32, name)) {
+                if (!inbounds(e, sizeof(u32)))
+                        return 0;
+                if (data)
+                        *data = le32_to_cpu(get_unaligned((u32 *) e->pos));
+                e->pos += sizeof(u32);
+                return 1;
+        }
+        return 0;
+}
+
+static bool unpack_u64(struct aa_ext *e, u64 *data, const char *name)
+{
+        if (unpack_nameX(e, AA_U64, name)) {
+                if (!inbounds(e, sizeof(u64)))
+                        return 0;
+                if (data)
+                        *data = le64_to_cpu(get_unaligned((u64 *) e->pos));
+                e->pos += sizeof(u64);
+                return 1;
+        }
+        return 0;
+}
+
+static size_t unpack_array(struct aa_ext *e, const char *name)
+{
+        if (unpack_nameX(e, AA_ARRAY, name)) {
+                int size;
+                if (!inbounds(e, sizeof(u16)))
+                        return 0;
+                size = (int)le16_to_cpu(get_unaligned((u16 *) e->pos));
+                e->pos += sizeof(u16);
+                return size;
+        }
+        return 0;
+}
+
+static size_t unpack_blob(struct aa_ext *e, char **blob, const char *name)
+{
+        if (unpack_nameX(e, AA_BLOB, name)) {
+                u32 size;
+                if (!inbounds(e, sizeof(u32)))
+                        return 0;
+                size = le32_to_cpu(get_unaligned((u32 *) e->pos));
+                e->pos += sizeof(u32);
+                if (inbounds(e, (size_t) size)) {
+                        *blob = e->pos;
+                        e->pos += size;
+                        return size;
+                }
+        }
+        return 0;
+}
+
+static int unpack_str(struct aa_ext *e, const char **string, const char *name)
+{
+        char *src_str;
+        size_t size = 0;
+        void *pos = e->pos;
+        *string = NULL;
+        if (unpack_nameX(e, AA_STRING, name)) {
+                size = unpack_u16_chunk(e, &src_str);
+                if (size) {
+                        /* strings are null terminated, length is size - 1 */
+                        if (src_str[size - 1] != 0)
+                                goto fail;
+                        *string = src_str;
+                }
+        }
+        return size;
+
+fail:
+        e->pos = pos;
+        return 0;
+}
+
+static int unpack_strdup(struct aa_ext *e, char **string, const char *name)
+{
+        const char *tmp;
+        void *pos = e->pos;
+        int res = unpack_str(e, &tmp, name);
+        *string = NULL;
+
+        if (!res)
+                return 0;
+
+        *string = kmemdup(tmp, res, GFP_KERNEL);
+        if (!*string) {
+                e->pos = pos;
+                return 0;
+        }
+
+        return res;
+}
+
+/**
+ * verify_accept - verify the accept tables of a dfa
+ * @dfa: dfa to verify accept tables of (NOT NULL)
+ * @flags: flags governing dfa
+ *
+ * Returns: 1 if valid accept tables else 0 if error
+ */
+static bool verify_accept(struct aa_dfa *dfa, int flags)
+{
+        int i;
+
+        /* verify accept permissions */
+        for (i = 0; i < dfa->tables[YYTD_ID_ACCEPT]->td_lolen; i++) {
+                int mode = ACCEPT_TABLE(dfa)[i];
+
+                if (mode & ~DFA_VALID_PERM_MASK)
+                        return 0;
+
+                if (ACCEPT_TABLE2(dfa)[i] & ~DFA_VALID_PERM2_MASK)
+                        return 0;
+        }
+        return 1;
+}
+
+/**
+ * unpack_dfa - unpack a file rule dfa
+ * @e: serialized data extent information (NOT NULL)
+ *
+ * returns dfa or ERR_PTR or NULL if no dfa
+ */
+static struct aa_dfa *unpack_dfa(struct aa_ext *e)
+{
+        char *blob = NULL;
+        size_t size;
+        struct aa_dfa *dfa = NULL;
+
+        size = unpack_blob(e, &blob, "aadfa");
+        if (size) {
+                /*
+                 * The dfa is aligned with in the blob to 8 bytes
+                 * from the beginning of the stream.
+                 */
+                size_t sz = blob - (char *)e->start;
+                size_t pad = ALIGN(sz, 8) - sz;
+                int flags = TO_ACCEPT1_FLAG(YYTD_DATA32) |
+                        TO_ACCEPT2_FLAG(YYTD_DATA32);
+
+
+                if (aa_g_paranoid_load)
+                        flags |= DFA_FLAG_VERIFY_STATES;
+
+                dfa = aa_dfa_unpack(blob + pad, size - pad, flags);
+
+                if (IS_ERR(dfa))
+                        return dfa;
+
+                if (!verify_accept(dfa, flags))
+                        goto fail;
+        }
+
+        return dfa;
+
+fail:
+        aa_put_dfa(dfa);
+        return ERR_PTR(-EPROTO);
+}
+
+/**
+ * unpack_trans_table - unpack a profile transition table
+ * @e: serialized data extent information  (NOT NULL)
+ * @profile: profile to add the accept table to (NOT NULL)
+ *
+ * Returns: 1 if table succesfully unpacked
+ */
+static bool unpack_trans_table(struct aa_ext *e, struct aa_profile *profile)
+{
+        void *pos = e->pos;
+
+        /* exec table is optional */
+        if (unpack_nameX(e, AA_STRUCT, "xtable")) {
+                int i, size;
+
+                size = unpack_array(e, NULL);
+                /* currently 4 exec bits and entries 0-3 are reserved iupcx */
+                if (size > 16 - 4)
+                        goto fail;
+                profile->file.trans.table = kzalloc(sizeof(char *) * size,
+                                                    GFP_KERNEL);
+                if (!profile->file.trans.table)
+                        goto fail;
+
+                profile->file.trans.size = size;
+                for (i = 0; i < size; i++) {
+                        char *str;
+                        int c, j, size = unpack_strdup(e, &str, NULL);
+                        /* unpack_strdup verifies that the last character is
+                         * null termination byte.
+                         */
+                        if (!size)
+                                goto fail;
+                        profile->file.trans.table[i] = str;
+                        /* verify that name doesn't start with space */
+                        if (isspace(*str))
+                                goto fail;
+
+                        /* count internal #  of internal \0 */
+                        for (c = j = 0; j < size - 2; j++) {
+                                if (!str[j])
+                                        c++;
+                        }
+                        if (*str == ':') {
+                                /* beginning with : requires an embedded \0,
+                                 * verify that exactly 1 internal \0 exists
+                                 * trailing \0 already verified by unpack_strdup
+                                 */
+                                if (c != 1)
+                                        goto fail;
+                                /* first character after : must be valid */
+                                if (!str[1])
+                                        goto fail;
+                        } else if (c)
+                                /* fail - all other cases with embedded \0 */
+                                goto fail;
+                }
+                if (!unpack_nameX(e, AA_ARRAYEND, NULL))
+                        goto fail;
+                if (!unpack_nameX(e, AA_STRUCTEND, NULL))
+                        goto fail;
+        }
+        return 1;
+
+fail:
+        aa_free_domain_entries(&profile->file.trans);
+        e->pos = pos;
+        return 0;
+}
+
+static bool unpack_rlimits(struct aa_ext *e, struct aa_profile *profile)
+{
+        void *pos = e->pos;
+
+        /* rlimits are optional */
+        if (unpack_nameX(e, AA_STRUCT, "rlimits")) {
+                int i, size;
+                u32 tmp = 0;
+                if (!unpack_u32(e, &tmp, NULL))
+                        goto fail;
+                profile->rlimits.mask = tmp;
+
+                size = unpack_array(e, NULL);
+                if (size > RLIM_NLIMITS)
+                        goto fail;
+                for (i = 0; i < size; i++) {
+                        u64 tmp = 0;
+                        int a = aa_map_resource(i);
+                        if (!unpack_u64(e, &tmp, NULL))
+                                goto fail;
+                        profile->rlimits.limits[a].rlim_max = tmp;
+                }
+                if (!unpack_nameX(e, AA_ARRAYEND, NULL))
+                        goto fail;
+                if (!unpack_nameX(e, AA_STRUCTEND, NULL))
+                        goto fail;
+        }
+        return 1;
+
+fail:
+        e->pos = pos;
+        return 0;
+}
+
+/**
+ * unpack_profile - unpack a serialized profile
+ * @e: serialized data extent information (NOT NULL)
+ *
+ * NOTE: unpack profile sets audit struct if there is a failure
+ */
+static struct aa_profile *unpack_profile(struct aa_ext *e)
+{
+        struct aa_profile *profile = NULL;
+        const char *name = NULL;
+        int error = -EPROTO;
+        kernel_cap_t tmpcap;
+        u32 tmp;
+
+        /* check that we have the right struct being passed */
+        if (!unpack_nameX(e, AA_STRUCT, "profile"))
+                goto fail;
+        if (!unpack_str(e, &name, NULL))
+                goto fail;
+
+        profile = aa_alloc_profile(name);
+        if (!profile)
+                return ERR_PTR(-ENOMEM);
+
+        /* profile renaming is optional */
+        (void) unpack_str(e, &profile->rename, "rename");
+
+        /* xmatch is optional and may be NULL */
+        profile->xmatch = unpack_dfa(e);
+        if (IS_ERR(profile->xmatch)) {
+                error = PTR_ERR(profile->xmatch);
+                profile->xmatch = NULL;
+                goto fail;
+        }
+        /* xmatch_len is not optional if xmatch is set */
+        if (profile->xmatch) {
+                if (!unpack_u32(e, &tmp, NULL))
+                        goto fail;
+                profile->xmatch_len = tmp;
+        }
+
+        /* per profile debug flags (complain, audit) */
+        if (!unpack_nameX(e, AA_STRUCT, "flags"))
+                goto fail;
+        if (!unpack_u32(e, &tmp, NULL))
+                goto fail;
+        if (tmp)
+                profile->flags |= PFLAG_HAT;
+        if (!unpack_u32(e, &tmp, NULL))
+                goto fail;
+        if (tmp)
+                profile->mode = APPARMOR_COMPLAIN;
+        if (!unpack_u32(e, &tmp, NULL))
+                goto fail;
+        if (tmp)
+                profile->audit = AUDIT_ALL;
+
+        if (!unpack_nameX(e, AA_STRUCTEND, NULL))
+                goto fail;
+
+        /* path_flags is optional */
+        if (unpack_u32(e, &profile->path_flags, "path_flags"))
+                profile->path_flags |= profile->flags & PFLAG_MEDIATE_DELETED;
+        else
+                /* set a default value if path_flags field is not present */
+                profile->path_flags = PFLAG_MEDIATE_DELETED;
+
+        if (!unpack_u32(e, &(profile->caps.allow.cap[0]), NULL))
+                goto fail;
+        if (!unpack_u32(e, &(profile->caps.audit.cap[0]), NULL))
+                goto fail;
+        if (!unpack_u32(e, &(profile->caps.quiet.cap[0]), NULL))
+                goto fail;
+        if (!unpack_u32(e, &tmpcap.cap[0], NULL))
+                goto fail;
+
+        if (unpack_nameX(e, AA_STRUCT, "caps64")) {
+                /* optional upper half of 64 bit caps */
+                if (!unpack_u32(e, &(profile->caps.allow.cap[1]), NULL))
+                        goto fail;
+                if (!unpack_u32(e, &(profile->caps.audit.cap[1]), NULL))
+                        goto fail;
+                if (!unpack_u32(e, &(profile->caps.quiet.cap[1]), NULL))
+                        goto fail;
+                if (!unpack_u32(e, &(tmpcap.cap[1]), NULL))
+                        goto fail;
+                if (!unpack_nameX(e, AA_STRUCTEND, NULL))
+                        goto fail;
+        }
+
+        if (unpack_nameX(e, AA_STRUCT, "capsx")) {
+                /* optional extended caps mediation mask */
+                if (!unpack_u32(e, &(profile->caps.extended.cap[0]), NULL))
+                        goto fail;
+                if (!unpack_u32(e, &(profile->caps.extended.cap[1]), NULL))
+                        goto fail;
+        }
+
+        if (!unpack_rlimits(e, profile))
+                goto fail;
+
+        /* get file rules */
+        profile->file.dfa = unpack_dfa(e);
+        if (IS_ERR(profile->file.dfa)) {
+                error = PTR_ERR(profile->file.dfa);
+                profile->file.dfa = NULL;
+                goto fail;
+        }
+
+        if (!unpack_u32(e, &profile->file.start, "dfa_start"))
+                /* default start state */
+                profile->file.start = DFA_START;
+
+        if (!unpack_trans_table(e, profile))
+                goto fail;
+
+        if (!unpack_nameX(e, AA_STRUCTEND, NULL))
+                goto fail;
+
+        return profile;
+
+fail:
+        if (profile)
+                name = NULL;
+        else if (!name)
+                name = "unknown";
+        audit_iface(profile, name, "failed to unpack profile", e, error);
+        aa_put_profile(profile);
+
+        return ERR_PTR(error);
+}
+
+/**
+ * verify_head - unpack serialized stream header
+ * @e: serialized data read head (NOT NULL)
+ * @ns: Returns - namespace if one is specified else NULL (NOT NULL)
+ *
+ * Returns: error or 0 if header is good
+ */
+static int verify_header(struct aa_ext *e, const char **ns)
+{
+        int error = -EPROTONOSUPPORT;
+        /* get the interface version */
+        if (!unpack_u32(e, &e->version, "version")) {
+                audit_iface(NULL, NULL, "invalid profile format", e, error);
+                return error;
+        }
+
+        /* check that the interface version is currently supported */
+        if (e->version != 5) {
+                audit_iface(NULL, NULL, "unsupported interface version", e,
+                            error);
+                return error;
+        }
+
+        /* read the namespace if present */
+        if (!unpack_str(e, ns, "namespace"))
+                *ns = NULL;
+
+        return 0;
+}
+
+static bool verify_xindex(int xindex, int table_size)
+{
+        int index, xtype;
+        xtype = xindex & AA_X_TYPE_MASK;
+        index = xindex & AA_X_INDEX_MASK;
+        if (xtype == AA_X_TABLE && index > table_size)
+                return 0;
+        return 1;
+}
+
+/* verify dfa xindexes are in range of transition tables */
+static bool verify_dfa_xindex(struct aa_dfa *dfa, int table_size)
+{
+        int i;
+        for (i = 0; i < dfa->tables[YYTD_ID_ACCEPT]->td_lolen; i++) {
+                if (!verify_xindex(dfa_user_xindex(dfa, i), table_size))
+                        return 0;
+                if (!verify_xindex(dfa_other_xindex(dfa, i), table_size))
+                        return 0;
+        }
+        return 1;
+}
+
+/**
+ * verify_profile - Do post unpack analysis to verify profile consistency
+ * @profile: profile to verify (NOT NULL)
+ *
+ * Returns: 0 if passes verification else error
+ */
+static int verify_profile(struct aa_profile *profile)
+{
+        if (aa_g_paranoid_load) {
+                if (profile->file.dfa &&
+                    !verify_dfa_xindex(profile->file.dfa,
+                                       profile->file.trans.size)) {
+                        audit_iface(profile, NULL, "Invalid named transition",
+                                    NULL, -EPROTO);
+                        return -EPROTO;
+                }
+        }
+
+        return 0;
+}
+
+/**
+ * aa_unpack - unpack packed binary profile data loaded from user space
+ * @udata: user data copied to kmem  (NOT NULL)
+ * @size: the size of the user data
+ * @ns: Returns namespace profile is in if specified else NULL (NOT NULL)
+ *
+ * Unpack user data and return refcounted allocated profile or ERR_PTR
+ *
+ * Returns: profile else error pointer if fails to unpack
+ */
+struct aa_profile *aa_unpack(void *udata, size_t size, const char **ns)
+{
+        struct aa_profile *profile = NULL;
+        int error;
+        struct aa_ext e = {
+                .start = udata,
+                .end = udata + size,
+                .pos = udata,
+        };
+
+        error = verify_header(&e, ns);
+        if (error)
+                return ERR_PTR(error);
+
+        profile = unpack_profile(&e);
+        if (IS_ERR(profile))
+                return profile;
+
+        error = verify_profile(profile);
+        if (error) {
+                aa_put_profile(profile);
+                profile = ERR_PTR(error);
+        }
+
+        /* return refcount */
+        return profile;
+}