increasing the 'auth' attempts allowed by pam_unix

Gagan Sidhu <broly@xxxxxxx> · Thu, 14 Feb 2019 13:37:02 -0700

hello.
First of all, my original inquiry is here: https://www.redhat.com/archives/pam-list/2018-May/msg00004.html

I think the issue is that the httpd daemon is “hammering” pam with too many “auths”, and thus when it begins to spit out

May 22 18:31:32 DD-WRT httpd[536]: pam_unix(httpd:auth): auth could not identify password for [root]
May 22 18:31:32 DD-WRT httpd[536]: pam_unix(httpd:auth): auth could not identify password for [root]

follwoed by

May 22 18:31:32 DD-WRT : Caught SIGSEGV (11) sent by kernel in ??? 
May 22 18:31:32 DD-WRT : Thread 2373: httpd 
May 22 18:31:32 DD-WRT : === Context: 
May 22 18:31:32 DD-WRT : ZERO:00000000   AT:00000001   V0:00000000   V1:00000001   A0:6677656e   A1:00000001 
May 22 18:31:32 DD-WRT :   A2:00000010   A3:74600471   T0:00000001   T1:00000fa6   T2:00000000   T3:006e7275 
May 22 18:31:32 DD-WRT :   T4:76dbae28   T5:77c28020   T6:004400b0   T7:746005b8   S0:746004b0   S1:77adda30 
May 22 18:31:32 DD-WRT :   S2:746005b0   S3:74600470   S4:76dbb920   S5:00000000   S6:00409804   S7:76dbb920 
May 22 18:31:32 DD-WRT :   T8:00000000   T9:77ad90e8   K0:7460049b   K1:00000000   GP:77bf7e20   SP:76dbaee8 
May 22 18:31:32 DD-WRT :   FP:76dbaf40   RA:77bb4484 
May 22 18:31:32 DD-WRT : === Backtrace: 
May 22 18:31:32 DD-WRT : # [0x77bb442c]: ra offset 44 
May 22 18:31:32 DD-WRT : # [0x77bb4418]: stack size 48 
May 22 18:31:32 DD-WRT : # [0x77bb45e8]: ra offset 36 
May 22 18:31:32 DD-WRT : # [0x77bb45d0]: stack size 40 
May 22 18:31:32 DD-WRT : # [0x77bfbb54]: ra offset 172 
May 22 18:31:32 DD-WRT : # [0x77bfbb28]: stack size 176 
May 22 18:31:32 DD-WRT : # [0x77b5768c]: stack size 32 
May 22 18:31:32 DD-WRT : # [0x77b57678]: stack size 32 
May 22 18:31:32 DD-WRT : # [0x77b5761c]: stack size 32 
May 22 18:31:32 DD-WRT : /lib/libc.so.6[0x77a54000](+0x00160474)[0x77bb4474] 
May 22 18:31:32 DD-WRT : /lib/libc.so.6[0x77a54000](__libc_thread_freeres+0x00000058)[0x77bb461c] 
May 22 18:31:32 DD-WRT : /lib/libpthread.so.0[0x77bf5000](+0x00006c84)[0x77bfbc84] 
May 22 18:31:32 DD-WRT : /lib/libc.so.6[0x77a54000](+0x001036ac)[0x77b576ac] 
May 22 18:31:32 DD-WRT : ???(+0)[0x77f9b030] 
May 22 18:31:32 DD-WRT : === Code: 
May 22 18:31:32 DD-WRT : 77bb4434:  afb10020 afb0001c 1260001c 26700040 00602025 8f8394f0 ac400000 00641821 
May 22 18:31:32 DD-WRT : 77bb4454:  24020001 8f9187ec a0620000 26720140 8e040000 00000000 10800009 00000000 
May 22 18:31:32 DD-WRT : 77bb4474: >8c820000 0220c825 0320f809 ae020000 8e040000 00000000 1480fff9 00000000 
May 22 18:31:32 DD-WRT : 77bb4494:  26100004 1650fff2 0220c825 0320f809 02602025 8fbc0010 00000000 8f8294e8 
May 22 18:31:32 DD-WRT : Caught SIGABRT (6) sent by tkill 
May 22 18:31:32 DD-WRT : Thread 2374: httpd 
May 22 18:31:32 DD-WRT : === Context: 
May 22 18:31:32 DD-WRT : ZERO:00000000   AT:00000001   V0:00000000   V1:74ffec00   A0:00000003   A1:74ffec00 
May 22 18:31:32 DD-WRT :   A2:00000000   A3:00000000   T0:00000000   T1:00000401   T2:00000001   T3:77fa7000 
May 22 18:31:32 DD-WRT :   T4:00002000   T5:fffffffc   T6:00100000   T7:00001072   S0:00000000   S1:74ffec00 
May 22 18:31:32 DD-WRT :   S2:77bf4000   S3:00000010   S4:77ae4c70   S5:77f9a000   S6:00000002   S7:00000002 
May 22 18:31:32 DD-WRT :   T8:77abf088   T9:77a85fb0   K0:00000010   K1:00000000   GP:77bf7e20   SP:74ffeb78 
May 22 18:31:32 DD-WRT :   FP:74ffee10   RA:77a87754 
May 22 18:31:32 DD-WRT : === Backtrace: 
May 22 18:31:32 DD-WRT : # [0x77a85fc0]: stack size 272 
May 22 18:31:32 DD-WRT : # [0x77a875e4]: ra offset 316 
May 22 18:31:32 DD-WRT : # [0x77a875dc]: stack size 320 
May 22 18:31:32 DD-WRT : /lib/libc.so.6[0x77a54000](gsignal+0x000000d0)[0x77a86080] 
May 22 18:31:32 DD-WRT : /lib/libc.so.6[0x77a54000](abort+0x00000184)[0x77a87754] 
May 22 18:31:32 DD-WRT : /lib/libc.so.6[0x77a54000](__libc_fatal+0x00000000)[0x77ace564] 
May 22 18:31:32 DD-WRT : /usr/lib/libutils.so[0x77c7f000](+0x00014b74)[0x77c93b74] 
May 22 18:31:32 DD-WRT : === Code: 
May 22 18:31:32 DD-WRT : 77a86040:  0000000c 00402025 2402107e 0000000c 00402825 02003025 240210aa 0000000c 
May 22 18:31:32 DD-WRT : 77a86060:  14e0000c 00408025 24040003 02202825 00003025 24070010 24021063 0000000c 
May 22 18:31:32 DD-WRT : 77a86080: >02001025 8fb1010c 8fb00108 03e00008 27bd0110 8f8294d8 7c03e83b 00431021 
May 22 18:31:32 DD-WRT : 77a860a0:  ac500000 1000fff0 2410ffff 00000000 3c1c0017 279c1d70 0399e021 04800005 
May 22 18:31:32 DD-WRT : Caught SIGABRT (6) sent by tkill 
May 22 18:31:32 DD-WRT : Thread 2370: httpd 
May 22 18:31:32 DD-WRT : === Context: 
May 22 18:31:32 DD-WRT : ZERO:00000000   AT:00000001   V0:00000000   V1:7789fc00   A0:00000003   A1:7789fc00 
May 22 18:31:32 DD-WRT :   A2:00000000   A3:00000000   T0:00000000   T1:00000401   T2:77f99000   T3:77fa7000 
May 22 18:31:32 DD-WRT :   T4:00002000   T5:fffffffc   T6:00100000   T7:00001072   S0:00000000   S1:7789fc00 
May 22 18:31:32 DD-WRT :   S2:77bf4000   S3:00000010   S4:77ae4c70   S5:77f99000   S6:00000002   S7:00000002 
May 22 18:31:32 DD-WRT :   T8:77abf088   T9:77a85fb0   K0:00000010   K1:00000000   GP:77bf7e20   SP:7789fb78 
May 22 18:31:32 DD-WRT :   FP:7789fe10   RA:77a87754 
May 22 18:31:32 DD-WRT : === Backtrace: 
May 22 18:31:32 DD-WRT : # [0x77a85fc0]: stack size 272 
May 22 18:31:32 DD-WRT : # [0x77a875e4]: ra offset 316 
May 22 18:31:32 DD-WRT : # [0x77a875dc]: stack size 320 
May 22 18:31:32 DD-WRT : /lib/libc.so.6[0x77a54000](gsignal+0x000000d0)[0x77a86080] 
May 22 18:31:32 DD-WRT : /lib/libc.so.6[0x77a54000](abort+0x00000184)[0x77a87754] 
May 22 18:31:32 DD-WRT : /lib/libc.so.6[0x77a54000](__libc_fatal+0x00000000)[0x77ace564] 
May 22 18:31:32 DD-WRT : /usr/lib/libutils.so[0x77c7f000](+0x00014b74)[0x77c93b74] 
May 22 18:31:32 DD-WRT : === Code: 
May 22 18:31:32 DD-WRT : 77a86040:  0000000c 00402025 2402107e 0000000c 00402825 02003025 240210aa 0000000c 
May 22 18:31:32 DD-WRT : 77a86060:  14e0000c 00408025 24040003 02202825 00003025 24070010 24021063 0000000c 
May 22 18:31:32 DD-WRT : 77a86080: >02001025 8fb1010c 8fb00108 03e00008 27bd0110 8f8294d8 7c03e83b 00431021 
May 22 18:31:32 DD-WRT : 77a860a0:  ac500000 1000fff0 2410ffff 00000000 3c1c0017 279c1d70 0399e021 04800005 

that it’s a result of too many ‘auth’ requests being sent to PAM, which eventually has the module return “could not identify password for [user]”.

My question is: is there a way to increase the number of auth attempts for this program? This specific page is trying to query 18-20 interfaces and then render their activity via SVG.
	-even though I’m only using one of the interfaces, the UI will draw all 18-20 anyways, so I suspect the daemon’s voluminous attempts (due to the SVG being a plot that’s updated constantly) results in this error, as some kind of throttling.

any tips? 

Thanks,
Gagan

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