[PATCH] Expand tilde for UNIX domain socket forwards.

[Todd C. Miller]

On Tue, 18 Aug 2015 09:41:47 +1000, Damien Miller wrote:

> Yeah, we should refactor it into a version that returns a ssherr.h code
> and (perhaps) leave the existing tilde_expand_filename() as a wrapper.

We could do something like this.  The name stinks but...

 - todd

Index: misc.c
===================================================================
RCS file: /cvs/src/usr.bin/ssh/misc.c,v
retrieving revision 1.97
diff -u -p -u -r1.97 misc.c
--- misc.c	24 Apr 2015 01:36:00 -0000	1.97
+++ misc.c	19 Aug 2015 02:28:18 -0000
@@ -50,6 +50,7 @@
 #include "xmalloc.h"
 #include "misc.h"
 #include "log.h"
+#include "ssherr.h"
 #include "ssh.h"
 
 /* remove newline at end of string */
@@ -499,29 +500,31 @@ freeargs(arglist *args)
  * Expands tildes in the file name.  Returns data allocated by xmalloc.
  * Warning: this calls getpw*.
  */
-char *
-tilde_expand_filename(const char *filename, uid_t uid)
+int
+tilde_expand_filename2(const char *filename, char **expanded, uid_t uid)
 {
 	const char *path, *sep;
 	char user[128], *ret;
 	struct passwd *pw;
-	u_int len, slash;
+	size_t len, slash;
 
-	if (*filename != '~')
-		return (xstrdup(filename));
+	if (*filename != '~') {
+		*expanded = xstrdup(filename);
+		return SSH_ERR_SUCCESS;
+	}
 	filename++;
 
 	path = strchr(filename, '/');
 	if (path != NULL && path > filename) {		/* ~user/path */
 		slash = path - filename;
 		if (slash > sizeof(user) - 1)
-			fatal("tilde_expand_filename: ~username too long");
+			return SSH_ERR_PATH_TOO_LONG;
 		memcpy(user, filename, slash);
 		user[slash] = '\0';
 		if ((pw = getpwnam(user)) == NULL)
-			fatal("tilde_expand_filename: No such user %s", user);
+			return SSH_ERR_UNKNOWN_USER;
 	} else if ((pw = getpwuid(uid)) == NULL)	/* ~/path */
-		fatal("tilde_expand_filename: No such uid %ld", (long)uid);
+		return SSH_ERR_UNKNOWN_USER;
 
 	/* Make sure directory has a trailing '/' */
 	len = strlen(pw->pw_dir);
@@ -534,10 +537,29 @@ tilde_expand_filename(const char *filena
 	if (path != NULL)
 		filename = path + 1;
 
-	if (xasprintf(&ret, "%s%s%s", pw->pw_dir, sep, filename) >= PATH_MAX)
-		fatal("tilde_expand_filename: Path too long");
+	if (xasprintf(ret, "%s%s%s", pw->pw_dir, sep, filename) >= PATH_MAX) {
+		free(ret);
+		return SSH_ERR_PATH_TOO_LONG;
+	}
+
+	*expanded = ret;
+	return SSH_ERR_SUCCESS;
+}
+
+/*
+ * Expands tildes in the file name.  Returns data allocated by xmalloc.
+ * Warning: this calls getpw*.
+ */
+char *
+tilde_expand_filename(const char *filename, uid_t uid)
+{
+	char *ret;
+	int rc;
 
-	return (ret);
+	rc = tilde_expand_filename2(filename, &ret, uid);
+	if (rc != SSH_ERR_SUCCESS)
+		fatal("%s: %s", __func__, ssh_err(rc));
+	return ret;
 }
 
 /*
Index: misc.h
===================================================================
RCS file: /cvs/src/usr.bin/ssh/misc.h,v
retrieving revision 1.54
diff -u -p -u -r1.54 misc.h
--- misc.h	15 Jul 2014 15:54:14 -0000	1.54
+++ misc.h	19 Aug 2015 02:27:37 -0000
@@ -49,6 +49,7 @@ char	*cleanhostname(char *);
 char	*colon(char *);
 long	 convtime(const char *);
 char	*tilde_expand_filename(const char *, uid_t);
+int	 tilde_expand_filename2(const char *, char **, uid_t);
 char	*percent_expand(const char *, ...) __attribute__((__sentinel__));
 char	*tohex(const void *, size_t);
 void	 sanitise_stdfd(void);
Index: ssherr.c
===================================================================
RCS file: /cvs/src/usr.bin/ssh/ssherr.c,v
retrieving revision 1.4
diff -u -p -u -r1.4 ssherr.c
--- ssherr.c	16 Feb 2015 22:13:32 -0000	1.4
+++ ssherr.c	19 Aug 2015 02:19:05 -0000
@@ -135,6 +135,10 @@ ssh_err(int n)
 		return "Connection corrupted";
 	case SSH_ERR_PROTOCOL_ERROR:
 		return "Protocol error";
+	case SSH_ERR_UNKNOWN_USER:
+		return "Unknown user";
+	case SSH_ERR_PATH_TOO_LONG:
+		return "Path too long";
 	default:
 		return "unknown error";
 	}
Index: ssherr.h
===================================================================
RCS file: /cvs/src/usr.bin/ssh/ssherr.h,v
retrieving revision 1.3
diff -u -p -u -r1.3 ssherr.h
--- ssherr.h	30 Jan 2015 01:13:33 -0000	1.3
+++ ssherr.h	19 Aug 2015 02:18:29 -0000
@@ -77,6 +77,8 @@
 #define SSH_ERR_CONN_TIMEOUT			-53
 #define SSH_ERR_CONN_CORRUPT			-54
 #define SSH_ERR_PROTOCOL_ERROR			-55
+#define SSH_ERR_UNKNOWN_USER			-56
+#define SSH_ERR_PATH_TOO_LONG			-57
 
 /* Translate a numeric error code to a human-readable error string */
 const char *ssh_err(int n);