From 71fa5b0a4c3cce55460de2f6d49e3a4a63f1b933 Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Mon, 10 Dec 2018 16:14:58 +0100 Subject: [PATCH] tls: introduce FEATURE_TLS_SHA1 to make SHA1 code optional When disabled: function old new delta xwrite_encrypted 580 579 -1 prf_hmac_sha256 222 217 -5 hmac_begin 158 149 -9 static.ciphers 32 20 -12 tls_handshake 2115 2095 -20 hmac 87 61 -26 ------------------------------------------------------------------------------ (add/remove: 0/0 grow/shrink: 0/6 up/down: 0/-73) Total: -73 bytes Signed-off-by: Denys Vlasenko --- networking/Config.src | 11 +++++++++++ networking/tls.c | 36 ++++++++++++++++++++++++++++++------ 2 files changed, 41 insertions(+), 6 deletions(-) diff --git a/networking/Config.src b/networking/Config.src index 2ce5287de..04d644bc9 100644 --- a/networking/Config.src +++ b/networking/Config.src @@ -46,6 +46,17 @@ config VERBOSE_RESOLUTION_ERRORS "can't resolve 'hostname.com'" and want to know more. This may increase size of your executable a bit. +config FEATURE_TLS_SHA1 + bool "In TLS code, support ciphers which use deprecated SHA1" + depends on TLS + default n + help + Selecting this option increases interoperability with very old + servers, but slightly increases code size. + + Most TLS servers support SHA256 today (2018), since SHA1 is + considered possibly insecure (although not yet definitely broken). + INSERT source networking/udhcp/Config.in diff --git a/networking/tls.c b/networking/tls.c index b0eb7b90c..3efb0519d 100644 --- a/networking/tls.c +++ b/networking/tls.c @@ -6,6 +6,8 @@ //config:config TLS //config: bool #No description makes it a hidden option //config: default n +//Note: +//Config.src also defines FEATURE_TLS_SHA1 option //kbuild:lib-$(CONFIG_TLS) += tls.o //kbuild:lib-$(CONFIG_TLS) += tls_pstm.o @@ -394,7 +396,7 @@ static void hash_handshake(tls_state_t *tls, const char *fmt, const void *buffer dump_hex(fmt, buffer, len); dbg(" (%u bytes) ", (int)len); len = sha_peek(&tls->hsd->handshake_hash_ctx, h); - if (len == SHA1_OUTSIZE) + if (ENABLE_FEATURE_TLS_SHA1 && len == SHA1_OUTSIZE) dump_hex("sha1:%s\n", h, len); else if (len == SHA256_OUTSIZE) @@ -421,6 +423,11 @@ typedef struct hmac_precomputed { } hmac_precomputed_t; typedef void md5sha_begin_func(md5sha_ctx_t *ctx) FAST_FUNC; +#if !ENABLE_FEATURE_TLS_SHA1 +#define hmac_begin(pre,key,key_size,begin) \ + hmac_begin(pre,key,key_size) +#define begin sha256_begin +#endif static void hmac_begin(hmac_precomputed_t *pre, uint8_t *key, unsigned key_size, md5sha_begin_func *begin) { uint8_t key_xor_ipad[SHA_INSIZE]; @@ -461,6 +468,7 @@ static void hmac_begin(hmac_precomputed_t *pre, uint8_t *key, unsigned key_size, md5sha_hash(&pre->hashed_key_xor_ipad, key_xor_ipad, SHA_INSIZE); md5sha_hash(&pre->hashed_key_xor_opad, key_xor_opad, SHA_INSIZE); } +#undef begin static unsigned hmac_sha_precomputed_v( hmac_precomputed_t *pre, @@ -498,6 +506,10 @@ static unsigned hmac_sha_precomputed(hmac_precomputed_t *pre_init, uint8_t *out, return len; } +#if !ENABLE_FEATURE_TLS_SHA1 +#define hmac(tls,out,key,key_size,...) \ + hmac(out,key,key_size, __VA_ARGS__) +#endif static unsigned hmac(tls_state_t *tls, uint8_t *out, uint8_t *key, unsigned key_size, ...) { hmac_precomputed_t pre; @@ -507,7 +519,7 @@ static unsigned hmac(tls_state_t *tls, uint8_t *out, uint8_t *key, unsigned key_ va_start(va, key_size); hmac_begin(&pre, key, key_size, - (tls->MAC_size == SHA256_OUTSIZE) + (ENABLE_FEATURE_TLS_SHA1 || tls->MAC_size == SHA256_OUTSIZE) ? sha256_begin : sha1_begin ); @@ -1466,15 +1478,17 @@ static ALWAYS_INLINE void fill_handshake_record_hdr(void *buf, unsigned type, un static void send_client_hello_and_alloc_hsd(tls_state_t *tls, const char *sni) { -#define NUM_CIPHERS (13 + ALLOW_RSA_NULL_SHA256) +#define NUM_CIPHERS (7 + 6 * ENABLE_FEATURE_TLS_SHA1 + ALLOW_RSA_NULL_SHA256) static const uint8_t ciphers[] = { 0x00,(1 + NUM_CIPHERS) * 2, //len16_be 0x00,0xFF, //not a cipher - TLS_EMPTY_RENEGOTIATION_INFO_SCSV /* ^^^^^^ RFC 5746 Renegotiation Indication Extension - some servers will refuse to work with us otherwise */ +#if ENABLE_FEATURE_TLS_SHA1 0xC0,0x09, // 1 TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA - ok: wget https://is.gd/ 0xC0,0x0A, // 2 TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA - ok: wget https://is.gd/ 0xC0,0x13, // 3 TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA - ok: openssl s_server ... -cipher ECDHE-RSA-AES128-SHA 0xC0,0x14, // 4 TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA - ok: openssl s_server ... -cipher ECDHE-RSA-AES256-SHA (might fail with older openssl) +#endif 0xC0,0x23, // 5 TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 - ok: wget https://is.gd/ // 0xC0,0x24, // TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384 - can't do SHA384 yet 0xC0,0x27, // 6 TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 - ok: openssl s_server ... -cipher ECDHE-RSA-AES128-SHA256 @@ -1485,12 +1499,16 @@ static void send_client_hello_and_alloc_hsd(tls_state_t *tls, const char *sni) 0xC0,0x2F, // 8 TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 - ok: openssl s_server ... -cipher ECDHE-RSA-AES128-GCM-SHA256 // 0xC0,0x30, // TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 - openssl s_server ... -cipher ECDHE-RSA-AES256-GCM-SHA384: "decryption failed or bad record mac" //possibly these too: +#if ENABLE_FEATURE_TLS_SHA1 // 0xC0,0x35, // TLS_ECDHE_PSK_WITH_AES_128_CBC_SHA // 0xC0,0x36, // TLS_ECDHE_PSK_WITH_AES_256_CBC_SHA +#endif // 0xC0,0x37, // TLS_ECDHE_PSK_WITH_AES_128_CBC_SHA256 // 0xC0,0x38, // TLS_ECDHE_PSK_WITH_AES_256_CBC_SHA384 - can't do SHA384 yet +#if ENABLE_FEATURE_TLS_SHA1 0x00,0x2F, // 9 TLS_RSA_WITH_AES_128_CBC_SHA - ok: openssl s_server ... -cipher AES128-SHA 0x00,0x35, //10 TLS_RSA_WITH_AES_256_CBC_SHA - ok: openssl s_server ... -cipher AES256-SHA +#endif 0x00,0x3C, //11 TLS_RSA_WITH_AES_128_CBC_SHA256 - ok: openssl s_server ... -cipher AES128-SHA256 0x00,0x3D, //12 TLS_RSA_WITH_AES_256_CBC_SHA256 - ok: openssl s_server ... -cipher AES256-SHA256 0x00,0x9C, //13 TLS_RSA_WITH_AES_128_GCM_SHA256 - ok: openssl s_server ... -cipher AES128-GCM-SHA256 @@ -1669,10 +1687,12 @@ static void get_server_hello(tls_state_t *tls) /* Set up encryption params based on selected cipher */ #if 0 +#if ENABLE_FEATURE_TLS_SHA1 0xC0,0x09, // 1 TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA - ok: wget https://is.gd/ 0xC0,0x0A, // 2 TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA - ok: wget https://is.gd/ 0xC0,0x13, // 3 TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA - ok: openssl s_server ... -cipher ECDHE-RSA-AES128-SHA 0xC0,0x14, // 4 TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA - ok: openssl s_server ... -cipher ECDHE-RSA-AES256-SHA (might fail with older openssl) +#endif 0xC0,0x23, // 5 TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 - ok: wget https://is.gd/ // 0xC0,0x24, // TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384 - can't do SHA384 yet 0xC0,0x27, // 6 TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 - ok: openssl s_server ... -cipher ECDHE-RSA-AES128-SHA256 @@ -1682,12 +1702,16 @@ static void get_server_hello(tls_state_t *tls) 0xC0,0x2F, // 8 TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 - ok: openssl s_server ... -cipher ECDHE-RSA-AES128-GCM-SHA256 // 0xC0,0x30, // TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 - openssl s_server ... -cipher ECDHE-RSA-AES256-GCM-SHA384: "decryption failed or bad record mac" //possibly these too: +#if ENABLE_FEATURE_TLS_SHA1 // 0xC0,0x35, // TLS_ECDHE_PSK_WITH_AES_128_CBC_SHA // 0xC0,0x36, // TLS_ECDHE_PSK_WITH_AES_256_CBC_SHA +#endif // 0xC0,0x37, // TLS_ECDHE_PSK_WITH_AES_128_CBC_SHA256 // 0xC0,0x38, // TLS_ECDHE_PSK_WITH_AES_256_CBC_SHA384 - can't do SHA384 yet +#if ENABLE_FEATURE_TLS_SHA1 0x00,0x2F, // 9 TLS_RSA_WITH_AES_128_CBC_SHA - ok: openssl s_server ... -cipher AES128-SHA 0x00,0x35, //10 TLS_RSA_WITH_AES_256_CBC_SHA - ok: openssl s_server ... -cipher AES256-SHA +#endif 0x00,0x3C, //11 TLS_RSA_WITH_AES_128_CBC_SHA256 - ok: openssl s_server ... -cipher AES128-SHA256 0x00,0x3D, //12 TLS_RSA_WITH_AES_256_CBC_SHA256 - ok: openssl s_server ... -cipher AES256-SHA256 0x00,0x9C, //13 TLS_RSA_WITH_AES_128_GCM_SHA256 - ok: openssl s_server ... -cipher AES128-GCM-SHA256 @@ -1706,7 +1730,7 @@ static void get_server_hello(tls_state_t *tls) /* Odd numbered C0xx use AES128 (even ones use AES256) */ tls->key_size = AES128_KEYSIZE; } - if (cipherid1 <= 0x14) { + if (ENABLE_FEATURE_TLS_SHA1 && cipherid1 <= 0x14) { tls->MAC_size = SHA1_OUTSIZE; } else if (cipherid1 >= 0x2B && cipherid1 <= 0x30) { @@ -1717,13 +1741,13 @@ static void get_server_hello(tls_state_t *tls) } } else { /* All 00xx are RSA */ - if (cipherid1 == 0x2F + if ((ENABLE_FEATURE_TLS_SHA1 && cipherid1 == 0x2F) || cipherid1 == 0x3C || cipherid1 == 0x9C ) { tls->key_size = AES128_KEYSIZE; } - if (cipherid1 <= 0x35) { + if (ENABLE_FEATURE_TLS_SHA1 && cipherid1 <= 0x35) { tls->MAC_size = SHA1_OUTSIZE; } else if (cipherid1 == 0x9C /*|| cipherid1 == 0x9D*/) { -- 2.25.1