[nginx] SSL: $ssl_ciphers (ticket #870).

[Maxim Dounin]

details:   http://hg.nginx.org/nginx/rev/ea93c7d8752a
branches:  
changeset: 6816:ea93c7d8752a
user:      Maxim Dounin <mdounin at mdounin.ru>
date:      Mon Dec 05 22:23:23 2016 +0300
description:
SSL: $ssl_ciphers (ticket #870).

The variable contains list of ciphers as supported by the client.
Known ciphers are listed by their names, unknown ones are shown
in hex, e.g., ""AES128-SHA:AES256-SHA:0x00ff".

The variable is fully supported only when using OpenSSL 1.0.2 and above.
With older version there is an attempt to provide some information
using SSL_get_shared_ciphers().  It only lists known ciphers though.
Moreover, as OpenSSL uses session data for SSL_get_shared_ciphers(),
and it doesn't store relevant data when serializing a session.  As
a result $ssl_ciphers is only available for new sessions (and not
available for reused ones) when using OpenSSL older than 1.0.2.

diffstat:

 src/event/ngx_event_openssl.c          |  84 ++++++++++++++++++++++++++++++++++
 src/event/ngx_event_openssl.h          |   2 +
 src/http/modules/ngx_http_ssl_module.c |   3 +
 src/stream/ngx_stream_ssl_module.c     |   3 +
 4 files changed, 92 insertions(+), 0 deletions(-)

diffs (132 lines):

diff --git a/src/event/ngx_event_openssl.c b/src/event/ngx_event_openssl.c
--- a/src/event/ngx_event_openssl.c
+++ b/src/event/ngx_event_openssl.c
@@ -3294,6 +3294,90 @@ ngx_ssl_get_cipher_name(ngx_connection_t
 
 
 ngx_int_t
+ngx_ssl_get_ciphers(ngx_connection_t *c, ngx_pool_t *pool, ngx_str_t *s)
+{
+#ifdef SSL_CTRL_GET_RAW_CIPHERLIST
+
+    int                n, i, bytes;
+    size_t             len;
+    u_char            *ciphers, *p;
+    const SSL_CIPHER  *cipher;
+
+    bytes = SSL_get0_raw_cipherlist(c->ssl->connection, NULL);
+    n = SSL_get0_raw_cipherlist(c->ssl->connection, &ciphers);
+
+    if (n <= 0) {
+        s->len = 0;
+        return NGX_OK;
+    }
+
+    len = 0;
+    n /= bytes;
+
+    for (i = 0; i < n; i++) {
+        cipher = SSL_CIPHER_find(c->ssl->connection, ciphers + i * bytes);
+
+        if (cipher) {
+            len += ngx_strlen(SSL_CIPHER_get_name(cipher));
+
+        } else {
+            len += sizeof("0x") - 1 + bytes * (sizeof("00") - 1);
+        }
+
+        len += sizeof(":") - 1;
+    }
+
+    s->data = ngx_pnalloc(pool, len);
+    if (s->data == NULL) {
+        return NGX_ERROR;
+    }
+
+    p = s->data;
+
+    for (i = 0; i < n; i++) {
+        cipher = SSL_CIPHER_find(c->ssl->connection, ciphers + i * bytes);
+
+        if (cipher) {
+            p = ngx_sprintf(p, "%s", SSL_CIPHER_get_name(cipher));
+
+        } else {
+            p = ngx_sprintf(p, "0x");
+            p = ngx_hex_dump(p, ciphers + i * bytes, bytes);
+        }
+
+        *p++ = ':';
+    }
+
+    p--;
+
+    s->len = p - s->data;
+
+#else
+
+    u_char  buf[4096];
+
+    if (SSL_get_shared_ciphers(c->ssl->connection, (char *) buf, 4096)
+        == NULL)
+    {
+        s->len = 0;
+        return NGX_OK;
+    }
+
+    s->len = ngx_strlen(buf);
+    s->data = ngx_pnalloc(pool, s->len);
+    if (s->data == NULL) {
+        return NGX_ERROR;
+    }
+
+    ngx_memcpy(s->data, buf, s->len);
+
+#endif
+
+    return NGX_OK;
+}
+
+
+ngx_int_t
 ngx_ssl_get_session_id(ngx_connection_t *c, ngx_pool_t *pool, ngx_str_t *s)
 {
     u_char        *buf;
diff --git a/src/event/ngx_event_openssl.h b/src/event/ngx_event_openssl.h
--- a/src/event/ngx_event_openssl.h
+++ b/src/event/ngx_event_openssl.h
@@ -191,6 +191,8 @@ ngx_int_t ngx_ssl_get_protocol(ngx_conne
     ngx_str_t *s);
 ngx_int_t ngx_ssl_get_cipher_name(ngx_connection_t *c, ngx_pool_t *pool,
     ngx_str_t *s);
+ngx_int_t ngx_ssl_get_ciphers(ngx_connection_t *c, ngx_pool_t *pool,
+    ngx_str_t *s);
 ngx_int_t ngx_ssl_get_session_id(ngx_connection_t *c, ngx_pool_t *pool,
     ngx_str_t *s);
 ngx_int_t ngx_ssl_get_session_reused(ngx_connection_t *c, ngx_pool_t *pool,
diff --git a/src/http/modules/ngx_http_ssl_module.c b/src/http/modules/ngx_http_ssl_module.c
--- a/src/http/modules/ngx_http_ssl_module.c
+++ b/src/http/modules/ngx_http_ssl_module.c
@@ -276,6 +276,9 @@ static ngx_http_variable_t  ngx_http_ssl
     { ngx_string("ssl_cipher"), NULL, ngx_http_ssl_static_variable,
       (uintptr_t) ngx_ssl_get_cipher_name, NGX_HTTP_VAR_CHANGEABLE, 0 },
 
+    { ngx_string("ssl_ciphers"), NULL, ngx_http_ssl_variable,
+      (uintptr_t) ngx_ssl_get_ciphers, NGX_HTTP_VAR_CHANGEABLE, 0 },
+
     { ngx_string("ssl_session_id"), NULL, ngx_http_ssl_variable,
       (uintptr_t) ngx_ssl_get_session_id, NGX_HTTP_VAR_CHANGEABLE, 0 },
 
diff --git a/src/stream/ngx_stream_ssl_module.c b/src/stream/ngx_stream_ssl_module.c
--- a/src/stream/ngx_stream_ssl_module.c
+++ b/src/stream/ngx_stream_ssl_module.c
@@ -182,6 +182,9 @@ static ngx_stream_variable_t  ngx_stream
     { ngx_string("ssl_cipher"), NULL, ngx_stream_ssl_static_variable,
       (uintptr_t) ngx_ssl_get_cipher_name, NGX_STREAM_VAR_CHANGEABLE, 0 },
 
+    { ngx_string("ssl_ciphers"), NULL, ngx_stream_ssl_variable,
+      (uintptr_t) ngx_ssl_get_ciphers, NGX_STREAM_VAR_CHANGEABLE, 0 },
+
     { ngx_string("ssl_session_id"), NULL, ngx_stream_ssl_variable,
       (uintptr_t) ngx_ssl_get_session_id, NGX_STREAM_VAR_CHANGEABLE, 0 },