On 20.01.2014 15:04, Yuto KAWAMURA wrote:
> 2014/1/16 Michal Privoznik <mprivozn@xxxxxxxxxx>:
>> On 15.01.2014 18:06, Yuto KAWAMURA(kawamuray) wrote:
>>> From: "Yuto KAWAMURA(kawamuray)" <kawamuray.dadada@xxxxxxxxx>
>>>
>>> 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
>>
>
> Thanks for review Michal.
> Fix patch for this bug is following.
> Regoards.
>
> diff --git a/tools/wireshark/src/packet-libvirt.c
> b/tools/wireshark/src/packet-libvirt.c
> index 2d0350c..d64ecce 100644
> --- a/tools/wireshark/src/packet-libvirt.c
> +++ b/tools/wireshark/src/packet-libvirt.c
> @@ -39,6 +39,7 @@ static int proto_libvirt = -1;
> static int hf_libvirt_length = -1;
> static int hf_libvirt_program = -1;
> static int hf_libvirt_version = -1;
> +static int hf_libvirt_procedure = -1;
> static int hf_libvirt_type = -1;
> static int hf_libvirt_serial = -1;
> static int hf_libvirt_status = -1;
> @@ -381,7 +382,7 @@ 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 +394,12 @@ 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) {
> - proto_tree_add_none_format(libvirt_tree, -1, tvb, offset,
> 4, "Unknown proc: %u", proc);
> + hf_proc = (int *)get_program_data(prog, VIR_PROGRAM_PROCHFVAR);
> + if (hf_proc != NULL && *hf_proc != -1) {
> + proto_tree_add_item(libvirt_tree, *hf_proc, tvb, offset,
> 4, ENC_NA);
> } else {
> - proto_tree_add_item(libvirt_tree, hf_proc, tvb, offset, 4, ENC_NA);
> + /* No string representation, but still useful displaying
> proc number */
> + proto_tree_add_item(libvirt_tree, hf_libvirt_procedure,
> tvb, offset, 4, ENC_NA);
> }
> offset += 4;
>
> @@ -446,6 +448,12 @@ proto_register_libvirt(void)
> NULL, 0x0,
> NULL, HFILL}
> },
> + { &hf_libvirt_procedure,
> + { "procedure", "libvirt.procedure",
> + FT_INT32, BASE_DEC,
> + NULL, 0x0,
> + NULL, HFILL}
> + },
> { &hf_libvirt_type,
> { "type", "libvirt.type",
> FT_INT32, BASE_DEC,
>
>
Yes, this fixes the problem. ACK. I'm squashing this in and pushing the
series. Thanks!
Michal
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