103 lines
2.8 KiB
C
103 lines
2.8 KiB
C
/*
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* Copyright (c) 2018 Samsung Electronics Co., Ltd. All Rights Reserved
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2
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* as published by the Free Software Foundation.
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*/
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#include <linux/bsearch.h>
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#include <linux/dsms.h>
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#include <linux/kallsyms.h>
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#include <linux/string.h>
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#include "dsms_access_control.h"
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#include "dsms_kernel_api.h"
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#include "dsms_test.h"
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typedef int (*cmp_fn_t)(const void *key, const void *element);
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/*
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* compare_to_policy_entry_key - compare a function name with the function
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* name of a policy entry
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* @function_name: function name
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* @entry: pointer to the policy entry
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*
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* Returns lexicographic order of the two compared function names
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*/
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__visible_for_testing int compare_policy_entries(const void *function_name, const void *entry)
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{
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return strncmp((const char *)function_name,
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((const struct dsms_policy_entry *)entry)->function_name, KSYM_NAME_LEN);
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}
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/*
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* find_policy_entry - find policy entry
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* @function_name: function name to find
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*
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* Returns a pointer to the policy entry for the given function,
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* or NULL if not found.
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*/
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__visible_for_testing struct dsms_policy_entry *find_policy_entry(const char *function_name)
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{
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void *entry;
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// see: https://github.com/torvalds/linux/blob/master/lib/bsearch.c
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entry = bsearch(function_name,
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dsms_policy,
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dsms_policy_size(),
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sizeof(*dsms_policy),
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(cmp_fn_t) compare_policy_entries);
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return (struct dsms_policy_entry *)entry;
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}
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int dsms_verify_access(const void *address)
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{
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const char *symname;
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unsigned long symsize;
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unsigned long offset;
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char *modname;
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char function_name[KSYM_NAME_LEN+1];
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int index;
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DSMS_LOG_DEBUG("%s: Caller function is %pS (%pF)", __func__,
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address, address);
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if (!address) {
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DSMS_LOG_ERROR("DENY: invalid caller address.");
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return DSMS_DENY;
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}
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symname = kallsyms_lookup((unsigned long)address,
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&symsize, &offset, &modname, function_name);
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if (!symname) {
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DSMS_LOG_ERROR("DENY: caller address not in kallsyms.");
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return DSMS_DENY;
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}
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function_name[KSYM_NAME_LEN] = 0;
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DSMS_LOG_DEBUG("%s: kallsyms caller modname = %s, function_name = '%s', offset = 0x%lx",
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__func__, modname, function_name, offset);
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if (modname != NULL) {
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DSMS_LOG_ERROR("DENY: function '%s' is not a kernel symbol",
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function_name);
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return DSMS_DENY; // not a kernel symbol
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}
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if (should_ignore_allowlist_suffix()) {
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for (index = 0; index < KSYM_NAME_LEN; index++)
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if ((function_name[index] == '.') || (function_name[index] == 0))
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break;
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function_name[index] = 0;
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}
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if (find_policy_entry(function_name) == NULL) {
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DSMS_LOG_ERROR("DENY: function '%s': is not allowed by policy",
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function_name);
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return DSMS_DENY;
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}
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return DSMS_SUCCESS;
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}
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