Merge pull request #5236 from gabor-mezei-arm/4926_base64_move_constant-time_functions
Move base64 constant-time functions to the new module
diff --git a/library/base64.c b/library/base64.c
index a516c1d..83daa0b 100644
--- a/library/base64.c
+++ b/library/base64.c
@@ -22,7 +22,7 @@
#if defined(MBEDTLS_BASE64_C)
#include "mbedtls/base64.h"
-#include "base64_invasive.h"
+#include "constant_time_internal.h"
#include <stdint.h>
@@ -38,41 +38,6 @@
#define BASE64_SIZE_T_MAX ( (size_t) -1 ) /* SIZE_T_MAX is not standard */
-/* Return 0xff if low <= c <= high, 0 otherwise.
- *
- * Constant flow with respect to c.
- */
-MBEDTLS_STATIC_TESTABLE
-unsigned char mbedtls_base64_mask_of_range( unsigned char low,
- unsigned char high,
- unsigned char c )
-{
- /* low_mask is: 0 if low <= c, 0x...ff if low > c */
- unsigned low_mask = ( (unsigned) c - low ) >> 8;
- /* high_mask is: 0 if c <= high, 0x...ff if c > high */
- unsigned high_mask = ( (unsigned) high - c ) >> 8;
- return( ~( low_mask | high_mask ) & 0xff );
-}
-
-/* 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_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_base64_mask_of_range( 0, 25, val ) & ( 'A' + val );
- digit |= mbedtls_base64_mask_of_range( 26, 51, val ) & ( 'a' + val - 26 );
- digit |= mbedtls_base64_mask_of_range( 52, 61, val ) & ( '0' + val - 52 );
- digit |= mbedtls_base64_mask_of_range( 62, 62, val ) & '+';
- digit |= mbedtls_base64_mask_of_range( 63, 63, val ) & '/';
- return( digit );
-}
-
/*
* Encode a buffer into base64 format
*/
@@ -113,12 +78,12 @@
C2 = *src++;
C3 = *src++;
- *p++ = mbedtls_base64_enc_char( ( C1 >> 2 ) & 0x3F );
- *p++ = mbedtls_base64_enc_char( ( ( ( C1 & 3 ) << 4 ) + ( C2 >> 4 ) )
+ *p++ = mbedtls_ct_base64_enc_char( ( C1 >> 2 ) & 0x3F );
+ *p++ = mbedtls_ct_base64_enc_char( ( ( ( C1 & 3 ) << 4 ) + ( C2 >> 4 ) )
& 0x3F );
- *p++ = mbedtls_base64_enc_char( ( ( ( C2 & 15 ) << 2 ) + ( C3 >> 6 ) )
+ *p++ = mbedtls_ct_base64_enc_char( ( ( ( C2 & 15 ) << 2 ) + ( C3 >> 6 ) )
& 0x3F );
- *p++ = mbedtls_base64_enc_char( C3 & 0x3F );
+ *p++ = mbedtls_ct_base64_enc_char( C3 & 0x3F );
}
if( i < slen )
@@ -126,12 +91,12 @@
C1 = *src++;
C2 = ( ( i + 1 ) < slen ) ? *src++ : 0;
- *p++ = mbedtls_base64_enc_char( ( C1 >> 2 ) & 0x3F );
- *p++ = mbedtls_base64_enc_char( ( ( ( C1 & 3 ) << 4 ) + ( C2 >> 4 ) )
+ *p++ = mbedtls_ct_base64_enc_char( ( C1 >> 2 ) & 0x3F );
+ *p++ = mbedtls_ct_base64_enc_char( ( ( ( C1 & 3 ) << 4 ) + ( C2 >> 4 ) )
& 0x3F );
if( ( i + 1 ) < slen )
- *p++ = mbedtls_base64_enc_char( ( ( C2 & 15 ) << 2 ) & 0x3F );
+ *p++ = mbedtls_ct_base64_enc_char( ( ( C2 & 15 ) << 2 ) & 0x3F );
else *p++ = '=';
*p++ = '=';
@@ -143,35 +108,6 @@
return( 0 );
}
-/* Given a Base64 digit, return its value.
- * If c is not a Base64 digit ('A'..'Z', 'a'..'z', '0'..'9', '+' or '/'),
- * return -1.
- *
- * The implementation assumes that letters are consecutive (e.g. ASCII
- * but not EBCDIC).
- *
- * The implementation is constant-flow (no branch or memory access depending
- * on the value of c) unless the compiler inlines and optimizes a specific
- * access.
- */
-MBEDTLS_STATIC_TESTABLE
-signed char mbedtls_base64_dec_value( unsigned char c )
-{
- unsigned char val = 0;
- /* For each range of digits, if c is in that range, mask val with
- * the corresponding value. Since c can only be in a single range,
- * only at most one masking will change val. Set val to one plus
- * the desired value so that it stays 0 if c is in none of the ranges. */
- val |= mbedtls_base64_mask_of_range( 'A', 'Z', c ) & ( c - 'A' + 0 + 1 );
- val |= mbedtls_base64_mask_of_range( 'a', 'z', c ) & ( c - 'a' + 26 + 1 );
- val |= mbedtls_base64_mask_of_range( '0', '9', c ) & ( c - '0' + 52 + 1 );
- val |= mbedtls_base64_mask_of_range( '+', '+', c ) & ( c - '+' + 62 + 1 );
- val |= mbedtls_base64_mask_of_range( '/', '/', c ) & ( c - '/' + 63 + 1 );
- /* At this point, val is 0 if c is an invalid digit and v+1 if c is
- * a digit with the value v. */
- return( val - 1 );
-}
-
/*
* Decode a base64-formatted buffer
*/
@@ -224,7 +160,7 @@
{
if( equals != 0 )
return( MBEDTLS_ERR_BASE64_INVALID_CHARACTER );
- if( mbedtls_base64_dec_value( src[i] ) < 0 )
+ if( mbedtls_ct_base64_dec_value( src[i] ) < 0 )
return( MBEDTLS_ERR_BASE64_INVALID_CHARACTER );
}
n++;
@@ -259,7 +195,7 @@
if( *src == '=' )
++equals;
else
- x |= mbedtls_base64_dec_value( *src );
+ x |= mbedtls_ct_base64_dec_value( *src );
if( ++accumulated_digits == 4 )
{
diff --git a/library/base64_invasive.h b/library/base64_invasive.h
deleted file mode 100644
index ed5f7cb..0000000
--- a/library/base64_invasive.h
+++ /dev/null
@@ -1,55 +0,0 @@
-/**
- * \file base_invasive.h
- *
- * \brief Base64 module: interfaces for invasive testing only.
- *
- * The interfaces in this file are intended for testing purposes only.
- * They SHOULD NOT be made available in library integrations except when
- * building the library for testing.
- */
-/*
- * 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.
- */
-#ifndef MBEDTLS_BASE64_INVASIVE_H
-#define MBEDTLS_BASE64_INVASIVE_H
-
-#include "common.h"
-
-#if defined(MBEDTLS_TEST_HOOKS)
-/* Return 0xff if low <= c <= high, 0 otherwise.
- *
- * Constant flow with respect to c.
- */
-unsigned char mbedtls_base64_mask_of_range( unsigned char low,
- unsigned char high,
- unsigned char c );
-
-/* Given a value in the range 0..63, return the corresponding Base64 digit.
- *
- * Operates in constant time (no branches or memory access depending on val).
- */
-unsigned char mbedtls_base64_enc_char( unsigned char val );
-
-/* Given a Base64 digit, return its value.
- * If c is not a Base64 digit ('A'..'Z', 'a'..'z', '0'..'9', '+' or '/'),
- * return -1.
- *
- * Operates in constant time (no branches or memory access depending on c).
- */
-signed char mbedtls_base64_dec_value( unsigned char c );
-#endif /* MBEDTLS_TEST_HOOKS */
-
-#endif /* MBEDTLS_BASE64_INVASIVE_H */
diff --git a/library/constant_time.c b/library/constant_time.c
index 9bb275c..d8870ae 100644
--- a/library/constant_time.c
+++ b/library/constant_time.c
@@ -40,6 +40,10 @@
#include "mbedtls/rsa.h"
#endif
+#if defined(MBEDTLS_BASE64_C)
+#include "constant_time_invasive.h"
+#endif
+
#include <string.h>
int mbedtls_ct_memcmp( const void *a,
@@ -150,6 +154,26 @@
#endif /* MBEDTLS_SSL_SOME_SUITES_USE_TLS_CBC */
+#if defined(MBEDTLS_BASE64_C)
+
+/* Return 0xff if low <= c <= high, 0 otherwise.
+ *
+ * Constant flow with respect to c.
+ */
+MBEDTLS_STATIC_TESTABLE
+unsigned char mbedtls_ct_uchar_mask_of_range( unsigned char low,
+ unsigned char high,
+ unsigned char c )
+{
+ /* low_mask is: 0 if low <= c, 0x...ff if low > c */
+ unsigned low_mask = ( (unsigned) c - low ) >> 8;
+ /* high_mask is: 0 if c <= high, 0x...ff if c > high */
+ unsigned high_mask = ( (unsigned) high - c ) >> 8;
+ return( ~( low_mask | high_mask ) & 0xff );
+}
+
+#endif /* MBEDTLS_BASE64_C */
+
unsigned mbedtls_ct_size_bool_eq( size_t x,
size_t y )
{
@@ -301,6 +325,41 @@
#endif /* MBEDTLS_BIGNUM_C */
+#if defined(MBEDTLS_BASE64_C)
+
+unsigned char mbedtls_ct_base64_enc_char( unsigned char value )
+{
+ unsigned char digit = 0;
+ /* For each range of values, if value is in that range, mask digit with
+ * the corresponding value. Since value can only be in a single range,
+ * only at most one masking will change digit. */
+ digit |= mbedtls_ct_uchar_mask_of_range( 0, 25, value ) & ( 'A' + value );
+ digit |= mbedtls_ct_uchar_mask_of_range( 26, 51, value ) & ( 'a' + value - 26 );
+ digit |= mbedtls_ct_uchar_mask_of_range( 52, 61, value ) & ( '0' + value - 52 );
+ digit |= mbedtls_ct_uchar_mask_of_range( 62, 62, value ) & '+';
+ digit |= mbedtls_ct_uchar_mask_of_range( 63, 63, value ) & '/';
+ return( digit );
+}
+
+signed char mbedtls_ct_base64_dec_value( unsigned char c )
+{
+ unsigned char val = 0;
+ /* For each range of digits, if c is in that range, mask val with
+ * the corresponding value. Since c can only be in a single range,
+ * only at most one masking will change val. Set val to one plus
+ * the desired value so that it stays 0 if c is in none of the ranges. */
+ val |= mbedtls_ct_uchar_mask_of_range( 'A', 'Z', c ) & ( c - 'A' + 0 + 1 );
+ val |= mbedtls_ct_uchar_mask_of_range( 'a', 'z', c ) & ( c - 'a' + 26 + 1 );
+ val |= mbedtls_ct_uchar_mask_of_range( '0', '9', c ) & ( c - '0' + 52 + 1 );
+ val |= mbedtls_ct_uchar_mask_of_range( '+', '+', c ) & ( c - '+' + 62 + 1 );
+ val |= mbedtls_ct_uchar_mask_of_range( '/', '/', c ) & ( c - '/' + 63 + 1 );
+ /* At this point, val is 0 if c is an invalid digit and v+1 if c is
+ * a digit with the value v. */
+ return( val - 1 );
+}
+
+#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.
diff --git a/library/constant_time_internal.h b/library/constant_time_internal.h
index ac18b56..053cf12 100644
--- a/library/constant_time_internal.h
+++ b/library/constant_time_internal.h
@@ -167,6 +167,35 @@
#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).
+ *
+ * \param value A value in the range 0..63.
+ *
+ * \return A base64 digit converted from \p value.
+ */
+unsigned char mbedtls_ct_base64_enc_char( unsigned char value );
+
+/** Given a Base64 digit, return its value.
+ *
+ * If c is not a Base64 digit ('A'..'Z', 'a'..'z', '0'..'9', '+' or '/'),
+ * return -1.
+ *
+ * The implementation assumes that letters are consecutive (e.g. ASCII
+ * but not EBCDIC).
+ *
+ * \param c A base64 digit.
+ *
+ * \return The value of the base64 digit \p c.
+ */
+signed char mbedtls_ct_base64_dec_value( unsigned char c );
+
+#endif /* MBEDTLS_BASE64_C */
+
#if defined(MBEDTLS_SSL_SOME_SUITES_USE_TLS_CBC)
/** Conditional memcpy without branches.
diff --git a/library/constant_time_invasive.h b/library/constant_time_invasive.h
new file mode 100644
index 0000000..4620ca1
--- /dev/null
+++ b/library/constant_time_invasive.h
@@ -0,0 +1,51 @@
+/**
+ * \file constant_time_invasive.h
+ *
+ * \brief Constant-time module: interfaces for invasive testing only.
+ *
+ * The interfaces in this file are intended for testing purposes only.
+ * They SHOULD NOT be made available in library integrations except when
+ * building the library for testing.
+ */
+/*
+ * 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.
+ */
+
+#ifndef MBEDTLS_CONSTANT_TIME_INVASIVE_H
+#define MBEDTLS_CONSTANT_TIME_INVASIVE_H
+
+#include "common.h"
+
+#if defined(MBEDTLS_TEST_HOOKS)
+
+/** Turn a value into a mask:
+ * - if \p low <= \p c <= \p high,
+ * return the all-bits 1 mask, aka (unsigned) -1
+ * - otherwise, return the all-bits 0 mask, aka 0
+ *
+ * \param low The value to analyze.
+ * \param high The value to analyze.
+ * \param c The value to analyze.
+ *
+ * \return All-bits-one if \p low <= \p c <= \p high, otherwise zero.
+ */
+unsigned char mbedtls_ct_uchar_mask_of_range( unsigned char low,
+ unsigned char high,
+ unsigned char c );
+
+#endif /* MBEDTLS_TEST_HOOKS */
+
+#endif /* MBEDTLS_CONSTANT_TIME_INVASIVE_H */
diff --git a/tests/suites/test_suite_base64.function b/tests/suites/test_suite_base64.function
index 67fbb67..7baa3d5 100644
--- a/tests/suites/test_suite_base64.function
+++ b/tests/suites/test_suite_base64.function
@@ -1,6 +1,7 @@
/* BEGIN_HEADER */
#include "mbedtls/base64.h"
-#include "base64_invasive.h"
+#include "constant_time_internal.h"
+#include "constant_time_invasive.h"
#include <test/constant_flow.h>
#if defined(MBEDTLS_TEST_HOOKS)
@@ -24,7 +25,7 @@
{
mbedtls_test_set_step( c );
TEST_CF_SECRET( &c, sizeof( c ) );
- unsigned char m = mbedtls_base64_mask_of_range( low, high, c );
+ unsigned char m = mbedtls_ct_uchar_mask_of_range( low, high, c );
TEST_CF_PUBLIC( &c, sizeof( c ) );
TEST_CF_PUBLIC( &m, sizeof( m ) );
if( low <= c && c <= high )
@@ -42,7 +43,7 @@
{
mbedtls_test_set_step( value );
TEST_CF_SECRET( &value, sizeof( value ) );
- unsigned char digit = mbedtls_base64_enc_char( value );
+ unsigned char digit = mbedtls_ct_base64_enc_char( value );
TEST_CF_PUBLIC( &value, sizeof( value ) );
TEST_CF_PUBLIC( &digit, sizeof( digit ) );
TEST_EQUAL( digit, base64_digits[value] );
@@ -66,7 +67,7 @@
else
expected = p - base64_digits;
TEST_CF_SECRET( &c, sizeof( c ) );
- signed char actual = mbedtls_base64_dec_value( c );
+ signed char actual = mbedtls_ct_base64_dec_value( c );
TEST_CF_PUBLIC( &c, sizeof( c ) );
TEST_CF_PUBLIC( &actual, sizeof( actual ) );
TEST_EQUAL( actual, expected );