feedc0de/wolfssl
1
0
Fork 0
forked from wolfSSL/wolfssl
Code Pull Requests Activity

Simplify TLS 1.2 session ID logic

Browse Source 
Optimize entropy use. Only generate the exact amount of random data that we will actually keep.

Refactor done as part of work on ZD18822
This commit is contained in:
Juliusz Sosinowicz
2024-10-22 10:55:15 +02:00
parent 846ef1570d
commit 2847cbfbad
1 changed files with 42 additions and 45 deletions
Download Patch File Download Diff File Expand all files Collapse all files

87
src/internal.c
View File

@@ -34510,6 +34510,29 @@ static int DoSessionTicket(WOLFSSL* ssl, const byte* input, word32* inOutIdx,
#ifndef WOLFSSL_NO_TLS12
static int getSessionID(WOLFSSL* ssl)
{
int sessIdSz = 0;
(void)ssl;
#ifndef NO_SESSION_CACHE
/* if no session cache don't send a session ID */
if (!ssl->options.sessionCacheOff)
sessIdSz = ID_LEN;
#endif
#ifdef HAVE_SESSION_TICKET
/* we may be echoing an ID as part of session tickets */
if (ssl->options.useTicket) {
/* echo session id sz can be 0,32 or bogus len in between */
sessIdSz = ssl->arrays->sessionIDSz;
if (sessIdSz > ID_LEN) {
WOLFSSL_MSG("Bad bogus session id len");
return BUFFER_ERROR;
}
}
#endif /* HAVE_SESSION_TICKET */
return sessIdSz;
}
/* handle generation of server_hello (2) */
int SendServerHello(WOLFSSL* ssl)
{
@@ -34518,17 +34541,18 @@ static int DoSessionTicket(WOLFSSL* ssl, const byte* input, word32* inOutIdx,
word16 length;
word32 idx = RECORD_HEADER_SZ + HANDSHAKE_HEADER_SZ;
int sendSz;
byte sessIdSz = ID_LEN;
#if defined(HAVE_TLS_EXTENSIONS) && defined(HAVE_SESSION_TICKET)
byte echoId = 0; /* ticket echo id flag */
#endif
byte cacheOff = 0; /* session cache off flag */
byte sessIdSz;
WOLFSSL_START(WC_FUNC_SERVER_HELLO_SEND);
WOLFSSL_ENTER("SendServerHello");
ret = getSessionID(ssl);
if (ret < 0)
return ret;
sessIdSz = (byte)ret;
length = VERSION_SZ + RAN_LEN
+ ID_LEN + ENUM_LEN
+ ENUM_LEN + sessIdSz
+ SUITE_LEN
+ ENUM_LEN;
@@ -34536,45 +34560,12 @@ static int DoSessionTicket(WOLFSSL* ssl, const byte* input, word32* inOutIdx,
ret = TLSX_GetResponseSize(ssl, server_hello, &length);
if (ret != 0)
return ret;
#ifdef HAVE_SESSION_TICKET
if (ssl->options.useTicket) {
/* echo session id sz can be 0,32 or bogus len in between */
sessIdSz = ssl->arrays->sessionIDSz;
if (sessIdSz > ID_LEN) {
WOLFSSL_MSG("Bad bogus session id len");
return BUFFER_ERROR;
}
if (!IsAtLeastTLSv1_3(ssl->version))
length -= (ID_LEN - sessIdSz); /* adjust ID_LEN assumption */
echoId = 1;
}
#endif /* HAVE_SESSION_TICKET */
#else
if (ssl->options.haveEMS) {
length += HELLO_EXT_SZ_SZ + HELLO_EXT_SZ;
}
#endif
/* is the session cache off at build or runtime */
#ifdef NO_SESSION_CACHE
cacheOff = 1;
#else
if (ssl->options.sessionCacheOff == 1) {
cacheOff = 1;
}
#endif
/* if no session cache don't send a session ID unless we're echoing
* an ID as part of session tickets */
if (cacheOff == 1
#if defined(HAVE_TLS_EXTENSIONS) && defined(HAVE_SESSION_TICKET)
&& echoId == 0
#endif
) {
length -= ID_LEN; /* adjust ID_LEN assumption */
sessIdSz = 0;
}
sendSz = length + HANDSHAKE_HEADER_SZ + RECORD_HEADER_SZ;
#ifdef WOLFSSL_DTLS
if (ssl->options.dtls) {
@@ -34605,11 +34596,7 @@ static int DoSessionTicket(WOLFSSL* ssl, const byte* input, word32* inOutIdx,
/* then random and session id */
if (!ssl->options.resuming) {
/* generate random part and session id */
ret = wc_RNG_GenerateBlock(ssl->rng, output + idx,
RAN_LEN + sizeof(sessIdSz) + sessIdSz);
if (ret != 0)
return ret;
word32 genRanLen = RAN_LEN;
#ifdef WOLFSSL_TLS13
if (TLSv1_3_Capable(ssl)) {
@@ -34617,6 +34604,7 @@ static int DoSessionTicket(WOLFSSL* ssl, const byte* input, word32* inOutIdx,
XMEMCPY(output + idx + RAN_LEN - (TLS13_DOWNGRADE_SZ + 1),
tls13Downgrade, TLS13_DOWNGRADE_SZ);
output[idx + RAN_LEN - 1] = (byte)IsAtLeastTLSv1_2(ssl);
genRanLen -= TLS13_DOWNGRADE_SZ + 1;
}
else
#endif
@@ -34628,12 +34616,21 @@ static int DoSessionTicket(WOLFSSL* ssl, const byte* input, word32* inOutIdx,
XMEMCPY(output + idx + RAN_LEN - (TLS13_DOWNGRADE_SZ + 1),
tls13Downgrade, TLS13_DOWNGRADE_SZ);
output[idx + RAN_LEN - 1] = 0;
genRanLen -= TLS13_DOWNGRADE_SZ + 1;
}
/* store info in SSL for later */
/* generate random part */
ret = wc_RNG_GenerateBlock(ssl->rng, output + idx, genRanLen);
if (ret != 0)
return ret;
XMEMCPY(ssl->arrays->serverRandom, output + idx, RAN_LEN);
idx += RAN_LEN;
/* generate session id */
output[idx++] = sessIdSz;
ret = wc_RNG_GenerateBlock(ssl->rng, output + idx, sessIdSz);
if (ret != 0)
return ret;
XMEMCPY(ssl->arrays->sessionID, output + idx, sessIdSz);
ssl->arrays->sessionIDSz = sessIdSz;
}