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![Colin Ian King](/assets/img/avatar_default.png)
Variable ret is being assigned a value that is never read. If the for-loop is entered then ret is immediately re-assigned a new value. If the for-loop is not executed ret is never read. The assignment is redundant and can be removed. Signed-off-by: Colin Ian King <colin.i.king@gmail.com> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
452 lines
10 KiB
C
452 lines
10 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Simple encoder primitives for ASN.1 BER/DER/CER
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*
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* Copyright (C) 2019 James.Bottomley@HansenPartnership.com
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*/
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#include <linux/asn1_encoder.h>
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#include <linux/bug.h>
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#include <linux/string.h>
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#include <linux/module.h>
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/**
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* asn1_encode_integer() - encode positive integer to ASN.1
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* @data: pointer to the pointer to the data
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* @end_data: end of data pointer, points one beyond last usable byte in @data
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* @integer: integer to be encoded
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*
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* This is a simplified encoder: it only currently does
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* positive integers, but it should be simple enough to add the
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* negative case if a use comes along.
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*/
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unsigned char *
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asn1_encode_integer(unsigned char *data, const unsigned char *end_data,
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s64 integer)
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{
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int data_len = end_data - data;
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unsigned char *d = &data[2];
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bool found = false;
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int i;
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if (WARN(integer < 0,
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"BUG: integer encode only supports positive integers"))
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return ERR_PTR(-EINVAL);
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if (IS_ERR(data))
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return data;
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/* need at least 3 bytes for tag, length and integer encoding */
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if (data_len < 3)
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return ERR_PTR(-EINVAL);
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/* remaining length where at d (the start of the integer encoding) */
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data_len -= 2;
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data[0] = _tag(UNIV, PRIM, INT);
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if (integer == 0) {
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*d++ = 0;
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goto out;
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}
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for (i = sizeof(integer); i > 0 ; i--) {
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int byte = integer >> (8 * (i - 1));
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if (!found && byte == 0)
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continue;
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/*
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* for a positive number the first byte must have bit
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* 7 clear in two's complement (otherwise it's a
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* negative number) so prepend a leading zero if
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* that's not the case
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*/
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if (!found && (byte & 0x80)) {
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/*
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* no check needed here, we already know we
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* have len >= 1
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*/
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*d++ = 0;
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data_len--;
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}
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found = true;
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if (data_len == 0)
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return ERR_PTR(-EINVAL);
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*d++ = byte;
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data_len--;
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}
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out:
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data[1] = d - data - 2;
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return d;
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}
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EXPORT_SYMBOL_GPL(asn1_encode_integer);
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/* calculate the base 128 digit values setting the top bit of the first octet */
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static int asn1_encode_oid_digit(unsigned char **_data, int *data_len, u32 oid)
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{
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unsigned char *data = *_data;
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int start = 7 + 7 + 7 + 7;
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int ret = 0;
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if (*data_len < 1)
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return -EINVAL;
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/* quick case */
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if (oid == 0) {
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*data++ = 0x80;
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(*data_len)--;
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goto out;
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}
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while (oid >> start == 0)
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start -= 7;
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while (start > 0 && *data_len > 0) {
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u8 byte;
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byte = oid >> start;
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oid = oid - (byte << start);
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start -= 7;
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byte |= 0x80;
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*data++ = byte;
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(*data_len)--;
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}
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if (*data_len > 0) {
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*data++ = oid;
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(*data_len)--;
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} else {
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ret = -EINVAL;
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}
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out:
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*_data = data;
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return ret;
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}
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/**
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* asn1_encode_oid() - encode an oid to ASN.1
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* @data: position to begin encoding at
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* @end_data: end of data pointer, points one beyond last usable byte in @data
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* @oid: array of oids
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* @oid_len: length of oid array
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*
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* this encodes an OID up to ASN.1 when presented as an array of OID values
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*/
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unsigned char *
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asn1_encode_oid(unsigned char *data, const unsigned char *end_data,
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u32 oid[], int oid_len)
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{
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int data_len = end_data - data;
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unsigned char *d = data + 2;
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int i, ret;
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if (WARN(oid_len < 2, "OID must have at least two elements"))
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return ERR_PTR(-EINVAL);
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if (WARN(oid_len > 32, "OID is too large"))
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return ERR_PTR(-EINVAL);
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if (IS_ERR(data))
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return data;
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/* need at least 3 bytes for tag, length and OID encoding */
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if (data_len < 3)
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return ERR_PTR(-EINVAL);
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data[0] = _tag(UNIV, PRIM, OID);
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*d++ = oid[0] * 40 + oid[1];
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data_len -= 3;
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for (i = 2; i < oid_len; i++) {
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ret = asn1_encode_oid_digit(&d, &data_len, oid[i]);
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if (ret < 0)
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return ERR_PTR(ret);
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}
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data[1] = d - data - 2;
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return d;
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}
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EXPORT_SYMBOL_GPL(asn1_encode_oid);
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/**
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* asn1_encode_length() - encode a length to follow an ASN.1 tag
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* @data: pointer to encode at
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* @data_len: pointer to remaining length (adjusted by routine)
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* @len: length to encode
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*
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* This routine can encode lengths up to 65535 using the ASN.1 rules.
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* It will accept a negative length and place a zero length tag
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* instead (to keep the ASN.1 valid). This convention allows other
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* encoder primitives to accept negative lengths as singalling the
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* sequence will be re-encoded when the length is known.
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*/
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static int asn1_encode_length(unsigned char **data, int *data_len, int len)
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{
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if (*data_len < 1)
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return -EINVAL;
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if (len < 0) {
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*((*data)++) = 0;
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(*data_len)--;
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return 0;
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}
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if (len <= 0x7f) {
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*((*data)++) = len;
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(*data_len)--;
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return 0;
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}
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if (*data_len < 2)
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return -EINVAL;
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if (len <= 0xff) {
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*((*data)++) = 0x81;
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*((*data)++) = len & 0xff;
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*data_len -= 2;
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return 0;
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}
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if (*data_len < 3)
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return -EINVAL;
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if (len <= 0xffff) {
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*((*data)++) = 0x82;
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*((*data)++) = (len >> 8) & 0xff;
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*((*data)++) = len & 0xff;
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*data_len -= 3;
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return 0;
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}
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if (WARN(len > 0xffffff, "ASN.1 length can't be > 0xffffff"))
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return -EINVAL;
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if (*data_len < 4)
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return -EINVAL;
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*((*data)++) = 0x83;
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*((*data)++) = (len >> 16) & 0xff;
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*((*data)++) = (len >> 8) & 0xff;
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*((*data)++) = len & 0xff;
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*data_len -= 4;
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return 0;
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}
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/**
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* asn1_encode_tag() - add a tag for optional or explicit value
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* @data: pointer to place tag at
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* @end_data: end of data pointer, points one beyond last usable byte in @data
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* @tag: tag to be placed
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* @string: the data to be tagged
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* @len: the length of the data to be tagged
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*
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* Note this currently only handles short form tags < 31.
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*
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* Standard usage is to pass in a @tag, @string and @length and the
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* @string will be ASN.1 encoded with @tag and placed into @data. If
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* the encoding would put data past @end_data then an error is
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* returned, otherwise a pointer to a position one beyond the encoding
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* is returned.
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*
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* To encode in place pass a NULL @string and -1 for @len and the
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* maximum allowable beginning and end of the data; all this will do
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* is add the current maximum length and update the data pointer to
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* the place where the tag contents should be placed is returned. The
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* data should be copied in by the calling routine which should then
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* repeat the prior statement but now with the known length. In order
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* to avoid having to keep both before and after pointers, the repeat
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* expects to be called with @data pointing to where the first encode
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* returned it and still NULL for @string but the real length in @len.
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*/
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unsigned char *
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asn1_encode_tag(unsigned char *data, const unsigned char *end_data,
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u32 tag, const unsigned char *string, int len)
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{
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int data_len = end_data - data;
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int ret;
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if (WARN(tag > 30, "ASN.1 tag can't be > 30"))
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return ERR_PTR(-EINVAL);
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if (!string && WARN(len > 127,
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"BUG: recode tag is too big (>127)"))
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return ERR_PTR(-EINVAL);
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if (IS_ERR(data))
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return data;
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if (!string && len > 0) {
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/*
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* we're recoding, so move back to the start of the
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* tag and install a dummy length because the real
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* data_len should be NULL
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*/
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data -= 2;
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data_len = 2;
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}
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if (data_len < 2)
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return ERR_PTR(-EINVAL);
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*(data++) = _tagn(CONT, CONS, tag);
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data_len--;
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ret = asn1_encode_length(&data, &data_len, len);
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if (ret < 0)
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return ERR_PTR(ret);
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if (!string)
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return data;
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if (data_len < len)
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return ERR_PTR(-EINVAL);
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memcpy(data, string, len);
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data += len;
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return data;
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}
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EXPORT_SYMBOL_GPL(asn1_encode_tag);
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/**
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* asn1_encode_octet_string() - encode an ASN.1 OCTET STRING
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* @data: pointer to encode at
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* @end_data: end of data pointer, points one beyond last usable byte in @data
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* @string: string to be encoded
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* @len: length of string
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*
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* Note ASN.1 octet strings may contain zeros, so the length is obligatory.
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*/
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unsigned char *
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asn1_encode_octet_string(unsigned char *data,
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const unsigned char *end_data,
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const unsigned char *string, u32 len)
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{
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int data_len = end_data - data;
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int ret;
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if (IS_ERR(data))
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return data;
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/* need minimum of 2 bytes for tag and length of zero length string */
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if (data_len < 2)
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return ERR_PTR(-EINVAL);
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*(data++) = _tag(UNIV, PRIM, OTS);
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data_len--;
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ret = asn1_encode_length(&data, &data_len, len);
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if (ret)
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return ERR_PTR(ret);
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if (data_len < len)
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return ERR_PTR(-EINVAL);
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memcpy(data, string, len);
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data += len;
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return data;
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}
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EXPORT_SYMBOL_GPL(asn1_encode_octet_string);
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/**
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* asn1_encode_sequence() - wrap a byte stream in an ASN.1 SEQUENCE
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* @data: pointer to encode at
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* @end_data: end of data pointer, points one beyond last usable byte in @data
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* @seq: data to be encoded as a sequence
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* @len: length of the data to be encoded as a sequence
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*
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* Fill in a sequence. To encode in place, pass NULL for @seq and -1
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* for @len; then call again once the length is known (still with NULL
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* for @seq). In order to avoid having to keep both before and after
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* pointers, the repeat expects to be called with @data pointing to
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* where the first encode placed it.
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*/
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unsigned char *
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asn1_encode_sequence(unsigned char *data, const unsigned char *end_data,
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const unsigned char *seq, int len)
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{
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int data_len = end_data - data;
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int ret;
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if (!seq && WARN(len > 127,
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"BUG: recode sequence is too big (>127)"))
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return ERR_PTR(-EINVAL);
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if (IS_ERR(data))
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return data;
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if (!seq && len >= 0) {
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/*
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* we're recoding, so move back to the start of the
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* sequence and install a dummy length because the
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* real length should be NULL
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*/
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data -= 2;
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data_len = 2;
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}
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if (data_len < 2)
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return ERR_PTR(-EINVAL);
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*(data++) = _tag(UNIV, CONS, SEQ);
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data_len--;
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ret = asn1_encode_length(&data, &data_len, len);
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if (ret)
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return ERR_PTR(ret);
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if (!seq)
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return data;
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if (data_len < len)
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return ERR_PTR(-EINVAL);
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memcpy(data, seq, len);
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data += len;
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return data;
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}
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EXPORT_SYMBOL_GPL(asn1_encode_sequence);
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/**
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* asn1_encode_boolean() - encode a boolean value to ASN.1
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* @data: pointer to encode at
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* @end_data: end of data pointer, points one beyond last usable byte in @data
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* @val: the boolean true/false value
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*/
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unsigned char *
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asn1_encode_boolean(unsigned char *data, const unsigned char *end_data,
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bool val)
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{
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int data_len = end_data - data;
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if (IS_ERR(data))
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return data;
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/* booleans are 3 bytes: tag, length == 1 and value == 0 or 1 */
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if (data_len < 3)
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return ERR_PTR(-EINVAL);
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*(data++) = _tag(UNIV, PRIM, BOOL);
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data_len--;
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asn1_encode_length(&data, &data_len, 1);
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if (val)
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*(data++) = 1;
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else
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*(data++) = 0;
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return data;
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}
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EXPORT_SYMBOL_GPL(asn1_encode_boolean);
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MODULE_LICENSE("GPL");
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