/*
 * 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/security/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
 * @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;
        struct apparmor_audit_data aad = {0,};
        sa.type = LSM_AUDIT_DATA_NONE;
        sa.aad = &aad;
        if (e)
                aad.iface.pos = e->pos - e->start;
        aad.iface.target = new;
        aad.name = name;
        aad.info = info;
        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 successfully 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, size2 = unpack_strdup(e, &str, NULL);
                        /* unpack_strdup verifies that the last character is
                         * null termination byte.
                         */
                        if (!size2)
                                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 < size2 - 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 tmp2 = 0;
                        int a = aa_map_resource(i);
                        if (!unpack_u64(e, &tmp2, NULL))
                                goto fail;
                        profile->rlimits.limits[a].rlim_max = tmp2;
                }
                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 i, 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_nameX(e, AA_STRUCTEND, NULL))
                        goto fail;
        }

        if (!unpack_rlimits(e, profile))
                goto fail;

        if (unpack_nameX(e, AA_STRUCT, "policydb")) {
                /* generic policy dfa - optional and may be NULL */
                profile->policy.dfa = unpack_dfa(e);
                if (IS_ERR(profile->policy.dfa)) {
                        error = PTR_ERR(profile->policy.dfa);
                        profile->policy.dfa = NULL;
                        goto fail;
                }
                if (!unpack_u32(e, &profile->policy.start[0], "start"))
                        /* default start state */
                        profile->policy.start[0] = DFA_START;
                /* setup class index */
                for (i = AA_CLASS_FILE; i <= AA_CLASS_LAST; i++) {
                        profile->policy.start[i] =
                                aa_dfa_next(profile->policy.dfa,
                                            profile->policy.start[0],
                                            i);
                }
                if (!unpack_nameX(e, AA_STRUCTEND, NULL))
                        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;
}