upstream commit

refactor authentication logging

optionally record successful auth methods and public credentials
used in a file accessible to user sessions

feedback and ok markus@

Upstream-ID: 090b93036967015717b9a54fd0467875ae9d32fb

auth.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: auth.c,v 1.121 2017/05/30 08:52:19 markus Exp $ */
+/* $OpenBSD: auth.c,v 1.122 2017/06/24 06:34:38 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  *
@@ -267,21 +267,41 @@ allowed_user(struct passwd * pw)
 	return 1;
 }
 
-void
-auth_info(Authctxt *authctxt, const char *fmt, ...)
+/*
+ * Formats any key left in authctxt->auth_method_key for inclusion in
+ * auth_log()'s message. Also includes authxtct->auth_method_info if present.
+ */
+static char *
+format_method_key(Authctxt *authctxt)
 {
-	va_list ap;
-        int i;
-
-	free(authctxt->info);
-	authctxt->info = NULL;
+	const struct sshkey *key = authctxt->auth_method_key;
+	const char *methinfo = authctxt->auth_method_info;
+	char *fp, *ret = NULL;
 
-	va_start(ap, fmt);
-	i = vasprintf(&authctxt->info, fmt, ap);
-	va_end(ap);
+	if (key == NULL)
+		return NULL;
 
-	if (i < 0 || authctxt->info == NULL)
-		fatal("vasprintf failed");
+	if (key_is_cert(key)) {
+		fp = sshkey_fingerprint(key->cert->signature_key,
+		    options.fingerprint_hash, SSH_FP_DEFAULT);
+		xasprintf(&ret, "%s ID %s (serial %llu) CA %s %s%s%s",
+		    sshkey_type(key), key->cert->key_id,
+		    (unsigned long long)key->cert->serial,
+		    sshkey_type(key->cert->signature_key),
+		    fp == NULL ? "(null)" : fp,
+		    methinfo == NULL ? "" : ", ",
+		    methinfo == NULL ? "" : methinfo);
+		free(fp);
+	} else {
+		fp = sshkey_fingerprint(key, options.fingerprint_hash,
+		    SSH_FP_DEFAULT);
+		xasprintf(&ret, "%s %s%s%s", sshkey_type(key),
+		    fp == NULL ? "(null)" : fp,
+		    methinfo == NULL ? "" : ", ",
+		    methinfo == NULL ? "" : methinfo);
+		free(fp);
+	}
+	return ret;
 }
 
 void
@@ -290,7 +310,8 @@ auth_log(Authctxt *authctxt, int authenticated, int partial,
 {
 	struct ssh *ssh = active_state; /* XXX */
 	void (*authlog) (const char *fmt,...) = verbose;
-	char *authmsg;
+	const char *authmsg;
+	char *extra = NULL;
 
 	if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
 		return;
@@ -309,6 +330,11 @@ auth_log(Authctxt *authctxt, int authenticated, int partial,
 	else
 		authmsg = authenticated ? "Accepted" : "Failed";
 
+	if ((extra = format_method_key(authctxt)) == NULL) {
+		if (authctxt->auth_method_info != NULL)
+			extra = xstrdup(authctxt->auth_method_info);
+	}
+
 	authlog("%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s",
 	    authmsg,
 	    method,
@@ -317,10 +343,10 @@ auth_log(Authctxt *authctxt, int authenticated, int partial,
 	    authctxt->user,
 	    ssh_remote_ipaddr(ssh),
 	    ssh_remote_port(ssh),
-	    authctxt->info != NULL ? ": " : "",
-	    authctxt->info != NULL ? authctxt->info : "");
-	free(authctxt->info);
-	authctxt->info = NULL;
+	    extra != NULL ? ": " : "",
+	    extra != NULL ? extra : "");
+
+	free(extra);
 
 #ifdef CUSTOM_FAILED_LOGIN
 	if (authenticated == 0 && !authctxt->postponed &&

auth.h

@@ -1,4 +1,4 @@
-/* $OpenBSD: auth.h,v 1.91 2017/05/30 14:29:59 markus Exp $ */
+/* $OpenBSD: auth.h,v 1.92 2017/06/24 06:34:38 djm Exp $ */
 
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
@@ -44,6 +44,7 @@
 
 struct ssh;
 struct sshkey;
+struct sshbuf;
 
 typedef struct Authctxt Authctxt;
 typedef struct Authmethod Authmethod;
@@ -62,26 +63,38 @@ struct Authctxt {
 	char		*service;
 	struct passwd	*pw;		/* set if 'valid' */
 	char		*style;
+
+	/* Method lists for multiple authentication */
+	char		**auth_methods;	/* modified from server config */
+	u_int		 num_auth_methods;
+
+	/* Authentication method-specific data */
+	void		*methoddata;
 	void		*kbdintctxt;
-	char		*info;		/* Extra info for next auth_log */
 #ifdef BSD_AUTH
 	auth_session_t	*as;
 #endif
-	char		**auth_methods;	/* modified from server config */
-	u_int		 num_auth_methods;
 #ifdef KRB5
 	krb5_context	 krb5_ctx;
 	krb5_ccache	 krb5_fwd_ccache;
 	krb5_principal	 krb5_user;
 	char		*krb5_ticket_file;
 	char		*krb5_ccname;
 #endif
-	Buffer		*loginmsg;
-	void		*methoddata;
+	struct sshbuf	*loginmsg;
+
+	/* Authentication keys already used; these will be refused henceforth */
+	struct sshkey	**prev_keys;
+	u_int		 nprev_keys;
 
-	struct sshkey	**prev_userkeys;
-	u_int		 nprev_userkeys;
+	/* Last used key and ancilliary information from active auth method */
+	struct sshkey	*auth_method_key;
+	char		*auth_method_info;
+
+	/* Information exposed to session */
+	struct sshbuf	*session_info;	/* Auth info for environment */
 };
+
 /*
  * Every authentication method has to handle authentication requests for
  * non-existing users, or for users that are not allowed to login. In this
@@ -120,10 +133,18 @@ int      auth_password(Authctxt *, const char *);
 int	 hostbased_key_allowed(struct passwd *, const char *, char *,
 	    struct sshkey *);
 int	 user_key_allowed(struct passwd *, struct sshkey *, int);
-void	 pubkey_auth_info(Authctxt *, const struct sshkey *, const char *, ...)
-	    __attribute__((__format__ (printf, 3, 4)));
-void	 auth2_record_userkey(Authctxt *, struct sshkey *);
-int	 auth2_userkey_already_used(Authctxt *, struct sshkey *);
+int	 auth2_key_already_used(Authctxt *, const struct sshkey *);
+
+/*
+ * Handling auth method-specific information for logging and prevention
+ * of key reuse during multiple authentication.
+ */
+void	 auth2_authctxt_reset_info(Authctxt *);
+void	 auth2_record_key(Authctxt *, int, const struct sshkey *);
+void	 auth2_record_info(Authctxt *authctxt, const char *, ...)
+	    __attribute__((__format__ (printf, 2, 3)))
+	    __attribute__((__nonnull__ (2)));
+void	 auth2_update_session_info(Authctxt *, const char *, const char *);
 
 struct stat;
 int	 auth_secure_path(const char *, struct stat *, const char *, uid_t,
@@ -150,9 +171,6 @@ void disable_forwarding(void);
 
 void	do_authentication2(Authctxt *);
 
-void	auth_info(Authctxt *authctxt, const char *, ...)
-	    __attribute__((__format__ (printf, 2, 3)))
-	    __attribute__((__nonnull__ (2)));
 void	auth_log(Authctxt *, int, int, const char *, const char *);
 void	auth_maxtries_exceeded(Authctxt *) __attribute__((noreturn));
 void	userauth_finish(struct ssh *, int, const char *, const char *);

auth2-gss.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: auth2-gss.c,v 1.25 2017/05/30 14:29:59 markus Exp $ */
+/* $OpenBSD: auth2-gss.c,v 1.26 2017/06/24 06:34:38 djm Exp $ */
 
 /*
  * Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved.
@@ -228,6 +228,7 @@ input_gssapi_exchange_complete(int type, u_int32_t plen, struct ssh *ssh)
 {
 	Authctxt *authctxt = ssh->authctxt;
 	int authenticated;
+	const char *displayname;
 
 	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 		fatal("No authentication or GSSAPI context");
@@ -241,6 +242,10 @@ input_gssapi_exchange_complete(int type, u_int32_t plen, struct ssh *ssh)
 
 	authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
 
+	if ((!use_privsep || mm_is_monitor()) &&
+	    (displayname = ssh_gssapi_displayname()) != NULL)
+		auth2_record_info(authctxt, "%s", displayname);
+
 	authctxt->postponed = 0;
 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
@@ -259,6 +264,7 @@ input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh)
 	Buffer b;
 	gss_buffer_desc mic, gssbuf;
 	u_int len;
+	const char *displayname;
 
 	if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 		fatal("No authentication or GSSAPI context");
@@ -282,6 +288,10 @@ input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh)
 	buffer_free(&b);
 	free(mic.value);
 
+	if ((!use_privsep || mm_is_monitor()) &&
+	    (displayname = ssh_gssapi_displayname()) != NULL)
+		auth2_record_info(authctxt, "%s", displayname);
+
 	authctxt->postponed = 0;
 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);

auth2-hostbased.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: auth2-hostbased.c,v 1.30 2017/05/30 14:29:59 markus Exp $ */
+/* $OpenBSD: auth2-hostbased.c,v 1.31 2017/06/24 06:34:38 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  *
@@ -137,7 +137,7 @@ userauth_hostbased(struct ssh *ssh)
 	sshbuf_dump(b, stderr);
 #endif
 
-	pubkey_auth_info(authctxt, key,
+	auth2_record_info(authctxt,
 	    "client user \"%.100s\", client host \"%.100s\"", cuser, chost);
 
 	/* test for allowed key and correct signature */
@@ -147,11 +147,11 @@ userauth_hostbased(struct ssh *ssh)
 	    sshbuf_ptr(b), sshbuf_len(b), ssh->compat)) == 0)
 		authenticated = 1;
 
+	auth2_record_key(authctxt, authenticated, key);
 	sshbuf_free(b);
 done:
 	debug2("%s: authenticated %d", __func__, authenticated);
-	if (key != NULL)
-		sshkey_free(key);
+	sshkey_free(key);
 	free(pkalg);
 	free(pkblob);
 	free(cuser);

auth2-pubkey.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: auth2-pubkey.c,v 1.67 2017/05/31 10:54:00 markus Exp $ */
+/* $OpenBSD: auth2-pubkey.c,v 1.68 2017/06/24 06:34:38 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  *
@@ -137,7 +137,7 @@ userauth_pubkey(struct ssh *ssh)
 		goto done;
 	}
 	fp = sshkey_fingerprint(key, options.fingerprint_hash, SSH_FP_DEFAULT);
-	if (auth2_userkey_already_used(authctxt, key)) {
+	if (auth2_key_already_used(authctxt, key)) {
 		logit("refusing previously-used %s key", sshkey_type(key));
 		goto done;
 	}
@@ -194,20 +194,17 @@ userauth_pubkey(struct ssh *ssh)
 #ifdef DEBUG_PK
 		sshbuf_dump(b, stderr);
 #endif
-		pubkey_auth_info(authctxt, key, NULL);
 
 		/* test for correct signature */
 		authenticated = 0;
 		if (PRIVSEP(user_key_allowed(authctxt->pw, key, 1)) &&
 		    PRIVSEP(sshkey_verify(key, sig, slen, sshbuf_ptr(b),
 		    sshbuf_len(b), ssh->compat)) == 0) {
 			authenticated = 1;
-			/* Record the successful key to prevent reuse */
-			auth2_record_userkey(authctxt, key);
-			key = NULL; /* Don't free below */
 		}
 		sshbuf_free(b);
 		free(sig);
+		auth2_record_key(authctxt, authenticated, key);
 	} else {
 		debug("%s: test whether pkalg/pkblob are acceptable for %s %s",
 		    __func__, sshkey_type(key), fp);
@@ -237,53 +234,14 @@ userauth_pubkey(struct ssh *ssh)
 		auth_clear_options();
 done:
 	debug2("%s: authenticated %d pkalg %s", __func__, authenticated, pkalg);
-	if (key != NULL)
-		sshkey_free(key);
+	sshkey_free(key);
 	free(userstyle);
 	free(pkalg);
 	free(pkblob);
 	free(fp);
 	return authenticated;
 }
 
-void
-pubkey_auth_info(Authctxt *authctxt, const struct sshkey *key,
-    const char *fmt, ...)
-{
-	char *fp, *extra;
-	va_list ap;
-	int i;
-
-	extra = NULL;
-	if (fmt != NULL) {
-		va_start(ap, fmt);
-		i = vasprintf(&extra, fmt, ap);
-		va_end(ap);
-		if (i < 0 || extra == NULL)
-			fatal("%s: vasprintf failed", __func__);
-	}
-
-	if (sshkey_is_cert(key)) {
-		fp = sshkey_fingerprint(key->cert->signature_key,
-		    options.fingerprint_hash, SSH_FP_DEFAULT);
-		auth_info(authctxt, "%s ID %s (serial %llu) CA %s %s%s%s", 
-		    sshkey_type(key), key->cert->key_id,
-		    (unsigned long long)key->cert->serial,
-		    sshkey_type(key->cert->signature_key),
-		    fp == NULL ? "(null)" : fp,
-		    extra == NULL ? "" : ", ", extra == NULL ? "" : extra);
-		free(fp);
-	} else {
-		fp = sshkey_fingerprint(key, options.fingerprint_hash,
-		    SSH_FP_DEFAULT);
-		auth_info(authctxt, "%s %s%s%s", sshkey_type(key),
-		    fp == NULL ? "(null)" : fp,
-		    extra == NULL ? "" : ", ", extra == NULL ? "" : extra);
-		free(fp);
-	}
-	free(extra);
-}
-
 /*
  * Splits 's' into an argument vector. Handles quoted string and basic
  * escape characters (\\, \", \'). Caller must free the argument vector
@@ -1148,36 +1106,6 @@ user_key_allowed(struct passwd *pw, struct sshkey *key, int auth_attempt)
 	return success;
 }
 
-/* Records a public key in the list of previously-successful keys */
-void
-auth2_record_userkey(Authctxt *authctxt, struct sshkey *key)
-{
-	struct sshkey **tmp;
-
-	if (authctxt->nprev_userkeys >= INT_MAX ||
-	    (tmp = recallocarray(authctxt->prev_userkeys,
-	    authctxt->nprev_userkeys, authctxt->nprev_userkeys + 1,
-	    sizeof(*tmp))) == NULL)
-		fatal("%s: recallocarray failed", __func__);
-	authctxt->prev_userkeys = tmp;
-	authctxt->prev_userkeys[authctxt->nprev_userkeys] = key;
-	authctxt->nprev_userkeys++;
-}
-
-/* Checks whether a key has already been used successfully for authentication */
-int
-auth2_userkey_already_used(Authctxt *authctxt, struct sshkey *key)
-{
-	u_int i;
-
-	for (i = 0; i < authctxt->nprev_userkeys; i++) {
-		if (sshkey_equal_public(key, authctxt->prev_userkeys[i])) {
-			return 1;
-		}
-	}
-	return 0;
-}
-
 Authmethod method_pubkey = {
 	"publickey",
 	userauth_pubkey,