/* * AppArmor security module * * This file contains AppArmor dfa based regular expression matching engine * * 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. */ #include <linux/errno.h> #include <linux/kernel.h> #include <linux/mm.h> #include <linux/slab.h> #include <linux/vmalloc.h> #include <linux/err.h> #include <linux/kref.h> #include "include/apparmor.h" #include "include/match.h" /** * unpack_table - unpack a dfa table (one of accept, default, base, next check) * @blob: data to unpack (NOT NULL) * @bsize: size of blob * * Returns: pointer to table else NULL on failure * * NOTE: must be freed by kvfree (not kmalloc) */ static struct table_header *unpack_table(char *blob, size_t bsize) { struct table_header *table = NULL; struct table_header th; size_t tsize; if (bsize < sizeof(struct table_header)) goto out; /* loaded td_id's start at 1, subtract 1 now to avoid doing * it every time we use td_id as an index */ th.td_id = be16_to_cpu(*(u16 *) (blob)) - 1; th.td_flags = be16_to_cpu(*(u16 *) (blob + 2)); th.td_lolen = be32_to_cpu(*(u32 *) (blob + 8)); blob += sizeof(struct table_header); if (!(th.td_flags == YYTD_DATA16 || th.td_flags == YYTD_DATA32 || th.td_flags == YYTD_DATA8)) goto out; tsize = table_size(th.td_lolen, th.td_flags); if (bsize < tsize) goto out; table = kvmalloc(tsize); if (table) { *table = th; if (th.td_flags == YYTD_DATA8) UNPACK_ARRAY(table->td_data, blob, th.td_lolen, u8, byte_to_byte); else if (th.td_flags == YYTD_DATA16) UNPACK_ARRAY(table->td_data, blob, th.td_lolen, u16, be16_to_cpu); else if (th.td_flags == YYTD_DATA32) UNPACK_ARRAY(table->td_data, blob, th.td_lolen, u32, be32_to_cpu); else goto fail; } out: /* if table was vmalloced make sure the page tables are synced * before it is used, as it goes live to all cpus. */ if (is_vmalloc_addr(table)) vm_unmap_aliases(); return table; fail: kvfree(table); return NULL; } /** * verify_dfa - verify that transitions and states in the tables are in bounds. * @dfa: dfa to test (NOT NULL) * @flags: flags controlling what type of accept table are acceptable * * Assumes dfa has gone through the first pass verification done by unpacking * NOTE: this does not valid accept table values * * Returns: %0 else error code on failure to verify */ static int verify_dfa(struct aa_dfa *dfa, int flags) { size_t i, state_count, trans_count; int error = -EPROTO; /* check that required tables exist */ if (!(dfa->tables[YYTD_ID_DEF] && dfa->tables[YYTD_ID_BASE] && dfa->tables[YYTD_ID_NXT] && dfa->tables[YYTD_ID_CHK])) goto out; /* accept.size == default.size == base.size */ state_count = dfa->tables[YYTD_ID_BASE]->td_lolen; if (ACCEPT1_FLAGS(flags)) { if (!dfa->tables[YYTD_ID_ACCEPT]) goto out; if (state_count != dfa->tables[YYTD_ID_ACCEPT]->td_lolen) goto out; } if (ACCEPT2_FLAGS(flags)) { if (!dfa->tables[YYTD_ID_ACCEPT2]) goto out; if (state_count != dfa->tables[YYTD_ID_ACCEPT2]->td_lolen) goto out; } if (state_count != dfa->tables[YYTD_ID_DEF]->td_lolen) goto out; /* next.size == chk.size */ trans_count = dfa->tables[YYTD_ID_NXT]->td_lolen; if (trans_count != dfa->tables[YYTD_ID_CHK]->td_lolen) goto out; /* if equivalence classes then its table size must be 256 */ if (dfa->tables[YYTD_ID_EC] && dfa->tables[YYTD_ID_EC]->td_lolen != 256) goto out; if (flags & DFA_FLAG_VERIFY_STATES) { for (i = 0; i < state_count; i++) { if (DEFAULT_TABLE(dfa)[i] >= state_count) goto out; /* TODO: do check that DEF state recursion terminates */ if (BASE_TABLE(dfa)[i] + 255 >= trans_count) { printk(KERN_ERR "AppArmor DFA next/check upper " "bounds error\n"); goto out; } } for (i = 0; i < trans_count; i++) { if (NEXT_TABLE(dfa)[i] >= state_count) goto out; if (CHECK_TABLE(dfa)[i] >= state_count) goto out; } } error = 0; out: return error; } /** * dfa_free - free a dfa allocated by aa_dfa_unpack * @dfa: the dfa to free (MAYBE NULL) * * Requires: reference count to dfa == 0 */ static void dfa_free(struct aa_dfa *dfa) { if (dfa) { int i; for (i = 0; i < ARRAY_SIZE(dfa->tables); i++) { kvfree(dfa->tables[i]); dfa->tables[i] = NULL; } kfree(dfa); } } /** * aa_dfa_free_kref - free aa_dfa by kref (called by aa_put_dfa) * @kr: kref callback for freeing of a dfa (NOT NULL) */ void aa_dfa_free_kref(struct kref *kref) { struct aa_dfa *dfa = container_of(kref, struct aa_dfa, count); dfa_free(dfa); } /** * aa_dfa_unpack - unpack the binary tables of a serialized dfa * @blob: aligned serialized stream of data to unpack (NOT NULL) * @size: size of data to unpack * @flags: flags controlling what type of accept tables are acceptable * * Unpack a dfa that has been serialized. To find information on the dfa * format look in Documentation/apparmor.txt * Assumes the dfa @blob stream has been aligned on a 8 byte boundry * * Returns: an unpacked dfa ready for matching or ERR_PTR on failure */ struct aa_dfa *aa_dfa_unpack(void *blob, size_t size, int flags) { int hsize; int error = -ENOMEM; char *data = blob; struct table_header *table = NULL; struct aa_dfa *dfa = kzalloc(sizeof(struct aa_dfa), GFP_KERNEL); if (!dfa) goto fail; kref_init(&dfa->count); error = -EPROTO; /* get dfa table set header */ if (size < sizeof(struct table_set_header)) goto fail; if (ntohl(*(u32 *) data) != YYTH_MAGIC) goto fail; hsize = ntohl(*(u32 *) (data + 4)); if (size < hsize) goto fail; dfa->flags = ntohs(*(u16 *) (data + 12)); data += hsize; size -= hsize; while (size > 0) { table = unpack_table(data, size); if (!table) goto fail; switch (table->td_id) { case YYTD_ID_ACCEPT: if (!(table->td_flags & ACCEPT1_FLAGS(flags))) goto fail; break; case YYTD_ID_ACCEPT2: if (!(table->td_flags & ACCEPT2_FLAGS(flags))) goto fail; break; case YYTD_ID_BASE: if (table->td_flags != YYTD_DATA32) goto fail; break; case YYTD_ID_DEF: case YYTD_ID_NXT: case YYTD_ID_CHK: if (table->td_flags != YYTD_DATA16) goto fail; break; case YYTD_ID_EC: if (table->td_flags != YYTD_DATA8) goto fail; break; default: goto fail; } /* check for duplicate table entry */ if (dfa->tables[table->td_id]) goto fail; dfa->tables[table->td_id] = table; data += table_size(table->td_lolen, table->td_flags); size -= table_size(table->td_lolen, table->td_flags); table = NULL; } error = verify_dfa(dfa, flags); if (error) goto fail; return dfa; fail: kvfree(table); dfa_free(dfa); return ERR_PTR(error); } /** * aa_dfa_match_len - traverse @dfa to find state @str stops at * @dfa: the dfa to match @str against (NOT NULL) * @start: the state of the dfa to start matching in * @str: the string of bytes to match against the dfa (NOT NULL) * @len: length of the string of bytes to match * * aa_dfa_match_len will match @str against the dfa and return the state it * finished matching in. The final state can be used to look up the accepting * label, or as the start state of a continuing match. * * This function will happily match again the 0 byte and only finishes * when @len input is consumed. * * Returns: final state reached after input is consumed */ unsigned int aa_dfa_match_len(struct aa_dfa *dfa, unsigned int start, const char *str, int len) { u16 *def = DEFAULT_TABLE(dfa); u32 *base = BASE_TABLE(dfa); u16 *next = NEXT_TABLE(dfa); u16 *check = CHECK_TABLE(dfa); unsigned int state = start, pos; if (state == 0) return 0; /* current state is <state>, matching character *str */ if (dfa->tables[YYTD_ID_EC]) { /* Equivalence class table defined */ u8 *equiv = EQUIV_TABLE(dfa); /* default is direct to next state */ for (; len; len--) { pos = base[state] + equiv[(u8) *str++]; if (check[pos] == state) state = next[pos]; else state = def[state]; } } else { /* default is direct to next state */ for (; len; len--) { pos = base[state] + (u8) *str++; if (check[pos] == state) state = next[pos]; else state = def[state]; } } return state; } /** * aa_dfa_next_state - traverse @dfa to find state @str stops at * @dfa: the dfa to match @str against (NOT NULL) * @start: the state of the dfa to start matching in * @str: the null terminated string of bytes to match against the dfa (NOT NULL) * * aa_dfa_next_state will match @str against the dfa and return the state it * finished matching in. The final state can be used to look up the accepting * label, or as the start state of a continuing match. * * Returns: final state reached after input is consumed */ unsigned int aa_dfa_match(struct aa_dfa *dfa, unsigned int start, const char *str) { return aa_dfa_match_len(dfa, start, str, strlen(str)); }