[Openvpn-devel,v4] push-peer-info: rearrange function generating peer info

Message ID 20220918220618.31112-1-a@unstable.cc
State New
Headers show
Series [Openvpn-devel,v4] push-peer-info: rearrange function generating peer info | expand

Commit Message

Antonio Quartulli Sept. 18, 2022, 10:06 p.m. UTC
This patch is supposed to implement no function change.
The only change in behaviour that can be observed is the IV_/UV_ variables
being printed in different order compared to before applying this patch.

However, order does not matter, so we don't need to retain it.

What this change really does is rearranging the push_peer_info() function
so that it becomes much more clear which variable is printed depending on
the peer-info detail level. The original code was mixed up, and figuring
the above out required reading this function multiple times.

This rearrangement puts everything in a switch/case block with sorted
peer-info details levels appearing one after the other.

While at it, the for loop extracting the wanted env variables has been
restructured a bit to avoid uber long conditions and extreme indentation.

Signed-off-by: Antonio Quartulli <a@unstable.cc>
---

NOTE: I tried to move this function to ssh_util.c to make it possible to
unit-test it. However, it requires a bunch of headers which make the whole
dependency chain explode..so I gave up.

Chanegs from v3:
* rebased on top of master (conflicted with "Implement exit notification
  via control channel")

Changes from v2:
* create helper function to push variable from env-set

Changes from v1:
* add spaces before case/default labels in switch block
---
 src/openvpn/ssl.c | 225 ++++++++++++++++++++++++++--------------------
 1 file changed, 129 insertions(+), 96 deletions(-)

Comments

Gert Doering Sept. 20, 2022, 4:42 p.m. UTC | #1
Hi,

On Mon, Sep 19, 2022 at 12:06:18AM +0200, Antonio Quartulli wrote:
> +    switch (session->opt->push_peer_info_detail)
>      {
> -        /* push version */
> -        buf_printf(&out, "IV_VER=%s\n", PACKAGE_VERSION);
> +        case 3:
> +        {
...
> +        }
>  
> +        /* fall through */

These {} brackets are not needed by C or our style guide.

Is this for uncrustify appeasement?  (I find them irritating)

gert
Antonio Quartulli Sept. 20, 2022, 7:25 p.m. UTC | #2
Hi,

On 20/09/2022 18:42, Gert Doering wrote:
> Hi,
> 
> On Mon, Sep 19, 2022 at 12:06:18AM +0200, Antonio Quartulli wrote:
>> +    switch (session->opt->push_peer_info_detail)
>>       {
>> -        /* push version */
>> -        buf_printf(&out, "IV_VER=%s\n", PACKAGE_VERSION);
>> +        case 3:
>> +        {
> ...
>> +        }
>>   
>> +        /* fall through */
> 
> These {} brackets are not needed by C or our style guide.

they are required when the first instruction after a case label is a 
variable declaration. So this is needed for case 3, but could be avoided 
for the other 2.

Cheers,
Selva Nair Sept. 20, 2022, 7:57 p.m. UTC | #3
On Tue, Sep 20, 2022 at 3:26 PM Antonio Quartulli <a@unstable.cc> wrote:

> Hi,
>
> On 20/09/2022 18:42, Gert Doering wrote:
> > Hi,
> >
> > On Mon, Sep 19, 2022 at 12:06:18AM +0200, Antonio Quartulli wrote:
> >> +    switch (session->opt->push_peer_info_detail)
> >>       {
> >> -        /* push version */
> >> -        buf_printf(&out, "IV_VER=%s\n", PACKAGE_VERSION);
> >> +        case 3:
> >> +        {
> > ...
> >> +        }
> >>
> >> +        /* fall through */
> >
> > These {} brackets are not needed by C or our style guide.
>
> they are required when the first instruction after a case label is a
> variable declaration. So this is needed for case 3, but could be avoided
> for the other 2.
>

IMO, we should have a policy of avoiding variable declarations within case:
clauses.

Whether its the first line after the case: label or not, if the scope is
not limited using {}, it leads to possible jumping over initialization. Its
so easy to overlook that. Unfortunately C (unlike C++) complains loudly
only if the declaration is next to the label.  One could always use {},
but that makes code hard to read. I think its much better to require that
all locals used within a switch block must be defined before all case:
labels.

Selva

Patch

diff --git a/src/openvpn/ssl.c b/src/openvpn/ssl.c
index d3f7a020..32579150 100644
--- a/src/openvpn/ssl.c
+++ b/src/openvpn/ssl.c
@@ -1910,6 +1910,44 @@  read_string_alloc(struct buffer *buf)
     return str;
 }
 
+/**
+ * Searches the environment variables set for variables starting with the
+ * specified pattern. If found, the variable string (i.e. VAR=VALUE) is
+ * copied to the out buffer provided as argument
+ *
+ * @param out       the output buffer where variables should be written to
+ * @param es        the environment variables set to search
+ * @param pattern   the pattern used to match variable names
+ */
+static void
+push_peer_info_env_var(struct buffer *out, const struct env_set *es, const char *pattern)
+{
+    for (const struct env_item *e = es->list; e; e = e->next)
+    {
+        /* ensure we have a string */
+        if (!e->string)
+        {
+            continue;
+        }
+
+        /* ensure string will fit output buffer */
+        if (!buf_safe(out, strlen(e->string) + 1))
+        {
+            continue;
+        }
+
+        /* don't accept any var except for those starting with the specified
+         * pattern
+         */
+        if (strncmp(e->string, pattern, strlen(pattern)) != 0)
+        {
+            continue;
+        }
+
+        buf_printf(out, "%s\n", e->string);
+    }
+}
+
 /**
  * Prepares the IV_ and UV_ variables that are part of the
  * exchange to signal the peer's capabilities. The amount
@@ -1932,137 +1970,132 @@  push_peer_info(struct buffer *buf, struct tls_session *session)
     bool ret = false;
     struct buffer out = alloc_buf_gc(512 * 3, &gc);
 
-    if (session->opt->push_peer_info_detail > 1)
+    switch (session->opt->push_peer_info_detail)
     {
-        /* push version */
-        buf_printf(&out, "IV_VER=%s\n", PACKAGE_VERSION);
+        case 3:
+        {
+            /* push mac addr */
+            struct route_gateway_info rgi;
+            get_default_gateway(&rgi, session->opt->net_ctx);
+            if (rgi.flags & RGI_HWADDR_DEFINED)
+            {
+                buf_printf(&out, "IV_HWADDR=%s\n", format_hex_ex(rgi.hwaddr, 6, 0, 1, ":", &gc));
+            }
+            buf_printf(&out, "IV_SSL=%s\n", get_ssl_library_version() );
+#if defined(_WIN32)
+            buf_printf(&out, "IV_PLAT_VER=%s\n", win32_version_string(&gc, false));
+#endif
+
+            /* push env vars that begin with UV_, IV_PLAT_VER= */
+            push_peer_info_env_var(&out, session->opt->es, "UV_");
+            push_peer_info_env_var(&out, session->opt->es, "IV_PLAT_VER=");
+        }
 
-        /* push platform */
+        /* fall through */
+        case 2:
+        {
+            /* push version */
+            buf_printf(&out, "IV_VER=%s\n", PACKAGE_VERSION);
+
+            /* push platform */
 #if defined(TARGET_LINUX)
-        buf_printf(&out, "IV_PLAT=linux\n");
+            buf_printf(&out, "IV_PLAT=linux\n");
 #elif defined(TARGET_SOLARIS)
-        buf_printf(&out, "IV_PLAT=solaris\n");
+            buf_printf(&out, "IV_PLAT=solaris\n");
 #elif defined(TARGET_OPENBSD)
-        buf_printf(&out, "IV_PLAT=openbsd\n");
+            buf_printf(&out, "IV_PLAT=openbsd\n");
 #elif defined(TARGET_DARWIN)
-        buf_printf(&out, "IV_PLAT=mac\n");
+            buf_printf(&out, "IV_PLAT=mac\n");
 #elif defined(TARGET_NETBSD)
-        buf_printf(&out, "IV_PLAT=netbsd\n");
+            buf_printf(&out, "IV_PLAT=netbsd\n");
 #elif defined(TARGET_FREEBSD)
-        buf_printf(&out, "IV_PLAT=freebsd\n");
+            buf_printf(&out, "IV_PLAT=freebsd\n");
 #elif defined(TARGET_ANDROID)
-        buf_printf(&out, "IV_PLAT=android\n");
+            buf_printf(&out, "IV_PLAT=android\n");
 #elif defined(_WIN32)
-        buf_printf(&out, "IV_PLAT=win\n");
+            buf_printf(&out, "IV_PLAT=win\n");
 #endif
-        /* Announce that we do not require strict sequence numbers with
-         * TCP. (TCP non-linear) */
-        buf_printf(&out, "IV_TCPNL=1\n");
-    }
 
-    /* These are the IV variable that are sent to peers in p2p mode */
-    if (session->opt->push_peer_info_detail > 0)
-    {
-        /* support for P_DATA_V2 */
-        int iv_proto = IV_PROTO_DATA_V2;
-
-        /* support for the --dns option */
-        iv_proto |= IV_PROTO_DNS_OPTION;
+            /* Announce that we do not require strict sequence numbers with
+             * TCP. (TCP non-linear) */
+            buf_printf(&out, "IV_TCPNL=1\n");
 
-        /* support for exit notify via control channel */
-        iv_proto |= IV_PROTO_CC_EXIT_NOTIFY;
+            /* push compression status */
+#ifdef USE_COMP
+            comp_generate_peer_info_string(&session->opt->comp_options, &out);
+#endif
 
-        /* support for receiving push_reply before sending
-         * push request, also signal that the client wants
-         * to get push-reply messages without without requiring a round
-         * trip for a push request message*/
-        if (session->opt->pull)
-        {
-            iv_proto |= IV_PROTO_REQUEST_PUSH;
-            iv_proto |= IV_PROTO_AUTH_PENDING_KW;
+            /* push env vars that begin with IV_GUI_VER= and IV_SSO= */
+            push_peer_info_env_var(&out, session->opt->es, "IV_GUI_VER=");
+            push_peer_info_env_var(&out, session->opt->es, "IV_SSO=");
         }
 
-        /* support for Negotiable Crypto Parameters */
-        if (session->opt->mode == MODE_SERVER || session->opt->pull)
+        /* fall through */
+        case 1:
         {
-            if (tls_item_in_cipher_list("AES-128-GCM", session->opt->config_ncp_ciphers)
-                && tls_item_in_cipher_list("AES-256-GCM", session->opt->config_ncp_ciphers))
-            {
+            /* support for P_DATA_V2 */
+            int iv_proto = IV_PROTO_DATA_V2;
+
+            /* support for the --dns option */
+            iv_proto |= IV_PROTO_DNS_OPTION;
 
-                buf_printf(&out, "IV_NCP=2\n");
+            /* support for exit notify via control channel */
+            iv_proto |= IV_PROTO_CC_EXIT_NOTIFY;
+
+            /* support for receiving push_reply before sending
+             * push request, also signal that the client wants
+             * to get push-reply messages without without requiring a round
+             * trip for a push request message*/
+            if (session->opt->pull)
+            {
+                iv_proto |= IV_PROTO_REQUEST_PUSH;
+                iv_proto |= IV_PROTO_AUTH_PENDING_KW;
             }
-        }
-        else
-        {
-            /* We are not using pull or p2mp server, instead do P2P NCP */
-            iv_proto |= IV_PROTO_NCP_P2P;
-        }
 
-        buf_printf(&out, "IV_CIPHERS=%s\n", session->opt->config_ncp_ciphers);
+            /* support for Negotiable Crypto Parameters */
+            if (session->opt->mode == MODE_SERVER || session->opt->pull)
+            {
+                if (tls_item_in_cipher_list("AES-128-GCM", session->opt->config_ncp_ciphers)
+                    && tls_item_in_cipher_list("AES-256-GCM", session->opt->config_ncp_ciphers))
+                {
+
+                    buf_printf(&out, "IV_NCP=2\n");
+                }
+            }
+            else
+            {
+                /* We are not using pull or p2mp server, instead do P2P NCP */
+                iv_proto |= IV_PROTO_NCP_P2P;
+            }
 
 #ifdef HAVE_EXPORT_KEYING_MATERIAL
-        iv_proto |= IV_PROTO_TLS_KEY_EXPORT;
+            iv_proto |= IV_PROTO_TLS_KEY_EXPORT;
 #endif
 
-        buf_printf(&out, "IV_PROTO=%d\n", iv_proto);
+            buf_printf(&out, "IV_PROTO=%d\n", iv_proto);
 
-        if (session->opt->push_peer_info_detail > 1)
-        {
-            /* push compression status */
-#ifdef USE_COMP
-            comp_generate_peer_info_string(&session->opt->comp_options, &out);
-#endif
-        }
+            buf_printf(&out, "IV_CIPHERS=%s\n", session->opt->config_ncp_ciphers);
 
-        if (session->opt->push_peer_info_detail > 2)
-        {
-            /* push mac addr */
-            struct route_gateway_info rgi;
-            get_default_gateway(&rgi, session->opt->net_ctx);
-            if (rgi.flags & RGI_HWADDR_DEFINED)
+            if (!write_string(buf, BSTR(&out), -1))
             {
-                buf_printf(&out, "IV_HWADDR=%s\n", format_hex_ex(rgi.hwaddr, 6, 0, 1, ":", &gc));
+                goto error;
             }
-            buf_printf(&out, "IV_SSL=%s\n", get_ssl_library_version() );
-#if defined(_WIN32)
-            buf_printf(&out, "IV_PLAT_VER=%s\n", win32_version_string(&gc, false));
-#endif
+            break;
         }
 
-        if (session->opt->push_peer_info_detail > 1)
-        {
-            struct env_set *es = session->opt->es;
-            /* push env vars that begin with UV_, IV_PLAT_VER and IV_GUI_VER */
-            for (struct env_item *e = es->list; e != NULL; e = e->next)
+        case 0:
+            if (!write_empty_string(buf))
             {
-                if (e->string)
-                {
-                    if ((((strncmp(e->string, "UV_", 3) == 0
-                           || strncmp(e->string, "IV_PLAT_VER=", sizeof("IV_PLAT_VER=") - 1) == 0)
-                          && session->opt->push_peer_info_detail > 2)
-                         || (strncmp(e->string, "IV_GUI_VER=", sizeof("IV_GUI_VER=") - 1) == 0)
-                         || (strncmp(e->string, "IV_SSO=", sizeof("IV_SSO=") - 1) == 0)
-                         )
-                        && buf_safe(&out, strlen(e->string) + 1))
-                    {
-                        buf_printf(&out, "%s\n", e->string);
-                    }
-                }
+                goto error;
             }
-        }
+            break;
 
-        if (!write_string(buf, BSTR(&out), -1))
-        {
-            goto error;
-        }
-    }
-    else
-    {
-        if (!write_empty_string(buf)) /* no peer info */
-        {
+        /* invalid value configured */
+        default:
+            msg(M_WARN, "Invalid peer-info-detail level %d", session->opt->push_peer_info_detail);
             goto error;
-        }
     }
+
     ret = true;
 
 error: