1

I'm trying to SSH into a device but I kept getting an error prior to authentication, namely "Invalid key length". I am scared to modify the device as I don't know what horrors that lie within are needed for it to work. Case in point: It seems that the manufacturer runs their entire GUI inside an Android app, that launches automatically shortly after startup, on Android 2.2, that runs on top of something that likes to show Tux when it boots.

What should I do to get SSH to even attempt to authenticate?

SSH - Debug:3

OpenSSH_7.6p1 Ubuntu-4ubuntu0.1, OpenSSL 1.0.2n  7 Dec 2017
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug2: resolving "192.168.1.120" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to 192.168.1.120 [192.168.1.120] port 22.
debug1: Connection established.
debug1: key_load_public: No such file or directory
debug1: identity file /home/husky/.ssh/id_rsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/husky/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/husky/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/husky/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/husky/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/husky/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/husky/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/husky/.ssh/id_ed25519-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_7.6p1 Ubuntu-4ubuntu0.1
debug1: Remote protocol version 2.0, remote software version dropbear_2012.55
debug1: no match: dropbear_2012.55
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to 192.168.1.120:22 as 'user'
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1,ext-info-c
debug2: host key algorithms: ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug2: ciphers ctos: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com
debug2: ciphers stoc: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com
debug2: MACs ctos: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,zlib@openssh.com,zlib
debug2: compression stoc: none,zlib@openssh.com,zlib
debug2: languages ctos: 
debug2: languages stoc: 
debug2: first_kex_follows 0 
debug2: reserved 0 
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: diffie-hellman-group1-sha1,diffie-hellman-group14-sha1
debug2: host key algorithms: ssh-rsa
debug2: ciphers ctos: aes128-ctr,3des-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes256-cbc,twofish256-cbc,twofish-cbc,twofish128-cbc
debug2: ciphers stoc: aes128-ctr,3des-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes256-cbc,twofish256-cbc,twofish-cbc,twofish128-cbc
debug2: MACs ctos: hmac-sha1-96,hmac-sha1,hmac-md5
debug2: MACs stoc: hmac-sha1-96,hmac-sha1,hmac-md5
debug2: compression ctos: zlib,zlib@openssh.com,none
debug2: compression stoc: zlib,zlib@openssh.com,none
debug2: languages ctos: 
debug2: languages stoc: 
debug2: first_kex_follows 0 
debug2: reserved 0 
debug1: kex: algorithm: diffie-hellman-group14-sha1
debug1: kex: host key algorithm: ssh-rsa
debug1: kex: server->client cipher: aes128-ctr MAC: hmac-sha1 compression: none
debug1: kex: client->server cipher: aes128-ctr MAC: hmac-sha1 compression: none
debug1: sending SSH2_MSG_KEXDH_INIT
debug2: bits set: 1022/2048
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEXDH_REPLY
debug3: receive packet: type 31
ssh_dispatch_run_fatal: Connection to 192.168.1.120 port 22: Invalid key length

Associated TCPDump -X Output

19:17:38.268011 IP husky-MS-7921.40324 > 9774d56d682e549c.ssh: Flags [S], seq 2347624957, win 29200, options [mss 1460,sackOK,TS val 2322116349 ecr 0,nop,wscale 7], length 0
    0x0000:  4500 003c af22 4000 4006 0768 c0a8 0169  E..<."@.@..h...i
    0x0010:  c0a8 0178 9d84 0016 8bed e9fd 0000 0000  ...x............
    0x0020:  a002 7210 04d2 0000 0204 05b4 0402 080a  ..r.............
    0x0030:  8a68 aefd 0000 0000 0103 0307            .h..........
19:17:39.096971 IP 9774d56d682e549c.ssh > husky-MS-7921.40324: Flags [S.], seq 1797888426, ack 2347624958, win 5792, options [mss 1460,sackOK,TS val 1805575304 ecr 2322116349,nop,wscale 1], length 0
    0x0000:  4510 003c 0000 4000 4006 b67a c0a8 0178  E..<..@.@..z...x
    0x0010:  c0a8 0169 0016 9d84 6b29 99aa 8bed e9fe  ...i....k)......
    0x0020:  a012 16a0 0b3c 0000 0204 05b4 0402 080a  .....<..........
    0x0030:  6b9e e488 8a68 aefd 0103 0301            k....h......
19:17:39.097047 IP husky-MS-7921.40324 > 9774d56d682e549c.ssh: Flags [.], ack 1, win 229, options [nop,nop,TS val 2322117178 ecr 1805575304], length 0
    0x0000:  4500 0034 af23 4000 4006 076f c0a8 0169  E..4.#@.@..o...i
    0x0010:  c0a8 0178 9d84 0016 8bed e9fe 6b29 99ab  ...x........k)..
    0x0020:  8010 00e5 4c80 0000 0101 080a 8a68 b23a  ....L........h.:
    0x0030:  6b9e e488                                k...
19:17:39.097935 IP husky-MS-7921.40324 > 9774d56d682e549c.ssh: Flags [P.], seq 1:42, ack 1, win 229, options [nop,nop,TS val 2322117179 ecr 1805575304], length 41
    0x0000:  4500 005d af24 4000 4006 0745 c0a8 0169  E..].$@.@..E...i
    0x0010:  c0a8 0178 9d84 0016 8bed e9fe 6b29 99ab  ...x........k)..
    0x0020:  8018 00e5 2826 0000 0101 080a 8a68 b23b  ....(&.......h.;
    0x0030:  6b9e e488 5353 482d 322e 302d 4f70 656e  k...SSH-2.0-Open
    0x0040:  5353 485f 372e 3670 3120 5562 756e 7475  SSH_7.6p1.Ubuntu
    0x0050:  2d34 7562 756e 7475 302e 310d 0a         -4ubuntu0.1..
19:17:39.102981 IP 9774d56d682e549c.ssh > husky-MS-7921.40324: Flags [.], ack 42, win 2896, options [nop,nop,TS val 1805575305 ecr 2322117179], length 0
    0x0000:  4510 0034 7d22 4000 4006 3960 c0a8 0178  E..4}"@.@.9`...x
    0x0010:  c0a8 0169 0016 9d84 6b29 99ab 8bed ea27  ...i....k).....'
    0x0020:  8010 0b50 41ea 0000 0101 080a 6b9e e489  ...PA.......k...
    0x0030:  8a68 b23b                                .h.;
19:17:39.121765 IP 9774d56d682e549c.ssh > husky-MS-7921.40324: Flags [P.], seq 1:27, ack 42, win 2896, options [nop,nop,TS val 1805575308 ecr 2322117179], length 26
    0x0000:  4510 004e 7d23 4000 4006 3945 c0a8 0178  E..N}#@.@.9E...x
    0x0010:  c0a8 0169 0016 9d84 6b29 99ab 8bed ea27  ...i....k).....'
    0x0020:  8018 0b50 a85d 0000 0101 080a 6b9e e48c  ...P.]......k...
    0x0030:  8a68 b23b 5353 482d 322e 302d 6472 6f70  .h.;SSH-2.0-drop
    0x0040:  6265 6172 5f32 3031 322e 3535 0d0a       bear_2012.55..
19:17:39.121807 IP husky-MS-7921.40324 > 9774d56d682e549c.ssh: Flags [.], ack 27, win 229, options [nop,nop,TS val 2322117202 ecr 1805575308], length 0
    0x0000:  4500 0034 af25 4000 4006 076d c0a8 0169  E..4.%@.@..m...i
    0x0010:  c0a8 0178 9d84 0016 8bed ea27 6b29 99c5  ...x.......'k)..
    0x0020:  8010 00e5 4c21 0000 0101 080a 8a68 b252  ....L!.......h.R
    0x0030:  6b9e e48c                                k...
19:17:39.121832 IP 9774d56d682e549c.ssh > husky-MS-7921.40324: Flags [P.], seq 27:483, ack 42, win 2896, options [nop,nop,TS val 1805575308 ecr 2322117179], length 456
    0x0000:  4510 01fc 7d24 4000 4006 3796 c0a8 0178  E...}$@.@.7....x
    0x0010:  c0a8 0169 0016 9d84 6b29 99c5 8bed ea27  ...i....k).....'
    0x0020:  8018 0b50 bd12 0000 0101 080a 6b9e e48c  ...P........k...
    0x0030:  8a68 b23b 0000 01c4 0814 ff98 9878 b227  .h.;.........x.'
    0x0040:  b6e9 0ef3 a65a 7d13 a857 0000 0036 6469  .....Z}..W...6di
    0x0050:  6666 6965 2d68 656c 6c6d 616e 2d67 726f  ffie-hellman-gro
    0x0060:  7570 312d 7368 6131 2c64 6966 6669 652d  up1-sha1,diffie-
    0x0070:  6865 6c6c 6d61 6e2d 6772 6f75 7031 342d  hellman-group14-
    0x0080:  7368 6131 0000 0007 7373 682d 7273 6100  sha1....ssh-rsa.
    0x0090:  0000 6761 6573 3132 382d 6374 722c 3364  ..gaes128-ctr,3d
    0x00a0:  6573 2d63 7472 2c61 6573 3235 362d 6374  es-ctr,aes256-ct
    0x00b0:  722c 6165 7331 3238 2d63 6263 2c33 6465  r,aes128-cbc,3de
    0x00c0:  732d 6362 632c 6165 7332 3536 2d63 6263  s-cbc,aes256-cbc
    0x00d0:  2c74 776f 6669 7368 3235 362d 6362 632c  ,twofish256-cbc,
    0x00e0:  7477 6f66 6973 682d 6362 632c 7477 6f66  twofish-cbc,twof
    0x00f0:  6973 6831 3238 2d63 6263 0000 0067 6165  ish128-cbc...gae
    0x0100:  7331 3238 2d63 7472 2c33 6465 732d 6374  s128-ctr,3des-ct
    0x0110:  722c 6165 7332 3536 2d63 7472 2c61 6573  r,aes256-ctr,aes
    0x0120:  3132 382d 6362 632c 3364 6573 2d63 6263  128-cbc,3des-cbc
    0x0130:  2c61 6573 3235 362d 6362 632c 7477 6f66  ,aes256-cbc,twof
    0x0140:  6973 6832 3536 2d63 6263 2c74 776f 6669  ish256-cbc,twofi
    0x0150:  7368 2d63 6263 2c74 776f 6669 7368 3132  sh-cbc,twofish12
    0x0160:  382d 6362 6300 0000 1f68 6d61 632d 7368  8-cbc....hmac-sh
    0x0170:  6131 2d39 362c 686d 6163 2d73 6861 312c  a1-96,hmac-sha1,
    0x0180:  686d 6163 2d6d 6435 0000 001f 686d 6163  hmac-md5....hmac
    0x0190:  2d73 6861 312d 3936 2c68 6d61 632d 7368  -sha1-96,hmac-sh
    0x01a0:  6131 2c68 6d61 632d 6d64 3500 0000 1a7a  a1,hmac-md5....z
    0x01b0:  6c69 622c 7a6c 6962 406f 7065 6e73 7368  lib,zlib@openssh
    0x01c0:  2e63 6f6d 2c6e 6f6e 6500 0000 1a7a 6c69  .com,none....zli
    0x01d0:  622c 7a6c 6962 406f 7065 6e73 7368 2e63  b,zlib@openssh.c
    0x01e0:  6f6d 2c6e 6f6e 6500 0000 0000 0000 0000  om,none.........
    0x01f0:  0000 0000 50a4 878c 1985 df0f            ....P.......
19:17:39.121856 IP husky-MS-7921.40324 > 9774d56d682e549c.ssh: Flags [.], ack 483, win 237, options [nop,nop,TS val 2322117202 ecr 1805575308], length 0
    0x0000:  4500 0034 af26 4000 4006 076c c0a8 0169  E..4.&@.@..l...i
    0x0010:  c0a8 0178 9d84 0016 8bed ea27 6b29 9b8d  ...x.......'k)..
    0x0020:  8010 00ed 4a51 0000 0101 080a 8a68 b252  ....JQ.......h.R
    0x0030:  6b9e e48c                                k...
19:17:39.122372 IP husky-MS-7921.40324 > 9774d56d682e549c.ssh: Flags [P.], seq 42:1402, ack 483, win 237, options [nop,nop,TS val 2322117203 ecr 1805575308], length 1360
    0x0000:  4500 0584 af27 4000 4006 021b c0a8 0169  E....'@.@......i
    0x0010:  c0a8 0178 9d84 0016 8bed ea27 6b29 9b8d  ...x.......'k)..
    0x0020:  8018 00ed e967 0000 0101 080a 8a68 b253  .....g.......h.S
    0x0030:  6b9e e48c 0000 054c 0514 b674 9c42 6a1c  k......L...t.Bj.
    0x0040:  dc13 73aa b729 dd39 7612 0000 0130 6375  ..s..).9v....0cu
    0x0050:  7276 6532 3535 3139 2d73 6861 3235 362c  rve25519-sha256,
    0x0060:  6375 7276 6532 3535 3139 2d73 6861 3235  curve25519-sha25
    0x0070:  3640 6c69 6273 7368 2e6f 7267 2c65 6364  6@libssh.org,ecd
    0x0080:  682d 7368 6132 2d6e 6973 7470 3235 362c  h-sha2-nistp256,
    0x0090:  6563 6468 2d73 6861 322d 6e69 7374 7033  ecdh-sha2-nistp3
    0x00a0:  3834 2c65 6364 682d 7368 6132 2d6e 6973  84,ecdh-sha2-nis
    0x00b0:  7470 3532 312c 6469 6666 6965 2d68 656c  tp521,diffie-hel
    0x00c0:  6c6d 616e 2d67 726f 7570 2d65 7863 6861  lman-group-excha
    0x00d0:  6e67 652d 7368 6132 3536 2c64 6966 6669  nge-sha256,diffi
    0x00e0:  652d 6865 6c6c 6d61 6e2d 6772 6f75 7031  e-hellman-group1
    0x00f0:  362d 7368 6135 3132 2c64 6966 6669 652d  6-sha512,diffie-
    0x0100:  6865 6c6c 6d61 6e2d 6772 6f75 7031 382d  hellman-group18-
    0x0110:  7368 6135 3132 2c64 6966 6669 652d 6865  sha512,diffie-he
    0x0120:  6c6c 6d61 6e2d 6772 6f75 702d 6578 6368  llman-group-exch
    0x0130:  616e 6765 2d73 6861 312c 6469 6666 6965  ange-sha1,diffie
    0x0140:  2d68 656c 6c6d 616e 2d67 726f 7570 3134  -hellman-group14
    0x0150:  2d73 6861 3235 362c 6469 6666 6965 2d68  -sha256,diffie-h
    0x0160:  656c 6c6d 616e 2d67 726f 7570 3134 2d73  ellman-group14-s
    0x0170:  6861 312c 6578 742d 696e 666f 2d63 0000  ha1,ext-info-c..
    0x0180:  0122 6563 6473 612d 7368 6132 2d6e 6973  ."ecdsa-sha2-nis
    0x0190:  7470 3235 362d 6365 7274 2d76 3031 406f  tp256-cert-v01@o
    0x01a0:  7065 6e73 7368 2e63 6f6d 2c65 6364 7361  penssh.com,ecdsa
    0x01b0:  2d73 6861 322d 6e69 7374 7033 3834 2d63  -sha2-nistp384-c
    0x01c0:  6572 742d 7630 3140 6f70 656e 7373 682e  ert-v01@openssh.
    0x01d0:  636f 6d2c 6563 6473 612d 7368 6132 2d6e  com,ecdsa-sha2-n
    0x01e0:  6973 7470 3532 312d 6365 7274 2d76 3031  istp521-cert-v01
    0x01f0:  406f 7065 6e73 7368 2e63 6f6d 2c73 7368  @openssh.com,ssh
    0x0200:  2d65 6432 3535 3139 2d63 6572 742d 7630  -ed25519-cert-v0
    0x0210:  3140 6f70 656e 7373 682e 636f 6d2c 7373  1@openssh.com,ss
    0x0220:  682d 7273 612d 6365 7274 2d76 3031 406f  h-rsa-cert-v01@o
    0x0230:  7065 6e73 7368 2e63 6f6d 2c65 6364 7361  penssh.com,ecdsa
    0x0240:  2d73 6861 322d 6e69 7374 7032 3536 2c65  -sha2-nistp256,e
    0x0250:  6364 7361 2d73 6861 322d 6e69 7374 7033  cdsa-sha2-nistp3
    0x0260:  3834 2c65 6364 7361 2d73 6861 322d 6e69  84,ecdsa-sha2-ni
    0x0270:  7374 7035 3231 2c73 7368 2d65 6432 3535  stp521,ssh-ed255
    0x0280:  3139 2c72 7361 2d73 6861 322d 3531 322c  19,rsa-sha2-512,
    0x0290:  7273 612d 7368 6132 2d32 3536 2c73 7368  rsa-sha2-256,ssh
    0x02a0:  2d72 7361 0000 006c 6368 6163 6861 3230  -rsa...lchacha20
    0x02b0:  2d70 6f6c 7931 3330 3540 6f70 656e 7373  -poly1305@openss
    0x02c0:  682e 636f 6d2c 6165 7331 3238 2d63 7472  h.com,aes128-ctr
    0x02d0:  2c61 6573 3139 322d 6374 722c 6165 7332  ,aes192-ctr,aes2
    0x02e0:  3536 2d63 7472 2c61 6573 3132 382d 6763  56-ctr,aes128-gc
    0x02f0:  6d40 6f70 656e 7373 682e 636f 6d2c 6165  m@openssh.com,ae
    0x0300:  7332 3536 2d67 636d 406f 7065 6e73 7368  s256-gcm@openssh
    0x0310:  2e63 6f6d 0000 006c 6368 6163 6861 3230  .com...lchacha20
    0x0320:  2d70 6f6c 7931 3330 3540 6f70 656e 7373  -poly1305@openss
    0x0330:  682e 636f 6d2c 6165 7331 3238 2d63 7472  h.com,aes128-ctr
    0x0340:  2c61 6573 3139 322d 6374 722c 6165 7332  ,aes192-ctr,aes2
    0x0350:  3536 2d63 7472 2c61 6573 3132 382d 6763  56-ctr,aes128-gc
    0x0360:  6d40 6f70 656e 7373 682e 636f 6d2c 6165  m@openssh.com,ae
    0x0370:  7332 3536 2d67 636d 406f 7065 6e73 7368  s256-gcm@openssh
    0x0380:  2e63 6f6d 0000 00d5 756d 6163 2d36 342d  .com....umac-64-
    0x0390:  6574 6d40 6f70 656e 7373 682e 636f 6d2c  etm@openssh.com,
    0x03a0:  756d 6163 2d31 3238 2d65 746d 406f 7065  umac-128-etm@ope
    0x03b0:  6e73 7368 2e63 6f6d 2c68 6d61 632d 7368  nssh.com,hmac-sh
    0x03c0:  6132 2d32 3536 2d65 746d 406f 7065 6e73  a2-256-etm@opens
    0x03d0:  7368 2e63 6f6d 2c68 6d61 632d 7368 6132  sh.com,hmac-sha2
    0x03e0:  2d35 3132 2d65 746d 406f 7065 6e73 7368  -512-etm@openssh
    0x03f0:  2e63 6f6d 2c68 6d61 632d 7368 6131 2d65  .com,hmac-sha1-e
    0x0400:  746d 406f 7065 6e73 7368 2e63 6f6d 2c75  tm@openssh.com,u
    0x0410:  6d61 632d 3634 406f 7065 6e73 7368 2e63  mac-64@openssh.c
    0x0420:  6f6d 2c75 6d61 632d 3132 3840 6f70 656e  om,umac-128@open
    0x0430:  7373 682e 636f 6d2c 686d 6163 2d73 6861  ssh.com,hmac-sha
    0x0440:  322d 3235 362c 686d 6163 2d73 6861 322d  2-256,hmac-sha2-
    0x0450:  3531 322c 686d 6163 2d73 6861 3100 0000  512,hmac-sha1...
    0x0460:  d575 6d61 632d 3634 2d65 746d 406f 7065  .umac-64-etm@ope
    0x0470:  6e73 7368 2e63 6f6d 2c75 6d61 632d 3132  nssh.com,umac-12
    0x0480:  382d 6574 6d40 6f70 656e 7373 682e 636f  8-etm@openssh.co
    0x0490:  6d2c 686d 6163 2d73 6861 322d 3235 362d  m,hmac-sha2-256-
    0x04a0:  6574 6d40 6f70 656e 7373 682e 636f 6d2c  etm@openssh.com,
    0x04b0:  686d 6163 2d73 6861 322d 3531 322d 6574  hmac-sha2-512-et
    0x04c0:  6d40 6f70 656e 7373 682e 636f 6d2c 686d  m@openssh.com,hm
    0x04d0:  6163 2d73 6861 312d 6574 6d40 6f70 656e  ac-sha1-etm@open
    0x04e0:  7373 682e 636f 6d2c 756d 6163 2d36 3440  ssh.com,umac-64@
    0x04f0:  6f70 656e 7373 682e 636f 6d2c 756d 6163  openssh.com,umac
    0x0500:  2d31 3238 406f 7065 6e73 7368 2e63 6f6d  -128@openssh.com
    0x0510:  2c68 6d61 632d 7368 6132 2d32 3536 2c68  ,hmac-sha2-256,h
    0x0520:  6d61 632d 7368 6132 2d35 3132 2c68 6d61  mac-sha2-512,hma
    0x0530:  632d 7368 6131 0000 001a 6e6f 6e65 2c7a  c-sha1....none,z
    0x0540:  6c69 6240 6f70 656e 7373 682e 636f 6d2c  lib@openssh.com,
    0x0550:  7a6c 6962 0000 001a 6e6f 6e65 2c7a 6c69  zlib....none,zli
    0x0560:  6240 6f70 656e 7373 682e 636f 6d2c 7a6c  b@openssh.com,zl
    0x0570:  6962 0000 0000 0000 0000 0000 0000 0000  ib..............
    0x0580:  0000 0000                                ....
19:17:39.170347 IP 9774d56d682e549c.ssh > husky-MS-7921.40324: Flags [.], ack 1402, win 4256, options [nop,nop,TS val 1805575323 ecr 2322117203], length 0
    0x0000:  4510 0034 7d25 4000 4006 395d c0a8 0178  E..4}%@.@.9]...x
    0x0010:  c0a8 0169 0016 9d84 6b29 9b8d 8bed ef77  ...i....k).....w
    0x0020:  8010 10a0 353e 0000 0101 080a 6b9e e49b  ....5>......k...
    0x0030:  8a68 b253                                .h.S
19:17:39.170364 IP husky-MS-7921.40324 > 9774d56d682e549c.ssh: Flags [P.], seq 1402:1674, ack 483, win 237, options [nop,nop,TS val 2322117251 ecr 1805575323], length 272
    0x0000:  4500 0144 af28 4000 4006 065a c0a8 0169  E..D.(@.@..Z...i
    0x0010:  c0a8 0178 9d84 0016 8bed ef77 6b29 9b8d  ...x.......wk)..
    0x0020:  8018 00ed 3a48 0000 0101 080a 8a68 b283  ....:H.......h..
    0x0030:  6b9e e49b 0000 010c 051e 0000 0101 009d  k...............
    0x0040:  a9cc 0026 23f5 7efd 6242 4704 58d2 51f6  ...&#.~.bBG.X.Q.
    0x0050:  d1b5 74e4 830f c22d 8f6b 5a29 0216 db21  ..t....-.kZ)...!
    0x0060:  6c93 bb75 4384 9bdb 3200 0372 0840 c851  l..uC...2..r.@.Q
    0x0070:  d863 3743 8bab cf29 ab4e 41c3 caba f7b3  .c7C...).NA.....
    0x0080:  b470 d50a 3a36 23be 474d ee47 4a1d 8ca5  .p..:6#.GM.GJ...
    0x0090:  ea8b 117b d4b4 6738 75b9 0245 0dc9 5348  ...{..g8u..E..SH
    0x00a0:  543f 395d 1ddd 370b e1e3 039d 4a4a 922b  T?9]..7.....JJ.+
    0x00b0:  a5d3 f995 6faa 697c 5744 f66f 7265 928a  ....o.i|WD.ore..
    0x00c0:  3ddd e7a6 15a8 62b3 a0fc d4d9 86f1 8070  =.....b........p
    0x00d0:  02b4 ca2d fbc9 95ae 565d 6b7c 1d9b a04f  ...-....V]k|...O
    0x00e0:  9b33 0731 398f be86 1e37 423a eaf4 16c5  .3.19....7B:....
    0x00f0:  bd89 c4c7 944c 6687 68a4 e9d4 3244 f9e9  .....Lf.h...2D..
    0x0100:  b78d 9384 48f5 38e4 a3eb 4e2d bedb 4a63  ....H.8...N-..Jc
    0x0110:  ebfb 5169 4bf9 7c68 4f2c b94b b8c4 8697  ..QiK.|hO,.K....
    0x0120:  2a1e c5c7 79c2 c760 c56b 52e8 da23 47eb  *...y..`.kR..#G.
    0x0130:  38a4 ed06 124b 7015 ec7c c046 c753 e300  8....Kp..|.F.S..
    0x0140:  0000 0000                                ....
19:17:39.176536 IP 9774d56d682e549c.ssh > husky-MS-7921.40324: Flags [.], ack 1674, win 5616, options [nop,nop,TS val 1805575324 ecr 2322117251], length 0
    0x0000:  4510 0034 7d26 4000 4006 395c c0a8 0178  E..4}&@.@.9\...x
    0x0010:  c0a8 0169 0016 9d84 6b29 9b8d 8bed f087  ...i....k)......
    0x0020:  8010 15f0 2ead 0000 0101 080a 6b9e e49c  ............k...
    0x0030:  8a68 b283                                .h..
19:17:39.860670 IP 9774d56d682e549c.ssh > husky-MS-7921.40324: Flags [P.], seq 483:1059, ack 1674, win 5616, options [nop,nop,TS val 1805575499 ecr 2322117251], length 576
    0x0000:  4510 0274 7d27 4000 4006 371b c0a8 0178  E..t}'@.@.7....x
    0x0010:  c0a8 0169 0016 9d84 6b29 9b8d 8bed f087  ...i....k)......
    0x0020:  8018 15f0 1a6b 0000 0101 080a 6b9e e54b  .....k......k..K
    0x0030:  8a68 b283 0000 023c 0a1f 0000 0094 0000  .h.....<........
    0x0040:  0007 7373 682d 7273 6100 0000 0125 0000  ..ssh-rsa....%..
    0x0050:  0080 6224 4307 0ff7 edaf 4a52 bf8c fd12  ..b$C.....JR....
    0x0060:  df9e 1bd1 c778 dfb3 f76d 2e17 d697 9688  .....x...m......
    0x0070:  ef1a f3f6 d3de 6b27 3ba4 a90e 6485 da63  ......k';...d..c
    0x0080:  f72d 4b4e 636c 77f3 a0cc 90c9 df18 a469  .-KNclw........i
    0x0090:  cfbb 7801 9ae0 f329 12c4 ed33 5d52 d2b5  ..x....)...3]R..
    0x00a0:  5646 6c0b e48e dbf3 9780 ede1 2cf0 882a  VFl.........,..*
    0x00b0:  d975 aa8e 8719 72f9 fb2c c6b2 e9ba 7130  .u....r..,....q0
    0x00c0:  b2fe edba 929f d79a 9cd1 817a f9c6 4a00  ...........z..J.
    0x00d0:  fc51 0000 0101 00fe 30eb 9ba8 f578 24b6  .Q......0....x$.
    0x00e0:  da22 fbf5 e3ed bfd2 e5b3 8bad fc50 a51c  ."...........P..
    0x00f0:  bbf4 fb5b 0539 8e70 3154 6c66 6a40 20c4  ...[.9.p1Tlfj@..
    0x0100:  aa5f 7be4 6d9d 20c1 f683 fd81 50fc 7dcb  ._{.m.......P.}.
    0x0110:  4016 300f 9991 24bf 01b9 20e6 8c9f 9115  @.0...$.........
    0x0120:  fe86 87c2 50a4 d175 d2db e807 f2b7 81ae  ....P..u........
    0x0130:  ed09 cbbf d734 bf67 5470 c511 fa5a af7d  .....4.gTp...Z.}
    0x0140:  c4c3 9da2 daf2 5673 d161 b4e3 b2f7 93c3  ......Vs.a......
    0x0150:  629e 2487 bc35 3b7c 7feb 4b1d 0fcb 2d05  b.$..5;|..K...-.
    0x0160:  7300 10fc a43f 0936 b8d2 f4cb 5c9e d16b  s....?.6....\..k
    0x0170:  9d75 558a ccf4 7a8d 9030 109d 703b 6c7e  .uU...z..0..p;l~
    0x0180:  1a0d c2a7 1266 4e28 960a 057e 9254 69fb  .....fN(...~.Ti.
    0x0190:  ec70 ce6d 151b 0d19 9672 1ca8 74b0 4298  .p.m.....r..t.B.
    0x01a0:  0216 ef33 6089 bbd5 f125 6d85 6e4c fb94  ...3`....%m.nL..
    0x01b0:  ab25 f7dc 14d7 711c 14bf 4198 2ae3 83d9  .%....q...A.*...
    0x01c0:  1a3e f723 4873 4fc3 b9f6 dec9 0b0d d8ad  .>.#HsO.........
    0x01d0:  8ef1 f9b9 d5d9 d000 0000 8f00 0000 0773  ...............s
    0x01e0:  7368 2d72 7361 0000 0080 2903 9a57 3507  sh-rsa....)..W5.
    0x01f0:  0c97 fcc7 5d22 783a f9b6 8e91 7390 d9d3  ....]"x:....s...
    0x0200:  0e81 c5df 0b01 a1e6 7494 25ae 2613 8b15  ........t.%.&...
    0x0210:  c1d8 c797 9dc1 0235 e0a0 fbaa a398 56e9  .......5......V.
    0x0220:  524f 88b7 1fc1 2d33 9183 b1cc d720 06d9  RO....-3........
    0x0230:  1018 ceed 0b04 a3b6 9135 10c2 a797 8fda  .........5......
    0x0240:  e87d 156c 7dec 2a73 edd2 d623 bc41 a294  .}.l}.*s...#.A..
    0x0250:  e32c 4c81 3300 fcfa 0aff 5ea4 bac4 511d  .,L.3.....^...Q.
    0x0260:  c93c 2b88 d23b 533f b89a 8253 3a82 464b  .<+..;S?...S:.FK
    0x0270:  8048 eedb                                .H..
19:17:39.860693 IP 9774d56d682e549c.ssh > husky-MS-7921.40324: Flags [P.], seq 1059:1075, ack 1674, win 5616, options [nop,nop,TS val 1805575499 ecr 2322117251], length 16
    0x0000:  4510 0044 7d28 4000 4006 394a c0a8 0178  E..D}(@.@.9J...x
    0x0010:  c0a8 0169 0016 9d84 6b29 9dcd 8bed f087  ...i....k)......
    0x0020:  8018 15f0 83cf 0000 0101 080a 6b9e e54b  ............k..K
    0x0030:  8a68 b283 0000 000c 0a15 148b ad67 39eb  .h...........g9.
    0x0040:  27d5 7a02                                '.z.
19:17:39.860704 IP husky-MS-7921.40324 > 9774d56d682e549c.ssh: Flags [.], ack 1075, win 246, options [nop,nop,TS val 2322117941 ecr 1805575499], length 0
    0x0000:  4500 0034 af29 4000 4006 0769 c0a8 0169  E..4.)@.@..i...i
    0x0010:  c0a8 0178 9d84 0016 8bed f087 6b29 9ddd  ...x........k)..
    0x0020:  8010 00f6 3df6 0000 0101 080a 8a68 b535  ....=........h.5
    0x0030:  6b9e e54b                                k..K
19:17:39.861176 IP husky-MS-7921.40324 > 9774d56d682e549c.ssh: Flags [F.], seq 1674, ack 1075, win 246, options [nop,nop,TS val 2322117942 ecr 1805575499], length 0
    0x0000:  4500 0034 af2a 4000 4006 0768 c0a8 0169  E..4.*@.@..h...i
    0x0010:  c0a8 0178 9d84 0016 8bed f087 6b29 9ddd  ...x........k)..
    0x0020:  8011 00f6 3df4 0000 0101 080a 8a68 b536  ....=........h.6
    0x0030:  6b9e e54b                                k..K
19:17:39.866337 IP 9774d56d682e549c.ssh > husky-MS-7921.40324: Flags [F.], seq 1075, ack 1675, win 5616, options [nop,nop,TS val 1805575501 ecr 2322117942], length 0
    0x0000:  4510 0034 7d29 4000 4006 3959 c0a8 0178  E..4})@.@.9Y...x
    0x0010:  c0a8 0169 0016 9d84 6b29 9ddd 8bed f088  ...i....k)......
    0x0020:  8011 15f0 28f7 0000 0101 080a 6b9e e54d  ....(.......k..M
    0x0030:  8a68 b536                                .h.6
19:17:39.866367 IP husky-MS-7921.40324 > 9774d56d682e549c.ssh: Flags [.], ack 1076, win 246, options [nop,nop,TS val 2322117947 ecr 1805575501], length 0
    0x0000:  4500 0034 af2b 4000 4006 0767 c0a8 0169  E..4.+@.@..g...i
    0x0010:  c0a8 0178 9d84 0016 8bed f088 6b29 9dde  ...x........k)..
    0x0020:  8010 00f6 3dec 0000 0101 080a 8a68 b53b  ....=........h.;
    0x0030:  6b9e e54d                                k..M
  • debug1: Remote protocol version 2.0, remote software version dropbear_2012.55 and debug1: no match: dropbear_2012.55. Search for "dropbear" and "dropbear_2012.55" with your favorite search engine. If it's 2012 software, somebody else has probably seen your problem. – waltinator Nov 18 '18 at 4:44
  • I have tried searching. Basically what I've found so far boiled down to "If you have OpenSSH-7.6 or later, you're SOL because of potentially-incompatible change #4" – Husky2490 Nov 18 '18 at 5:33
1

After combing through diffs between version 7.5p1 and later versions of OpenSSH, I finally found what I had to patch to get it to work.

As stated in this answer on Stack Overflow, the cause for this is due to a change in the minimum key length to 1024 bytes that was implemented in versions 7.6 and 7.6p1. The reason for this change is because of a security concern raised by RSA in 2003 that recommended that a 1024 byte minimum be used for new keys starting in 2010 due to the rapidly increasing computer power and affordability dictated by Moore's Law (Original source cited by Wikipedia).

The Fix

To get around this you need to revert this change. Luckily, you only need to change one line to do that.

In sshkey.h, around line 50-ish a constant named SSH_RSA_MINIMUM_MODULUS_SIZE is defined. The line should look something like this (arrow points towards line):

  # define EC_POINT void
  #endif /* WITH_OPENSSL */

> #define SSH_RSA_MINIMUM_MODULUS_SIZE  1024
  #define SSH_KEY_MAX_SIGN_DATA_SIZE    (1 << 20)

  struct sshbuf;

All you need to do is change the value of this constant to something lower like 768 (what it was in version 7.5)

I successfully implemented this fix in the latest version (7.9p1) but in theory you could do it to any version between that and 7.6 inclusive.

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