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[fedora-virt] [PATCH] Add pipe support to guestfish



This patch adds support for pipes to guestfish, so you can pipe output
from a guestfish command through a command on the host.  The canonical
example is:

><fs> hexdump /bin/ls | less

Another example, looking for root backdoors in the password file:

><fs> cat /etc/passwd | awk -F: '$3 == 0 { print }' | grep -v ^root:

Anything right of the first pipe symbol gets passed to the local
shell, thus expansion, redirection and so on work on that.

Rich.

>From 57de1f4b17aba957ac18b64fccef66d2f21241d9 Mon Sep 17 00:00:00 2001
From: Richard W.M. Jones <rjones redhat com>
Date: Sat, 27 Jun 2009 15:00:48 +0200
Subject: [PATCH] Guestfish pipes.

---
 fish/fish.c   |   86 +++++++++++++++++++++++++++++++++++++++++++++++----------
 fish/fish.h   |    2 +-
 fish/glob.c   |    2 +-
 guestfish.pod |   26 +++++++++++++++++
 4 files changed, 99 insertions(+), 17 deletions(-)

diff --git a/fish/fish.c b/fish/fish.c
index 5e8a6e9..5b0a065 100644
--- a/fish/fish.c
+++ b/fish/fish.c
@@ -29,6 +29,8 @@
 #include <signal.h>
 #include <assert.h>
 #include <ctype.h>
+#include <sys/types.h>
+#include <sys/wait.h>
 
 #ifdef HAVE_LIBREADLINE
 #include <readline/readline.h>
@@ -138,9 +140,15 @@ main (int argc, char *argv[])
   struct mp *mp;
   char *p, *file = NULL;
   int c, inspector = 0;
+  struct sigaction sa;
 
   initialize_readline ();
 
+  memset (&sa, 0, sizeof sa);
+  sa.sa_handler = SIG_IGN;
+  sa.sa_flags = SA_RESTART;
+  sigaction (SIGPIPE, &sa, NULL);
+
   /* guestfs_create is meant to be a lightweight operation, so
    * it's OK to do it early here.
    */
@@ -462,6 +470,8 @@ script (int prompt)
 	      "\n"));
 
   while (!quit) {
+    char *pipe = NULL;
+
     exit_on_error = global_exit_on_error;
 
     buf = rl_gets (prompt);
@@ -522,9 +532,8 @@ script (int prompt)
 
     /* Get the parameters. */
     while (*p && i < sizeof argv / sizeof argv[0]) {
-      /* Parameters which start with quotes or square brackets
-       * are treated specially.  Bare parameters are delimited
-       * by whitespace.
+      /* Parameters which start with quotes or pipes are treated
+       * specially.  Bare parameters are delimited by whitespace.
        */
       if (*p == '"') {
 	p++;
@@ -556,6 +565,10 @@ script (int prompt)
 	}
 	p[len] = '\0';
 	pend = p[len+1] ? &p[len+2] : &p[len+1];
+      } else if (*p == '|') {
+	*p = '\0';
+	pipe = p+1;
+	continue;
 	/*
       } else if (*p == '[') {
 	int c = 1;
@@ -607,7 +620,7 @@ script (int prompt)
     argv[i] = NULL;
 
   got_command:
-    if (issue_command (cmd, argv) == -1) {
+    if (issue_command (cmd, argv, pipe) == -1) {
       if (exit_on_error) exit (1);
     }
 
@@ -636,18 +649,51 @@ cmdline (char *argv[], int optind, int argc)
     optind++;
 
   if (optind == argc) {
-    if (issue_command (cmd, params) == -1) exit (1);
+    if (issue_command (cmd, params, NULL) == -1) exit (1);
   } else {
     argv[optind] = NULL;
-    if (issue_command (cmd, params) == -1) exit (1);
+    if (issue_command (cmd, params, NULL) == -1) exit (1);
     cmdline (argv, optind+1, argc);
   }
 }
 
 int
-issue_command (const char *cmd, char *argv[])
+issue_command (const char *cmd, char *argv[], const char *pipecmd)
 {
   int argc;
+  int stdout_saved_fd = -1;
+  int pid = 0;
+  int r;
+
+  /* For | ... commands.  Annoyingly we can't use popen(3) here. */
+  if (pipecmd) {
+    int fd[2];
+
+    fflush (stdout);
+    pipe (fd);
+    pid = fork ();
+    if (pid == -1) {
+      perror ("fork");
+      return -1;
+    }
+
+    if (pid == 0) {		/* Child process. */
+      close (fd[1]);
+      dup2 (fd[0], 0);
+
+      r = system (pipecmd);
+      if (r == -1) {
+	perror (pipecmd);
+	_exit (1);
+      }
+      _exit (WEXITSTATUS (r));
+    }
+
+    stdout_saved_fd = dup (1);
+    close (fd[0]);
+    dup2 (fd[1], 1);
+    close (fd[1]);
+  }
 
   for (argc = 0; argv[argc] != NULL; ++argc)
     ;
@@ -657,29 +703,39 @@ issue_command (const char *cmd, char *argv[])
       list_commands ();
     else
       display_command (argv[0]);
-    return 0;
+    r = 0;
   }
   else if (strcasecmp (cmd, "quit") == 0 ||
 	   strcasecmp (cmd, "exit") == 0 ||
 	   strcasecmp (cmd, "q") == 0) {
     quit = 1;
-    return 0;
+    r = 0;
   }
   else if (strcasecmp (cmd, "alloc") == 0 ||
 	   strcasecmp (cmd, "allocate") == 0)
-    return do_alloc (cmd, argc, argv);
+    r = do_alloc (cmd, argc, argv);
   else if (strcasecmp (cmd, "echo") == 0)
-    return do_echo (cmd, argc, argv);
+    r = do_echo (cmd, argc, argv);
   else if (strcasecmp (cmd, "edit") == 0 ||
 	   strcasecmp (cmd, "vi") == 0 ||
 	   strcasecmp (cmd, "emacs") == 0)
-    return do_edit (cmd, argc, argv);
+    r = do_edit (cmd, argc, argv);
   else if (strcasecmp (cmd, "lcd") == 0)
-    return do_lcd (cmd, argc, argv);
+    r = do_lcd (cmd, argc, argv);
   else if (strcasecmp (cmd, "glob") == 0)
-    return do_glob (cmd, argc, argv);
+    r = do_glob (cmd, argc, argv);
   else
-    return run_action (cmd, argc, argv);
+    r = run_action (cmd, argc, argv);
+
+  if (pipecmd) {
+    fflush (stdout);
+    close (1);
+    dup2 (stdout_saved_fd, 1);
+    close (stdout_saved_fd);
+    waitpid (pid, NULL, 0);
+  }
+
+  return r;
 }
 
 void
diff --git a/fish/fish.h b/fish/fish.h
index 8815807..8f57595 100644
--- a/fish/fish.h
+++ b/fish/fish.h
@@ -34,7 +34,7 @@
 extern guestfs_h *g;
 extern int quit;
 extern int verbose;
-extern int issue_command (const char *cmd, char *argv[]);
+extern int issue_command (const char *cmd, char *argv[], const char *pipe);
 extern void pod2text (const char *heading, const char *body);
 extern void list_builtin_commands (void);
 extern void display_builtin_command (const char *cmd);
diff --git a/fish/glob.c b/fish/glob.c
index f20da84..a8ac58a 100644
--- a/fish/glob.c
+++ b/fish/glob.c
@@ -147,7 +147,7 @@ glob_issue (char *cmd, int argc,
   }
   printf ("\n");
 
-  if (issue_command (argv[0], &argv[1]) == -1)
+  if (issue_command (argv[0], &argv[1], NULL) == -1)
     *r = -1;			/* ... but don't exit */
 
   for (i = argc-1; i >= 1; --i) {
diff --git a/guestfish.pod b/guestfish.pod
index 0870b9e..26312fe 100644
--- a/guestfish.pod
+++ b/guestfish.pod
@@ -282,6 +282,32 @@ will create a directory C<local> on the host, and then export
 the contents of C</remote> on the mounted filesystem to
 C<local/remote-data.tar.gz>.  (See C<tgz-out>).
 
+=head1 PIPES
+
+Use C<command E<lt>spaceE<gt> | command> to pipe the output of the
+first command (a guestfish command) to the second command (any host
+command).  For example:
+
+ cat /etc/passwd | awk -F: '$3 == 0 { print }'
+
+(where C<cat> is the guestfish cat command, but C<awk> is the host awk
+program).  The above command would list all accounts in the guest
+filesystem which have UID 0, ie. root accounts including backdoors.
+Other examples:
+
+ hexdump /bin/ls | head
+ list-devices | tail -1
+
+The space before the pipe symbol is required, any space after the pipe
+symbol is optional.  Everything after the pipe symbol is just passed
+straight to the host shell, so it can contain redirections, globs and
+anything else that makes sense on the host side.
+
+To use a literal argument which begins with a pipe symbol, you have
+to quote it, eg:
+
+ echo "|"
+
 =head1 EXIT ON ERROR BEHAVIOUR
 
 By default, guestfish will ignore any errors when in interactive mode
-- 
1.6.2.2



-- 
Richard Jones, Emerging Technologies, Red Hat  http://et.redhat.com/~rjones
virt-df lists disk usage of guests without needing to install any
software inside the virtual machine.  Supports Linux and Windows.
http://et.redhat.com/~rjones/virt-df/


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