diff -up openssh-7.4p1/auth2.c.expose-pam openssh-7.4p1/auth2.c

--- openssh-7.4p1/auth2.c.expose-pam	2016-12-23 15:40:26.768447868 +0100

+++ openssh-7.4p1/auth2.c	2016-12-23 15:40:26.818447876 +0100

@@ -310,6 +310,7 @@ userauth_finish(Authctxt *authctxt, int

     const char *submethod)

 {

 	char *methods;

+	char *prev_auth_details;

 	int partial = 0;

 	if (!authctxt->valid && authenticated)

@@ -340,6 +341,18 @@ userauth_finish(Authctxt *authctxt, int

 	if (authctxt->postponed)

 		return;

+	if (authenticated || partial) {

+		prev_auth_details = authctxt->auth_details;

+		xasprintf(&authctxt->auth_details, "%s%s%s%s%s",

+		    prev_auth_details ? prev_auth_details : "",

+		    prev_auth_details ? ", " : "", method,

+		    authctxt->last_details ? ": " : "",

+		    authctxt->last_details ? authctxt->last_details : "");

+		free(prev_auth_details);

+	}

+	free(authctxt->last_details);

+	authctxt->last_details = NULL;

+

 #ifdef USE_PAM

 	if (options.use_pam && authenticated) {

 		if (!PRIVSEP(do_pam_account())) {

diff -up openssh-7.4p1/auth2-gss.c.expose-pam openssh-7.4p1/auth2-gss.c

--- openssh-7.4p1/auth2-gss.c.expose-pam	2016-12-23 15:40:26.769447868 +0100

+++ openssh-7.4p1/auth2-gss.c	2016-12-23 15:40:26.818447876 +0100

@@ -276,6 +276,9 @@ input_gssapi_exchange_complete(int type,

 	authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user,

 	    authctxt->pw));

+	if (authenticated)

+		authctxt->last_details = ssh_gssapi_get_displayname();

+

 	authctxt->postponed = 0;

 	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);

 	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);

@@ -322,6 +325,9 @@ input_gssapi_mic(int type, u_int32_t ple

 	else

 		logit("GSSAPI MIC check failed");

+	if (authenticated)

+		authctxt->last_details = ssh_gssapi_get_displayname();

+

 	buffer_free(&b);

 	if (micuser != authctxt->user)

 		free(micuser);

diff -up openssh-7.4p1/auth2-hostbased.c.expose-pam openssh-7.4p1/auth2-hostbased.c

--- openssh-7.4p1/auth2-hostbased.c.expose-pam	2016-12-23 15:40:26.731447862 +0100

+++ openssh-7.4p1/auth2-hostbased.c	2016-12-23 15:40:26.818447876 +0100

@@ -60,7 +60,7 @@ userauth_hostbased(Authctxt *authctxt)

 {

 	Buffer b;

 	Key *key = NULL;

-	char *pkalg, *cuser, *chost, *service;

+	char *pkalg, *cuser, *chost, *service, *pubkey;

 	u_char *pkblob, *sig;

 	u_int alen, blen, slen;

 	int pktype;

@@ -140,15 +140,21 @@ userauth_hostbased(Authctxt *authctxt)

 	buffer_dump(&b);

 #endif

-	pubkey_auth_info(authctxt, key,

-	    "client user \"%.100s\", client host \"%.100s\"", cuser, chost);

+	pubkey = sshkey_format_oneline(key, options.fingerprint_hash);

+	auth_info(authctxt,

+	    "%s, client user \"%.100s\", client host \"%.100s\"",

+	    pubkey, cuser, chost);

 	/* test for allowed key and correct signature */

 	authenticated = 0;

 	if (PRIVSEP(hostbased_key_allowed(authctxt->pw, cuser, chost, key)) &&

 	    PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),

-			buffer_len(&b))) == 1)

+			buffer_len(&b))) == 1) {

 		authenticated = 1;

+		authctxt->last_details = pubkey;

+	} else {

+		free(pubkey);

+	}

 	buffer_free(&b);

 done:

diff -up openssh-7.4p1/auth2-pubkey.c.expose-pam openssh-7.4p1/auth2-pubkey.c

--- openssh-7.4p1/auth2-pubkey.c.expose-pam	2016-12-23 15:40:26.746447864 +0100

+++ openssh-7.4p1/auth2-pubkey.c	2016-12-23 15:40:26.819447876 +0100

@@ -79,7 +79,7 @@ userauth_pubkey(Authctxt *authctxt)

 {

 	Buffer b;

 	Key *key = NULL;

-	char *pkalg, *userstyle, *fp = NULL;

+	char *pkalg, *userstyle, *pubkey, *fp = NULL;

 	u_char *pkblob, *sig;

 	u_int alen, blen, slen;

 	int have_sig, pktype;

@@ -177,7 +177,8 @@ userauth_pubkey(Authctxt *authctxt)

 #ifdef DEBUG_PK

 		buffer_dump(&b);

 #endif

-		pubkey_auth_info(authctxt, key, NULL);

+		pubkey = sshkey_format_oneline(key, options.fingerprint_hash);

+		auth_info(authctxt, "%s", pubkey);

 		/* test for correct signature */

 		authenticated = 0;

@@ -185,9 +186,12 @@ userauth_pubkey(Authctxt *authctxt)

 		    PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),

 		    buffer_len(&b))) == 1) {

 			authenticated = 1;

+			authctxt->last_details = pubkey;

 			/* Record the successful key to prevent reuse */

 			auth2_record_userkey(authctxt, key);

 			key = NULL; /* Don't free below */

+		} else {

+			free(pubkey);

 		}

 		buffer_free(&b);

 		free(sig);

@@ -228,7 +232,7 @@ done:

 void

 pubkey_auth_info(Authctxt *authctxt, const Key *key, const char *fmt, ...)

 {

-	char *fp, *extra;

+	char *extra, *pubkey;

 	va_list ap;

 	int i;

@@ -238,27 +242,13 @@ pubkey_auth_info(Authctxt *authctxt, con

 		i = vasprintf(&extra, fmt, ap);

 		va_end(ap);

 		if (i < 0 || extra == NULL)

-			fatal("%s: vasprintf failed", __func__);	

+			fatal("%s: vasprintf failed", __func__);

 	}

-	if (key_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", 

-		    key_type(key), key->cert->key_id,

-		    (unsigned long long)key->cert->serial,

-		    key_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", key_type(key),

-		    fp == NULL ? "(null)" : fp,

-		    extra == NULL ? "" : ", ", extra == NULL ? "" : extra);

-		free(fp);

-	}

+	pubkey = sshkey_format_oneline(key, options.fingerprint_hash);

+	auth_info(authctxt, "%s%s%s", pubkey, extra == NULL ? "" : ", ",

+	    extra == NULL ? "" : extra);

+	free(pubkey);

 	free(extra);

 }

diff -up openssh-7.4p1/auth.h.expose-pam openssh-7.4p1/auth.h

--- openssh-7.4p1/auth.h.expose-pam	2016-12-23 15:40:26.782447870 +0100

+++ openssh-7.4p1/auth.h	2016-12-23 15:40:26.819447876 +0100

@@ -84,6 +84,9 @@ struct Authctxt {

 	struct sshkey	**prev_userkeys;

 	u_int		 nprev_userkeys;

+

+	char		*last_details;

+	char		*auth_details;

 };

 /*

  * Every authentication method has to handle authentication requests for

diff -up openssh-7.4p1/auth-pam.c.expose-pam openssh-7.4p1/auth-pam.c

--- openssh-7.4p1/auth-pam.c.expose-pam	2016-12-23 15:40:26.731447862 +0100

+++ openssh-7.4p1/auth-pam.c	2016-12-23 15:40:26.819447876 +0100

@@ -688,6 +688,11 @@ sshpam_init_ctx(Authctxt *authctxt)

 		return (NULL);

 	}

+	/* Notify PAM about any already successful auth methods */

+	if (options.expose_auth_methods >= EXPOSE_AUTHMETH_PAMONLY &&

+			authctxt->auth_details)

+		do_pam_putenv("SSH_USER_AUTH", authctxt->auth_details);

+

 	ctxt = xcalloc(1, sizeof *ctxt);

 	/* Start the authentication thread */

diff -up openssh-7.4p1/gss-serv.c.expose-pam openssh-7.4p1/gss-serv.c

--- openssh-7.4p1/gss-serv.c.expose-pam	2016-12-23 15:40:26.808447874 +0100

+++ openssh-7.4p1/gss-serv.c	2016-12-23 15:40:26.819447876 +0100

@@ -441,6 +441,16 @@ ssh_gssapi_do_child(char ***envp, u_int

 }

 /* Privileged */

+char*

+ssh_gssapi_get_displayname(void)

+{

+	if (gssapi_client.displayname.length != 0 &&

+	    gssapi_client.displayname.value != NULL)

+		return strdup((char *)gssapi_client.displayname.value);

+	return NULL;

+}

+

+/* Privileged */

 int

 ssh_gssapi_userok(char *user, struct passwd *pw)

 {

diff -up openssh-7.4p1/monitor.c.expose-pam openssh-7.4p1/monitor.c

--- openssh-7.4p1/monitor.c.expose-pam	2016-12-23 15:40:26.794447872 +0100

+++ openssh-7.4p1/monitor.c	2016-12-23 15:41:16.473455863 +0100

@@ -300,6 +300,7 @@ monitor_child_preauth(Authctxt *_authctx

 {

 	struct mon_table *ent;

 	int authenticated = 0, partial = 0;

+	char *prev_auth_details;

 	debug3("preauth child monitor started");

@@ -330,6 +331,18 @@ monitor_child_preauth(Authctxt *_authctx

 		auth_submethod = NULL;

 		authenticated = (monitor_read(pmonitor, mon_dispatch, &ent) == 1);

+		if (authenticated) {

+			prev_auth_details = authctxt->auth_details;

+			xasprintf(&authctxt->auth_details, "%s%s%s%s%s",

+			    prev_auth_details ? prev_auth_details : "",

+			    prev_auth_details ? ", " : "", auth_method,

+			    authctxt->last_details ? ": " : "",

+			    authctxt->last_details ? authctxt->last_details : "");

+			free(prev_auth_details);

+		}

+		free(authctxt->last_details);

+		authctxt->last_details = NULL;

+

 		/* Special handling for multiple required authentications */

 		if (options.num_auth_methods != 0) {

 			if (authenticated &&

@@ -1417,6 +1430,10 @@ mm_answer_keyverify(int sock, Buffer *m)

 	debug3("%s: key %p signature %s",

 	    __func__, key, (verified == 1) ? "verified" : "unverified");

+	if (verified == 1)

+		authctxt->last_details = sshkey_format_oneline(key,

+		    options.fingerprint_hash);

+

 	/* If auth was successful then record key to ensure it isn't reused */

 	if (verified == 1 && key_blobtype == MM_USERKEY)

 		auth2_record_userkey(authctxt, key);

@@ -1860,6 +1877,9 @@ mm_answer_gss_userok(int sock, Buffer *m

 	auth_method = "gssapi-with-mic";

+	if (authenticated)

+		authctxt->last_details = ssh_gssapi_get_displayname();

+

 	/* Monitor loop will terminate if authenticated */

 	return (authenticated);

 }

diff -up openssh-7.4p1/servconf.c.expose-pam openssh-7.4p1/servconf.c

--- openssh-7.4p1/servconf.c.expose-pam	2016-12-23 15:40:26.810447875 +0100

+++ openssh-7.4p1/servconf.c	2016-12-23 15:44:04.691482920 +0100

@@ -171,6 +171,7 @@ initialize_server_options(ServerOptions

 	options->version_addendum = NULL;

 	options->use_kuserok = -1;

 	options->enable_k5users = -1;

+	options->expose_auth_methods = -1;

 	options->fingerprint_hash = -1;

 	options->disable_forwarding = -1;

 }

@@ -354,6 +355,8 @@ fill_default_server_options(ServerOption

 		options->use_kuserok = 1;

 	if (options->enable_k5users == -1)

 		options->enable_k5users = 0;

+	if (options->expose_auth_methods == -1)

+		options->expose_auth_methods = EXPOSE_AUTHMETH_NEVER;

 	if (options->fwd_opts.streamlocal_bind_mask == (mode_t)-1)

 		options->fwd_opts.streamlocal_bind_mask = 0177;

 	if (options->fwd_opts.streamlocal_bind_unlink == -1)

@@ -439,6 +442,7 @@ typedef enum {

 	sAuthenticationMethods, sHostKeyAgent, sPermitUserRC,

 	sStreamLocalBindMask, sStreamLocalBindUnlink,

 	sAllowStreamLocalForwarding, sFingerprintHash, sDisableForwarding,

+	sExposeAuthenticationMethods,

 	sDeprecated, sIgnore, sUnsupported

 } ServerOpCodes;

@@ -595,6 +599,7 @@ static struct {

 	{ "allowstreamlocalforwarding", sAllowStreamLocalForwarding, SSHCFG_ALL },

 	{ "fingerprinthash", sFingerprintHash, SSHCFG_GLOBAL },

 	{ "disableforwarding", sDisableForwarding, SSHCFG_ALL },

+	{ "exposeauthenticationmethods", sExposeAuthenticationMethods, SSHCFG_ALL },

 	{ NULL, sBadOption, 0 }

 };

@@ -984,6 +989,12 @@ static const struct multistate multistat

 	{ "local",			FORWARD_LOCAL },

 	{ NULL, -1 }

 };

+static const struct multistate multistate_exposeauthmeth[] = {

+	{ "never",			EXPOSE_AUTHMETH_NEVER },

+	{ "pam-only",			EXPOSE_AUTHMETH_PAMONLY },

+	{ "pam-and-env",		EXPOSE_AUTHMETH_PAMENV },

+	{ NULL, -1}

+};

 int

 process_server_config_line(ServerOptions *options, char *line,

@@ -1902,6 +1913,11 @@ process_server_config_line(ServerOptions

 			options->fingerprint_hash = value;

 		break;

+	case sExposeAuthenticationMethods:

+		intptr = &options->expose_auth_methods;

+		multistate_ptr = multistate_exposeauthmeth;

+		goto parse_multistate;

+

 	case sDeprecated:

 	case sIgnore:

 	case sUnsupported:

@@ -2060,6 +2076,7 @@ copy_set_server_options(ServerOptions *d

 	M_CP_INTOPT(enable_k5users);

 	M_CP_INTOPT(rekey_limit);

 	M_CP_INTOPT(rekey_interval);

+	M_CP_INTOPT(expose_auth_methods);

 	/*

 	 * The bind_mask is a mode_t that may be unsigned, so we can't use

@@ -2176,6 +2193,8 @@ fmt_intarg(ServerOpCodes code, int val)

 		return fmt_multistate_int(val, multistate_tcpfwd);

 	case sFingerprintHash:

 		return ssh_digest_alg_name(val);

+	case sExposeAuthenticationMethods:

+		return fmt_multistate_int(val, multistate_exposeauthmeth);

 	default:

 		switch (val) {

 		case 0:

@@ -2356,6 +2375,7 @@ dump_config(ServerOptions *o)

 	dump_cfg_fmtint(sUsePrivilegeSeparation, use_privsep);

 	dump_cfg_fmtint(sKerberosUseKuserok, o->use_kuserok);

 	dump_cfg_fmtint(sGssEnablek5users, o->enable_k5users);

+	dump_cfg_fmtint(sExposeAuthenticationMethods, o->expose_auth_methods);

 	dump_cfg_fmtint(sFingerprintHash, o->fingerprint_hash);

 	/* string arguments */

diff -up openssh-7.4p1/servconf.h.expose-pam openssh-7.4p1/servconf.h

--- openssh-7.4p1/servconf.h.expose-pam	2016-12-23 15:40:26.810447875 +0100

+++ openssh-7.4p1/servconf.h	2016-12-23 15:40:26.821447876 +0100

@@ -48,6 +48,11 @@

 #define FORWARD_LOCAL		(1<<1)

 #define FORWARD_ALLOW		(FORWARD_REMOTE|FORWARD_LOCAL)

+/* Expose AuthenticationMethods */

+#define EXPOSE_AUTHMETH_NEVER   0

+#define EXPOSE_AUTHMETH_PAMONLY 1

+#define EXPOSE_AUTHMETH_PAMENV  2

+

 #define DEFAULT_AUTH_FAIL_MAX	6	/* Default for MaxAuthTries */

 #define DEFAULT_SESSIONS_MAX	10	/* Default for MaxSessions */

@@ -195,6 +200,8 @@ typedef struct {

 	char   *auth_methods[MAX_AUTH_METHODS];

 	int	fingerprint_hash;

+

+	int	expose_auth_methods; /* EXPOSE_AUTHMETH_* above */

 }       ServerOptions;

 /* Information about the incoming connection as used by Match */

diff -up openssh-7.4p1/session.c.expose-pam openssh-7.4p1/session.c

--- openssh-7.4p1/session.c.expose-pam	2016-12-23 15:40:26.794447872 +0100

+++ openssh-7.4p1/session.c	2016-12-23 15:40:26.821447876 +0100

@@ -997,6 +997,12 @@ copy_environment(char **source, char ***

 		}

 		*var_val++ = '\0';

+		if (options.expose_auth_methods < EXPOSE_AUTHMETH_PAMENV &&

+				strcmp(var_name, "SSH_USER_AUTH") == 0) {

+			free(var_name);

+			continue;

+		}

+

 		debug3("Copy environment: %s=%s", var_name, var_val);

 		child_set_env(env, envsize, var_name, var_val);

@@ -1173,6 +1179,11 @@ do_setup_env(Session *s, const char *she

 	}

 #endif /* USE_PAM */

+	if (options.expose_auth_methods >= EXPOSE_AUTHMETH_PAMENV &&

+			s->authctxt->auth_details)

+		child_set_env(&env, &envsize, "SSH_USER_AUTH",

+		     s->authctxt->auth_details);

+

 	if (auth_sock_name != NULL)

 		child_set_env(&env, &envsize, SSH_AUTHSOCKET_ENV_NAME,

 		    auth_sock_name);

@@ -2561,6 +2572,9 @@ do_cleanup(Authctxt *authctxt)

 	if (authctxt == NULL)

 		return;

+	free(authctxt->auth_details);

+	authctxt->auth_details = NULL;

+

 #ifdef USE_PAM

 	if (options.use_pam) {

 		sshpam_cleanup();

diff -up openssh-7.4p1/ssh.1.expose-pam openssh-7.4p1/ssh.1

--- openssh-7.4p1/ssh.1.expose-pam	2016-12-23 15:40:26.810447875 +0100

+++ openssh-7.4p1/ssh.1	2016-12-23 15:40:26.822447877 +0100

@@ -1421,6 +1421,10 @@ server IP address, and server port numbe

 This variable contains the original command line if a forced command

 is executed.

 It can be used to extract the original arguments.

+.It Ev SSH_USER_AUTH

+This variable contains, for SSH2 only, a comma-separated list of authentication

+methods that were successfuly used to authenticate. When possible, these

+methods are extended with detailed information on the credential used.

 .It Ev SSH_TTY

 This is set to the name of the tty (path to the device) associated

 with the current shell or command.

diff -up openssh-7.4p1/sshd_config.5.expose-pam openssh-7.4p1/sshd_config.5

--- openssh-7.4p1/sshd_config.5.expose-pam	2016-12-23 15:40:26.822447877 +0100

+++ openssh-7.4p1/sshd_config.5	2016-12-23 15:45:22.411495421 +0100

@@ -570,6 +570,21 @@ Disables all forwarding features, includ

 TCP and StreamLocal.

 This option overrides all other forwarding-related options and may

 simplify restricted configurations.

+.It Cm ExposeAuthenticationMethods

+When using SSH2, this option controls the exposure of the list of

+successful authentication methods to PAM during the authentication

+and to the shell environment via the

+.Cm SSH_USER_AUTH

+variable. See the description of this variable for more details.

+Valid options are:

+.Cm never

+(Do not expose successful authentication methods),

+.Cm pam-only

+(Only expose them to PAM during authentication, not afterwards),

+.Cm pam-and-env

+(Expose them to PAM and keep them in the shell environment).

+The default is

+.Cm never .

 .It Cm FingerprintHash

 Specifies the hash algorithm used when logging key fingerprints.

 Valid options are:

diff -up openssh-7.4p1/ssh-gss.h.expose-pam openssh-7.4p1/ssh-gss.h

--- openssh-7.4p1/ssh-gss.h.expose-pam	2016-12-23 15:40:26.811447875 +0100

+++ openssh-7.4p1/ssh-gss.h	2016-12-23 15:40:26.823447877 +0100

@@ -159,6 +159,7 @@ int ssh_gssapi_server_check_mech(Gssctxt

     const char *);

 OM_uint32 ssh_gssapi_server_ctx(Gssctxt **, gss_OID);

 int ssh_gssapi_userok(char *name, struct passwd *);

+char* ssh_gssapi_get_displayname(void);

 OM_uint32 ssh_gssapi_checkmic(Gssctxt *, gss_buffer_t, gss_buffer_t);

 void ssh_gssapi_do_child(char ***, u_int *);

 void ssh_gssapi_cleanup_creds(void);

diff -up openssh-7.4p1/sshkey.c.expose-pam openssh-7.4p1/sshkey.c

--- openssh-7.4p1/sshkey.c.expose-pam	2016-12-23 15:40:26.777447869 +0100

+++ openssh-7.4p1/sshkey.c	2016-12-23 15:40:26.823447877 +0100

@@ -57,6 +57,7 @@

 #define SSHKEY_INTERNAL

 #include "sshkey.h"

 #include "match.h"

+#include "xmalloc.h"

 /* openssh private key file format */

 #define MARK_BEGIN		"-----BEGIN OPENSSH PRIVATE KEY-----\n"

@@ -1191,6 +1192,30 @@ sshkey_fingerprint(const struct sshkey *

 	return retval;

 }

+char *

+sshkey_format_oneline(const struct sshkey *key, int dgst_alg)

+{

+	char *fp, *result;

+

+	if (sshkey_is_cert(key)) {

+		fp = sshkey_fingerprint(key->cert->signature_key, dgst_alg,

+		    SSH_FP_DEFAULT);

+		xasprintf(&result, "%s ID %s (serial %llu) CA %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);

+		free(fp);

+	} else {

+		fp = sshkey_fingerprint(key, dgst_alg, SSH_FP_DEFAULT);

+		xasprintf(&result, "%s %s", sshkey_type(key),

+		    fp == NULL ? "(null)" : fp);

+		free(fp);

+	}

+

+	return result;

+}

+

 #ifdef WITH_SSH1

 /*

  * Reads a multiple-precision integer in decimal from the buffer, and advances

diff -up openssh-7.4p1/sshkey.h.expose-pam openssh-7.4p1/sshkey.h

--- openssh-7.4p1/sshkey.h.expose-pam	2016-12-23 15:40:26.777447869 +0100

+++ openssh-7.4p1/sshkey.h	2016-12-23 15:40:26.823447877 +0100

@@ -124,6 +124,7 @@ char		*sshkey_fingerprint(const struct s

     int, enum sshkey_fp_rep);

 int		 sshkey_fingerprint_raw(const struct sshkey *k,

     int, u_char **retp, size_t *lenp);

+char		*sshkey_format_oneline(const struct sshkey *k, int dgst_alg);

 const char	*sshkey_type(const struct sshkey *);

 const char	*sshkey_cert_type(const struct sshkey *);

 int		 sshkey_write(const struct sshkey *, FILE *);