From 11b8c55bc9c9ac3639cda50e5f3e15d6eb4443a3 Mon Sep 17 00:00:00 2001
From: Mattias Andrée <maandree@operamail.com>
Date: Tue, 19 Nov 2013 00:23:59 +0100
Subject: m + spawn shell
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Signed-off-by: Mattias Andrée <maandree@operamail.com>
---
 Makefile       |  5 ++--
 src/cerberus.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++++++++-----
 src/cerberus.h |  2 ++
 3 files changed, 83 insertions(+), 9 deletions(-)

diff --git a/Makefile b/Makefile
index 4e29083..6e73c52 100644
--- a/Makefile
+++ b/Makefile
@@ -16,7 +16,8 @@ _SS = $(SBIN)
 
 TTY_GROUP = tty
 DEFAULT_HOME = /
-DEFAULT_SHELL = $(BIN)/sh
+DEFAULT_SH = sh
+DEFAULT_SHELL = $(BIN)/$(DEFAULT_SH)
 DEFAULT_TERM = dumb
 VCS = $(DEV)/vcs
 VCSA = $(DEV)/vcsa
@@ -28,7 +29,7 @@ VCS_LEN = $(shell vcs="$(VCS)" ; echo "$${$(H)vcs}")
 VCSA_LEN = $(shell vcsa="$(VCSA)" ; echo "$${$(H)vcsa}")
 VCS_VCSA_LEN = $(shell (echo $(VCS_LEN) ; echo $(VCSA_LEN)) | sort -n | tail -n 1)
 
-STR_DEFS = TTY_GROUP DEFAULT_HOME DEFAULT_SHELL DEFAULT_TERM PATH PATH_ROOT VCS VCSA
+STR_DEFS = TTY_GROUP DEFAULT_HOME DEFAULT_SH DEFAULT_SHELL DEFAULT_TERM PATH PATH_ROOT VCS VCSA
 INT_DEFS = VCS_LEN VCSA_LEN VCS_VCSA_LEN
 
 STR_CPPFLAGS = $(foreach D, $(STR_DEFS), -D'$(D)="$($(D))"')
diff --git a/src/cerberus.c b/src/cerberus.c
index f60f64c..3a5dd5d 100644
--- a/src/cerberus.c
+++ b/src/cerberus.c
@@ -36,7 +36,7 @@ int main(int argc, char** argv)
   char preserve_env = 0;
   char skip_auth = 0;
   #ifdef USE_TTY_GROUP
-  gid_t tty_group = 0;
+  static gid_t tty_group = 0;
   struct group* group;
   #endif
   struct passwd* entry;
@@ -179,17 +179,88 @@ int main(int argc, char** argv)
   reenable_echo();
   
   
-  /* Login */
+  /* Partial login */
   /* TODO verify that user is enabled */
-  set_user(entry);
-  /* TODO set supplemental groups */
+  chown_tty(entry->pw_uid, tty_group, 0);
   chdir_home(entry);
   ensure_shell(entry);
   set_environ(entry, preserve_env);
   
-  
-  /* Reset terminal ownership and mode */
-  chown_tty(0, tty_group, 0);
+  {
+    pid_t pid = fork();
+    /* vfork cannot be used as the child changes the user,
+       the parent would not be able to chown the TTY */
+    
+    if (pid == -1)
+      {
+	perror("fork");
+	return 1;
+      }
+    else if (pid == 0)
+      {
+	int child_argc = 0;
+	char** child_argv = malloc(5 * sizeof(char*));
+	int n = 0;
+	char* sh = entry->pw_shell;
+	char* login_sh;
+        
+	/* Partial login */
+	/* TODO set supplemental groups */
+	set_user(entry);
+	
+	while (*(sh + n++))
+	  ;
+	
+	login_sh = malloc((n + (strchr(sh, ' ') ? 5 : 1)) * sizeof(char));
+	if (login_sh == NULL)
+	  {
+	    perror("malloc");
+	    sleep(ERROR_SLEEP);
+	    _exit(1);
+	  }
+	
+	if (strchr(sh, ' '))
+	  {
+	    login_sh += 5;
+	    strcpy(login_sh, "exec ");
+	    *(login_sh + n) = 0;
+	    
+	    *(child_argv + child_argc++) = DEFAULT_SHELL;
+	    *(child_argv + child_argc++) = "-" DEFAULT_SH;
+	    *(child_argv + child_argc++) = "-c";
+	    *(child_argv + child_argc++) = login_sh - 5;
+	  }
+	else
+	  {
+	    int i;
+	    for (i = n - 1; i >= 0; i--)
+	      if (*(sh + i) == '/')
+		{
+		  i++;
+		  break;
+		}
+	    
+	    login_sh = malloc((n + 1) * sizeof(char));
+	    *login_sh++ = '-';
+	    strcpy(login_sh, sh + i);
+	    *(login_sh + n) = 0;
+	    
+	    *(child_argv + child_argc++) = sh;
+	    *(child_argv + child_argc++) = login_sh - 1;
+	  }
+        
+	*(child_argv + child_argc) = NULL;
+        execvp(*child_argv, child_argv + 1);
+      }
+    else
+      {
+	int _status;
+	waitpid(pid, &_status, 0);
+	
+	/* Reset terminal ownership and mode */
+	chown_tty(0, tty_group, 0);
+      }
+  }
   
   return 0;
 }
diff --git a/src/cerberus.h b/src/cerberus.h
index a4ba19a..b5501a4 100644
--- a/src/cerberus.h
+++ b/src/cerberus.h
@@ -24,8 +24,10 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <signal.h>
+#include <string.h>
 #include <pwd.h>
 #include <errno.h>
+#include <sys/wait.h>
 #ifdef USE_TTY_GROUP
 #include <grp.h>
 #endif
-- 
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