dropbear: adjust configuration

- add new options:
  - DROPBEAR_DEFAULT_MAX_DURATION
  - DROPBEAR_MAX_PUBKEY_QUERIES
- fix DROPBEAR_MLKEM768 description (fixes commit d8ff2d8cba)

Signed-off-by: Konstantin Demin <rockdrilla@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/23217
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

package/network/services/dropbear/Config.in

@@ -535,6 +535,28 @@ menu "Resource limits"
 			Possible values: 1 to 80 (from src/sysoptions.h)
 			Default: 10
 
+	config DROPBEAR_MAX_PUBKEY_QUERIES
+		int "Max. public key queries per session"
+		range 1 80
+		default 15
+		help
+			Default maximum number of public key queries per session (server option).
+
+			Public key queries aren't a risk for brute forcing authentication,
+			but can be a user enumeration/privacy concern if an attacker
+			attempts to iterate known public keys such as those published by GitHub.
+
+			This limit has a trade-off. Having a smaller limit reduces the number
+			of legitimate public keys that can be presented by a client/ssh agent.
+
+			That is still a risk against a single host,
+			but this limit may deter internet-wide scanning.
+
+			If -T argument or DROPBEAR_MAX_AUTH_TRIES is larger that will be used instead.
+
+			Possible values: 1 to 80 (same as for DROPBEAR_MAX_AUTH_TRIES)
+			Default: 15
+
 	config DROPBEAR_UNAUTH_CLOSE_DELAY
 		int "Delay closing unauth. connections (seconds)"
 		range 0 3600
@@ -640,6 +662,21 @@ menu "Resource limits"
 			Possible values: 0 to 604800 (7 days)
 			Default: 0 (disabled).
 
+	config DROPBEAR_DEFAULT_MAX_DURATION
+		int "Default max. session duration (seconds)"
+		range 0 604800
+		default 0
+		help
+			If session duration exceeds specified limit, disconnect.
+			Applies to both server and client.
+
+			Note: values below 30 seconds are not recommended.
+
+			This can be changed at run-time with the -M argument.
+
+			Possible values: 0 to 604800 (7 days)
+			Default: 0 (disabled).
+
 endmenu
 ## </RESOURCE LIMITS>
 
@@ -984,7 +1021,7 @@ menu "Encryption options"
 
 			Post-quantum KEM can avoid harvest-now-decrypt-later style attacks.
 
-			Default: enabled, except devices with very small flash.
+			Default: disabled.
 
 	config DROPBEAR_SNTRUP761
 		bool "sntrup761 [POST-QUANTUM]"

package/network/services/dropbear/Makefile

@@ -32,7 +32,7 @@ PKG_CONFIG_DEPENDS:= \
 	CONFIG_DROPBEAR_DO_HOST_LOOKUP CONFIG_DROPBEAR_SVR_PUBKEY_OPTIONS CONFIG_DROPBEAR_LASTLOG CONFIG_DROPBEAR_LASTLOG_PATH CONFIG_DROPBEAR_WTMP CONFIG_DROPBEAR_WTMP_PATH CONFIG_DROPBEAR_UTMP CONFIG_DROPBEAR_UTMP_PATH CONFIG_DROPBEAR_PUTUTLINE CONFIG_DROPBEAR_LOGINFUNC \
 	CONFIG_DROPBEAR_REEXEC CONFIG_DROPBEAR_ZLIB CONFIG_DROPBEAR_DELAY_HOSTKEY CONFIG_DROPBEAR_SVR_AGENTFWD CONFIG_DROPBEAR_SVR_REMOTETCPFWD CONFIG_DROPBEAR_SVR_LOCALTCPFWD CONFIG_DROPBEAR_SVR_LOCALSTREAMFWD CONFIG_DROPBEAR_X11FWD CONFIG_DROPBEAR_SCP CONFIG_DROPBEAR_SFTPSERVER \
 	CONFIG_DROPBEAR_DBCLIENT CONFIG_DROPBEAR_USER_ALGO_LIST CONFIG_DROPBEAR_USE_SSH_CONFIG CONFIG_DROPBEAR_CLI_IMMEDIATE_AUTH CONFIG_DROPBEAR_USE_PASSWORD_ENV CONFIG_DROPBEAR_CLI_ASKPASS_HELPER CONFIG_DROPBEAR_CLI_AGENTFWD CONFIG_DROPBEAR_CLI_LOCALTCPFWD CONFIG_DROPBEAR_CLI_REMOTETCPFWD CONFIG_DROPBEAR_CLI_PROXYCMD CONFIG_DROPBEAR_CLI_NETCAT CONFIG_DROPBEAR_CLI_MULTIHOP \
-	CONFIG_DROPBEAR_KEX_REKEY_TIMEOUT CONFIG_DROPBEAR_KEX_REKEY_DATA CONFIG_DROPBEAR_AUTH_TIMEOUT CONFIG_DROPBEAR_MAX_AUTH_TRIES CONFIG_DROPBEAR_UNAUTH_CLOSE_DELAY CONFIG_DROPBEAR_MAX_UNAUTH_PER_IP CONFIG_DROPBEAR_MAX_UNAUTH_CLIENTS CONFIG_DROPBEAR_DEFAULT_RECV_WINDOW CONFIG_DROPBEAR_DEFAULT_KEEPALIVE CONFIG_DROPBEAR_DEFAULT_KEEPALIVE_LIMIT CONFIG_DROPBEAR_DEFAULT_IDLE_TIMEOUT \
+	CONFIG_DROPBEAR_KEX_REKEY_TIMEOUT CONFIG_DROPBEAR_KEX_REKEY_DATA CONFIG_DROPBEAR_AUTH_TIMEOUT CONFIG_DROPBEAR_MAX_AUTH_TRIES CONFIG_DROPBEAR_UNAUTH_CLOSE_DELAY CONFIG_DROPBEAR_MAX_UNAUTH_PER_IP CONFIG_DROPBEAR_MAX_UNAUTH_CLIENTS CONFIG_DROPBEAR_DEFAULT_RECV_WINDOW CONFIG_DROPBEAR_DEFAULT_KEEPALIVE CONFIG_DROPBEAR_DEFAULT_KEEPALIVE_LIMIT CONFIG_DROPBEAR_DEFAULT_IDLE_TIMEOUT CONFIG_DROPBEAR_MAX_PUBKEY_QUERIES CONFIG_DROPBEAR_DEFAULT_MAX_DURATION \
 	CONFIG_DROPBEAR_3DES CONFIG_DROPBEAR_AES128 CONFIG_DROPBEAR_AES256 CONFIG_DROPBEAR_CHACHA20POLY1305 \
 	CONFIG_DROPBEAR_ENABLE_CTR_MODE CONFIG_DROPBEAR_ENABLE_CBC_MODE CONFIG_DROPBEAR_ENABLE_GCM_MODE \
 	CONFIG_DROPBEAR_SHA1_96_HMAC CONFIG_DROPBEAR_SHA1_HMAC CONFIG_DROPBEAR_SHA2_256_HMAC CONFIG_DROPBEAR_SHA2_512_HMAC \
@@ -130,10 +130,12 @@ DB_OPT_COMMON = \
 	DEFAULT_IDLE_TIMEOUT,$(CONFIG_DROPBEAR_DEFAULT_IDLE_TIMEOUT) \
 	DEFAULT_KEEPALIVE_LIMIT,$(CONFIG_DROPBEAR_DEFAULT_KEEPALIVE_LIMIT) \
 	DEFAULT_KEEPALIVE,$(CONFIG_DROPBEAR_DEFAULT_KEEPALIVE) \
+	DEFAULT_MAX_DURATION,$(CONFIG_DROPBEAR_DEFAULT_MAX_DURATION) \
 	DEFAULT_RECV_WINDOW,$(CONFIG_DROPBEAR_DEFAULT_RECV_WINDOW) \
 	KEX_REKEY_DATA,$(CONFIG_DROPBEAR_KEX_REKEY_DATA) \
 	KEX_REKEY_TIMEOUT,$(CONFIG_DROPBEAR_KEX_REKEY_TIMEOUT) \
 	MAX_AUTH_TRIES,$(CONFIG_DROPBEAR_MAX_AUTH_TRIES) \
+	MAX_PUBKEY_QUERIES,$(CONFIG_DROPBEAR_MAX_PUBKEY_QUERIES) \
 	MAX_UNAUTH_CLIENTS,$(CONFIG_DROPBEAR_MAX_UNAUTH_CLIENTS) \
 	MAX_UNAUTH_PER_IP,$(CONFIG_DROPBEAR_MAX_UNAUTH_PER_IP) \
 	UNAUTH_CLOSE_DELAY,$(CONFIG_DROPBEAR_UNAUTH_CLOSE_DELAY) \