[git commit] tls: introduce FEATURE_TLS_SHA1 to make SHA1 code optional
Denys Vlasenko
vda.linux at googlemail.com
Mon Dec 10 15:14:58 UTC 2018
commit: https://git.busybox.net/busybox/commit/?id=71fa5b0a4c3cce55460de2f6d49e3a4a63f1b933
branch: https://git.busybox.net/busybox/commit/?id=refs/heads/master
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 <vda.linux at googlemail.com>
---
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*/) {
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