This one has me perplexed. OpenSSH6.4p1 on a FreeBSD 7 box (I know it's
old; it's being replaced this month). I can't spot anything changed in
OpenSSH commit logs or git blame of the current file.
I ssh into the box from a system with OpenSSH6.6p1 and three keys
loaded, RSA, ECDSA and ED25519.
As expected, key_from_blob and key_fingerprint complain about the
ED25519 key in the agent, because they can't handle it. Not a problem.
However, in this scenario, "ssh-add -l" will only produce output to
stdout if stdout is a tty.
"ssh-add -L" reliably produces output to stdout.
"ssh-add -l" reliably produces output to stdout _unless_ it can't parse
one of the blobs from the agent.
ktrace outputs of the working and non-working scenarios below. As you
can see, in the broken scenario there's no I/O to stdout.
Can anyone explain what's going on, please?
-Phil
% ktrace ssh-add -l 2>/dev/null
3072 8b:c1:ae:d1:48:5d:a1:c6:1b:3d:50:e1:6b:cd:65:32 /home/pdp/.ssh/id_rsa (RSA)
521 ee:2e:72:bc:53:6d:c2:57:42:2a:3d:e3:67:85:27:a6 /home/pdp/.ssh/id_ecdsa (ECDSA)
% kdump |less
----------------------------8< cut here >8------------------------------
63697 ssh-add CALL socket(PF_LOCAL,SOCK_STREAM,0)
63697 ssh-add RET socket 3
63697 ssh-add CALL fcntl(0x3,F_SETFD,FD_CLOEXEC)
63697 ssh-add RET fcntl 0
63697 ssh-add CALL connect(0x3,0x7fffffffdd80,0x6a)
63697 ssh-add NAMI "/tmp/ssh-fEfqnn0cp4/agent.63353"
63697 ssh-add RET connect 0
63697 ssh-add CALL write(0x3,0x7fffffffd930,0x4)
[... ssh-agent communications, reads back keys, etc ]
63697 ssh-add CALL read(0x3,0x7fffffffd930,0x2d8)
63697 ssh-add GIO fd 3 read 728 bytes
[...]
63697 ssh-add RET read 728/0x2d8
63697 ssh-add CALL fstat(0x1,0x7fffffffd420)
63697 ssh-add RET fstat 0
63697 ssh-add CALL ioctl(0x1,TIOCGETA,0x7fffffffd480)
63697 ssh-add RET ioctl 0
63697 ssh-add CALL write(0x1,0x80202c000,0x51)
63697 ssh-add GIO fd 1 wrote 81 bytes
"3072 8b:c1:ae:d1:48:5d:a1:c6:1b:3d:50:e1:6b:cd:65:32 /home/pdp/.ssh/id_rsa (RSA)
"
63697 ssh-add RET write 81/0x51
63697 ssh-add CALL write(0x1,0x80202c000,0x54)
63697 ssh-add GIO fd 1 wrote 84 bytes
"521 ee:2e:72:bc:53:6d:c2:57:42:2a:3d:e3:67:85:27:a6 /home/pdp/.ssh/id_ecdsa (ECDSA)
"
63697 ssh-add RET write 84/0x54
63697 ssh-add CALL write(0x2,0x7fffffffd7f0,0x2f)
63697 ssh-add GIO fd 2 wrote 47 bytes
"key_from_blob: remaining bytes in key blob 36\r
"
63697 ssh-add RET write 47/0x2f
63697 ssh-add CALL write(0x2,0x7fffffffd880,0x32)
63697 ssh-add GIO fd 2 wrote 50 bytes
"key_fingerprint: null from key_fingerprint_raw()\r
"
63697 ssh-add RET write 50/0x32
63697 ssh-add CALL exit(0xff)
----------------------------8< cut here >8------------------------------
% ktrace ssh-add -l 2>/dev/null | cat
----------------------------8< cut here >8------------------------------
64004 ssh-add CALL socket(PF_LOCAL,SOCK_STREAM,0)
64004 ssh-add RET socket 3
64004 ssh-add CALL fcntl(0x3,F_SETFD,FD_CLOEXEC)
64004 ssh-add RET fcntl 0
64004 ssh-add CALL connect(0x3,0x7fffffffdd90,0x6a)
64004 ssh-add NAMI "/tmp/ssh-74wsYwRh3v/agent.62945"
64004 ssh-add RET connect 0
64004 ssh-add CALL write(0x3,0x7fffffffd940,0x4)
[... ssh-agent communications, reads back keys, etc ]
64004 ssh-add CALL read(0x3,0x7fffffffd940,0x2d8)
64004 ssh-add GIO fd 3 read 728 bytes
[...]
64004 ssh-add RET read 728/0x2d8
64004 ssh-add CALL fstat(0x1,0x7fffffffd430)
64004 ssh-add RET fstat 0
64004 ssh-add CALL write(0x2,0x7fffffffd800,0x2f)
64004 ssh-add GIO fd 2 wrote 47 bytes
"key_from_blob: remaining bytes in key blob 36\r
"
64004 ssh-add RET write 47/0x2f
64004 ssh-add CALL write(0x2,0x7fffffffd890,0x32)
64004 ssh-add GIO fd 2 wrote 50 bytes
"key_fingerprint: null from key_fingerprint_raw()\r
"
64004 ssh-add RET write 50/0x32
64004 ssh-add CALL exit(0xff)
----------------------------8< cut here >8------------------------------
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