Root/lib/oid_registry.c

1/* ASN.1 Object identifier (OID) registry
2 *
3 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
10 */
11
12#include <linux/module.h>
13#include <linux/export.h>
14#include <linux/oid_registry.h>
15#include <linux/kernel.h>
16#include <linux/errno.h>
17#include <linux/bug.h>
18#include "oid_registry_data.c"
19
20MODULE_DESCRIPTION("OID Registry");
21MODULE_AUTHOR("Red Hat, Inc.");
22MODULE_LICENSE("GPL");
23
24/**
25 * look_up_OID - Find an OID registration for the specified data
26 * @data: Binary representation of the OID
27 * @datasize: Size of the binary representation
28 */
29enum OID look_up_OID(const void *data, size_t datasize)
30{
31    const unsigned char *octets = data;
32    enum OID oid;
33    unsigned char xhash;
34    unsigned i, j, k, hash;
35    size_t len;
36
37    /* Hash the OID data */
38    hash = datasize - 1;
39
40    for (i = 0; i < datasize; i++)
41        hash += octets[i] * 33;
42    hash = (hash >> 24) ^ (hash >> 16) ^ (hash >> 8) ^ hash;
43    hash &= 0xff;
44
45    /* Binary search the OID registry. OIDs are stored in ascending order
46     * of hash value then ascending order of size and then in ascending
47     * order of reverse value.
48     */
49    i = 0;
50    k = OID__NR;
51    while (i < k) {
52        j = (i + k) / 2;
53
54        xhash = oid_search_table[j].hash;
55        if (xhash > hash) {
56            k = j;
57            continue;
58        }
59        if (xhash < hash) {
60            i = j + 1;
61            continue;
62        }
63
64        oid = oid_search_table[j].oid;
65        len = oid_index[oid + 1] - oid_index[oid];
66        if (len > datasize) {
67            k = j;
68            continue;
69        }
70        if (len < datasize) {
71            i = j + 1;
72            continue;
73        }
74
75        /* Variation is most likely to be at the tail end of the
76         * OID, so do the comparison in reverse.
77         */
78        while (len > 0) {
79            unsigned char a = oid_data[oid_index[oid] + --len];
80            unsigned char b = octets[len];
81            if (a > b) {
82                k = j;
83                goto next;
84            }
85            if (a < b) {
86                i = j + 1;
87                goto next;
88            }
89        }
90        return oid;
91    next:
92        ;
93    }
94
95    return OID__NR;
96}
97EXPORT_SYMBOL_GPL(look_up_OID);
98
99/*
100 * sprint_OID - Print an Object Identifier into a buffer
101 * @data: The encoded OID to print
102 * @datasize: The size of the encoded OID
103 * @buffer: The buffer to render into
104 * @bufsize: The size of the buffer
105 *
106 * The OID is rendered into the buffer in "a.b.c.d" format and the number of
107 * bytes is returned. -EBADMSG is returned if the data could not be intepreted
108 * and -ENOBUFS if the buffer was too small.
109 */
110int sprint_oid(const void *data, size_t datasize, char *buffer, size_t bufsize)
111{
112    const unsigned char *v = data, *end = v + datasize;
113    unsigned long num;
114    unsigned char n;
115    size_t ret;
116    int count;
117
118    if (v >= end)
119        return -EBADMSG;
120
121    n = *v++;
122    ret = count = snprintf(buffer, bufsize, "%u.%u", n / 40, n % 40);
123    buffer += count;
124    bufsize -= count;
125    if (bufsize == 0)
126        return -ENOBUFS;
127
128    while (v < end) {
129        num = 0;
130        n = *v++;
131        if (!(n & 0x80)) {
132            num = n;
133        } else {
134            num = n & 0x7f;
135            do {
136                if (v >= end)
137                    return -EBADMSG;
138                n = *v++;
139                num <<= 7;
140                num |= n & 0x7f;
141            } while (n & 0x80);
142        }
143        ret += count = snprintf(buffer, bufsize, ".%lu", num);
144        buffer += count;
145        bufsize -= count;
146        if (bufsize == 0)
147            return -ENOBUFS;
148    }
149
150    return ret;
151}
152EXPORT_SYMBOL_GPL(sprint_oid);
153
154/**
155 * sprint_OID - Print an Object Identifier into a buffer
156 * @oid: The OID to print
157 * @buffer: The buffer to render into
158 * @bufsize: The size of the buffer
159 *
160 * The OID is rendered into the buffer in "a.b.c.d" format and the number of
161 * bytes is returned.
162 */
163int sprint_OID(enum OID oid, char *buffer, size_t bufsize)
164{
165    int ret;
166
167    BUG_ON(oid >= OID__NR);
168
169    ret = sprint_oid(oid_data + oid_index[oid],
170             oid_index[oid + 1] - oid_index[oid],
171             buffer, bufsize);
172    BUG_ON(ret == -EBADMSG);
173    return ret;
174}
175EXPORT_SYMBOL_GPL(sprint_OID);
176

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