Subject: [PATCH] Fix CVE-2017-16927

sesman: scpv0, accept variable length data fields

Upstream-Status: Backport 

---
 sesman/libscp/libscp_v0.c | 32 +++++++++++++++++++++++++-------
 1 file changed, 25 insertions(+), 7 deletions(-)

diff --git a/sesman/libscp/libscp_v0.c b/sesman/libscp/libscp_v0.c
index 5a0c8bf..5693407 100644
--- a/sesman/libscp/libscp_v0.c
+++ b/sesman/libscp/libscp_v0.c
@@ -161,7 +161,7 @@ scp_v0s_accept(struct SCP_CONNECTION *c, struct SCP_SESSION **s, int skipVchk)
     struct SCP_SESSION *session = 0;
     tui16 sz;
     tui32 code = 0;
-    char buf[257];
+    char *buf = 0;
 
     if (!skipVchk)
     {
@@ -226,27 +226,31 @@ scp_v0s_accept(struct SCP_CONNECTION *c, struct SCP_SESSION **s, int skipVchk)
 
         /* reading username */
         in_uint16_be(c->in_s, sz);
-        buf[sz] = '\0';
+        buf = g_new0(char, sz);
         in_uint8a(c->in_s, buf, sz);
-
+        buf[sz] = '\0';
         if (0 != scp_session_set_username(session, buf))
         {
             scp_session_destroy(session);
             log_message(LOG_LEVEL_WARNING, "[v0:%d] connection aborted: error setting username", __LINE__);
+            g_free(buf);
             return SCP_SERVER_STATE_INTERNAL_ERR;
         }
+        g_free(buf);
 
         /* reading password */
         in_uint16_be(c->in_s, sz);
-        buf[sz] = '\0';
+        buf = g_new0(char, sz);
         in_uint8a(c->in_s, buf, sz);
-
+        buf[sz] = '\0';
         if (0 != scp_session_set_password(session, buf))
         {
             scp_session_destroy(session);
             log_message(LOG_LEVEL_WARNING, "[v0:%d] connection aborted: error setting password", __LINE__);
+            g_free(buf);
             return SCP_SERVER_STATE_INTERNAL_ERR;
         }
+        g_free(buf);
 
         /* width */
         in_uint16_be(c->in_s, sz);
@@ -272,9 +276,11 @@ scp_v0s_accept(struct SCP_CONNECTION *c, struct SCP_SESSION **s, int skipVchk)
 
             if (sz > 0)
             {
+                buf = g_new0(char, sz);
                 in_uint8a(c->in_s, buf, sz);
                 buf[sz] = '\0';
                 scp_session_set_domain(session, buf);
+                g_free(buf);
             }
         }
 
@@ -285,9 +291,11 @@ scp_v0s_accept(struct SCP_CONNECTION *c, struct SCP_SESSION **s, int skipVchk)
 
             if (sz > 0)
             {
+                buf = g_new0(char, sz);
                 in_uint8a(c->in_s, buf, sz);
                 buf[sz] = '\0';
                 scp_session_set_program(session, buf);
+                g_free(buf);
             }
         }
 
@@ -298,9 +306,11 @@ scp_v0s_accept(struct SCP_CONNECTION *c, struct SCP_SESSION **s, int skipVchk)
 
             if (sz > 0)
             {
+                buf = g_new0(char, sz);
                 in_uint8a(c->in_s, buf, sz);
                 buf[sz] = '\0';
                 scp_session_set_directory(session, buf);
+                g_free(buf);
             }
         }
 
@@ -311,9 +321,11 @@ scp_v0s_accept(struct SCP_CONNECTION *c, struct SCP_SESSION **s, int skipVchk)
 
             if (sz > 0)
             {
+                buf = g_new0(char, sz);
                 in_uint8a(c->in_s, buf, sz);
                 buf[sz] = '\0';
                 scp_session_set_client_ip(session, buf);
+                g_free(buf);
             }
         }
     }
@@ -332,29 +344,35 @@ scp_v0s_accept(struct SCP_CONNECTION *c, struct SCP_SESSION **s, int skipVchk)
         scp_session_set_type(session, SCP_GW_AUTHENTICATION);
         /* reading username */
         in_uint16_be(c->in_s, sz);
-        buf[sz] = '\0';
+        buf = g_new0(char, sz);
         in_uint8a(c->in_s, buf, sz);
+        buf[sz] = '\0';
 
         /* g_writeln("Received user name: %s",buf); */
         if (0 != scp_session_set_username(session, buf))
         {
             scp_session_destroy(session);
             /* until syslog merge log_message(s_log, LOG_LEVEL_WARNING, "[v0:%d] connection aborted: error setting        username", __LINE__);*/
+            g_free(buf);
             return SCP_SERVER_STATE_INTERNAL_ERR;
         }
+        g_free(buf);
 
         /* reading password */
         in_uint16_be(c->in_s, sz);
-        buf[sz] = '\0';
+        buf = g_new0(char, sz);
         in_uint8a(c->in_s, buf, sz);
+        buf[sz] = '\0';
 
         /* g_writeln("Received password: %s",buf); */
         if (0 != scp_session_set_password(session, buf))
         {
             scp_session_destroy(session);
             /* until syslog merge log_message(s_log, LOG_LEVEL_WARNING, "[v0:%d] connection aborted: error setting password", __LINE__); */
+            g_free(buf);
             return SCP_SERVER_STATE_INTERNAL_ERR;
         }
+        g_free(buf);
     }
     else
     {
-- 
2.7.4