From cdd4bc0b411d6834952434b80313b5ee0b131db0 Mon Sep 17 00:00:00 2001
From: Franklin Wei <git@fwei.tk>
Date: Sat, 5 Dec 2015 13:20:26 -0500
Subject: telnet support

---
 Makefile      |  2 +-
 src/client.c  |  9 +++++++++
 src/netcosm.h |  8 ++++++++
 src/telnet.c  | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/telnet.h  | 20 ++++++++++++++++++++
 5 files changed, 99 insertions(+), 1 deletion(-)
 create mode 100644 src/telnet.c
 create mode 100644 src/telnet.h

diff --git a/Makefile b/Makefile
index 45107c1..0539e7d 100644
--- a/Makefile
+++ b/Makefile
@@ -2,7 +2,7 @@ CC = clang
 OUT = build
 PLATFORM = unix
 
-NETCOSM_OBJ = src/server.o src/client.o src/auth.o
+NETCOSM_OBJ = src/server.o src/client.o src/auth.o src/telnet.o
 
 CFLAGS = -O0 -g -I src/ -I target/$(PLATFORM) -Wall -Wextra
 LDFLAGS = -lgcrypt
diff --git a/src/client.c b/src/client.c
index 5555bd5..18c390c 100644
--- a/src/client.c
+++ b/src/client.c
@@ -13,6 +13,11 @@ void __attribute__((format(printf,1,2))) out(const char *fmt, ...)
     write(client_fd, buf, sizeof(buf));
 }
 
+void out_raw(const unsigned char *buf, size_t len)
+{
+    write(client_fd, buf, len);
+}
+
 #define BUFSZ 128
 
 char *client_read(void)
@@ -32,6 +37,8 @@ tryagain:
     printf("Read '%s'\n", buf);
     if(buf[0] & 0x80)
     {
+        telnet_handle_command((unsigned char*)buf);
+
         free(buf);
         goto tryagain;
     }
@@ -54,6 +61,8 @@ void client_main(int fd, struct sockaddr_in *addr, int total)
 {
     client_fd = fd;
 
+    telnet_init();
+
     char *ip = inet_ntoa(addr->sin_addr);
     printf("New client %s\n", ip);
     printf("Total clients: %d\n", total);
diff --git a/src/netcosm.h b/src/netcosm.h
index 4f04e5b..c8566da 100644
--- a/src/netcosm.h
+++ b/src/netcosm.h
@@ -18,6 +18,8 @@
 #include <time.h>
 #include <unistd.h>
 
+#include "telnet.h"
+
 #define USERFILE "users.dat"
 #define MAX_FAILURES 3
 #define NETCOSM_VERSION "v0.1"
@@ -40,3 +42,9 @@ struct authinfo_t auth_check(const char*, const char*);
 /* add or change a user */
 bool add_change_user(const char *user2, const char *pass2, int level);
 bool auth_remove(const char*);
+void telnet_handle_command(const unsigned char*);
+#define ARRAYLEN(x) (sizeof(x)/sizeof(x[0]))
+
+void out(const char *fmt, ...) __attribute__((format(printf,1,2)));
+void out_raw(const unsigned char*, size_t);
+void telnet_init(void);
diff --git a/src/telnet.c b/src/telnet.c
new file mode 100644
index 0000000..2e86195
--- /dev/null
+++ b/src/telnet.c
@@ -0,0 +1,61 @@
+#include "netcosm.h"
+
+void telnet_handle_command(const unsigned char *buf)
+{
+    bool cmd = false;
+
+    while(*buf)
+    {
+        unsigned char c = *buf;
+
+        const struct telnet_cmd {
+            int val;
+            const char *name;
+        } commands[] = {
+            {  IAC,     "IAC"     },
+            {  DONT,    "DONT"    },
+            {  DO,      "DO"      },
+            {  WONT,    "WONT"    },
+            {  WILL,    "WILL"    },
+            {  GA,      "GA"      },
+            {  AYT,     "AYT"     },
+            {  NOP,     "NOP"     },
+            {  SB,      "SB"      },
+            {  SE,      "SE"      },
+            {  ECHO,    "ECHO"    },
+            {  SGA,     "SGA"     },
+            {  STATUS,  "STATUS"  },
+            {  NAWS,    "NAWS"    }
+        };
+
+        for(unsigned int i = 0; i < ARRAYLEN(commands); ++i)
+        {
+            if(c == commands[i].val)
+            {
+                printf("%s ", commands[i].name);
+                cmd = true;
+                goto found;
+            }
+        }
+        printf("??? ");
+    found:
+
+        ++buf;
+    }
+
+    if(cmd)
+        printf("\n");
+}
+
+void telnet_init(void)
+{
+    const unsigned char init_seq[] = {
+        IAC, WONT, SGA,
+        IAC, DONT, SGA,
+        IAC, WONT, NAWS,
+        IAC, DONT, NAWS,
+        IAC, WONT, STATUS,
+        IAC, DONT, STATUS,
+    };
+    out_raw(init_seq, ARRAYLEN(init_seq));
+}
diff --git a/src/telnet.h b/src/telnet.h
new file mode 100644
index 0000000..475cfce
--- /dev/null
+++ b/src/telnet.h
@@ -0,0 +1,20 @@
+/* commands */
+
+#define IAC 255
+#define DONT 254
+#define DO 253
+#define WONT 252
+#define WILL 251
+#define SB 250
+#define GA 249
+#define EL 248
+#define EC 247
+#define AYT 246
+#define NOP 241
+#define SE 240
+
+/* options */
+#define ECHO 1
+#define SGA 3
+#define STATUS 5
+#define NAWS 31
-- 
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