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openssl-1_1.29123
openssl-Provide-some-constant-time-functions-fo...
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File openssl-Provide-some-constant-time-functions-for-dealing-wit.patch of Package openssl-1_1.29123
From 2688e7a0beb0f5e76a98749f25b978ddfb40ac7f Mon Sep 17 00:00:00 2001 From: Matt Caswell <matt@openssl.org> Date: Wed, 19 Oct 2016 17:13:13 +0100 Subject: [PATCH] Provide some constant time functions for dealing with size_t values Also implement the using of them Reviewed-by: Rich Salz <rsalz@openssl.org> --- include/internal/constant_time_locl.h | 49 ++++++++++++++++++++++++++++++++++ ssl/record/ssl3_record.c | 38 +++++++++++++------------- ssl/s3_cbc.c | 8 ++--- 3 files changed, 73 insertions(+), 22 deletions(-) --- a/include/internal/constant_time_locl.h +++ b/include/internal/constant_time_locl.h @@ -10,6 +10,7 @@ #ifndef HEADER_CONSTANT_TIME_LOCL_H # define HEADER_CONSTANT_TIME_LOCL_H +# include <stdlib.h> # include <openssl/e_os2.h> /* For 'ossl_inline' */ #ifdef __cplusplus @@ -103,12 +104,22 @@ static ossl_inline uint64_t constant_tim return 0 - (a >> 63); } +static ossl_inline size_t constant_time_msb_s(size_t a) +{ + return 0 - (a >> (sizeof(a) * 8 - 1)); +} + static ossl_inline unsigned int constant_time_lt(unsigned int a, unsigned int b) { return constant_time_msb(a ^ ((a ^ b) | ((a - b) ^ b))); } +static ossl_inline size_t constant_time_lt_s(size_t a, size_t b) +{ + return constant_time_msb_s(a ^ ((a ^ b) | ((a - b) ^ b))); +} + static ossl_inline unsigned char constant_time_lt_8(unsigned int a, unsigned int b) { @@ -126,17 +137,32 @@ static ossl_inline unsigned int constant return ~constant_time_lt(a, b); } +static ossl_inline size_t constant_time_ge_s(size_t a, size_t b) +{ + return ~constant_time_lt_s(a, b); +} + static ossl_inline unsigned char constant_time_ge_8(unsigned int a, unsigned int b) { return (unsigned char)(constant_time_ge(a, b)); } +static ossl_inline unsigned char constant_time_ge_8_s(size_t a, size_t b) +{ + return (unsigned char)(constant_time_ge_s(a, b)); +} + static ossl_inline unsigned int constant_time_is_zero(unsigned int a) { return constant_time_msb(~a & (a - 1)); } +static ossl_inline size_t constant_time_is_zero_s(size_t a) +{ + return constant_time_msb_s(~a & (a - 1)); +} + static ossl_inline unsigned char constant_time_is_zero_8(unsigned int a) { return (unsigned char)(constant_time_is_zero(a)); @@ -148,12 +174,22 @@ static ossl_inline unsigned int constant return constant_time_is_zero(a ^ b); } +static ossl_inline size_t constant_time_eq_s(size_t a, size_t b) +{ + return constant_time_is_zero_s(a ^ b); +} + static ossl_inline unsigned char constant_time_eq_8(unsigned int a, unsigned int b) { return (unsigned char)(constant_time_eq(a, b)); } +static ossl_inline unsigned char constant_time_eq_8_s(size_t a, size_t b) +{ + return (unsigned char)(constant_time_eq_s(a, b)); +} + static ossl_inline unsigned int constant_time_eq_int(int a, int b) { return constant_time_eq((unsigned)(a), (unsigned)(b)); @@ -171,6 +207,13 @@ static ossl_inline unsigned int constant return (mask & a) | (~mask & b); } +static ossl_inline size_t constant_time_select_s(size_t mask, + size_t a, + size_t b) +{ + return (mask & a) | (~mask & b); +} + static ossl_inline unsigned char constant_time_select_8(unsigned char mask, unsigned char a, unsigned char b) @@ -178,6 +221,12 @@ static ossl_inline unsigned char constan return (unsigned char)(constant_time_select(mask, a, b)); } +static ossl_inline int constant_time_select_int_s(size_t mask, int a, int b) +{ + return (int)(constant_time_select((unsigned)mask, (unsigned)(a), + (unsigned)(b))); +} + static ossl_inline int constant_time_select_int(unsigned int mask, int a, int b) { --- a/ssl/record/ssl3_record.c +++ b/ssl/record/ssl3_record.c @@ -1096,7 +1096,8 @@ int tls1_mac(SSL *ssl, SSL3_RECORD *rec, int ssl3_cbc_remove_padding(SSL3_RECORD *rec, unsigned block_size, unsigned mac_size) { - unsigned padding_length, good; + unsigned padding_length; + size_t good; const unsigned overhead = 1 /* padding length byte */ + mac_size; /* @@ -1106,11 +1107,11 @@ int ssl3_cbc_remove_padding(SSL3_RECORD return 0; padding_length = rec->data[rec->length - 1]; - good = constant_time_ge(rec->length, padding_length + overhead); + good = constant_time_ge_s(rec->length, padding_length + overhead); /* SSLv3 requires that the padding is minimal. */ - good &= constant_time_ge(block_size, padding_length + 1); + good &= constant_time_ge_s(block_size, padding_length + 1); rec->length -= good & (padding_length + 1); - return constant_time_select_int(good, 1, -1); + return constant_time_select_int_s(good, 1, -1); } /*- @@ -1130,7 +1131,8 @@ int tls1_cbc_remove_padding(const SSL *s SSL3_RECORD *rec, unsigned block_size, unsigned mac_size) { - unsigned padding_length, good, to_check, i; + unsigned padding_length, to_check, i; + size_t good; const unsigned overhead = 1 /* padding length byte */ + mac_size; /* Check if version requires explicit IV */ if (SSL_USE_EXPLICIT_IV(s)) { @@ -1157,7 +1159,7 @@ int tls1_cbc_remove_padding(const SSL *s return 1; } - good = constant_time_ge(rec->length, overhead + padding_length); + good = constant_time_ge_s(rec->length, overhead + padding_length); /* * The padding consists of a length byte at the end of the record and * then that many bytes of padding, all with the same value as the length @@ -1172,7 +1174,7 @@ int tls1_cbc_remove_padding(const SSL *s to_check = rec->length; for (i = 0; i < to_check; i++) { - unsigned char mask = constant_time_ge_8(padding_length, i); + unsigned char mask = constant_time_ge_8_s(padding_length, i); unsigned char b = rec->data[rec->length - 1 - i]; /* * The final |padding_length+1| bytes should all have the value @@ -1185,10 +1187,10 @@ int tls1_cbc_remove_padding(const SSL *s * If any of the final |padding_length+1| bytes had the wrong value, one * or more of the lower eight bits of |good| will be cleared. */ - good = constant_time_eq(0xff, good & 0xff); + good = constant_time_eq_s(0xff, good & 0xff); rec->length -= good & (padding_length + 1); - return constant_time_select_int(good, 1, -1); + return constant_time_select_int_s(good, 1, -1); } /*- @@ -1232,8 +1234,8 @@ void ssl3_cbc_copy_mac(unsigned char *ou * MAC's position can only vary by 255 bytes. */ unsigned scan_start = 0; - unsigned i, j; - unsigned rotate_offset; + size_t i, j; + size_t rotate_offset; OPENSSL_assert(rec->orig_len >= md_size); OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE); @@ -1250,15 +1252,15 @@ void ssl3_cbc_copy_mac(unsigned char *ou rotate_offset = 0; memset(rotated_mac, 0, md_size); for (i = scan_start, j = 0; i < rec->orig_len; i++) { - unsigned mac_started = constant_time_eq(i, mac_start); - unsigned mac_ended = constant_time_lt(i, mac_end); + unsigned mac_started = constant_time_eq_s(i, mac_start); + unsigned mac_ended = constant_time_lt_s(i, mac_end); unsigned char b = rec->data[i]; in_mac |= mac_started; in_mac &= mac_ended; rotate_offset |= j & mac_started; rotated_mac[j++] |= b & in_mac; - j &= constant_time_lt(j, md_size); + j &= constant_time_lt_s(j, md_size); } /* Now rotate the MAC */ @@ -1268,17 +1270,17 @@ void ssl3_cbc_copy_mac(unsigned char *ou /* in case cache-line is 32 bytes, touch second line */ ((volatile unsigned char *)rotated_mac)[rotate_offset ^ 32]; out[j++] = rotated_mac[rotate_offset++]; - rotate_offset &= constant_time_lt(rotate_offset, md_size); + rotate_offset &= constant_time_lt_s(rotate_offset, md_size); } #else memset(out, 0, md_size); rotate_offset = md_size - rotate_offset; - rotate_offset &= constant_time_lt(rotate_offset, md_size); + rotate_offset &= constant_time_lt_s(rotate_offset, md_size); for (i = 0; i < md_size; i++) { for (j = 0; j < md_size; j++) - out[j] |= rotated_mac[i] & constant_time_eq_8(j, rotate_offset); + out[j] |= rotated_mac[i] & constant_time_eq_8_s(j, rotate_offset); rotate_offset++; - rotate_offset &= constant_time_lt(rotate_offset, md_size); + rotate_offset &= constant_time_lt_s(rotate_offset, md_size); } #endif } --- a/ssl/s3_cbc.c +++ b/ssl/s3_cbc.c @@ -399,8 +399,8 @@ int ssl3_cbc_digest_record(const EVP_MD_ for (i = num_starting_blocks; i <= num_starting_blocks + variance_blocks; i++) { unsigned char block[MAX_HASH_BLOCK_SIZE]; - unsigned char is_block_a = constant_time_eq_8(i, index_a); - unsigned char is_block_b = constant_time_eq_8(i, index_b); + unsigned char is_block_a = constant_time_eq_8_s(i, index_a); + unsigned char is_block_b = constant_time_eq_8_s(i, index_b); for (j = 0; j < md_block_size; j++) { unsigned char b = 0, is_past_c, is_past_cp1; if (k < header_length) @@ -409,8 +409,8 @@ int ssl3_cbc_digest_record(const EVP_MD_ b = data[k - header_length]; k++; - is_past_c = is_block_a & constant_time_ge_8(j, c); - is_past_cp1 = is_block_a & constant_time_ge_8(j, c + 1); + is_past_c = is_block_a & constant_time_ge_8_s(j, c); + is_past_cp1 = is_block_a & constant_time_ge_8_s(j, c + 1); /* * If this is the block containing the end of the application * data, and we are at the offset for the 0x80 value, then
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