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#!/usr/bin/python
#
# sslsniff Captures data on read/recv or write/send functions of OpenSSL,
# GnuTLS and NSS
# For Linux, uses BCC, eBPF.
#
# USAGE: sslsniff.py [-h] [-p PID] [-c COMM] [-o] [-g] [-d]
#
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 12-Aug-2016 Adrian Lopez Created this.
# 13-Aug-2016 Mark Drayton Fix SSL_Read
# 17-Aug-2016 Adrian Lopez Capture GnuTLS and add options
#
from __future__ import print_function
from bcc import BPF
import argparse
# arguments
examples = """examples:
./sslsniff # sniff OpenSSL and GnuTLS functions
./sslsniff -p 181 # sniff PID 181 only
./sslsniff -c curl # sniff curl command only
./sslsniff --no-openssl # don't show OpenSSL calls
./sslsniff --no-gnutls # don't show GnuTLS calls
./sslsniff --no-nss # don't show NSS calls
"""
parser = argparse.ArgumentParser(
description="Sniff SSL data",
formatter_class=argparse.RawDescriptionHelpFormatter,
epilog=examples)
parser.add_argument("-p", "--pid", type=int, help="sniff this PID only.")
parser.add_argument("-c", "--comm",
help="sniff only commands matching string.")
parser.add_argument("-o", "--no-openssl", action="store_false", dest="openssl",
help="do not show OpenSSL calls.")
parser.add_argument("-g", "--no-gnutls", action="store_false", dest="gnutls",
help="do not show GnuTLS calls.")
parser.add_argument("-n", "--no-nss", action="store_false", dest="nss",
help="do not show NSS calls.")
parser.add_argument('-d', '--debug', dest='debug', action='count', default=0,
help='debug mode.')
parser.add_argument("--ebpf", action="store_true",
help=argparse.SUPPRESS)
args = parser.parse_args()
prog = """
#include <linux/ptrace.h>
#include <linux/sched.h> /* For TASK_COMM_LEN */
struct probe_SSL_data_t {
u64 timestamp_ns;
u32 pid;
char comm[TASK_COMM_LEN];
char v0[464];
u32 len;
};
BPF_PERF_OUTPUT(perf_SSL_write);
int probe_SSL_write(struct pt_regs *ctx, void *ssl, void *buf, int num) {
u32 pid = bpf_get_current_pid_tgid();
FILTER
struct probe_SSL_data_t __data = {0};
__data.timestamp_ns = bpf_ktime_get_ns();
__data.pid = pid;
__data.len = num;
bpf_get_current_comm(&__data.comm, sizeof(__data.comm));
if ( buf != 0) {
bpf_probe_read(&__data.v0, sizeof(__data.v0), buf);
}
perf_SSL_write.perf_submit(ctx, &__data, sizeof(__data));
return 0;
}
BPF_PERF_OUTPUT(perf_SSL_read);
BPF_HASH(bufs, u32, u64);
int probe_SSL_read_enter(struct pt_regs *ctx, void *ssl, void *buf, int num) {
u32 pid = bpf_get_current_pid_tgid();
FILTER
bufs.update(&pid, (u64*)&buf);
return 0;
}
int probe_SSL_read_exit(struct pt_regs *ctx, void *ssl, void *buf, int num) {
u32 pid = bpf_get_current_pid_tgid();
FILTER
u64 *bufp = bufs.lookup(&pid);
if (bufp == 0) {
return 0;
}
struct probe_SSL_data_t __data = {0};
__data.timestamp_ns = bpf_ktime_get_ns();
__data.pid = pid;
__data.len = PT_REGS_RC(ctx);
bpf_get_current_comm(&__data.comm, sizeof(__data.comm));
if (bufp != 0) {
bpf_probe_read(&__data.v0, sizeof(__data.v0), (char *)*bufp);
}
bufs.delete(&pid);
perf_SSL_read.perf_submit(ctx, &__data, sizeof(__data));
return 0;
}
"""
if args.pid:
prog = prog.replace('FILTER', 'if (pid != %d) { return 0; }' % args.pid)
else:
prog = prog.replace('FILTER', '')
if args.debug or args.ebpf:
print(prog)
if args.ebpf:
exit()
b = BPF(text=prog)
# It looks like SSL_read's arguments aren't available in a return probe so you
# need to stash the buffer address in a map on the function entry and read it
# on its exit (Mark Drayton)
#
if args.openssl:
b.attach_uprobe(name="ssl", sym="SSL_write", fn_name="probe_SSL_write",
pid=args.pid or -1)
b.attach_uprobe(name="ssl", sym="SSL_read", fn_name="probe_SSL_read_enter",
pid=args.pid or -1)
b.attach_uretprobe(name="ssl", sym="SSL_read",
fn_name="probe_SSL_read_exit", pid=args.pid or -1)
if args.gnutls:
b.attach_uprobe(name="gnutls", sym="gnutls_record_send",
fn_name="probe_SSL_write", pid=args.pid or -1)
b.attach_uprobe(name="gnutls", sym="gnutls_record_recv",
fn_name="probe_SSL_read_enter", pid=args.pid or -1)
b.attach_uretprobe(name="gnutls", sym="gnutls_record_recv",
fn_name="probe_SSL_read_exit", pid=args.pid or -1)
if args.nss:
b.attach_uprobe(name="nspr4", sym="PR_Write", fn_name="probe_SSL_write",
pid=args.pid or -1)
b.attach_uprobe(name="nspr4", sym="PR_Send", fn_name="probe_SSL_write",
pid=args.pid or -1)
b.attach_uprobe(name="nspr4", sym="PR_Read", fn_name="probe_SSL_read_enter",
pid=args.pid or -1)
b.attach_uretprobe(name="nspr4", sym="PR_Read",
fn_name="probe_SSL_read_exit", pid=args.pid or -1)
b.attach_uprobe(name="nspr4", sym="PR_Recv", fn_name="probe_SSL_read_enter",
pid=args.pid or -1)
b.attach_uretprobe(name="nspr4", sym="PR_Recv",
fn_name="probe_SSL_read_exit", pid=args.pid or -1)
# define output data structure in Python
TASK_COMM_LEN = 16 # linux/sched.h
MAX_BUF_SIZE = 464 # Limited by the BPF stack
# header
print("%-12s %-18s %-16s %-6s %-6s" % ("FUNC", "TIME(s)", "COMM", "PID",
"LEN"))
# process event
start = 0
def print_event_write(cpu, data, size):
print_event(cpu, data, size, "WRITE/SEND", "perf_SSL_write")
def print_event_read(cpu, data, size):
print_event(cpu, data, size, "READ/RECV", "perf_SSL_read")
def print_event(cpu, data, size, rw, evt):
global start
event = b[evt].event(data)
# Filter events by command
if args.comm:
if not args.comm == event.comm:
return
if start == 0:
start = event.timestamp_ns
time_s = (float(event.timestamp_ns - start)) / 1000000000
s_mark = "-" * 5 + " DATA " + "-" * 5
e_mark = "-" * 5 + " END DATA " + "-" * 5
truncated_bytes = event.len - MAX_BUF_SIZE
if truncated_bytes > 0:
e_mark = "-" * 5 + " END DATA (TRUNCATED, " + str(truncated_bytes) + \
" bytes lost) " + "-" * 5
fmt = "%-12s %-18.9f %-16s %-6d %-6d\n%s\n%s\n%s\n\n"
print(fmt % (rw, time_s, event.comm.decode('utf-8', 'replace'),
event.pid, event.len, s_mark,
event.v0.decode('utf-8', 'replace'), e_mark))
b["perf_SSL_write"].open_perf_buffer(print_event_write)
b["perf_SSL_read"].open_perf_buffer(print_event_read)
while 1:
try:
b.perf_buffer_poll()
except KeyboardInterrupt:
exit()
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