nginx 1.25.3.1 http2 segfault with ja3 patch added

[macskas]

I cannot reproduce the error with curl, I can't see it in the logs(segfaults before the log) and there are like 4k rps on a single server, so debug logs are not really an option :( In the core I see the orignal request url with gdb. But thats about it. If I call the url directly there is no error.

Today I tested with and without ja3 patch. Same build process (official openresty builder). With ja3, there is a segfault in every 10 minutes, without it no segfault at all.

The core contains sensitive information so I cannot share it publicly,

built with OpenSSL 1.1.1w 11 Sep 2023
TLS SNI support enabled
configure arguments: --prefix=/usr/local/openresty/nginx --with-cc-opt='-O2 -DNGX_LUA_ABORT_AT_PANIC -I/usr/local/openresty/zlib/include -I/usr/local/openresty/pcre/include -I/usr/local/openresty/openssl111/include' --add-module=../ngx_devel_kit-0.3.3 --add-module=../echo-nginx-module-0.63 --add-module=../xss-nginx-module-0.06 --add-module=../ngx_coolkit-0.2 --add-module=../set-misc-nginx-module-0.33 --add-module=../form-input-nginx-module-0.12 --add-module=../encrypted-session-nginx-module-0.09 --add-module=../srcache-nginx-module-0.33 --add-module=../ngx_lua-0.10.26 --add-module=../ngx_lua_upstream-0.07 --add-module=../headers-more-nginx-module-0.37 --add-module=../array-var-nginx-module-0.06 --add-module=../memc-nginx-module-0.20 --add-module=../redis2-nginx-module-0.15 --add-module=../redis-nginx-module-0.3.9 --add-module=../ngx_stream_lua-0.0.14 --with-ld-opt='-Wl,-rpath,/usr/local/openresty/luajit/lib -L/usr/local/openresty/zlib/lib -L/usr/local/openresty/pcre/lib -L/usr/local/openresty/openssl111/lib -Wl,-rpath,/usr/local/openresty/zlib/lib:/usr/local/openresty/pcre/lib:/usr/local/openresty/openssl111/lib -Wl,-rpath,' --with-pcre-jit --with-stream --with-stream_ssl_module --with-stream_ssl_preread_module
--with-http_v2_module --without-mail_pop3_module --without-mail_imap_module --without-mail_smtp_module --with-http_stub_status_module --with-http_realip_module --with-http_addition_module --with-http_auth_request_module --with-http_secure_link_module --with-http_random_index_module --with-http_gzip_static_module --with-http_sub_module --with-http_dav_module --with-http_flv_module --with-http_mp4_module --with-http_gunzip_module --with-threads --add-dynamic-module=/tmp/modules/brotli --add-dynamic-module=/tmp/modules/geoip2 --add-module=/tmp/modules/nginx-ssl-fingerprint --with-stream --without-pcre2 --with-http_ssl_module

I know this is not much:

(gdb) info shared
From                To                  Syms Read   Shared Object Library
0x00007eff33311220  0x00007eff33312179  Yes         /lib/x86_64-linux-gnu/libdl.so.2
0x00007eff332f3ae0  0x00007eff33303535  Yes         /lib/x86_64-linux-gnu/libpthread.so.0
0x00007eff332b4040  0x00007eff332c8c80  Yes (*)     /lib/x86_64-linux-gnu/libcrypt.so.1
0x00007eff3322e670  0x00007eff3329423d  Yes         /usr/local/openresty/luajit/lib/libluajit-5.1.so.2
0x00007eff331b62c0  0x00007eff33205e5d  Yes (*)     /usr/local/openresty/pcre/lib/libpcre.so.1
0x00007eff3313d750  0x00007eff3318974a  Yes (*)     /usr/local/openresty/openssl111/lib/libssl.so.1.1
0x00007eff32eca000  0x00007eff3305b260  Yes (*)     /usr/local/openresty/openssl111/lib/libcrypto.so.1.1
0x00007eff32e36280  0x00007eff32e4765b  Yes (*)     /usr/local/openresty/zlib/lib/libz.so.1
0x00007eff32c63630  0x00007eff32dd84bd  Yes         /lib/x86_64-linux-gnu/libc.so.6
0x00007eff3331f100  0x00007eff33341684  Yes         /lib64/ld-linux-x86-64.so.2
0x00007eff32aff3c0  0x00007eff32ba5fa8  Yes         /lib/x86_64-linux-gnu/libm.so.6
0x00007eff32ada5e0  0x00007eff32aeb055  Yes (*)     /lib/x86_64-linux-gnu/libgcc_s.so.1
0x00007eff32ac15c0  0x00007eff32ac7a1c  Yes         /lib/x86_64-linux-gnu/libnss_files.so.2
0x00007eff333173e0  0x00007eff3331864c  Yes         /usr/local/openresty/nginx/modules/ngx_http_geoip2_module.so
0x00007eff32ab2300  0x00007eff32ab4e5c  Yes (*)     /lib/x86_64-linux-gnu/libmaxminddb.so.0
0x00007eff271766e0  0x00007eff2717a0c1  Yes         /usr/local/openresty/lualib/cjson.so
0x00007eff270fefa0  0x00007eff27123300  Yes (*)     /lib/x86_64-linux-gnu/libnss_systemd.so.2
(*): Shared library is missing debugging information.

Core was generated by `nginx: worker process                                                 '.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  ngx_palloc_large (pool=0x55d85c102a00, size=<optimized out>) at src/core/ngx_palloc.c:228
228	src/core/ngx_palloc.c: No such file or directory.
(gdb) bt
#0  ngx_palloc_large (pool=0x55d85c102a00, size=<optimized out>) at src/core/ngx_palloc.c:228
#1  0x000055d85a2614ff in ngx_palloc (pool=<optimized out>, size=<optimized out>) at src/core/ngx_palloc.c:131
#2  0x000055d85a2d8a75 in ngx_http_v2_add_header (h2c=h2c@entry=0x55d85c18a500, header=header@entry=0x55d85c18a5a0) at src/http/v2/ngx_http_v2_table.c:212
#3  0x000055d85a2d6c4b in ngx_http_v2_state_process_header (h2c=0x55d85c18a500, 
    pos=0x55d85bf57d56 "A\217%\225ȕ\350\067r\364\032)5K\220\364\377S\260I|\245\211\323M\037C\256\272\fA\244ǩ\217\063\246\232?ߚh\372\035u\320b\r&=Ly\246\217\276\320\001w\376\276X\371\373", <incomplete sequence \355>, 
    end=0x55d85bf57e70 "\177\222\235)\255\027\030cǏ\v\216\241\321!\252_ϟ?@\212AH\264\245I'Y\006I\177\207%\207B\026A\222_@\212AH\264\245I'Z\223\310_\203!\354G@\212AH\264\245I'ZB\241?\204-5\247\327s\223\235)\255\027\030cǏ\v\216\241\321!\252_ϟ,\177P\222\233٫\372RB\313@\322_\245#\263\351OhL\237Q\234\">\213W\337h") at src/http/v2/ngx_http_v2.c:1778
#4  0x000055d85a2d736f in ngx_http_v2_state_field_huff (h2c=<optimized out>, pos=<optimized out>, end=<optimized out>) at src/http/v2/ngx_http_v2.c:1617
#5  0x000055d85a2d7608 in ngx_http_v2_state_field_len (h2c=h2c@entry=0x55d85c18a500, pos=<optimized out>, 
    end=end@entry=0x55d85bf57e70 "\177\222\235)\255\027\030cǏ\v\216\241\321!\252_ϟ?@\212AH\264\245I'Y\006I\177\207%\207B\026A\222_@\212AH\264\245I'Z\223\310_\203!\354G@\212AH\264\245I'ZB\241?\204-5\247\327s\223\235)\255\027\030cǏ\v\216\241\321!\252_ϟ,\177P\222\233٫\372RB\313@\322_\245#\263\351OhL\237Q\234\">\213W\337h") at src/http/v2/ngx_http_v2.c:1575
#6  0x000055d85a2d7886 in ngx_http_v2_state_header_block (h2c=0x55d85c18a500, pos=<optimized out>, 
    end=0x55d85bf57e70 "\177\222\235)\255\027\030cǏ\v\216\241\321!\252_ϟ?@\212AH\264\245I'Y\006I\177\207%\207B\026A\222_@\212AH\264\245I'Z\223\310_\203!\354G@\212AH\264\245I'ZB\241?\204-5\247\327s\223\235)\255\027\030cǏ\v\216\241\321!\252_ϟ,\177P\222\233٫\372RB\313@\322_\245#\263\351OhL\237Q\234\">\213W\337h") at src/http/v2/ngx_http_v2.c:1491
#7  0x000055d85a2d5145 in ngx_http_v2_read_handler (rev=0x7eff26bb8d70) at src/http/v2/ngx_http_v2.c:432
#8  0x000055d85a28a596 in ngx_epoll_process_events (cycle=<optimized out>, timer=<optimized out>, flags=<optimized out>) at src/event/modules/ngx_epoll_module.c:901
#9  0x000055d85a280978 in ngx_process_events_and_timers (cycle=cycle@entry=0x55d85bd276d0) at src/event/ngx_event.c:258
#10 0x000055d85a288690 in ngx_worker_process_cycle (cycle=cycle@entry=0x55d85bd276d0, data=data@entry=0x5) at src/os/unix/ngx_process_cycle.c:793
#11 0x000055d85a286f8d in ngx_spawn_process (cycle=cycle@entry=0x55d85bd276d0, proc=proc@entry=0x55d85a288610 <ngx_worker_process_cycle>, data=data@entry=0x5, name=name@entry=0x55d85a3a3ceb "worker process", respawn=respawn@entry=-3)
    at src/os/unix/ngx_process.c:199
#12 0x000055d85a288ba4 in ngx_start_worker_processes (cycle=cycle@entry=0x55d85bd276d0, n=8, type=type@entry=-3) at src/os/unix/ngx_process_cycle.c:382
#13 0x000055d85a289442 in ngx_master_process_cycle (cycle=0x55d85bd276d0) at src/os/unix/ngx_process_cycle.c:135
#14 0x000055d85a25ed7a in main (argc=<optimized out>, argv=<optimized out>) at src/core/nginx.c:387

f 0
(gdb) info local
p = 0x55d85bfe8990
n = 2
large = 0x9f5d259b3eb91b2

(gdb) p *pool
$38 = {d = {last = 0x55d85c102bfc "\330U", end = 0x55d85c102c00 "\020\002", next = 0x55d85c002ef0, failed = 1}, max = 432, current = 0x55d85c102a00, chain = 0x0, large = 0x55d85c0030d8, cleanup = 0x55d85c002fa0, log = 0x55d85c102a60}

f 2
#2  0x000055d85a2d8a75 in ngx_http_v2_add_header (h2c=h2c@entry=0x55d85c18a500, header=header@entry=0x55d85c18a5a0) at src/http/v2/ngx_http_v2_table.c:212
$12 = {connection = 0x7eff26d3e180, http_connection = 0x55d85c102ac0, total_bytes = 130, payload_bytes = 0, processing = 1, frames = 0, idle = 3, new_streams = 1, refused_streams = 0, priority_limit = 256, send_window = 65535, 
  recv_window = 2147483647, init_window = 65535, frame_size = 16384, waiting = {prev = 0x55d85c18a570, next = 0x55d85c18a570}, state = {sid = 1, length = 282, padding = 0, flags = 5, incomplete = 0, keep_pool = 1, parse_name = 0, 
    parse_value = 0, index = 1, header = {name = {len = 5, data = 0x55d85a3abcbe ":path"}, value = {len = 165, 
        data = 0x55d85c0ea340 "***SENSITIVE INFO (url)***"}}, header_limit = 32576, 
    field_state = 0 '\000', field_start = 0x55d85c0ea340 "***SENSITIVE INFO (url)***", 
    field_end = 0x55d85c0ea3e5 "", field_rest = 0, pool = 0x55d85c0ea2f0, stream = 0x55d85bfc9ee0, buffer = '\000' <repeats 15 times>, buffer_used = 0, handler = 0x55d85a2d77e0 <ngx_http_v2_state_header_block>}, hpack = {
    entries = 0x55d85c204dc0, added = 0, deleted = 0, reused = 0, allocated = 64, size = 4096, free = 4096, storage = 0x0, pos = 0x0}, pool = 0x55d85c032990, free_frames = 0x0, free_fake_connections = 0x0, 
  streams_index = 0x55d85c002fb8, last_out = 0x0, dependencies = {prev = 0x55d85bfc0398, next = 0x55d85bfc0398}, closed = {prev = 0x55d85c18a698, next = 0x55d85c18a698}, closed_nodes = 0, last_sid = 1, lingering_time = 0, 
  settings_ack = 1, table_update = 1, blocked = 1, goaway = 0, fp_fingerprinted = 0, fp_settings = {len = 35, data = 0x55d85c0030b8 "\001"}, fp_windowupdate = 0, fp_priorities = {len = 4, data = 0x55d85bfc02f0 "\001"}, 
  fp_pseudoheaders = {len = 2, data = 0x55d85bfc0310 "ce\374[\330U"}, fp_str = {len = 0, data = 0x0}}

(gdb) p header
$13 = (ngx_http_v2_header_t *) 0x55d85c18a5a0
(gdb) p header->name
$14 = {len = 5, data = 0x55d85a3abcbe ":path"}
(gdb) p header->value
$15 = {len = 165, data = 0x55d85c0ea340 "***SENSITIVE INFO (url)***"}
(gdb) p h2c->hpack
$17 = {entries = 0x55d85c204dc0, added = 0, deleted = 0, reused = 0, allocated = 64, size = 4096, free = 4096, storage = 0x0, pos = 0x0}
(gdb) p **h2c->hpack->entries
$20 = {name = {len = 94387745532352, data = 0x55d85bd08010 "\a"}, value = {len = 0, data = 0x0}}
(gdb) p *h2c->connection
$24 = {data = 0x55d85c18a500, read = 0x7eff26bb8d70, write = 0x7eff26a37d70, fd = 49, recv = 0x55d85a28fc60 <ngx_ssl_recv>, send = 0x55d85a290100 <ngx_ssl_write>, recv_chain = 0x55d85a290040 <ngx_ssl_recv_chain>, 
  send_chain = 0x55d85a290530 <ngx_ssl_send_chain>, listening = 0x55d85bd27f10, sent = 58, log = 0x55d85c102a60, pool = 0x55d85c102a00, type = 1, sockaddr = 0x55d85c102a50, socklen = 16, addr_text = {len = 12, 
    data = 0x55d85c102ab0 "84.*IP****"}, proxy_protocol = 0x0, ssl = 0x55d85c102b18, udp = 0x0, local_sockaddr = 0x55d85bf44430, local_socklen = 16, buffer = 0x0, queue = {prev = 0x7eff26d38748, next = 0x7eff26d38fb8}, 
  number = 737234, start_time = 84136899431, requests = 1, buffered = 0, log_error = 2, timedout = 0, error = 0, destroyed = 0, pipeline = 0, idle = 1, reusable = 0, close = 0, shared = 0, sendfile = 0, sndlowat = 0, tcp_nodelay = 1, 
  tcp_nopush = 0, need_last_buf = 0, need_flush_buf = 0, sendfile_task = 0x0}
(gdb) p *h2c->connection->pool
$25 = {d = {last = 0x55d85c102bfc "\330U", end = 0x55d85c102c00 "\020\002", next = 0x55d85c002ef0, failed = 1}, max = 432, current = 0x55d85c102a00, chain = 0x0, large = 0x55d85c0030d8, cleanup = 0x55d85c002fa0, log = 0x55d85c102a60}
(gdb) 

(gdb) f 3
#3  0x000055d85a2d6c4b in ngx_http_v2_state_process_header (h2c=0x55d85c18a500, 
    pos=0x55d85bf57d56 "A\217%\225ȕ\350\067r\364\032)5K\220\364\377S\260I|\245\211\323M\037C\256\272\fA\244ǩ\217\063\246\232?ߚh\372\035u\320b\r&=Ly\246\217\276\320\001w\376\276X\371\373", <incomplete sequence \355>, 
    end=0x55d85bf57e70 "\177\222\235)\255\027\030cǏ\v\216\241\321!\252_ϟ?@\212AH\264\245I'Y\006I\177\207%\207B\026A\222_@\212AH\264\245I'Z\223\310_\203!\354G@\212AH\264\245I'ZB\241?\204-5\247\327s\223\235)\255\027\030cǏ\v\216\241\321!\252_ϟ,\177P\222\233٫\372RB\313@\322_\245#\263\351OhL\237Q\234\">\213W\337h") at src/http/v2/ngx_http_v2.c:1778
1778	src/http/v2/ngx_http_v2.c: No such file or directory.
(gdb) p pos
$39 = (u_char *) 0x55d85bf57d56 "A\217%\225ȕ\350\067r\364\032)5K\220\364\377S\260I|\245\211\323M\037C\256\272\fA\244ǩ\217\063\246\232?ߚh\372\035u\320b\r&=Ly\246\217\276\320\001w\376\276X\371\373", <incomplete sequence \355>
(gdb) p end
$42 = (u_char *) 0x55d85bf57e70 "\177\222\235)\255\027\030cǏ\v\216\241\321!\252_ϟ?@\212AH\264\245I'Y\006I\177\207%\207B\026A\222_@\212AH\264\245I'Z\223\310_\203!\354G@\212AH\264\245I'ZB\241?\204-5\247\327s\223\235)\255\027\030cǏ\v\216\241\321!\252_ϟ,\177P\222\233٫\372RB\313@\322_\245#\263\351OhL\237Q\234\">\213W\337h"
(gdb) p *h2c->connection->log
$47 = {log_level = 4, file = 0x55d85bd27a70, connection = 737234, disk_full_time = 0, handler = 0x55d85a2a1a30 <ngx_http_log_error>, data = 0x55d85c102b00, writer = 0x0, wdata = 0x0, 
  action = 0x55d85a3aaaec "processing HTTP/2 connection", next = 0x0}
(gdb) p **h2c->streams_index
$51 = {id = 1, index = 0x0, parent = 0xffffffffffffffff, queue = {prev = 0x55d85c18a688, next = 0x55d85c18a688}, children = {prev = 0x55d85bfc03a8, next = 0x55d85bfc03a8}, reuse = {prev = 0x0, next = 0x0}, rank = 1, weight = 16, 
  rel_weight = 0.0625, stream = 0x55d85bfc9ee0}

(gdb) p *ngx_cycle
$57 = {conf_ctx = 0x55d85bd28978, pool = 0x55d85bd27680, log = 0x55d85bd276e8, new_log = {log_level = 4, file = 0x55d85bd27a70, connection = 0, disk_full_time = 0, handler = 0x0, data = 0x0, writer = 0x0, wdata = 0x0, action = 0x0, 
    next = 0x0}, log_use_stderr = 0, files = 0x0, free_connections = 0x7eff26d384b0, free_connection_n = 16278, modules = 0x55d85bd290e0, modules_n = 107, modules_used = 1, reusable_connections_queue = {prev = 0x7eff26d39468, 
    next = 0x7eff26d3c528}, reusable_connections_n = 93, connections_reuse_time = 0, listening = {elts = 0x55d85bd27de8, nelts = 7, size = 296, nalloc = 10, pool = 0x55d85bd27680}, paths = {elts = 0x55d85bd27a08, nelts = 6, size = 8, 
    nalloc = 10, pool = 0x55d85bd27680}, config_dump = {elts = 0x55d85bd27a58, nelts = 0, size = 24, nalloc = 1, pool = 0x55d85bd27680}, config_dump_rbtree = {root = 0x55d85bd27820, sentinel = 0x55d85bd27820, 
    insert = 0x55d85a2664c0 <ngx_str_rbtree_insert_value>}, config_dump_sentinel = {key = 0, left = 0x0, right = 0x0, parent = 0x0, color = 0 '\000', data = 0 '\000'}, open_files = {last = 0x55d85bd27850, part = {
      elts = 0x55d85bd27a70, nelts = 1, next = 0x0}, size = 40, nalloc = 20, pool = 0x55d85bd27680}, shared_memory = {last = 0x55d85bd4c108, part = {elts = 0x55d85bd27d90, nelts = 1, next = 0x55d85bd4bfd0}, size = 88, nalloc = 1, 
    pool = 0x55d85bd27680}, connection_n = 16384, files_n = 0, connections = 0x7eff26d37010, read_events = 0x7eff26bb6010, write_events = 0x7eff26a35010, old_cycle = 0x0, conf_file = {len = 42, 
    data = 0x55d85bd279ba "/usr/local/openresty/nginx/conf/nginx.conf"}, conf_param = {len = 29, data = 0x55d85bd279e5 "daemon on; master_process on;\032\063\377~"}, conf_prefix = {len = 32, 
    data = 0x55d85bd27970 "/usr/local/openresty/nginx/conf//usr/local/openresty/nginx/logs/error.log"}, prefix = {len = 27, data = 0x55d85bd27990 "/usr/local/openresty/nginx/logs/error.log"}, error_log = {len = 14, 
    data = 0x55d85bd279ab "logs/error.log"}, lock_file = {len = 43, data = 0x55d85bf446fc "/usr/local/openresty/nginx/logs/nginx.lock.accept"}, hostname = {len = 24, data = 0x55d85bd290c8 "*************\200?Z\330U"}, 
  intercept_error_log_handler = 0x0, intercept_error_log_data = 0x0, entered_logger = 0}

[phuslu]

seems there're a buffer overflow in ja3, let me try to figure out.

[macskas]

If you need help in testing / debugging I can build & deploy in 15 minutes to see if a fix works. I also shared a private github repo with the last core & binary & debug symbols.

[macskas]

I had time to check up on this. I created a patch where I check allocation success & etc and its working just fine now, no segfaults.
I think this might have been the main issue in ngx_http_v2.c:

        if (!h2c->fp_fingerprinted && h2c->fp_settings.len < 32) {
            h2c->fp_settings.data[h2c->fp_settings.len] = (uint8_t)id;
            *(uint32_t*)(h2c->fp_settings.data + h2c->fp_settings.len + 1)  = (uint32_t)value;
            h2c->fp_settings.len += 5;
        }

I am not familiar with ngx internal data structures so I checked every allocation and variables to make sure there is no issue with them, but might not needed at all at the end. So please somehow keep only the necessary checks you know its needed.
nginx-patch.tar.gz

[morpig]

@macskas do you have fork repository with your fix? not file attachment

[macskas]

@macskas do you have fork repository with your fix? not file attachment

I created a fork & run the test for the changes: https://github.com/macskas/nginx-ssl-fingerprint

[dedok]

Hello @macskas @morpig,

Planning to use this module also, and I well know NGINX structures & ideoms. @macskas checked your patch, seems most of the fixes are valid. But I think that the root cause is inside patch of openssl lib, ex: https://github.com/phuslu/nginx-ssl-fingerprint/blob/master/patches/openssl.openssl-3.2.patch#L121, openssl checks ret: https://github.com/openssl/openssl/blob/master/include/internal/packet.h#L431; I believe it could memcpy NULL or something like that. Anyway I will test this idea.

Btw quite not sure why h2 patch is so complicated. I believe it could be simplified.

By the end of this week or/and middle of the next week I'm planning to introduce patch, some of fixes I would like to take from yours (checking of npalloc() is correct fix, it should be checked).

I will keep you posted here.

[phuslu]

I believe it could memcpy NULL or something like that.

checked the openssl internal codes, I agreed with your points. I will also try fix it. thanks!

[dedok]

Hello @phuslu thanks for the reply,

I made a fix actually and I also prepared patches for next version of nginx and openssl 3.4. I need time to test it under heavy workload. I will send you PR in this repo. Also made a small refactoring and probably speedup a bit your implementation.

Btw @macskas could you also help me with testing under heavy workload?

[phuslu]

@dedok looking forwarding and thanks again!

[dedok]

Hello @phuslu and @macskas ,

I made a bit more changes (all changes described in to PR), PR: #55. @phuslu if you need any addition comments about changes please let me know and we can call and I can describe internal Nginx's structure and why I do that changes, if needed.

PS
We are going to test this module (with changes) at the next under heavy workload with functional testing as well. @phuslu also saw your commit, thx for it I did the same in OpenSSL 3.4 patch (we are using this version, and sorry I focused only on this version).