telnet: prevent SEGV if we are requested TELOPT_NEW_ENVIRON.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

diff --git a/networking/telnet.c b/networking/telnet.c
index 09f75cc..ec3db0c 100644 (file)
--- a/networking/telnet.c
+++ b/networking/telnet.c
@@ -299,7 +299,7 @@ static void put_iac_subopt(byte c, char *str)
 static void put_iac_subopt_autologin(void)
 {
        int len = strlen(G.autologin) + 6;      // (2 + 1 + 1 + strlen + 2)
-       const char *user = "USER";
+       const char *p = "USER";
 
        if (G.iaclen + len > IACBUFSIZE)
                iac_flush();
@@ -310,13 +310,14 @@ static void put_iac_subopt_autologin(void)
        put_iac(TELQUAL_IS);
        put_iac(NEW_ENV_VAR);
 
-       while (*user)
-               put_iac(*user++);
+       while (*p)
+               put_iac(*p++);
 
        put_iac(NEW_ENV_VALUE);
 
-       while (*G.autologin)
-               put_iac(*G.autologin++);
+       p = G.autologin;
+       while (*p)
+               put_iac(*p++);
 
        put_iac(IAC);
        put_iac(SE);
@@ -441,7 +442,6 @@ static void to_sga(void)
 static void to_ttype(void)
 {
        /* Tell server we will (or won't) do TTYPE */
-
        if (G.ttype)
                put_iac2(WILL, TELOPT_TTYPE);
        else
@@ -453,7 +453,6 @@ static void to_ttype(void)
 static void to_new_environ(void)
 {
        /* Tell server we will (or will not) do AUTOLOGIN */
-
        if (G.autologin)
                put_iac2(WILL, TELOPT_NEW_ENVIRON);
        else
@@ -505,12 +504,12 @@ static int subneg(byte c)
                        G.telstate = TS_SUB2;
 #if ENABLE_FEATURE_TELNET_TTYPE
                else
-               if (c == TELOPT_TTYPE)
+               if (c == TELOPT_TTYPE && G.ttype)
                        put_iac_subopt(TELOPT_TTYPE, G.ttype);
 #endif
 #if ENABLE_FEATURE_TELNET_AUTOLOGIN
                else
-               if (c == TELOPT_NEW_ENVIRON)
+               if (c == TELOPT_NEW_ENVIRON && G.autologin)
                        put_iac_subopt_autologin();
 #endif
                break;