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Move mbedtls_ct_base64_(enc|dec)_char into base64.c

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Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
This commit is contained in:
Dave Rodgman 2023-05-09 09:49:01 +01:00
parent 36ad151b20
commit 0ee9683987
4 changed files with 74 additions and 65 deletions
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29
include/mbedtls/base64.h
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@ -87,6 +87,35 @@ int mbedtls_base64_self_test(int verbose);
#endif /* MBEDTLS_SELF_TEST */
#if defined(MBEDTLS_TEST_HOOKS)
/** 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_TEST_HOOKS */
#ifdef __cplusplus
}
#endif

33
library/base64.c
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@ -33,6 +33,39 @@
#include "mbedtls/platform.h"
#endif /* MBEDTLS_SELF_TEST */
MBEDTLS_STATIC_TESTABLE
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;
}
MBEDTLS_STATIC_TESTABLE
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;
}
/*
* Encode a buffer into base64 format
*/

36
library/constant_time.c
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@ -212,7 +212,6 @@ size_t mbedtls_ct_size_mask_ge(size_t x,
*
* 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)
@ -344,41 +343,6 @@ 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 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.

41
library/constant_time_internal.h
View File

@ -185,35 +185,6 @@ 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).
*
* \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_MAC)
/** Conditional memcpy without branches.
@ -360,4 +331,16 @@ int mbedtls_ct_rsaes_pkcs1_v15_unpadding(unsigned char *input,
#endif /* MBEDTLS_PKCS1_V15 && MBEDTLS_RSA_C && ! MBEDTLS_RSA_ALT */
#if defined(MBEDTLS_BASE64_C)
/* Return 0xff if low <= c <= high, 0 otherwise.
*
* Constant flow with respect to c.
*/
unsigned char mbedtls_ct_uchar_mask_of_range(unsigned char low,
unsigned char high,
unsigned char c);
#endif /* MBEDTLS_BASE64_C */
#endif /* MBEDTLS_CONSTANT_TIME_INTERNAL_H */