[Buildroot] boot failure

[Buildroot] boot failure

[Enoch W.]

Hi,

Recent buildroot versions, updated from git master, start getting stuck with:

random: dropbear: uninitialized urandom read (32 bytes read)

Any clue?

Thanks, Enoch.
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[Buildroot] boot failure

[Peter Korsgaard]

>>>>> "Enoch" == Enoch W <ixew@hotmail.com> writes:

 > Hi,
 > Recent buildroot versions, updated from git master, start getting stuck with:

 > random: dropbear: uninitialized urandom read (32 bytes read)

This normally means that something (in this case dropbear) tries to get
/dev/{,u}random data from the kernel very early.

What is your configuration / what have you customized related to
dropbear? We by default run dropbear with the -R option to only generate
the host keys on the first connection, so this shouldn't happen.

I can also not reproduce it here:

Initializing random number generator... done.
Starting network: 8139cp 0000:00:0c.0 eth0: link up, 100Mbps, full-duplex, lpa 0x05E1
udhcpc: started, v1.28.3
udhcpc: sending discover
udhcpc: sending select for 10.0.2.15
udhcpc: lease of 10.0.2.15 obtained, lease time 86400
deleting routers
adding dns 10.0.2.3
OK
Starting dropbear sshd: OK

Welcome to Buildroot
buildroot login:


Looking closer, I do see that dropbear indeed tries to read 32 bytes
from /dev/urandom at startup. I'm not sure if that is something new or
if it has always been like that. You better ask on the dropbear mailing
list (dropbear at ucc.asn.au) for more details:

# strace -e open,read,getrandom dropbear -R -F
open("/lib//libc.so.0", O_RDONLY)       = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0 \343\0\0004\0\0\0"..., 4096) = 4096
open("/etc/dropbear/dropbear_rsa_host_key", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)
open("/etc/dropbear/dropbear_dss_host_key", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)
open("/etc/dropbear/dropbear_ecdsa_host_key", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)
open("/dev/urandom", O_RDONLY|O_LARGEFILE) = 3
read(3, "\35=\2109\343Z(\251\325\211F0o'*\206s\247\242\336\336\313\207\262\273W\260:j\32\370\270", 32) = 32

-- 
Bye, Peter Korsgaard

[Buildroot] boot failure

[Giulio Benetti]

Hi,

Il 06/05/2018 10:32, Peter Korsgaard ha scritto:
>>>>>> "Enoch" == Enoch W <ixew@hotmail.com> writes:
> 
>   > Hi,
>   > Recent buildroot versions, updated from git master, start getting stuck with:
> 
>   > random: dropbear: uninitialized urandom read (32 bytes read)
> 
> This normally means that something (in this case dropbear) tries to get
> /dev/{,u}random data from the kernel very early.
> 
> What is your configuration / what have you customized related to
> dropbear? We by default run dropbear with the -R option to only generate
> the host keys on the first connection, so this shouldn't happen.
> 
> I can also not reproduce it here:
> 
> Initializing random number generator... done.
> Starting network: 8139cp 0000:00:0c.0 eth0: link up, 100Mbps, full-duplex, lpa 0x05E1
> udhcpc: started, v1.28.3
> udhcpc: sending discover
> udhcpc: sending select for 10.0.2.15
> udhcpc: lease of 10.0.2.15 obtained, lease time 86400
> deleting routers
> adding dns 10.0.2.3
> OK
> Starting dropbear sshd: OK
> 
> Welcome to Buildroot
> buildroot login:
> 
> 
> Looking closer, I do see that dropbear indeed tries to read 32 bytes
> from /dev/urandom at startup. I'm not sure if that is something new or
> if it has always been like that. You better ask on the dropbear mailing
> list (dropbear at ucc.asn.au) for more details:
> 
> # strace -e open,read,getrandom dropbear -R -F
> open("/lib//libc.so.0", O_RDONLY)       = 3
> read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0 \343\0\0004\0\0\0"..., 4096) = 4096
> open("/etc/dropbear/dropbear_rsa_host_key", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)
> open("/etc/dropbear/dropbear_dss_host_key", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)
> open("/etc/dropbear/dropbear_ecdsa_host_key", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)
> open("/dev/urandom", O_RDONLY|O_LARGEFILE) = 3
> read(3, "\35=\2109\343Z(\251\325\211F0o'*\206s\247\242\336\336\313\207\262\273W\260:j\32\370\270", 32) = 32
> 

I'm experimenting the same thing with udev, this is my log:
"
[    5.334345] udevd[83]: starting version 3.2.5 

[    5.352869] random: udevd: uninitialized urandom read (16 bytes read) 

[    5.380840] random: udevd: uninitialized urandom read (16 bytes read) 

[    5.387495] random: udevd: uninitialized urandom read (16 bytes read) 

[    5.468700] udevd[84]: starting eudev-3.2.5 

[    6.445387] urandom_read: 1 callbacks suppressed 

[    6.445397] random: dd: uninitialized urandom read (512 bytes read) 

[    6.561425] random: dbus-uuidgen: uninitialized urandom read (12 
bytes read)
[    6.68793 random: dbus-uuidgen: uninitialized urandom read (8 bytes 
read)
[    6.894495] random: crng init done 

[    6.897924] random: 2 urandom warning(s) missed due to ratelimiting
"

Since complains with dropbear with Enoch and udev with me,
it seems something kernel related, need to debug it.

Kind regards

-- 
Giulio Benetti
CTO

MICRONOVA SRL
Sede: Via A. Niedda 3 - 35010 Vigonza (PD)
Tel. 049/8931563 - Fax 049/8931346
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Iscritta al Reg. Imprese di Padova N. 02663420285
Numero R.E.A. 258642

[Buildroot] boot failure

[Jaap Crezee]

Hello all,
> I'm experimenting the same thing with udev, this is my log:
> "
> [??? 5.334345] udevd[83]: starting version 3.2.5
> [??? 5.352869] random: udevd: uninitialized urandom read (16 bytes read)
> [??? 5.380840] random: udevd: uninitialized urandom read (16 bytes read)
> [??? 5.387495] random: udevd: uninitialized urandom read (16 bytes read)
> [??? 5.468700] udevd[84]: starting eudev-3.2.5
> [??? 6.445387] urandom_read: 1 callbacks suppressed
> [??? 6.445397] random: dd: uninitialized urandom read (512 bytes read)
> [??? 6.561425] random: dbus-uuidgen: uninitialized urandom read (12 bytes read)
> [??? 6.68793 random: dbus-uuidgen: uninitialized urandom read (8 bytes read)
> [??? 6.894495] random: crng init done
> [??? 6.897924] random: 2 urandom warning(s) missed due to ratelimiting
> "
> 
> Since complains with dropbear with Enoch and udev with me,
> it seems something kernel related, need to debug it.


Please try using packages like rngd & haveged to make sure all RNG hardware features are used to initialize the kernel random number generator as
early as possible. If you can generate (sort of random) interrupts during boot that will also help to speed up the initialisation.


Jaap