asn1write.c

00001 /*
00002  * ASN.1 buffer writing functionality
00003  *
00004  *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
00005  *  SPDX-License-Identifier: Apache-2.0
00006  *
00007  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
00008  *  not use this file except in compliance with the License.
00009  *  You may obtain a copy of the License at
00010  *
00011  *  http://www.apache.org/licenses/LICENSE-2.0
00012  *
00013  *  Unless required by applicable law or agreed to in writing, software
00014  *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
00015  *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00016  *  See the License for the specific language governing permissions and
00017  *  limitations under the License.
00018  *
00019  *  This file is part of mbed TLS (https://tls.mbed.org)
00020  */
00021 
00022 #if !defined(MBEDTLS_CONFIG_FILE)
00023 #include "mbedtls/config.h"
00024 #else
00025 #include MBEDTLS_CONFIG_FILE
00026 #endif
00027 
00028 #if defined(MBEDTLS_ASN1_WRITE_C)
00029 
00030 #include "mbedtls/asn1write.h"
00031 
00032 #include <string.h>
00033 
00034 #if defined(MBEDTLS_PLATFORM_C)
00035 #include "mbedtls/platform.h"
00036 #else
00037 #include <stdlib.h>
00038 #define mbedtls_calloc    calloc
00039 #define mbedtls_free       free
00040 #endif
00041 
00042 int mbedtls_asn1_write_len( unsigned char **p, unsigned char *start, size_t len )
00043 {
00044     if( len < 0x80 )
00045     {
00046         if( *p - start < 1 )
00047             return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00048 
00049         *--(*p) = (unsigned char) len;
00050         return( 1 );
00051     }
00052 
00053     if( len <= 0xFF )
00054     {
00055         if( *p - start < 2 )
00056             return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00057 
00058         *--(*p) = (unsigned char) len;
00059         *--(*p) = 0x81;
00060         return( 2 );
00061     }
00062 
00063     if( *p - start < 3 )
00064         return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00065 
00066     // We assume we never have lengths larger than 65535 bytes
00067     //
00068     *--(*p) = len % 256;
00069     *--(*p) = ( len / 256 ) % 256;
00070     *--(*p) = 0x82;
00071 
00072     return( 3 );
00073 }
00074 
00075 int mbedtls_asn1_write_tag( unsigned char **p, unsigned char *start, unsigned char tag )
00076 {
00077     if( *p - start < 1 )
00078         return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00079 
00080     *--(*p) = tag;
00081 
00082     return( 1 );
00083 }
00084 
00085 int mbedtls_asn1_write_raw_buffer( unsigned char **p, unsigned char *start,
00086                            const unsigned char *buf, size_t size )
00087 {
00088     size_t len = 0;
00089 
00090     if( *p < start || (size_t)( *p - start ) < size )
00091         return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00092 
00093     len = size;
00094     (*p) -= len;
00095     memcpy( *p, buf, len );
00096 
00097     return( (int) len );
00098 }
00099 
00100 #if defined(MBEDTLS_BIGNUM_C)
00101 int mbedtls_asn1_write_mpi( unsigned char **p, unsigned char *start, const mbedtls_mpi *X )
00102 {
00103     int ret;
00104     size_t len = 0;
00105 
00106     // Write the MPI
00107     //
00108     len = mbedtls_mpi_size( X );
00109 
00110     if( *p < start || (size_t)( *p - start ) < len )
00111         return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00112 
00113     (*p) -= len;
00114     MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( X, *p, len ) );
00115 
00116     // DER format assumes 2s complement for numbers, so the leftmost bit
00117     // should be 0 for positive numbers and 1 for negative numbers.
00118     //
00119     if( X->s  ==1 && **p & 0x80 )
00120     {
00121         if( *p - start < 1 )
00122             return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00123 
00124         *--(*p) = 0x00;
00125         len += 1;
00126     }
00127 
00128     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
00129     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_INTEGER ) );
00130 
00131     ret = (int) len;
00132 
00133 cleanup:
00134     return( ret );
00135 }
00136 #endif /* MBEDTLS_BIGNUM_C */
00137 
00138 int mbedtls_asn1_write_null( unsigned char **p, unsigned char *start )
00139 {
00140     int ret;
00141     size_t len = 0;
00142 
00143     // Write NULL
00144     //
00145     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, 0) );
00146     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_NULL ) );
00147 
00148     return( (int) len );
00149 }
00150 
00151 int mbedtls_asn1_write_oid( unsigned char **p, unsigned char *start,
00152                     const char *oid, size_t oid_len )
00153 {
00154     int ret;
00155     size_t len = 0;
00156 
00157     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start,
00158                                   (const unsigned char *) oid, oid_len ) );
00159     MBEDTLS_ASN1_CHK_ADD( len , mbedtls_asn1_write_len( p, start, len ) );
00160     MBEDTLS_ASN1_CHK_ADD( len , mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_OID ) );
00161 
00162     return( (int) len );
00163 }
00164 
00165 int mbedtls_asn1_write_algorithm_identifier( unsigned char **p, unsigned char *start,
00166                                      const char *oid, size_t oid_len,
00167                                      size_t par_len )
00168 {
00169     int ret;
00170     size_t len = 0;
00171 
00172     if( par_len == 0 )
00173         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_null( p, start ) );
00174     else
00175         len += par_len;
00176 
00177     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_oid( p, start, oid, oid_len ) );
00178 
00179     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
00180     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start,
00181                                        MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) );
00182 
00183     return( (int) len );
00184 }
00185 
00186 int mbedtls_asn1_write_bool( unsigned char **p, unsigned char *start, int boolean )
00187 {
00188     int ret;
00189     size_t len = 0;
00190 
00191     if( *p - start < 1 )
00192         return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00193 
00194     *--(*p) = (boolean) ? 255 : 0;
00195     len++;
00196 
00197     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
00198     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_BOOLEAN ) );
00199 
00200     return( (int) len );
00201 }
00202 
00203 int mbedtls_asn1_write_int( unsigned char **p, unsigned char *start, int val )
00204 {
00205     int ret;
00206     size_t len = 0;
00207 
00208     // TODO negative values and values larger than 128
00209     // DER format assumes 2s complement for numbers, so the leftmost bit
00210     // should be 0 for positive numbers and 1 for negative numbers.
00211     //
00212     if( *p - start < 1 )
00213         return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00214 
00215     len += 1;
00216     *--(*p) = val;
00217 
00218     if( val > 0 && **p & 0x80 )
00219     {
00220         if( *p - start < 1 )
00221             return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00222 
00223         *--(*p) = 0x00;
00224         len += 1;
00225     }
00226 
00227     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
00228     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_INTEGER ) );
00229 
00230     return( (int) len );
00231 }
00232 
00233 int mbedtls_asn1_write_printable_string( unsigned char **p, unsigned char *start,
00234                                  const char *text, size_t text_len )
00235 {
00236     int ret;
00237     size_t len = 0;
00238 
00239     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start,
00240                   (const unsigned char *) text, text_len ) );
00241 
00242     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
00243     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_PRINTABLE_STRING ) );
00244 
00245     return( (int) len );
00246 }
00247 
00248 int mbedtls_asn1_write_ia5_string( unsigned char **p, unsigned char *start,
00249                            const char *text, size_t text_len )
00250 {
00251     int ret;
00252     size_t len = 0;
00253 
00254     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start,
00255                   (const unsigned char *) text, text_len ) );
00256 
00257     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
00258     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_IA5_STRING ) );
00259 
00260     return( (int) len );
00261 }
00262 
00263 int mbedtls_asn1_write_bitstring( unsigned char **p, unsigned char *start,
00264                           const unsigned char *buf, size_t bits )
00265 {
00266     int ret;
00267     size_t len = 0, size;
00268 
00269     size = ( bits / 8 ) + ( ( bits % 8 ) ? 1 : 0 );
00270 
00271     // Calculate byte length
00272     //
00273     if( *p < start || (size_t)( *p - start ) < size + 1 )
00274         return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00275 
00276     len = size + 1;
00277     (*p) -= size;
00278     memcpy( *p, buf, size );
00279 
00280     // Write unused bits
00281     //
00282     *--(*p) = (unsigned char) (size * 8 - bits);
00283 
00284     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
00285     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_BIT_STRING ) );
00286 
00287     return( (int) len );
00288 }
00289 
00290 int mbedtls_asn1_write_octet_string( unsigned char **p, unsigned char *start,
00291                              const unsigned char *buf, size_t size )
00292 {
00293     int ret;
00294     size_t len = 0;
00295 
00296     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start, buf, size ) );
00297 
00298     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
00299     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_OCTET_STRING ) );
00300 
00301     return( (int) len );
00302 }
00303 
00304 mbedtls_asn1_named_data *mbedtls_asn1_store_named_data( mbedtls_asn1_named_data **head,
00305                                         const char *oid, size_t oid_len,
00306                                         const unsigned char *val,
00307                                         size_t val_len )
00308 {
00309     mbedtls_asn1_named_data *cur;
00310 
00311     if( ( cur = mbedtls_asn1_find_named_data( *head, oid, oid_len ) ) == NULL )
00312     {
00313         // Add new entry if not present yet based on OID
00314         //
00315         if( ( cur = mbedtls_calloc( 1, sizeof(mbedtls_asn1_named_data) ) ) == NULL )
00316             return( NULL );
00317 
00318         cur->oid.len = oid_len;
00319         cur->oid.p = mbedtls_calloc( 1, oid_len );
00320         if( cur->oid.p == NULL )
00321         {
00322             mbedtls_free( cur );
00323             return( NULL );
00324         }
00325 
00326         memcpy( cur->oid.p, oid, oid_len );
00327 
00328         cur->val.len = val_len;
00329         cur->val.p = mbedtls_calloc( 1, val_len );
00330         if( cur->val.p == NULL )
00331         {
00332             mbedtls_free( cur->oid.p );
00333             mbedtls_free( cur );
00334             return( NULL );
00335         }
00336 
00337         cur->next = *head;
00338         *head = cur;
00339     }
00340     else if( cur->val.len < val_len )
00341     {
00342         // Enlarge existing value buffer if needed
00343         //
00344         mbedtls_free( cur->val.p );
00345         cur->val.p = NULL;
00346 
00347         cur->val.len = val_len;
00348         cur->val.p = mbedtls_calloc( 1, val_len );
00349         if( cur->val.p == NULL )
00350         {
00351             mbedtls_free( cur->oid.p );
00352             mbedtls_free( cur );
00353             return( NULL );
00354         }
00355     }
00356 
00357     if( val != NULL )
00358         memcpy( cur->val.p, val, val_len );
00359 
00360     return( cur );
00361 }
00362 #endif /* MBEDTLS_ASN1_WRITE_C */