/* * 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, 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, 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, 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, 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 ); /* DER represents 0 with a sign bit (0=nonnegative) and 7 value bits, not * as 0 digits. We need to end up with 020100, not with 0200. */ if( len == 0 ) len = 1; 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, 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, 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, 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, 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, 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, unsigned char *start, int val ) { return( asn1_write_tagged_int( p, start, val, MBEDTLS_ASN1_INTEGER ) ); } int mbedtls_asn1_write_enum( unsigned char **p, 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, 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, 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, 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, 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, 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, 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, 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 */