OpenSSH with no prompts PAM auth fails.

It appears some OpenSSH servers now send a PAM auth request without any
prompts.  This triggers an error from cryptlib.  following is the level
3 debug output from cryptlib on a refused connection, and I've attached
a patch against the latest non-beta release (3.4.2) that fixes it
(basically allows no prompts for PAM auth).

debug2: load_server_config: filename /etc/ssh/sshd_config
debug2: load_server_config: done config len = 188
debug2: parse_server_config: config /etc/ssh/sshd_config len 188
debug3: /etc/ssh/sshd_config:129 setting Subsystem sftp  
 /usr/libexec/sftp-server
debug1: HPN Buffer Size: 65536
debug1: sshd version OpenSSH_6.6.1p1_hpn13v11 FreeBSD-20140420, OpenSSL
1.0.1j-freebsd 15 Oct 2014
debug3: Incorrect RSA1 identifier
debug1: key_parse_private2: missing begin marker
debug1: read PEM private key done: type RSA
debug3: Incorrect RSA1 identifier
debug3: Could not load "/etc/ssh/ssh_host_rsa_key" as a RSA1 public key
debug1: private host key: #0 type 1 RSA
debug3: Incorrect RSA1 identifier
debug1: key_parse_private2: missing begin marker
debug1: read PEM private key done: type DSA
debug3: Incorrect RSA1 identifier
debug3: Could not load "/etc/ssh/ssh_host_dsa_key" as a RSA1 public key
debug1: private host key: #1 type 2 DSA
debug3: Incorrect RSA1 identifier
debug1: key_parse_private2: missing begin marker
debug1: read PEM private key done: type ECDSA
debug3: Incorrect RSA1 identifier
debug3: Could not load "/etc/ssh/ssh_host_ecdsa_key" as a RSA1 public key
debug1: private host key: #2 type 3 ECDSA
debug3: Incorrect RSA1 identifier
debug3: Incorrect RSA1 identifier
debug3: Could not load "/etc/ssh/ssh_host_ed25519_key" as a RSA1 public key
debug1: private host key: #3 type 4 ED25519
debug1: rexec_argv[0]='/usr/sbin/sshd'
debug1: rexec_argv[1]='-Dddd'
debug1: rexec_argv[2]='-p'
debug1: rexec_argv[3]='1887'
debug2: fd 3 setting O_NONBLOCK
debug3: ssh_sock_set_v6only: set socket 3 IPV6_V6ONLY
debug1: Bind to port 1887 on ::.
debug1: Server TCP RWIN socket size: 65536
debug1: HPN Buffer Size: 65536
Server listening on :: port 1887.
debug2: fd 4 setting O_NONBLOCK
debug1: Bind to port 1887 on 0.0.0.0.
debug1: Server TCP RWIN socket size: 65536
debug1: HPN Buffer Size: 65536
Server listening on 0.0.0.0 port 1887.
debug1: fd 5 clearing O_NONBLOCK
debug1: Server will not fork when running in debugging mode.
debug3: send_rexec_state: entering fd = 8 config len 188
debug3: ssh_msg_send: type 0
debug3: send_rexec_state: done
debug1: rexec start in 5 out 5 newsock 5 pipe -1 sock 8
debug1: inetd sockets after dupping: 3, 3
debug1: res_init()
Connection from ::1 port 50860 on ::1 port 1887
debug1: HPN Disabled: 0, HPN Buffer Size: 65536
debug1: Client protocol version 2.0; client software version cryptlib
debug1: no match: cryptlib
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.6.1_hpn13v11 FreeBSD-20140420
debug2: fd 3 setting O_NONBLOCK
debug3: ssh_sandbox_init: preparing capsicum sandbox
debug2: Network child is on pid 43805
debug3: preauth child monitor started
debug3: privsep user:group 22:22 [preauth]
debug1: permanently_set_uid: 22/22 [preauth]
debug1: list_hostkey_types:
ssh-rsa,ssh-dss,ecdsa-sha2-nistp256,ssh-ed25519 [preauth]
debug1: SSH2_MSG_KEXINIT sent [preauth]
debug1: SSH2_MSG_KEXINIT received [preauth]
debug2: kex_parse_kexinit:
[email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
[preauth]
debug2: kex_parse_kexinit:
ssh-rsa,ssh-dss,ecdsa-sha2-nistp256,ssh-ed25519 [preauth]
debug2: kex_parse_kexinit:
aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,[email protected],[email protected],[email protected],aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected]
[preauth]
debug2: kex_parse_kexinit:
aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,[email protected],[email protected],[email protected],aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected]
[preauth]
debug2: kex_parse_kexinit:
[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-md5,hmac-sha1,[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
[preauth]
debug2: kex_parse_kexinit:
[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-md5,hmac-sha1,[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
[preauth]
debug2: kex_parse_kexinit: none,[email protected] [preauth]
debug2: kex_parse_kexinit: none,[email protected] [preauth]
debug2: kex_parse_kexinit:  [preauth]
debug2: kex_parse_kexinit:  [preauth]
debug2: kex_parse_kexinit: first_kex_follows 0  [preauth]
debug2: kex_parse_kexinit: reserved 0  [preauth]
debug2: kex_parse_kexinit: diffie-hellman-group-exchange-sha256 [preauth]
debug2: kex_parse_kexinit: ssh-rsa [preauth]
debug2: kex_parse_kexinit: 3des-cbc [preauth]
debug2: kex_parse_kexinit: 3des-cbc [preauth]
debug2: kex_parse_kexinit: hmac-sha2-256 [preauth]
debug2: kex_parse_kexinit: hmac-sha2-256 [preauth]
debug2: kex_parse_kexinit: none [preauth]
debug2: kex_parse_kexinit: none [preauth]
debug2: kex_parse_kexinit:  [preauth]
debug2: kex_parse_kexinit:  [preauth]
debug2: kex_parse_kexinit: first_kex_follows 0  [preauth]
debug2: kex_parse_kexinit: reserved 0  [preauth]
debug2: mac_setup: setup hmac-sha2-256 [preauth]
debug1: kex: client->server 3des-cbc hmac-sha2-256 none [preauth]
debug2: mac_setup: setup hmac-sha2-256 [preauth]
debug1: kex: server->client 3des-cbc hmac-sha2-256 none [preauth]
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received [preauth]
debug3: mm_request_send entering: type 0 [preauth]
debug3: mm_choose_dh: waiting for MONITOR_ANS_MODULI [preauth]
debug3: mm_request_receive_expect entering: type 1 [preauth]
debug3: mm_request_receive entering [preauth]
debug3: mm_request_receive entering
debug3: monitor_read: checking request 0
debug3: mm_answer_moduli: got parameters: 1024 1024 8192
debug3: mm_request_send entering: type 1
debug2: monitor_read: 0 used once, disabling now
debug3: mm_choose_dh: remaining 0 [preauth]
debug1: SSH2_MSG_KEX_DH_GEX_GROUP sent [preauth]
debug2: bits set: 532/1024 [preauth]
debug1: expecting SSH2_MSG_KEX_DH_GEX_INIT [preauth]
debug2: bits set: 507/1024 [preauth]
debug3: mm_key_sign entering [preauth]
debug3: mm_request_send entering: type 6 [preauth]
debug3: mm_key_sign: waiting for MONITOR_ANS_SIGN [preauth]
debug3: mm_request_receive_expect entering: type 7 [preauth]
debug3: mm_request_receive entering [preauth]
debug3: mm_request_receive entering
debug3: monitor_read: checking request 6
debug3: mm_answer_sign
debug3: mm_answer_sign: signature 0x8040858c0(271)
debug3: mm_request_send entering: type 7
debug2: monitor_read: 6 used once, disabling now
debug1: SSH2_MSG_KEX_DH_GEX_REPLY sent [preauth]
debug2: kex_derive_keys [preauth]
debug2: set_newkeys: mode 1 [preauth]
debug1: SSH2_MSG_NEWKEYS sent [preauth]
debug1: expecting SSH2_MSG_NEWKEYS [preauth]
debug2: set_newkeys: mode 0 [preauth]
debug1: SSH2_MSG_NEWKEYS received [preauth]
debug1: KEX done [preauth]
debug3: Trying to reverse map address ::1. [preauth]
debug1: userauth-request for user admin service ssh-connection method
password [preauth]
debug1: attempt 0 failures 0 [preauth]
debug3: mm_getpwnamallow entering [preauth]
debug3: mm_request_send entering: type 8 [preauth]
debug3: mm_getpwnamallow: waiting for MONITOR_ANS_PWNAM [preauth]
debug3: mm_request_receive_expect entering: type 9 [preauth]
debug3: mm_request_receive entering [preauth]
debug3: mm_request_receive entering
debug3: monitor_read: checking request 8
debug3: mm_answer_pwnamallow
debug3: Trying to reverse map address ::1.
debug2: parse_server_config: config reprocess config len 188
debug3: mm_answer_pwnamallow: sending MONITOR_ANS_PWNAM: 1
debug3: mm_request_send entering: type 9
debug2: monitor_read: 8 used once, disabling now
debug2: input_userauth_request: setting up authctxt for admin [preauth]
debug3: mm_start_pam entering [preauth]
debug3: mm_request_send entering: type 100 [preauth]
debug3: mm_inform_authserv entering [preauth]
debug3: mm_request_send entering: type 4 [preauth]
debug3: mm_request_receive entering
debug3: monitor_read: checking request 100
debug1: PAM: initializing for "admin"
debug1: PAM: setting PAM_RHOST to "localhost"
debug2: monitor_read: 100 used once, disabling now
debug2: Unrecognized authentication method name: password [preauth]
debug3: userauth_finish: failure partial=0 next
methods="publickey,keyboard-interactive" [preauth]
debug1: userauth-request for user admin service ssh-connection method
keyboard-interactive [preauth]
debug1: attempt 1 failures 1 [preauth]
debug2: input_userauth_request: try method keyboard-interactive [preauth]
debug1: keyboard-interactive devs  [preauth]
debug1: auth2_challenge: user=admin devs= [preauth]
debug1: kbdint_alloc: devices 'pam' [preauth]
debug2: auth2_challenge_start: devices pam [preauth]
debug2: kbdint_next_device: devices <empty> [preauth]
debug1: auth2_challenge_start: trying authentication method 'pam' [preauth]
debug3: mm_sshpam_init_ctx [preauth]
debug3: mm_request_send entering: type 104 [preauth]
debug3: mm_sshpam_init_ctx: waiting for MONITOR_ANS_PAM_INIT_CTX [preauth]
debug3: mm_request_receive_expect entering: type 105 [preauth]
debug3: mm_request_receive entering [preauth]
debug3: mm_request_receive entering
debug3: monitor_read: checking request 4
debug3: mm_answer_authserv: service=ssh-connection, style=
debug2: monitor_read: 4 used once, disabling now
debug3: mm_request_receive entering
debug3: monitor_read: checking request 104
debug3: mm_answer_pam_init_ctx
debug3: PAM: sshpam_init_ctx entering
debug3: mm_request_send entering: type 105
debug3: mm_sshpam_query [preauth]
debug3: mm_request_send entering: type 106 [preauth]
debug3: mm_sshpam_query: waiting for MONITOR_ANS_PAM_QUERY [preauth]
debug3: mm_request_receive_expect entering: type 107 [preauth]
debug3: mm_request_receive entering [preauth]
debug3: mm_request_receive entering
debug3: monitor_read: checking request 106
debug3: mm_answer_pam_query
debug3: PAM: sshpam_query entering
debug3: ssh_msg_recv entering
debug3: PAM: sshpam_thread_conv entering, 1 messages
debug3: ssh_msg_send: type 1
debug3: ssh_msg_recv entering
debug3: mm_request_send entering: type 107
debug3: mm_sshpam_query: pam_query returned 0 [preauth]
Postponed keyboard-interactive for admin from ::1 port 50860 ssh2 [preauth]
debug3: mm_sshpam_respond [preauth]
debug3: mm_request_send entering: type 108 [preauth]
debug3: mm_sshpam_respond: waiting for MONITOR_ANS_PAM_RESPOND [preauth]
debug3: mm_request_receive_expect entering: type 109 [preauth]
debug3: mm_request_receive entering [preauth]
debug3: mm_request_receive entering
debug3: monitor_read: checking request 108
debug3: mm_answer_pam_respond
debug2: PAM: sshpam_respond entering, 1 responses
debug3: ssh_msg_send: type 6
debug3: mm_request_send entering: type 109
debug3: mm_sshpam_respond: pam_respond returned 1 [preauth]
debug3: mm_sshpam_query [preauth]
debug3: mm_request_send entering: type 106 [preauth]
debug3: mm_sshpam_query: waiting for MONITOR_ANS_PAM_QUERY [preauth]
debug3: mm_request_receive_expect entering: type 107 [preauth]
debug3: mm_request_receive entering [preauth]
debug3: mm_request_receive entering
debug3: monitor_read: checking request 106
debug3: mm_answer_pam_query
debug3: PAM: sshpam_query entering
debug3: ssh_msg_recv entering
debug1: do_pam_account: called
debug3: PAM: do_pam_account pam_acct_mgmt = 0 (success)
debug3: ssh_msg_send: type 0
debug3: PAM: import_environments entering
debug3: sshpam_password_change_required 0
debug3: PAM: num env strings 0
debug1: PAM: num PAM env strings 0
debug3: mm_request_send entering: type 107
debug3: mm_sshpam_query: pam_query returned 0 [preauth]
Postponed keyboard-interactive/pam for admin from ::1 port 50860 ssh2
[preauth]
Received disconnect from ::1: 10:  [preauth]
debug1: do_cleanup [preauth]
debug3: PAM: sshpam_thread_cleanup entering [preauth]
debug1: monitor_read_log: child log fd closed
debug3: mm_request_receive entering
debug1: do_cleanup
debug1: PAM: cleanup
debug3: PAM: sshpam_thread_cleanup entering
debug1: Killing privsep child 43805

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--- ../cl/session/ssh2_authc.c	2012-09-10 22:40:52.000000000 -0700
+++ session/ssh2_authc.c	2015-03-20 21:23:03.000000000 -0700
@@ -529,7 +529,7 @@
 		if( !cryptStatusError( status ) )
 			{
 			status = CRYPT_OK;	/* readUint32() returns a count value */
-			if( noPrompts <= 0 || noPrompts > 4 )
+			if( noPrompts < 0 || noPrompts > 4 )
 				{
 				/* Requesting zero or more than a small number of prompts is 
 				   suspicious */
@@ -537,37 +537,39 @@
 				}
 			}
 		}
-	if( cryptStatusOK( status ) )
-		status = readString32( &stream, promptBuffer, 
-							   CRYPT_MAX_TEXTSIZE, &promptLength );
-	sMemDisconnect( &stream );
-	if( cryptStatusError( status ) )
-		{
-		retExt( status,
-				( status, SESSION_ERRINFO, 
-				  "Invalid PAM authentication request packet" ) );
-		}
+	if ( noPrompts > 0 ) {
+		if( cryptStatusOK( status ) )
+			status = readString32( &stream, promptBuffer, 
+								   CRYPT_MAX_TEXTSIZE, &promptLength );
+		sMemDisconnect( &stream );
+		if( cryptStatusError( status ) )
+			{
+			retExt( status,
+					( status, SESSION_ERRINFO, 
+					  "Invalid PAM authentication request packet" ) );
+			}
 
-	/* Make sure that we're being asked for some form of password 
-	   authentication.  This assumes that the prompt string begins with the 
-	   word "password" (which always seems to be the case), if it isn't then 
-	   it may be necessary to do a substring search */
-	if( promptLength < 8 || strCompare( promptBuffer, "Password", 8 ) )
-		{
+		/* Make sure that we're being asked for some form of password 
+		   authentication.  This assumes that the prompt string begins with the 
+		   word "password" (which always seems to be the case), if it isn't then 
+		   it may be necessary to do a substring search */
+		if( promptLength < 8 || strCompare( promptBuffer, "Password", 8 ) )
+			{
 		/* The following may produce somewhat inconsistent results in terms
 		   of what it reports because it's unclear what 'name' actually is, 
 		   on the off chance that something fills this in it could produce
 		   a less appropriate error message than the prompt, but we 
 		   opportunistically try it in case it contains something useful */
-		retExt( CRYPT_ERROR_BADDATA,
-				( CRYPT_ERROR_BADDATA, SESSION_ERRINFO, 
-				  "Server requested unknown PAM authentication type '%s'", 
-				  ( nameLength > 0 ) ? \
-				  sanitiseString( nameBuffer, CRYPT_MAX_TEXTSIZE, \
-								  nameLength ) : \
-				  sanitiseString( promptBuffer, CRYPT_MAX_TEXTSIZE, \
-								  promptLength ) ) );
-		}
+			retExt( CRYPT_ERROR_BADDATA,
+					( CRYPT_ERROR_BADDATA, SESSION_ERRINFO, 
+					  "Server requested unknown PAM authentication type '%s'", 
+					  ( nameLength > 0 ) ? \
+					  sanitiseString( nameBuffer, CRYPT_MAX_TEXTSIZE, \
+									  nameLength ) : \
+					  sanitiseString( promptBuffer, CRYPT_MAX_TEXTSIZE, \
+									  promptLength ) ) );
+			}
+	}
 
 	REQUIRES( passwordPtr != NULL && \
 			  passwordPtr->valueLength > 0 && \