[tor-bugs] #7077 [Tor]: Tor exits with 'descriptor at <address> begins with unexpected string ""'

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#7077: Tor exits with 'descriptor at <address> begins with unexpected string ""'
-----------------------+----------------------------------------------------
 Reporter:  jackhill   |          Owner:                    
     Type:  defect     |         Status:  new               
 Priority:  normal     |      Milestone:  Tor: 0.2.2.x-final
Component:  Tor        |        Version:                    
 Keywords:  tor-relay  |         Parent:                    
   Points:             |   Actualpoints:                    
-----------------------+----------------------------------------------------

Comment(by webmeister):

 My relay
 [https://atlas.torproject.org/#details/F42293743B0BC4A33C80A542A451EE6C64B27DE9
 TaurNuFuin] (Tor 0.2.3.25) shows the same problem. Currently I have four
 such messages in my logs:

 {{{
 Dec 20 18:27:12.000 [err] descriptor at 0x2c05d1c8 begins with unexpected
 string "".  Is another process running in our data directory?  Exiting.
 Dec 29 02:54:53.000 [err] descriptor at 0x2aa7d520 begins with unexpected
 string "".  Is another process running in our data directory?  Exiting.
 Jan 03 03:30:43.000 [err] descriptor at 0x2bd2a750 begins with unexpected
 string "".  Is another process running in our data directory?  Exiting.
 Jan 05 21:09:26.000 [err] descriptor at 0x2bdfda68 begins with unexpected
 string "".  Is another process running in our data directory?  Exiting.
 }}}

 Each time I restarted Tor several hours later and it continued to run
 fine. Three of these four times after restarting different warnings
 appeared in the log (right after the "Reloaded microdescriptor cache."
 notice):

 {{{
 Dec 20 23:28:41.000 [warn] Error reading router descriptor: signature does
 not match.

 Dec 29 02:56:25.000 [warn] crypto error while reading public key from
 string: bad end line (in PEM routines:PEM_read_bio)
 Dec 29 02:56:25.000 [warn] parse error: Couldn't parse public key.
 Dec 29 02:56:25.000 [warn] Error tokenizing router descriptor.
 Dec 29 02:56:29.000 [warn] Parse error: missing onion-key element.
 Dec 29 02:56:29.000 [warn] Error tokenizing router descriptor.

 Jan 05 22:46:02.000 [warn] parse error: Malformed object: mismatched end
 tag SIGNATURE
 Jan 05 22:46:02.000 [warn] Error tokenizing router descriptor.
 }}}

 The relay is the only service running on a Pogoplug POGO-P24 V3 using Arch
 Linux ARM. Its file system is located on an USB flash drive. The error
 occurred for the first time after I had exchanged the flash drive with a
 different model. Can this be simply a faulty flash drive? Then again the
 system was only running for four days on the first flash drive, so this
 might be completely unrelated.

 Another idea: The kernel on this device is rather old. Due to the special
 hardware 2.6.31.6 is the newest version available. Might this influence
 the behaviour?

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/7077#comment:6>
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