[exim-cvs] OpenSSL: increase STEK strength to 256b

Gitweb: https://git.exim.org/exim.git/commitdiff/4d93129fffa7e0f92b83ebca52fc188f4d13d6e6

Commit:     4d93129fffa7e0f92b83ebca52fc188f4d13d6e6
Parent:     43e2db44c657b07340368eae5dd05e51eab829fb
Author:     Jeremy Harris <jgh146exb@???>
AuthorDate: Sat May 4 16:53:57 2019 +0100
Committer:  Jeremy Harris <jgh146exb@???>
CommitDate: Sat May 4 16:53:57 2019 +0100

    OpenSSL: increase STEK strength to 256b
---
 src/src/tls-openssl.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/src/src/tls-openssl.c b/src/src/tls-openssl.c
index 824212d..c40af65 100644
--- a/src/src/tls-openssl.c
+++ b/src/src/tls-openssl.c
@@ -372,7 +372,7 @@ static int tls_server_stapling_cb(SSL *s, void *arg);

-/* Daemon-called key create/rotate */
+/* Daemon-called, before every connection, key create/rotate */
 #ifdef EXPERIMENTAL_TLS_RESUME
 static void tk_init(void);
 static int tls_exdata_idx = -1;
@@ -840,25 +840,24 @@ typedef struct {            /* Session ticket encryption key */
   uschar     name[16];

   const EVP_CIPHER *    aes_cipher;
-  uschar        aes_key[16];    /* size needed depends on cipher. aes_128 implies 128/8 = 16? */
+  uschar        aes_key[32];    /* size needed depends on cipher. aes_128 implies 128/8 = 16? */
   const EVP_MD *    hmac_hash;
   uschar        hmac_key[16];
   time_t        renew;
   time_t        expire;
 } exim_stek;

-/*XXX for now just always create/find the one key.
-Worry about rotation and overlap later. */
-
-static exim_stek exim_tk;
-static exim_stek exim_tk_old;
+static exim_stek exim_tk;    /* current key */
+static exim_stek exim_tk_old;    /* previous key */

static void
tk_init(void)
{
+time_t t = time(NULL);
+
if (exim_tk.name[0])
{
- if (exim_tk.renew >= time(NULL)) return;
+ if (exim_tk.renew >= t) return;
exim_tk_old = exim_tk;
}

@@ -870,10 +869,10 @@ if (RAND_bytes(exim_tk.hmac_key, sizeof(exim_tk.hmac_key)) <= 0) return;
if (RAND_bytes(exim_tk.name+1, sizeof(exim_tk.name)-1) <= 0) return;

exim_tk.name[0] = 'E';
-exim_tk.aes_cipher = EVP_aes_128_cbc();
+exim_tk.aes_cipher = EVP_aes_256_cbc();
exim_tk.hmac_hash = EVP_sha256();
-exim_tk.expire = time(NULL) + ssl_session_timeout;
-exim_tk.renew = exim_tk.expire - ssl_session_timeout/2;
+exim_tk.expire = t + ssl_session_timeout;
+exim_tk.renew = t + ssl_session_timeout/2;
}

static exim_stek *