Re: [libvirt] [PATCH RESEND v4 1/2] Introduce Libvirt Wireshark dissector

On 15.01.2014 18:06, Yuto KAWAMURA(kawamuray) wrote: > From: "Yuto KAWAMURA(kawamuray)" <kawamuray.dadada(a)gmail.com&gt; > > Introduce Wireshark dissector plugin which adds support to Wireshark > for dissecting libvirt RPC protocol. > Added following files to build Wireshark dissector from libvirt source > tree. > * tools/wireshark/*: Source tree of Wireshark dissector plugin. > > Added followings to configure.ac or Makefile.am. > configure.ac > * --with-wireshark-dissector: Enable support for building Wireshark > dissector. > * --with-ws-plugindir: Specify wireshark plugin directory that dissector > will installed. > * Added tools/wireshark/{Makefile,src/Makefile} to AC_CONFIG_FILES. > Makefile.am > * Added tools/wireshark/ to SUBDIR. > --- > .gitignore | 2 + > Makefile.am | 3 +- > cfg.mk | 8 +- > configure.ac | 72 ++- > tools/wireshark/Makefile.am | 22 + > tools/wireshark/README.md | 31 + > tools/wireshark/src/Makefile.am | 42 ++ > tools/wireshark/src/packet-libvirt.c | 512 ++++++++++++++++ > tools/wireshark/src/packet-libvirt.h | 128 ++++ > tools/wireshark/util/genxdrstub.pl | 1011 +++++++++++++++++++++++++++++++ > tools/wireshark/util/make-dissector-reg | 198 ++++++ > 11 files changed, 2023 insertions(+), 6 deletions(-) > create mode 100644 tools/wireshark/Makefile.am > create mode 100644 tools/wireshark/README.md > create mode 100644 tools/wireshark/src/Makefile.am > create mode 100644 tools/wireshark/src/packet-libvirt.c > create mode 100644 tools/wireshark/src/packet-libvirt.h > create mode 100755 tools/wireshark/util/genxdrstub.pl > create mode 100755 tools/wireshark/util/make-dissector-reg > > diff --git a/tools/wireshark/src/packet-libvirt.c b/tools/wireshark/src/packet-libvirt.c > new file mode 100644 > index 0000000..2d0350c > --- /dev/null > +++ b/tools/wireshark/src/packet-libvirt.c > +static void > +dissect_libvirt_message(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) > +{ > + goffset offset; > + guint32 prog, proc, type, serial, status; > + const value_string *vs; > + > + col_set_str(pinfo->cinfo, COL_PROTOCOL, "Libvirt"); > + col_clear(pinfo->cinfo, COL_INFO); > + > + offset = 4; /* End of length field */ > + prog = tvb_get_ntohl(tvb, offset); offset += 4; > + offset += 4; /* Ignore version header field */ > + proc = tvb_get_ntohl(tvb, offset); offset += 4; > + type = tvb_get_ntohl(tvb, offset); offset += 4; > + serial = tvb_get_ntohl(tvb, offset); offset += 4; > + status = tvb_get_ntohl(tvb, offset); offset += 4; > + > + col_add_fstr(pinfo->cinfo, COL_INFO, "Prog=%s", > + val_to_str(prog, program_strings, "%x")); > + > + vs = get_program_data(prog, VIR_PROGRAM_PROCSTRINGS); > + if (vs == NULL) { > + col_append_fstr(pinfo->cinfo, COL_INFO, " Proc=%u", proc); > + } else { > + col_append_fstr(pinfo->cinfo, COL_INFO, " Proc=%s", val_to_str(proc, vs, "%d")); > + } > + > + col_append_fstr(pinfo->cinfo, COL_INFO, " Type=%s Serial=%u Status=%s", > + val_to_str(type, type_strings, "%d"), serial, > + val_to_str(status, status_strings, "%d")); > + > + if (tree) { > + gint hf_proc; > + proto_item *ti; > + proto_tree *libvirt_tree; > + > + ti = proto_tree_add_item(tree, proto_libvirt, tvb, 0, tvb_length(tvb), ENC_NA); > + libvirt_tree = proto_item_add_subtree(ti, ett_libvirt); > + > + offset = 0; > + proto_tree_add_item(libvirt_tree, hf_libvirt_length, tvb, offset, 4, ENC_NA); offset += 4; > + proto_tree_add_item(libvirt_tree, hf_libvirt_program, tvb, offset, 4, ENC_NA); offset += 4; > + proto_tree_add_item(libvirt_tree, hf_libvirt_version, tvb, offset, 4, ENC_NA); offset += 4; > + > + hf_proc = *(int *)get_program_data(prog, VIR_PROGRAM_PROCHFVAR); There's a possible NULL dereference here. get_program might return NULL in case @prog is not one of REMOTE, QEMU, LXC, KEEPALIVE. This can possibly happen and it did for me indeed: Program terminated with signal 11, Segmentation fault. #0 0x00007fac1cc60a86 in dissect_libvirt_message (tvb=0x387acc0, pinfo=0x7fffb9a03100, tree=0x3883090) at packet-libvirt.c:396 396 hf_proc = *(int *)get_program_data(prog, VIR_PROGRAM_PROCHFVAR); (gdb) bt #0 0x00007fac1cc60a86 in dissect_libvirt_message (tvb=0x387acc0, pinfo=0x7fffb9a03100, tree=0x3883090) at packet-libvirt.c:396 #1 0x00000034469198fe in tcp_dissect_pdus () from /usr/lib64/libwireshark.so.3 #2 0x00007fac1cc60c0c in dissect_libvirt (tvb=0x3879aa0, pinfo=0x7fffb9a03100, tree=0x3883090) at packet-libvirt.c:424 #3 0x00000034462dff54 in ?? () from /usr/lib64/libwireshark.so.3 #4 0x00000034462e0608 in ?? () from /usr/lib64/libwireshark.so.3 #5 0x00000034462e0e0c in ?? () from /usr/lib64/libwireshark.so.3 #6 0x00000034462e0e67 in dissector_try_uint () from /usr/lib64/libwireshark.so.3 ... (gdb) p /x VIR_PROGRAM_PROCHFVAR $1 = 0x0 (gdb) p /x prog $2 = 0xd21c44f9 This happened if I used sasl for authentication (auth_tcp="sasl" listen_tcp=1 listen_tls=0) > + if (hf_proc == -1) { > + proto_tree_add_none_format(libvirt_tree, -1, tvb, offset, 4, "Unknown proc: %u", proc); > + } else { > + proto_tree_add_item(libvirt_tree, hf_proc, tvb, offset, 4, ENC_NA); > + } > + offset += 4; I've tried to fixed this by applying: @@ -381,7 +381,7 @@ dissect_libvirt_message(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) val_to_str(status, status_strings, "%d")); if (tree) { - gint hf_proc; + gint *hf_proc; proto_item *ti; proto_tree *libvirt_tree; @@ -393,11 +393,11 @@ dissect_libvirt_message(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) proto_tree_add_item(libvirt_tree, hf_libvirt_program, tvb, offset, 4, ENC_NA); offset += 4; proto_tree_add_item(libvirt_tree, hf_libvirt_version, tvb, offset, 4, ENC_NA); offset += 4; - hf_proc = *(int *)get_program_data(prog, VIR_PROGRAM_PROCHFVAR); - if (hf_proc == -1) { + hf_proc = (int *)get_program_data(prog, VIR_PROGRAM_PROCHFVAR); + if (!hf_proc || *hf_proc == -1) { proto_tree_add_none_format(libvirt_tree, -1, tvb, offset, 4, "Unknown proc: %u", proc); } else { - proto_tree_add_item(libvirt_tree, hf_proc, tvb, offset, 4, ENC_NA); + proto_tree_add_item(libvirt_tree, *hf_proc, tvb, offset, 4, ENC_NA); } offset += 4; but it worked only partially as then I was seeing this error messages (but no segfault :) ): 12:29:09 Warn Dissector bug, protocol libvirt, in packet 32: proto.c:1854: failed assertion "(guint)hfindex < gpa_hfinfo.len" (Unregistered hf!) The error message kept repeating over and over again. The rest of the patch looks okay. Once you fix this (sending a follow-up patch is just fine) I'll push this. Thanks for taking care of the dissector! Michal