Dict proxy client returning empty string instead of multiline string

[Aki Tuomi]

This will be fixed on next release, 2.2.26. We won't backport it to
latest stable, sorry.

Aki


On 18.10.2016 15:36, Pierre Jaury wrote:
> Hello,
>
> I can confirm the issue is fixed. Do you have a policy to backport the
> patch at least to the latest stable?
>
> Regards,
>
> On 10/17/2016 11:45 PM, Aki Tuomi wrote:
>>>>>>>>>> On 10/16/2016 11:16 PM, Pierre Jaury wrote:
>>>>>>>>>>> Hello,
>>>>>>>>>>>
>>>>>>>>>>> I am using a dict proxy for my sieve extdata plugin to access some
>>>>>>>>>>> fields from an SQLite database (autoreply text and other
>>>>>>>>>>> database-configured items).
>>>>>>>>>>>
>>>>>>>>>>> All tests are performed against version 2.2.25.
>>>>>>>>>>>
>>>>>>>>>>>   $ dovecot --version
>>>>>>>>>>>   2.2.25 (7be1766)
>>>>>>>>>>>
>>>>>>>>>>> My configuration looks like:
>>>>>>>>>>>
>>>>>>>>>>>   dict {
>>>>>>>>>>>     sieve = sqlite:/etc/dovecot/pigeonhole-sieve.dict
>>>>>>>>>>>   }
>>>>>>>>>>>
>>>>>>>>>>>   [...]
>>>>>>>>>>>   sieve_extdata_dict_uri = proxy::sieve
>>>>>>>>>>>
>>>>>>>>>>> I am able to read pretty much any attribute without any issue, except
>>>>>>>>>>> when the value contains a special character like "\r" or "\n". By using
>>>>>>>>>>> the doveadm dict client, I narrowed it down to the dictionary management
>>>>>>>>>>> part (either server, protocol or client).
>>>>>>>>>>>
>>>>>>>>>>> I was suspecting escaping functions from "lib/strescape.c" (mostly
>>>>>>>>>>> str_tabescape and its counterpart, used by "lib-dict/client.c"), so I
>>>>>>>>>>> monitored socket communications. It seems that escaping is done properly
>>>>>>>>>>> on the server and the socket is not an issue either.
>>>>>>>>>>>
>>>>>>>>>>> The following strace dump results from running "doveadm dict get"
>>>>>>>>>>> against the dict socket:
>>>>>>>>>>>
>>>>>>>>>>>   connect(8, {sa_family=AF_UNIX, sun_path="..."}, 110) = 0
>>>>>>>>>>>   fstat(8, {st_mode=S_IFSOCK|0777, st_size=0, ...}) = 0
>>>>>>>>>>>   [...]
>>>>>>>>>>>   write(8, "H2\t0\t0\tadmin at domain.tld\tsieve\n", 30) = 30
>>>>>>>>>>>   [...]
>>>>>>>>>>>   read(8, "Otest\1r\1ntest\n", 8192)      = 14
>>>>>>>>>>>
>>>>>>>>>>> Indeed "\1r" and "\1n" are the escape sequences used by
>>>>>>>>>>> "lib/strescape.c". I went deeped and debugged the call to "dict_lookup"
>>>>>>>>>>> performed by doveadm. Indeed the client gets the proper string from the
>>>>>>>>>>> socket and to my surprise, it is properly unescaped.
>>>>>>>>>>>
>>>>>>>>>>> Then, in "client_dict_lookup" ("lib-dict/dict-client.c"), the call to
>>>>>>>>>>> "p_strdup" returns an empty string (null byte set at the target address).
>>>>>>>>>>>
>>>>>>>>>>> Before the call to the dict "->lookup" attribute (client_dict_lookup):
>>>>>>>>>>>
>>>>>>>>>>>    RAX: 0x7ffff73a37c0 (push   r14)
>>>>>>>>>>>    RBX: 0x6831b8 ("priv/reply_body")
>>>>>>>>>>>    RCX: 0x7fffffffe240 --> 0x682a60 --> 0x6831b8 ("priv/reply_body")
>>>>>>>>>>>    RDX: 0x6831b8 ("priv/reply_body")
>>>>>>>>>>>    RSI: 0x683288 --> 0x7ffff7653120 --> 0x7ffff73ea620 ([...])
>>>>>>>>>>>    RDI: 0x690ad0 --> 0x7ffff7400713 --> 0x75250079786f7270 ('proxy')
>>>>>>>>>>>
>>>>>>>>>>>    0x7ffff73a1f10 <dict_lookup+32>:	mov    rcx,r11 (value_r)
>>>>>>>>>>>    0x7ffff73a1f13 <dict_lookup+35>:	mov    rdx,r8 (key)
>>>>>>>>>>>    0x7ffff73a1f16 <dict_lookup+38>:	mov    rsi,r10 (pool)
>>>>>>>>>>>    0x7ffff73a1f19 <dict_lookup+41>:	mov    rdi,r9 (dict)
>>>>>>>>>>>    0x7ffff73a1f1c <dict_lookup+44>:	add    rsp,0x8
>>>>>>>>>>> => 0x7ffff73a1f20 <dict_lookup+48>:	jmp    rax
>>>>>>>>>>>
>>>>>>>>>>> Before the call to p_strdup in "client_dict_lookup":
>>>>>>>>>>>
>>>>>>>>>>>    RSI: 0x6832d8 ("test\r\ntest") (lookup.result.value)
>>>>>>>>>>>    RDI: 0x683288 --> 0x7ffff7653120 --> [...] (pool)
>>>>>>>>>>>    RAX: 0x0 (result)
>>>>>>>>>>>
>>>>>>>>>>>    0x7ffff73a384f:	nop
>>>>>>>>>>>    0x7ffff73a3850:	mov    rsi,QWORD PTR [rsp+0x8]
>>>>>>>>>>>    0x7ffff73a3855:	mov    rdi,r14
>>>>>>>>>>> => 0x7ffff73a3858:	call   0x7ffff736d3c0 <p_strdup at plt>
>>>>>>>>>>>    0x7ffff73a385d:	mov    QWORD PTR [r13+0x0],rax
>>>>>>>>>>>    0x7ffff73a3861:	mov    rsi,QWORD PTR [rsp+0x18]
>>>>>>>>>>>    0x7ffff73a3866:	xor    rsi,QWORD PTR fs:0x28
>>>>>>>>>>>    0x7ffff73a386f:	mov    eax,ebx
>>>>>>>>>>>
>>>>>>>>>>> After the call:
>>>>>>>>>>>
>>>>>>>>>>>    0x7ffff73a3850:	mov    rsi,QWORD PTR [rsp+0x8]
>>>>>>>>>>>    0x7ffff73a3855:	mov    rdi,r14
>>>>>>>>>>>    0x7ffff73a3858:	call   0x7ffff736d3c0 <p_strdup at plt>
>>>>>>>>>>> => 0x7ffff73a385d:	mov    QWORD PTR [r13+0x0],rax
>>>>>>>>>>>    0x7ffff73a3861:	mov    rsi,QWORD PTR [rsp+0x18]
>>>>>>>>>>>    0x7ffff73a3866:	xor    rsi,QWORD PTR fs:0x28
>>>>>>>>>>>    0x7ffff73a386f:	mov    eax,ebx
>>>>>>>>>>>    0x7ffff73a3871:	jne    0x7ffff73a38da
>>>>>>>>>>>
>>>>>>>>>>>    RSI: 0x0
>>>>>>>>>>>    RDI: 0x6832d8 --> 0x0
>>>>>>>>>>>    RAX: 0x6832d8 --> 0x0 (result)
>>>>>>>>>>>
>>>>>>>>>>> It is worth noting that I can reproduce the exact same execution flow
>>>>>>>>>>> with a non-multiline result string (lookup.result.value) that is
>>>>>>>>>>> properly copied by "p_strdup" and returned in RAX, then displayed by
>>>>>>>>>>> doveadm.
>>>>>>>>>>>
>>>>>>>>>>> I am not familiar with the pooling mechanism hidden behind the call to
>>>>>>>>>>> p_strdump and not quite sure why this behaviour is emerging. Maybe I am
>>>>>>>>>>> even miles away from an understanding of the issue here, but it sounds
>>>>>>>>>>> to me like something is wrong in the way "p_strdup" performs the copy.
>>>>>>>>>>>
>>>>>>>>>>> Hope this helps,
>>>>>>>>>>> kaiyou.
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>> Fixed with https://github.com/dovecot/core/commit/4f051c3082080b9d69ef12c3720c683cff34b0da
>>
>> Aki Tuomi
>>