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Move mbedtls_ct_base64_enc_char function to the constant-time module

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Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
This commit is contained in:
Gabor Mezei 2021-11-15 16:18:54 +01:00
parent 28d611559e
commit 9a4074aa1e
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GPG Key ID: 106F5A41ECC305BD
3 changed files with 29 additions and 19 deletions
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20
library/base64.c
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@ -23,6 +23,7 @@
#include "mbedtls/base64.h"
#include "base64_invasive.h"
#include "constant_time_internal.h"
#include <stdint.h>
@ -38,25 +39,6 @@
#define BASE64_SIZE_T_MAX ( (size_t) -1 ) /* SIZE_T_MAX is not standard */
/* Given a value in the range 0..63, return the corresponding Base64 digit.
* The implementation assumes that letters are consecutive (e.g. ASCII
* but not EBCDIC).
*/
MBEDTLS_STATIC_TESTABLE
unsigned char mbedtls_ct_base64_enc_char( unsigned char val )
{
unsigned char digit = 0;
/* For each range of values, if val is in that range, mask digit with
* the corresponding value. Since val can only be in a single range,
* only at most one masking will change digit. */
digit |= mbedtls_ct_uchar_mask_of_range( 0, 25, val ) & ( 'A' + val );
digit |= mbedtls_ct_uchar_mask_of_range( 26, 51, val ) & ( 'a' + val - 26 );
digit |= mbedtls_ct_uchar_mask_of_range( 52, 61, val ) & ( '0' + val - 52 );
digit |= mbedtls_ct_uchar_mask_of_range( 62, 62, val ) & '+';
digit |= mbedtls_ct_uchar_mask_of_range( 63, 63, val ) & '/';
return( digit );
}
/*
* Encode a buffer into base64 format
*/

22
library/constant_time.c
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@ -324,6 +324,28 @@ void mbedtls_ct_mpi_uint_cond_assign( size_t n,
#endif /* MBEDTLS_BIGNUM_C */
#if defined(MBEDTLS_BASE64_C)
/* Given a value in the range 0..63, return the corresponding Base64 digit.
* The implementation assumes that letters are consecutive (e.g. ASCII
* but not EBCDIC).
*/
unsigned char mbedtls_ct_base64_enc_char( unsigned char val )
{
unsigned char digit = 0;
/* For each range of values, if val is in that range, mask digit with
* the corresponding value. Since val can only be in a single range,
* only at most one masking will change digit. */
digit |= mbedtls_ct_uchar_mask_of_range( 0, 25, val ) & ( 'A' + val );
digit |= mbedtls_ct_uchar_mask_of_range( 26, 51, val ) & ( 'a' + val - 26 );
digit |= mbedtls_ct_uchar_mask_of_range( 52, 61, val ) & ( '0' + val - 52 );
digit |= mbedtls_ct_uchar_mask_of_range( 62, 62, val ) & '+';
digit |= mbedtls_ct_uchar_mask_of_range( 63, 63, val ) & '/';
return( digit );
}
#endif /* MBEDTLS_BASE64_C */
#if defined(MBEDTLS_PKCS1_V15) && defined(MBEDTLS_RSA_C) && !defined(MBEDTLS_RSA_ALT)
/** Shift some data towards the left inside a buffer.

6
library/constant_time_internal.h
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@ -167,6 +167,12 @@ void mbedtls_ct_mpi_uint_cond_assign( size_t n,
#endif /* MBEDTLS_BIGNUM_C */
#if defined(MBEDTLS_BASE64_C)
unsigned char mbedtls_ct_base64_enc_char( unsigned char val );
#endif /* MBEDTLS_BASE64_C */
#if defined(MBEDTLS_SSL_SOME_SUITES_USE_TLS_CBC)
/** Conditional memcpy without branches.