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/* asn1.c --- Wrapper around pseudo-ASN.1 token format.
* Copyright (C) 2003-2022 Simon Josefsson
*
* This file is part of the GNU Generic Security Service Library.
*
* This file is free software: you can redistribute it and/or modify
* it under the terms of either:
*
* * the GNU Lesser General Public License as published by the Free
* Software Foundation; either version 3 of the License, or (at
* your option) any later version.
*
* or
*
* * the GNU General Public License as published by the Free Software
* Foundation; either version 2 of the License, or (at your option)
* any later version.
*
* or both in parallel, as here.
*
* This file is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received copies of the GNU General Public License
* and the GNU Lesser General Public License along with this file. If
* not, see <http://www.gnu.org/licenses/>.
*
*/
#include "internal.h"
/*
* The following two functions borrowed from libtasn.1, under LGPL.
* Copyright (C) 2002 Fabio Fiorina.
*/
static void
_gss_asn1_length_der (size_t len, unsigned char *ans, size_t *ans_len)
{
size_t k;
unsigned char temp[sizeof (len)];
if (len < 128)
{
if (ans != NULL)
ans[0] = (unsigned char) len;
*ans_len = 1;
}
else
{
k = 0;
while (len)
{
temp[k++] = len & 0xFF;
len = len >> 8;
}
*ans_len = k + 1;
if (ans != NULL)
{
ans[0] = ((unsigned char) k & 0x7F) + 128;
while (k--)
ans[*ans_len - 1 - k] = temp[k];
}
}
}
static size_t
_gss_asn1_get_length_der (const char *der, size_t der_len, size_t *len)
{
size_t ans;
size_t k, punt;
*len = 0;
if (der_len <= 0)
return 0;
if (!(der[0] & 128))
{
/* short form */
*len = 1;
return (unsigned char) der[0];
}
else
{
/* Long form */
k = (unsigned char) der[0] & 0x7F;
punt = 1;
if (k)
{ /* definite length method */
ans = 0;
while (punt <= k && punt < der_len)
{
size_t last = ans;
ans = ans * 256 + (unsigned char) der[punt++];
if (ans < last)
/* we wrapped around, no bignum support... */
return -2;
}
}
else
{ /* indefinite length method */
ans = -1;
}
*len = punt;
return ans;
}
}
OM_uint32
_gss_encapsulate_token_prefix (const char *prefix, size_t prefixlen,
const char *in, size_t inlen,
const char *oid, OM_uint32 oidlen,
void **out, size_t *outlen)
{
size_t oidlenlen;
size_t asn1len, asn1lenlen;
unsigned char *p;
if (prefix == NULL)
prefixlen = 0;
_gss_asn1_length_der (oidlen, NULL, &oidlenlen);
asn1len = 1 + oidlenlen + oidlen + prefixlen + inlen;
_gss_asn1_length_der (asn1len, NULL, &asn1lenlen);
*outlen = 1 + asn1lenlen + asn1len;
p = *out = malloc (*outlen);
if (!p)
return -1;
*p++ = '\x60';
_gss_asn1_length_der (asn1len, p, &asn1lenlen);
p += asn1lenlen;
*p++ = '\x06';
_gss_asn1_length_der (oidlen, p, &oidlenlen);
p += oidlenlen;
memcpy (p, oid, oidlen);
p += oidlen;
if (prefixlen > 0)
{
memcpy (p, prefix, prefixlen);
p += prefixlen;
}
memcpy (p, in, inlen);
return 0;
}
/**
* gss_encapsulate_token:
* @input_token: (buffer, opaque, read) Buffer with GSS-API context token data.
* @token_oid: (Object ID, read) Object identifier of token.
* @output_token: (buffer, opaque, modify) Encapsulated token data;
* caller must release with gss_release_buffer().
*
* Add the mechanism-independent token header to GSS-API context token
* data. This is used for the initial token of a GSS-API context
* establishment sequence. It incorporates an identifier of the
* mechanism type to be used on that context, and enables tokens to be
* interpreted unambiguously at GSS-API peers. See further section
* 3.1 of RFC 2743. This function is standardized in RFC 6339.
*
* Returns:
*
* `GSS_S_COMPLETE`: Indicates successful completion, and that output
* parameters holds correct information.
*
* `GSS_S_FAILURE`: Indicates that encapsulation failed for reasons
* unspecified at the GSS-API level.
**/
extern OM_uint32
gss_encapsulate_token (gss_const_buffer_t input_token,
gss_const_OID token_oid, gss_buffer_t output_token)
{
int rc;
if (!input_token)
return GSS_S_CALL_INACCESSIBLE_READ;
if (!token_oid)
return GSS_S_CALL_INACCESSIBLE_READ;
if (!output_token)
return GSS_S_CALL_INACCESSIBLE_WRITE;
rc = _gss_encapsulate_token_prefix (NULL, 0,
input_token->value,
input_token->length,
token_oid->elements,
token_oid->length,
&output_token->value,
&output_token->length);
if (rc != 0)
return GSS_S_FAILURE;
return GSS_S_COMPLETE;
}
int
_gss_decapsulate_token (const char *in, size_t inlen,
char **oid, size_t *oidlen,
char **out, size_t *outlen)
{
size_t i;
size_t asn1lenlen;
if (inlen-- == 0)
return -1;
if (*in++ != '\x60')
return -1;
i = inlen;
asn1lenlen = _gss_asn1_get_length_der (in, inlen, &i);
if (inlen < i)
return -1;
inlen -= i;
in += i;
if (inlen != asn1lenlen)
return -1;
if (inlen-- == 0)
return -1;
if (*in++ != '\x06')
return -1;
i = inlen;
asn1lenlen = _gss_asn1_get_length_der (in, inlen, &i);
if (inlen < i)
return -1;
inlen -= i;
in += i;
if (inlen < asn1lenlen)
return -1;
*oidlen = asn1lenlen;
*oid = (char *) in;
inlen -= asn1lenlen;
in += asn1lenlen;
if (outlen)
*outlen = inlen;
if (out)
*out = (char *) in;
return 0;
}
/**
* gss_decapsulate_token:
* @input_token: (buffer, opaque, read) Buffer with GSS-API context token.
* @token_oid: (Object ID, read) Expected object identifier of token.
* @output_token: (buffer, opaque, modify) Decapsulated token data;
* caller must release with gss_release_buffer().
*
* Remove the mechanism-independent token header from an initial
* GSS-API context token. Unwrap a buffer in the
* mechanism-independent token format. This is the reverse of
* gss_encapsulate_token(). The translation is loss-less, all data is
* preserved as is. This function is standardized in RFC 6339.
*
* Return value:
*
* `GSS_S_COMPLETE`: Indicates successful completion, and that output
* parameters holds correct information.
*
* `GSS_S_DEFECTIVE_TOKEN`: Means that the token failed consistency
* checks (e.g., OID mismatch or ASN.1 DER length errors).
*
* `GSS_S_FAILURE`: Indicates that decapsulation failed for reasons
* unspecified at the GSS-API level.
**/
OM_uint32
gss_decapsulate_token (gss_const_buffer_t input_token,
gss_const_OID token_oid, gss_buffer_t output_token)
{
gss_OID_desc tmpoid;
char *oid = NULL, *out = NULL;
size_t oidlen = 0, outlen = 0;
if (!input_token)
return GSS_S_CALL_INACCESSIBLE_READ;
if (!token_oid)
return GSS_S_CALL_INACCESSIBLE_READ;
if (!output_token)
return GSS_S_CALL_INACCESSIBLE_WRITE;
if (_gss_decapsulate_token ((char *) input_token->value,
input_token->length,
&oid, &oidlen, &out, &outlen) != 0)
return GSS_S_DEFECTIVE_TOKEN;
tmpoid.length = oidlen;
tmpoid.elements = oid;
if (!gss_oid_equal (token_oid, &tmpoid))
return GSS_S_DEFECTIVE_TOKEN;
output_token->length = outlen;
output_token->value = malloc (outlen);
if (!output_token->value)
return GSS_S_FAILURE;
memcpy (output_token->value, out, outlen);
return GSS_S_COMPLETE;
}
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