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mbedtls/library/asn1write.c
Werner Lewis e59a531455 Fix memcpy() UB in mbedtls_asn1_named_data() 
Removes a case in mbedtls_asn1_named_data() where memcpy() could be
called with a null pointer and zero length. A test case is added for
this code path, to catch the undefined behavior when running tests with
UBSan.

Signed-off-by: Werner Lewis <werner.lewis@arm.com>
2022-05-04 11:45:06 +01:00

481 lines
14 KiB
C
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/*
* ASN.1 buffer writing functionality
*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "common.h"
#if defined(MBEDTLS_ASN1_WRITE_C)
#include "mbedtls/asn1write.h"
#include "mbedtls/error.h"
#include <string.h>
#if defined(MBEDTLS_PLATFORM_C)
#include "mbedtls/platform.h"
#else
#include <stdlib.h>
#define mbedtls_calloc calloc
#define mbedtls_free free
#endif
int mbedtls_asn1_write_len( unsigned char **p, const unsigned char *start, size_t len )
{
if( len < 0x80 )
{
if( *p - start < 1 )
return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
*--(*p) = (unsigned char) len;
return( 1 );
}
if( len <= 0xFF )
{
if( *p - start < 2 )
return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
*--(*p) = (unsigned char) len;
*--(*p) = 0x81;
return( 2 );
}
if( len <= 0xFFFF )
{
if( *p - start < 3 )
return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
*--(*p) = MBEDTLS_BYTE_0( len );
*--(*p) = MBEDTLS_BYTE_1( len );
*--(*p) = 0x82;
return( 3 );
}
if( len <= 0xFFFFFF )
{
if( *p - start < 4 )
return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
*--(*p) = MBEDTLS_BYTE_0( len );
*--(*p) = MBEDTLS_BYTE_1( len );
*--(*p) = MBEDTLS_BYTE_2( len );
*--(*p) = 0x83;
return( 4 );
}
#if SIZE_MAX > 0xFFFFFFFF
if( len <= 0xFFFFFFFF )
#endif
{
if( *p - start < 5 )
return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
*--(*p) = MBEDTLS_BYTE_0( len );
*--(*p) = MBEDTLS_BYTE_1( len );
*--(*p) = MBEDTLS_BYTE_2( len );
*--(*p) = MBEDTLS_BYTE_3( len );
*--(*p) = 0x84;
return( 5 );
}
#if SIZE_MAX > 0xFFFFFFFF
return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
#endif
}
int mbedtls_asn1_write_tag( unsigned char **p, const unsigned char *start, unsigned char tag )
{
if( *p - start < 1 )
return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
*--(*p) = tag;
return( 1 );
}
int mbedtls_asn1_write_raw_buffer( unsigned char **p, const unsigned char *start,
const unsigned char *buf, size_t size )
{
size_t len = 0;
if( *p < start || (size_t)( *p - start ) < size )
return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
len = size;
(*p) -= len;
memcpy( *p, buf, len );
return( (int) len );
}
#if defined(MBEDTLS_BIGNUM_C)
int mbedtls_asn1_write_mpi( unsigned char **p, const unsigned char *start, const mbedtls_mpi *X )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t len = 0;
// Write the MPI
//
len = mbedtls_mpi_size( X );
if( *p < start || (size_t)( *p - start ) < len )
return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
(*p) -= len;
MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( X, *p, len ) );
// DER format assumes 2s complement for numbers, so the leftmost bit
// should be 0 for positive numbers and 1 for negative numbers.
//
if( X->s ==1 && **p & 0x80 )
{
if( *p - start < 1 )
return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
*--(*p) = 0x00;
len += 1;
}
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_INTEGER ) );
ret = (int) len;
cleanup:
return( ret );
}
#endif /* MBEDTLS_BIGNUM_C */
int mbedtls_asn1_write_null( unsigned char **p, const unsigned char *start )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t len = 0;
// Write NULL
//
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, 0) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_NULL ) );
return( (int) len );
}
int mbedtls_asn1_write_oid( unsigned char **p, const unsigned char *start,
const char *oid, size_t oid_len )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t len = 0;
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start,
(const unsigned char *) oid, oid_len ) );
MBEDTLS_ASN1_CHK_ADD( len , mbedtls_asn1_write_len( p, start, len ) );
MBEDTLS_ASN1_CHK_ADD( len , mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_OID ) );
return( (int) len );
}
int mbedtls_asn1_write_algorithm_identifier( unsigned char **p, const unsigned char *start,
const char *oid, size_t oid_len,
size_t par_len )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t len = 0;
if( par_len == 0 )
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_null( p, start ) );
else
len += par_len;
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_oid( p, start, oid, oid_len ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start,
MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) );
return( (int) len );
}
int mbedtls_asn1_write_bool( unsigned char **p, const unsigned char *start, int boolean )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t len = 0;
if( *p - start < 1 )
return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
*--(*p) = (boolean) ? 255 : 0;
len++;
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_BOOLEAN ) );
return( (int) len );
}
static int asn1_write_tagged_int( unsigned char **p, const unsigned char *start, int val, int tag )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t len = 0;
do
{
if( *p - start < 1 )
return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
len += 1;
*--(*p) = val & 0xff;
val >>= 8;
}
while( val > 0 );
if( **p & 0x80 )
{
if( *p - start < 1 )
return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
*--(*p) = 0x00;
len += 1;
}
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, tag ) );
return( (int) len );
}
int mbedtls_asn1_write_int( unsigned char **p, const unsigned char *start, int val )
{
return( asn1_write_tagged_int( p, start, val, MBEDTLS_ASN1_INTEGER ) );
}
int mbedtls_asn1_write_enum( unsigned char **p, const unsigned char *start, int val )
{
return( asn1_write_tagged_int( p, start, val, MBEDTLS_ASN1_ENUMERATED ) );
}
int mbedtls_asn1_write_tagged_string( unsigned char **p, const unsigned char *start, int tag,
const char *text, size_t text_len )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t len = 0;
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start,
(const unsigned char *) text, text_len ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, tag ) );
return( (int) len );
}
int mbedtls_asn1_write_utf8_string( unsigned char **p, const unsigned char *start,
const char *text, size_t text_len )
{
return( mbedtls_asn1_write_tagged_string(p, start, MBEDTLS_ASN1_UTF8_STRING, text, text_len) );
}
int mbedtls_asn1_write_printable_string( unsigned char **p, const unsigned char *start,
const char *text, size_t text_len )
{
return( mbedtls_asn1_write_tagged_string(p, start, MBEDTLS_ASN1_PRINTABLE_STRING, text, text_len) );
}
int mbedtls_asn1_write_ia5_string( unsigned char **p, const unsigned char *start,
const char *text, size_t text_len )
{
return( mbedtls_asn1_write_tagged_string(p, start, MBEDTLS_ASN1_IA5_STRING, text, text_len) );
}
int mbedtls_asn1_write_named_bitstring( unsigned char **p,
const unsigned char *start,
const unsigned char *buf,
size_t bits )
{
size_t unused_bits, byte_len;
const unsigned char *cur_byte;
unsigned char cur_byte_shifted;
unsigned char bit;
byte_len = ( bits + 7 ) / 8;
unused_bits = ( byte_len * 8 ) - bits;
/*
* Named bitstrings require that trailing 0s are excluded in the encoding
* of the bitstring. Trailing 0s are considered part of the 'unused' bits
* when encoding this value in the first content octet
*/
if( bits != 0 )
{
cur_byte = buf + byte_len - 1;
cur_byte_shifted = *cur_byte >> unused_bits;
for( ; ; )
{
bit = cur_byte_shifted & 0x1;
cur_byte_shifted >>= 1;
if( bit != 0 )
break;
bits--;
if( bits == 0 )
break;
if( bits % 8 == 0 )
cur_byte_shifted = *--cur_byte;
}
}
return( mbedtls_asn1_write_bitstring( p, start, buf, bits ) );
}
int mbedtls_asn1_write_bitstring( unsigned char **p, const unsigned char *start,
const unsigned char *buf, size_t bits )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t len = 0;
size_t unused_bits, byte_len;
byte_len = ( bits + 7 ) / 8;
unused_bits = ( byte_len * 8 ) - bits;
if( *p < start || (size_t)( *p - start ) < byte_len + 1 )
return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
len = byte_len + 1;
/* Write the bitstring. Ensure the unused bits are zeroed */
if( byte_len > 0 )
{
byte_len--;
*--( *p ) = buf[byte_len] & ~( ( 0x1 << unused_bits ) - 1 );
( *p ) -= byte_len;
memcpy( *p, buf, byte_len );
}
/* Write unused bits */
*--( *p ) = (unsigned char)unused_bits;
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_BIT_STRING ) );
return( (int) len );
}
int mbedtls_asn1_write_octet_string( unsigned char **p, const unsigned char *start,
const unsigned char *buf, size_t size )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
size_t len = 0;
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start, buf, size ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_OCTET_STRING ) );
return( (int) len );
}
/* This is a copy of the ASN.1 parsing function mbedtls_asn1_find_named_data(),
* which is replicated to avoid a dependency ASN1_WRITE_C on ASN1_PARSE_C. */
static mbedtls_asn1_named_data *asn1_find_named_data(
mbedtls_asn1_named_data *list,
const char *oid, size_t len )
{
while( list != NULL )
{
if( list->oid.len == len &&
memcmp( list->oid.p, oid, len ) == 0 )
{
break;
}
list = list->next;
}
return( list );
}
mbedtls_asn1_named_data *mbedtls_asn1_store_named_data(
mbedtls_asn1_named_data **head,
const char *oid, size_t oid_len,
const unsigned char *val,
size_t val_len )
{
mbedtls_asn1_named_data *cur;
if( ( cur = asn1_find_named_data( *head, oid, oid_len ) ) == NULL )
{
// Add new entry if not present yet based on OID
//
cur = (mbedtls_asn1_named_data*)mbedtls_calloc( 1,
sizeof(mbedtls_asn1_named_data) );
if( cur == NULL )
return( NULL );
cur->oid.len = oid_len;
cur->oid.p = mbedtls_calloc( 1, oid_len );
if( cur->oid.p == NULL )
{
mbedtls_free( cur );
return( NULL );
}
memcpy( cur->oid.p, oid, oid_len );
cur->val.len = val_len;
if( val_len != 0 )
{
cur->val.p = mbedtls_calloc( 1, val_len );
if( cur->val.p == NULL )
{
mbedtls_free( cur->oid.p );
mbedtls_free( cur );
return( NULL );
}
}
cur->next = *head;
*head = cur;
}
else if( val_len == 0 )
{
mbedtls_free( cur->val.p );
cur->val.p = NULL;
}
else if( cur->val.len != val_len )
{
/*
* Enlarge existing value buffer if needed
* Preserve old data until the allocation succeeded, to leave list in
* a consistent state in case allocation fails.
*/
void *p = mbedtls_calloc( 1, val_len );
if( p == NULL )
return( NULL );
mbedtls_free( cur->val.p );
cur->val.p = p;
cur->val.len = val_len;
}
if( val != NULL && val_len != 0 )
memcpy( cur->val.p, val, val_len );
return( cur );
}
#endif /* MBEDTLS_ASN1_WRITE_C */
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