oid_registry.c

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/* ASN.1 Object identifier (OID) registry
 *
 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#include <linux/export.h>
#include <linux/oid_registry.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/bug.h>
#include "oid_registry_data.c"

enum OID look_up_OID(const void *data, size_t datasize)
{
    const unsigned char *octets = data;
    enum OID oid;
    unsigned char xhash;
    unsigned i, j, k, hash;
    size_t len;

    /* Hash the OID data */
    hash = datasize - 1;

    for (i = 0; i < datasize; i++)
        hash += octets[i] * 33;
    hash = (hash >> 24) ^ (hash >> 16) ^ (hash >> 8) ^ hash;
    hash &= 0xff;

    /* Binary search the OID registry.  OIDs are stored in ascending order
     * of hash value then ascending order of size and then in ascending
     * order of reverse value.
     */
    i = 0;
    k = OID__NR;
    while (i < k) {
        j = (i + k) / 2;

        xhash = oid_search_table[j].hash;
        if (xhash > hash) {
            k = j;
            continue;
        }
        if (xhash < hash) {
            i = j + 1;
            continue;
        }

        oid = oid_search_table[j].oid;
        len = oid_index[oid + 1] - oid_index[oid];
        if (len > datasize) {
            k = j;
            continue;
        }
        if (len < datasize) {
            i = j + 1;
            continue;
        }

        /* Variation is most likely to be at the tail end of the
         * OID, so do the comparison in reverse.
         */
        while (len > 0) {
            unsigned char a = oid_data[oid_index[oid] + --len];
            unsigned char b = octets[len];
            if (a > b) {
                k = j;
                goto next;
            }
            if (a < b) {
                i = j + 1;
                goto next;
            }
        }
        return oid;
    next:
        ;
    }

    return OID__NR;
}
EXPORT_SYMBOL_GPL(look_up_OID);

/*
 * sprint_OID - Print an Object Identifier into a buffer
 * @data: The encoded OID to print
 * @datasize: The size of the encoded OID
 * @buffer: The buffer to render into
 * @bufsize: The size of the buffer
 *
 * The OID is rendered into the buffer in "a.b.c.d" format and the number of
 * bytes is returned.  -EBADMSG is returned if the data could not be intepreted
 * and -ENOBUFS if the buffer was too small.
 */
int sprint_oid(const void *data, size_t datasize, char *buffer, size_t bufsize)
{
    const unsigned char *v = data, *end = v + datasize;
    unsigned long num;
    unsigned char n;
    size_t ret;
    int count;

    if (v >= end)
        return -EBADMSG;

    n = *v++;
    ret = count = snprintf(buffer, bufsize, "%u.%u", n / 40, n % 40);
    buffer += count;
    bufsize -= count;
    if (bufsize == 0)
        return -ENOBUFS;

    while (v < end) {
        num = 0;
        n = *v++;
        if (!(n & 0x80)) {
            num = n;
        } else {
            num = n & 0x7f;
            do {
                if (v >= end)
                    return -EBADMSG;
                n = *v++;
                num <<= 7;
                num |= n & 0x7f;
            } while (n & 0x80);
        }
        ret += count = snprintf(buffer, bufsize, ".%lu", num);
        buffer += count;
        bufsize -= count;
        if (bufsize == 0)
            return -ENOBUFS;
    }

    return ret;
}
EXPORT_SYMBOL_GPL(sprint_oid);

int sprint_OID(enum OID oid, char *buffer, size_t bufsize)
{
    int ret;

    BUG_ON(oid >= OID__NR);

    ret = sprint_oid(oid_data + oid_index[oid],
             oid_index[oid + 1] - oid_index[oid],
             buffer, bufsize);
    BUG_ON(ret == -EBADMSG);
    return ret;
}
EXPORT_SYMBOL_GPL(sprint_OID);