diff options
Diffstat (limited to 'security/apparmor/match.c')
| -rw-r--r-- | security/apparmor/match.c | 792 |
1 files changed, 792 insertions, 0 deletions
diff --git a/security/apparmor/match.c b/security/apparmor/match.c new file mode 100644 index 000000000..3e9e1eaf9 --- /dev/null +++ b/security/apparmor/match.c @@ -0,0 +1,792 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * AppArmor security module + * + * This file contains AppArmor dfa based regular expression matching engine + * + * Copyright (C) 1998-2008 Novell/SUSE + * Copyright 2009-2012 Canonical Ltd. + */ + +#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/lib.h" +#include "include/match.h" + +#define base_idx(X) ((X) & 0xffffff) + +static char nulldfa_src[] = { + #include "nulldfa.in" +}; +struct aa_dfa *nulldfa; + +static char stacksplitdfa_src[] = { + #include "stacksplitdfa.in" +}; +struct aa_dfa *stacksplitdfa; + +int aa_setup_dfa_engine(void) +{ + int error; + + nulldfa = aa_dfa_unpack(nulldfa_src, sizeof(nulldfa_src), + TO_ACCEPT1_FLAG(YYTD_DATA32) | + TO_ACCEPT2_FLAG(YYTD_DATA32)); + if (IS_ERR(nulldfa)) { + error = PTR_ERR(nulldfa); + nulldfa = NULL; + return error; + } + + stacksplitdfa = aa_dfa_unpack(stacksplitdfa_src, + sizeof(stacksplitdfa_src), + TO_ACCEPT1_FLAG(YYTD_DATA32) | + TO_ACCEPT2_FLAG(YYTD_DATA32)); + if (IS_ERR(stacksplitdfa)) { + aa_put_dfa(nulldfa); + nulldfa = NULL; + error = PTR_ERR(stacksplitdfa); + stacksplitdfa = NULL; + return error; + } + + return 0; +} + +void aa_teardown_dfa_engine(void) +{ + aa_put_dfa(stacksplitdfa); + aa_put_dfa(nulldfa); +} + +/** + * 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 kfree) + */ +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(*(__be16 *) (blob)) - 1; + if (th.td_id > YYTD_ID_MAX) + goto out; + th.td_flags = be16_to_cpu(*(__be16 *) (blob + 2)); + th.td_lolen = be32_to_cpu(*(__be32 *) (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; + + /* if we have a table it must have some entries */ + if (th.td_lolen == 0) + goto out; + tsize = table_size(th.td_lolen, th.td_flags); + if (bsize < tsize) + goto out; + + table = kvzalloc(tsize, GFP_KERNEL); + if (table) { + table->td_id = th.td_id; + table->td_flags = th.td_flags; + table->td_lolen = th.td_lolen; + if (th.td_flags == YYTD_DATA8) + UNPACK_ARRAY(table->td_data, blob, th.td_lolen, + u8, u8, byte_to_byte); + else if (th.td_flags == YYTD_DATA16) + UNPACK_ARRAY(table->td_data, blob, th.td_lolen, + u16, __be16, be16_to_cpu); + else if (th.td_flags == YYTD_DATA32) + UNPACK_ARRAY(table->td_data, blob, th.td_lolen, + u32, __be32, be32_to_cpu); + else + goto fail; + /* 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(); + } + +out: + return table; +fail: + kvfree(table); + return NULL; +} + +/** + * verify_table_headers - verify that the tables headers are as expected + * @tables - array of dfa tables to check (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_table_headers(struct table_header **tables, int flags) +{ + size_t state_count, trans_count; + int error = -EPROTO; + + /* check that required tables exist */ + if (!(tables[YYTD_ID_DEF] && tables[YYTD_ID_BASE] && + tables[YYTD_ID_NXT] && tables[YYTD_ID_CHK])) + goto out; + + /* accept.size == default.size == base.size */ + state_count = tables[YYTD_ID_BASE]->td_lolen; + if (ACCEPT1_FLAGS(flags)) { + if (!tables[YYTD_ID_ACCEPT]) + goto out; + if (state_count != tables[YYTD_ID_ACCEPT]->td_lolen) + goto out; + } + if (ACCEPT2_FLAGS(flags)) { + if (!tables[YYTD_ID_ACCEPT2]) + goto out; + if (state_count != tables[YYTD_ID_ACCEPT2]->td_lolen) + goto out; + } + if (state_count != tables[YYTD_ID_DEF]->td_lolen) + goto out; + + /* next.size == chk.size */ + trans_count = tables[YYTD_ID_NXT]->td_lolen; + if (trans_count != tables[YYTD_ID_CHK]->td_lolen) + goto out; + + /* if equivalence classes then its table size must be 256 */ + if (tables[YYTD_ID_EC] && tables[YYTD_ID_EC]->td_lolen != 256) + goto out; + + error = 0; +out: + return error; +} + +/** + * verify_dfa - verify that transitions and states in the tables are in bounds. + * @dfa: dfa to test (NOT NULL) + * + * 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) +{ + size_t i, state_count, trans_count; + int error = -EPROTO; + + state_count = dfa->tables[YYTD_ID_BASE]->td_lolen; + trans_count = dfa->tables[YYTD_ID_NXT]->td_lolen; + if (state_count == 0) + goto out; + for (i = 0; i < state_count; i++) { + if (!(BASE_TABLE(dfa)[i] & MATCH_FLAG_DIFF_ENCODE) && + (DEFAULT_TABLE(dfa)[i] >= state_count)) + goto out; + if (BASE_TABLE(dfa)[i] & MATCH_FLAGS_INVALID) { + pr_err("AppArmor DFA state with invalid match flags"); + goto out; + } + if ((BASE_TABLE(dfa)[i] & MATCH_FLAG_DIFF_ENCODE)) { + if (!(dfa->flags & YYTH_FLAG_DIFF_ENCODE)) { + pr_err("AppArmor DFA diff encoded transition state without header flag"); + goto out; + } + } + if ((BASE_TABLE(dfa)[i] & MATCH_FLAG_OOB_TRANSITION)) { + if (base_idx(BASE_TABLE(dfa)[i]) < dfa->max_oob) { + pr_err("AppArmor DFA out of bad transition out of range"); + goto out; + } + if (!(dfa->flags & YYTH_FLAG_OOB_TRANS)) { + pr_err("AppArmor DFA out of bad transition state without header flag"); + goto out; + } + } + if (base_idx(BASE_TABLE(dfa)[i]) + 255 >= trans_count) { + pr_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; + } + + /* Now that all the other tables are verified, verify diffencoding */ + for (i = 0; i < state_count; i++) { + size_t j, k; + + for (j = i; + (BASE_TABLE(dfa)[j] & MATCH_FLAG_DIFF_ENCODE) && + !(BASE_TABLE(dfa)[j] & MARK_DIFF_ENCODE); + j = k) { + k = DEFAULT_TABLE(dfa)[j]; + if (j == k) + goto out; + if (k < j) + break; /* already verified */ + BASE_TABLE(dfa)[j] |= MARK_DIFF_ENCODE; + } + } + 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/admin-guide/LSM/apparmor.rst + * Assumes the dfa @blob stream has been aligned on a 8 byte boundary + * + * 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(*(__be32 *) data) != YYTH_MAGIC) + goto fail; + + hsize = ntohl(*(__be32 *) (data + 4)); + if (size < hsize) + goto fail; + + dfa->flags = ntohs(*(__be16 *) (data + 12)); + if (dfa->flags & ~(YYTH_FLAGS)) + goto fail; + + /* + * TODO: needed for dfa to support more than 1 oob + * if (dfa->flags & YYTH_FLAGS_OOB_TRANS) { + * if (hsize < 16 + 4) + * goto fail; + * dfa->max_oob = ntol(*(__be32 *) (data + 16)); + * if (dfa->max <= MAX_OOB_SUPPORTED) { + * pr_err("AppArmor DFA OOB greater than supported\n"); + * goto fail; + * } + * } + */ + dfa->max_oob = 1; + + 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_table_headers(dfa->tables, flags); + if (error) + goto fail; + + if (flags & DFA_FLAG_VERIFY_STATES) { + error = verify_dfa(dfa); + if (error) + goto fail; + } + + return dfa; + +fail: + kvfree(table); + dfa_free(dfa); + return ERR_PTR(error); +} + +#define match_char(state, def, base, next, check, C) \ +do { \ + u32 b = (base)[(state)]; \ + unsigned int pos = base_idx(b) + (C); \ + if ((check)[pos] != (state)) { \ + (state) = (def)[(state)]; \ + if (b & MATCH_FLAG_DIFF_ENCODE) \ + continue; \ + break; \ + } \ + (state) = (next)[pos]; \ + break; \ +} while (1) + +/** + * 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; + + 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); + for (; len; len--) + match_char(state, def, base, next, check, + equiv[(u8) *str++]); + } else { + /* default is direct to next state */ + for (; len; len--) + match_char(state, def, base, next, check, (u8) *str++); + } + + return state; +} + +/** + * aa_dfa_match - 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_match 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) +{ + u16 *def = DEFAULT_TABLE(dfa); + u32 *base = BASE_TABLE(dfa); + u16 *next = NEXT_TABLE(dfa); + u16 *check = CHECK_TABLE(dfa); + unsigned int state = start; + + 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 */ + while (*str) + match_char(state, def, base, next, check, + equiv[(u8) *str++]); + } else { + /* default is direct to next state */ + while (*str) + match_char(state, def, base, next, check, (u8) *str++); + } + + return state; +} + +/** + * aa_dfa_next - step one character to the next state in the dfa + * @dfa: the dfa to traverse (NOT NULL) + * @state: the state to start in + * @c: the input character to transition on + * + * aa_dfa_match will step through the dfa by one input character @c + * + * Returns: state reach after input @c + */ +unsigned int aa_dfa_next(struct aa_dfa *dfa, unsigned int state, + const char c) +{ + u16 *def = DEFAULT_TABLE(dfa); + u32 *base = BASE_TABLE(dfa); + u16 *next = NEXT_TABLE(dfa); + u16 *check = CHECK_TABLE(dfa); + + /* current state is <state>, matching character *str */ + if (dfa->tables[YYTD_ID_EC]) { + /* Equivalence class table defined */ + u8 *equiv = EQUIV_TABLE(dfa); + match_char(state, def, base, next, check, equiv[(u8) c]); + } else + match_char(state, def, base, next, check, (u8) c); + + return state; +} + +unsigned int aa_dfa_outofband_transition(struct aa_dfa *dfa, unsigned int state) +{ + u16 *def = DEFAULT_TABLE(dfa); + u32 *base = BASE_TABLE(dfa); + u16 *next = NEXT_TABLE(dfa); + u16 *check = CHECK_TABLE(dfa); + u32 b = (base)[(state)]; + + if (!(b & MATCH_FLAG_OOB_TRANSITION)) + return DFA_NOMATCH; + + /* No Equivalence class remapping for outofband transitions */ + match_char(state, def, base, next, check, -1); + + return state; +} + +/** + * aa_dfa_match_until - traverse @dfa until accept state or end of input + * @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) + * @retpos: first character in str after match OR end of string + * + * aa_dfa_match 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_until(struct aa_dfa *dfa, unsigned int start, + const char *str, const char **retpos) +{ + u16 *def = DEFAULT_TABLE(dfa); + u32 *base = BASE_TABLE(dfa); + u16 *next = NEXT_TABLE(dfa); + u16 *check = CHECK_TABLE(dfa); + u32 *accept = ACCEPT_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 */ + while (*str) { + pos = base_idx(base[state]) + equiv[(u8) *str++]; + if (check[pos] == state) + state = next[pos]; + else + state = def[state]; + if (accept[state]) + break; + } + } else { + /* default is direct to next state */ + while (*str) { + pos = base_idx(base[state]) + (u8) *str++; + if (check[pos] == state) + state = next[pos]; + else + state = def[state]; + if (accept[state]) + break; + } + } + + *retpos = str; + return state; +} + +/** + * aa_dfa_matchn_until - traverse @dfa until accept or @n bytes consumed + * @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) + * @n: length of the string of bytes to match + * @retpos: first character in str after match OR str + n + * + * 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 @n input is consumed. + * + * Returns: final state reached after input is consumed + */ +unsigned int aa_dfa_matchn_until(struct aa_dfa *dfa, unsigned int start, + const char *str, int n, const char **retpos) +{ + u16 *def = DEFAULT_TABLE(dfa); + u32 *base = BASE_TABLE(dfa); + u16 *next = NEXT_TABLE(dfa); + u16 *check = CHECK_TABLE(dfa); + u32 *accept = ACCEPT_TABLE(dfa); + unsigned int state = start, pos; + + *retpos = NULL; + 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 (; n; n--) { + pos = base_idx(base[state]) + equiv[(u8) *str++]; + if (check[pos] == state) + state = next[pos]; + else + state = def[state]; + if (accept[state]) + break; + } + } else { + /* default is direct to next state */ + for (; n; n--) { + pos = base_idx(base[state]) + (u8) *str++; + if (check[pos] == state) + state = next[pos]; + else + state = def[state]; + if (accept[state]) + break; + } + } + + *retpos = str; + return state; +} + +#define inc_wb_pos(wb) \ +do { \ + wb->pos = (wb->pos + 1) & (WB_HISTORY_SIZE - 1); \ + wb->len = (wb->len + 1) & (WB_HISTORY_SIZE - 1); \ +} while (0) + +/* For DFAs that don't support extended tagging of states */ +static bool is_loop(struct match_workbuf *wb, unsigned int state, + unsigned int *adjust) +{ + unsigned int pos = wb->pos; + unsigned int i; + + if (wb->history[pos] < state) + return false; + + for (i = 0; i <= wb->len; i++) { + if (wb->history[pos] == state) { + *adjust = i; + return true; + } + if (pos == 0) + pos = WB_HISTORY_SIZE; + pos--; + } + + *adjust = i; + return true; +} + +static unsigned int leftmatch_fb(struct aa_dfa *dfa, unsigned int start, + const char *str, struct match_workbuf *wb, + unsigned int *count) +{ + 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; + + AA_BUG(!dfa); + AA_BUG(!str); + AA_BUG(!wb); + AA_BUG(!count); + + *count = 0; + 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 */ + while (*str) { + unsigned int adjust; + + wb->history[wb->pos] = state; + pos = base_idx(base[state]) + equiv[(u8) *str++]; + if (check[pos] == state) + state = next[pos]; + else + state = def[state]; + if (is_loop(wb, state, &adjust)) { + state = aa_dfa_match(dfa, state, str); + *count -= adjust; + goto out; + } + inc_wb_pos(wb); + (*count)++; + } + } else { + /* default is direct to next state */ + while (*str) { + unsigned int adjust; + + wb->history[wb->pos] = state; + pos = base_idx(base[state]) + (u8) *str++; + if (check[pos] == state) + state = next[pos]; + else + state = def[state]; + if (is_loop(wb, state, &adjust)) { + state = aa_dfa_match(dfa, state, str); + *count -= adjust; + goto out; + } + inc_wb_pos(wb); + (*count)++; + } + } + +out: + if (!state) + *count = 0; + return state; +} + +/** + * aa_dfa_leftmatch - 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) + * @count: current count of longest left. + * + * aa_dfa_match 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_leftmatch(struct aa_dfa *dfa, unsigned int start, + const char *str, unsigned int *count) +{ + DEFINE_MATCH_WB(wb); + + /* TODO: match for extended state dfas */ + + return leftmatch_fb(dfa, start, str, &wb, count); +} |