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( len <= 0xFFFF )
00064     {
00065         if( *p - start < 3 )
00066             return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00067 
00068         *--(*p) = ( len       ) & 0xFF;
00069         *--(*p) = ( len >>  8 ) & 0xFF;
00070         *--(*p) = 0x82;
00071         return( 3 );
00072     }
00073 
00074     if( len <= 0xFFFFFF )
00075     {
00076         if( *p - start < 4 )
00077             return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00078 
00079         *--(*p) = ( len       ) & 0xFF;
00080         *--(*p) = ( len >>  8 ) & 0xFF;
00081         *--(*p) = ( len >> 16 ) & 0xFF;
00082         *--(*p) = 0x83;
00083         return( 4 );
00084     }
00085 
00086     if( len <= 0xFFFFFFFF )
00087     {
00088         if( *p - start < 5 )
00089             return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00090 
00091         *--(*p) = ( len       ) & 0xFF;
00092         *--(*p) = ( len >>  8 ) & 0xFF;
00093         *--(*p) = ( len >> 16 ) & 0xFF;
00094         *--(*p) = ( len >> 24 ) & 0xFF;
00095         *--(*p) = 0x84;
00096         return( 5 );
00097     }
00098 
00099     return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
00100 }
00101 
00102 int mbedtls_asn1_write_tag( unsigned char **p, unsigned char *start, unsigned char tag )
00103 {
00104     if( *p - start < 1 )
00105         return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00106 
00107     *--(*p) = tag;
00108 
00109     return( 1 );
00110 }
00111 
00112 int mbedtls_asn1_write_raw_buffer( unsigned char **p, unsigned char *start,
00113                            const unsigned char *buf, size_t size )
00114 {
00115     size_t len = 0;
00116 
00117     if( *p < start || (size_t)( *p - start ) < size )
00118         return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00119 
00120     len = size;
00121     (*p) -= len;
00122     memcpy( *p, buf, len );
00123 
00124     return( (int) len );
00125 }
00126 
00127 #if defined(MBEDTLS_BIGNUM_C)
00128 int mbedtls_asn1_write_mpi( unsigned char **p, unsigned char *start, const mbedtls_mpi *X )
00129 {
00130     int ret;
00131     size_t len = 0;
00132 
00133     // Write the MPI
00134     //
00135     len = mbedtls_mpi_size( X );
00136 
00137     if( *p < start || (size_t)( *p - start ) < len )
00138         return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00139 
00140     (*p) -= len;
00141     MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( X, *p, len ) );
00142 
00143     // DER format assumes 2s complement for numbers, so the leftmost bit
00144     // should be 0 for positive numbers and 1 for negative numbers.
00145     //
00146     if( X->s  ==1 && **p & 0x80 )
00147     {
00148         if( *p - start < 1 )
00149             return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00150 
00151         *--(*p) = 0x00;
00152         len += 1;
00153     }
00154 
00155     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
00156     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_INTEGER ) );
00157 
00158     ret = (int) len;
00159 
00160 cleanup:
00161     return( ret );
00162 }
00163 #endif /* MBEDTLS_BIGNUM_C */
00164 
00165 int mbedtls_asn1_write_null( unsigned char **p, unsigned char *start )
00166 {
00167     int ret;
00168     size_t len = 0;
00169 
00170     // Write NULL
00171     //
00172     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, 0) );
00173     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_NULL ) );
00174 
00175     return( (int) len );
00176 }
00177 
00178 int mbedtls_asn1_write_oid( unsigned char **p, unsigned char *start,
00179                     const char *oid, size_t oid_len )
00180 {
00181     int ret;
00182     size_t len = 0;
00183 
00184     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start,
00185                                   (const unsigned char *) oid, oid_len ) );
00186     MBEDTLS_ASN1_CHK_ADD( len , mbedtls_asn1_write_len( p, start, len ) );
00187     MBEDTLS_ASN1_CHK_ADD( len , mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_OID ) );
00188 
00189     return( (int) len );
00190 }
00191 
00192 int mbedtls_asn1_write_algorithm_identifier( unsigned char **p, unsigned char *start,
00193                                      const char *oid, size_t oid_len,
00194                                      size_t par_len )
00195 {
00196     int ret;
00197     size_t len = 0;
00198 
00199     if( par_len == 0 )
00200         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_null( p, start ) );
00201     else
00202         len += par_len;
00203 
00204     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_oid( p, start, oid, oid_len ) );
00205 
00206     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
00207     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start,
00208                                        MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) );
00209 
00210     return( (int) len );
00211 }
00212 
00213 int mbedtls_asn1_write_bool( unsigned char **p, unsigned char *start, int boolean )
00214 {
00215     int ret;
00216     size_t len = 0;
00217 
00218     if( *p - start < 1 )
00219         return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00220 
00221     *--(*p) = (boolean) ? 255 : 0;
00222     len++;
00223 
00224     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
00225     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_BOOLEAN ) );
00226 
00227     return( (int) len );
00228 }
00229 
00230 int mbedtls_asn1_write_int( unsigned char **p, unsigned char *start, int val )
00231 {
00232     int ret;
00233     size_t len = 0;
00234 
00235     if( *p - start < 1 )
00236         return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00237 
00238     len += 1;
00239     *--(*p) = val;
00240 
00241     if( val > 0 && **p & 0x80 )
00242     {
00243         if( *p - start < 1 )
00244             return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00245 
00246         *--(*p) = 0x00;
00247         len += 1;
00248     }
00249 
00250     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
00251     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_INTEGER ) );
00252 
00253     return( (int) len );
00254 }
00255 
00256 int mbedtls_asn1_write_printable_string( unsigned char **p, unsigned char *start,
00257                                  const char *text, size_t text_len )
00258 {
00259     int ret;
00260     size_t len = 0;
00261 
00262     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start,
00263                   (const unsigned char *) text, text_len ) );
00264 
00265     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
00266     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_PRINTABLE_STRING ) );
00267 
00268     return( (int) len );
00269 }
00270 
00271 int mbedtls_asn1_write_ia5_string( unsigned char **p, unsigned char *start,
00272                            const char *text, size_t text_len )
00273 {
00274     int ret;
00275     size_t len = 0;
00276 
00277     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start,
00278                   (const unsigned char *) text, text_len ) );
00279 
00280     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
00281     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_IA5_STRING ) );
00282 
00283     return( (int) len );
00284 }
00285 
00286 int mbedtls_asn1_write_bitstring( unsigned char **p, unsigned char *start,
00287                           const unsigned char *buf, size_t bits )
00288 {
00289     int ret;
00290     size_t len = 0, size;
00291 
00292     size = ( bits / 8 ) + ( ( bits % 8 ) ? 1 : 0 );
00293 
00294     // Calculate byte length
00295     //
00296     if( *p < start || (size_t)( *p - start ) < size + 1 )
00297         return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00298 
00299     len = size + 1;
00300     (*p) -= size;
00301     memcpy( *p, buf, size );
00302 
00303     // Write unused bits
00304     //
00305     *--(*p) = (unsigned char) (size * 8 - bits);
00306 
00307     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
00308     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_BIT_STRING ) );
00309 
00310     return( (int) len );
00311 }
00312 
00313 int mbedtls_asn1_write_octet_string( unsigned char **p, unsigned char *start,
00314                              const unsigned char *buf, size_t size )
00315 {
00316     int ret;
00317     size_t len = 0;
00318 
00319     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start, buf, size ) );
00320 
00321     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
00322     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_OCTET_STRING ) );
00323 
00324     return( (int) len );
00325 }
00326 
00327 mbedtls_asn1_named_data *mbedtls_asn1_store_named_data( mbedtls_asn1_named_data **head,
00328                                         const char *oid, size_t oid_len,
00329                                         const unsigned char *val,
00330                                         size_t val_len )
00331 {
00332     mbedtls_asn1_named_data *cur;
00333 
00334     if( ( cur = mbedtls_asn1_find_named_data( *head, oid, oid_len ) ) == NULL )
00335     {
00336         // Add new entry if not present yet based on OID
00337         //
00338         cur = (mbedtls_asn1_named_data*)mbedtls_calloc( 1,
00339                                             sizeof(mbedtls_asn1_named_data) );
00340         if( cur == NULL )
00341             return( NULL );
00342 
00343         cur->oid.len = oid_len;
00344         cur->oid.p = mbedtls_calloc( 1, oid_len );
00345         if( cur->oid.p == NULL )
00346         {
00347             mbedtls_free( cur );
00348             return( NULL );
00349         }
00350 
00351         memcpy( cur->oid.p, oid, oid_len );
00352 
00353         cur->val.len = val_len;
00354         cur->val.p = mbedtls_calloc( 1, val_len );
00355         if( cur->val.p == NULL )
00356         {
00357             mbedtls_free( cur->oid.p );
00358             mbedtls_free( cur );
00359             return( NULL );
00360         }
00361 
00362         cur->next = *head;
00363         *head = cur;
00364     }
00365     else if( cur->val.len < val_len )
00366     {
00367         /*
00368          * Enlarge existing value buffer if needed
00369          * Preserve old data until the allocation succeeded, to leave list in
00370          * a consistent state in case allocation fails.
00371          */
00372         void *p = mbedtls_calloc( 1, val_len );
00373         if( p == NULL )
00374             return( NULL );
00375 
00376         mbedtls_free( cur->val.p );
00377         cur->val.p = p;
00378         cur->val.len = val_len;
00379     }
00380 
00381     if( val != NULL )
00382         memcpy( cur->val.p, val, val_len );
00383 
00384     return( cur );
00385 }
00386 #endif /* MBEDTLS_ASN1_WRITE_C */