openssh unix dev - Jan 2002 - [PATCH] Add user-dependent IdentityFile to OpenSSH-3.0.2p1

Here is a patch to allow private key files to be placed system wide (for
all users) in a secure (non-NFS) mounted location on systems where home
directories are NFS mounted. This is especially important for users who use
blank passphrases rather than ssh-agent (a good example of where this is
necessary is for tunnelling lpd through ssh on systems that run lpd as user
lp).

IdentityFile now accepts the same %u, %h, %% options that
AuthorizedKeysFile accepts (see man sshd). For example, one can specify a
user-dependent IdentityFile in ssh_config:

IdentityFile /ssh/%u/id_rsa 

This patch and others are maintained on the 
http://www.math.ualberta.ca/imaging/snfs/

-- John Bowman
University of Alberta

diff -ur openssh-3.0.2p1/auth.c openssh-3.0.2p1I/auth.c
--- openssh-3.0.2p1/auth.c	Sun Nov 11 17:06:07 2001
+++ openssh-3.0.2p1I/auth.c	Sun Jan 27 12:05:14 2002
@@ -44,7 +44,6 @@
 #include "auth.h"
 #include "auth-options.h"
 #include "canohost.h"
-#include "buffer.h"
 #include "bufaux.h"
 #include "uidswap.h"
 #include "tildexpand.h"
@@ -239,62 +238,6 @@
 	return 0;
 }
 
-
-/*
- * Given a template and a passwd structure, build a filename
- * by substituting % tokenised options. Currently, %% becomes '%',
- * %h becomes the home directory and %u the username.
- *
- * This returns a buffer allocated by xmalloc.
- */
-char *
-expand_filename(const char *filename, struct passwd *pw)
-{
-	Buffer buffer;
-	char *file;
-	const char *cp;
-
-	/*
-	 * Build the filename string in the buffer by making the appropriate
-	 * substitutions to the given file name.
-	 */
-	buffer_init(&buffer);
-	for (cp = filename; *cp; cp++) {
-		if (cp[0] == '%' && cp[1] == '%') {
-			buffer_append(&buffer, "%", 1);
-			cp++;
-			continue;
-		}
-		if (cp[0] == '%' && cp[1] == 'h') {
-			buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir));
-			cp++;
-			continue;
-		}
-		if (cp[0] == '%' && cp[1] == 'u') {
-			buffer_append(&buffer, pw->pw_name,
-			     strlen(pw->pw_name));
-			cp++;
-			continue;
-		}
-		buffer_append(&buffer, cp, 1);
-	}
-	buffer_append(&buffer, "\0", 1);
-
-	/*
-	 * Ensure that filename starts anchored. If not, be backward
-	 * compatible and prepend the '%h/'
-	 */
-	file = xmalloc(MAXPATHLEN);
-	cp = buffer_ptr(&buffer);
-	if (*cp != '/')
-		snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp);
-	else
-		strlcpy(file, cp, MAXPATHLEN);
-
-	buffer_free(&buffer);
-	return file;
-}
-
 char *
 authorized_keys_file(struct passwd *pw)
 {
diff -ur openssh-3.0.2p1/auth.h openssh-3.0.2p1I/auth.h
--- openssh-3.0.2p1/auth.h	Tue Jul  3 22:46:57 2001
+++ openssh-3.0.2p1I/auth.h	Sun Jan 27 12:05:14 2002
@@ -138,7 +138,6 @@
 
 struct passwd * auth_get_user(void);
 
-char	*expand_filename(const char *, struct passwd *);
 char	*authorized_keys_file(struct passwd *);
 char	*authorized_keys_file2(struct passwd *);
 
diff -ur openssh-3.0.2p1/ssh.c openssh-3.0.2p1I/ssh.c
--- openssh-3.0.2p1/ssh.c	Sun Nov 11 16:52:04 2001
+++ openssh-3.0.2p1I/ssh.c	Sun Jan 27 12:05:14 2002
@@ -1212,9 +1212,13 @@
 		key_free(public);
 	}
 #endif /* SMARTCARD */
+	struct passwd *pw;
+	pw=getpwuid(original_real_uid);
+	if (!pw) fatal("Unknown user id: %d", original_real_uid);
 	for (; i < options.num_identity_files; i++) {
 		filename = tilde_expand_filename(options.identity_files[i],
 		    original_real_uid);
+		filename = expand_filename(filename,pw);
 		public = key_load_public(filename, NULL);
 		debug("identity file %s type %d", filename,
 		    public ? public->type : -1);
diff -ur openssh-3.0.2p1/tildexpand.c openssh-3.0.2p1I/tildexpand.c
--- openssh-3.0.2p1/tildexpand.c	Wed Aug 15 17:19:22 2001
+++ openssh-3.0.2p1I/tildexpand.c	Sun Jan 27 12:05:14 2002
@@ -16,6 +16,7 @@
 #include "xmalloc.h"
 #include "log.h"
 #include "tildexpand.h"
+#include "buffer.h"
 
 /*
  * Expands tildes in the file name.  Returns data allocated by xmalloc.
@@ -47,7 +48,7 @@
 	if (userlen == 0)
 		pw = getpwuid(my_uid);		/* Own home directory. */
 	else {
-		/* Tilde refers to someone elses home directory. */
+		/* Tilde refers to someone else's home directory. */
 		if (userlen > sizeof(user) - 1)
 			fatal("User name after tilde too long.");
 		memcpy(user, filename, userlen);
@@ -70,3 +71,58 @@
 	snprintf(expanded, len, "%s%s%s", pw->pw_dir,
strcmp(pw->pw_dir, "/") ? "/" : "", cp + 1);
 	return expanded;
 }
+
+/*
+ * Given a template and a passwd structure, build a filename
+ * by substituting % tokenised options. Currently, %% becomes '%',
+ * %h becomes the home directory and %u the username.
+ *
+ * This returns a buffer allocated by xmalloc.
+ */
+char *
+expand_filename(const char *filename, struct passwd *pw)
+{
+	Buffer buffer;
+	char *file;
+	const char *cp;
+
+	/*
+	 * Build the filename string in the buffer by making the appropriate
+	 * substitutions to the given file name.
+	 */
+	buffer_init(&buffer);
+	for (cp = filename; *cp; cp++) {
+		if (cp[0] == '%' && cp[1] == '%') {
+			buffer_append(&buffer, "%", 1);
+			cp++;
+			continue;
+		}
+		if (cp[0] == '%' && cp[1] == 'h') {
+			buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir));
+			cp++;
+			continue;
+		}
+		if (cp[0] == '%' && cp[1] == 'u') {
+			buffer_append(&buffer, pw->pw_name,
+			     strlen(pw->pw_name));
+			cp++;
+			continue;
+		}
+		buffer_append(&buffer, cp, 1);
+	}
+	buffer_append(&buffer, "\0", 1);
+
+	/*
+	 * Ensure that filename starts anchored. If not, be backward
+	 * compatible and prepend the '%h/'
+	 */
+	file = xmalloc(MAXPATHLEN);
+	cp = buffer_ptr(&buffer);
+	if (*cp != '/')
+		snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp);
+	else
+		strlcpy(file, cp, MAXPATHLEN);
+
+	buffer_free(&buffer);
+	return file;
+}
diff -ur openssh-3.0.2p1/tildexpand.h openssh-3.0.2p1I/tildexpand.h
--- openssh-3.0.2p1/tildexpand.h	Tue Jul  3 22:46:58 2001
+++ openssh-3.0.2p1I/tildexpand.h	Sun Jan 27 12:05:14 2002
@@ -13,3 +13,4 @@
  */
 
 char	*tilde_expand_filename(const char *, uid_t);
+char	*expand_filename(const char *, struct passwd *);

> IdentityFile now accepts the same %u, %h, %% options that
> AuthorizedKeysFile accepts (see man sshd). For example, one can specify a
> user-dependent IdentityFile in ssh_config:
>
> IdentityFile /ssh/%u/id_rsa
I like this, but if we're going to be supporting % variables, I'd like
to
see them supported generically a la Samba.  ProxyCommand supports %h and %p,
for example, and it starts getting unweildy to mark which substittues what.
Perhaps throw a unified parser into readconf.c/ssh.c?

That being said, it's really, really useful to have access to % variables.

--Dan