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Subject: Re: [PATCH][WIP][v2] Fix out-of-buffer-boundary reads

Re: [PATCH][WIP][v2] Fix out-of-buffer-boundary reads

From: Yuriy M. Kaminskiy <yumkam_at_gmail.com>
Date: Sun, 31 Mar 2019 21:22:50 +0300

On 31.03.2019 14:23, Yuriy M. Kaminskiy wrote:
> FTR, (some) problems that was addressed by this patch was (apparently
> independently) rediscovered 3 years later, assigned CVE-2019-38{55...63}
> and fixed (differently; I have not checked if fixed code covers all
> cases was covered by my patch).
>
> BTW, _libssh2_check_length() that is extensively used by current code is
> broken/incorrect; e.g. suppose
>
> buf->dataptr = buf->data, buf->len = 5, len = 0xfffffff7
>
> then _libssh2_check_length(buf, len) will return 1; uh-doh.
>
> With obvious security implications.
>
> (No, I'm not going to compose patch to be ignored for another 3 years).

Ah, yeah, forgot to look at 1.8.x branch. No _check_length there, but
other problematic code present instead:

   uint32_t len = _libssh2_ntohu32(data + 5);
   ...
   if((len + 9) < datalen)

Broken when len > UINT32_MAX - 9.

   if(datalen >= 9) {
       message_len = _libssh2_ntohu32(data + 5);
       if(message_len < datalen-13) {

Broken when datalen >= 9 && datalen < 13 (and there are more similar code).

etc.

> On 2016-03-27 22:28 , Yuriy M. Kaminskiy wrote:
>> Ping? I'd like to stress out this issue has security imlications. At
>> very least, DoS (and this is not a standalone application, so it is not
>> a minor issue), and maybe host memory exposure too. (However, it is only
>> heap over-reads, without heap/stack over-writes, so no risk of
>> escalating to remote code execution).
>>
>> On 02/25/16 03:10 , Yuriy M. Kaminskiy wrote:
>>> "George Garner (online)" <ggarner_online_at_gmgsystemsinc.com> writes:
>>> [...]
>>>> 3. Where is the p_len/group_order parameter validated? In
>>>> kex_method_diffie_hellman_group_exchange_sha256_key_exchange it is
>>>> converted from network byte order and accepted at face value. What
>>>> happens if a malicious packet is received with a bogus value for
>>>> p_len?
>>>
>>> Maybe I miss something, but it looks like this defect (blindly trust
>>> various 32-bit length that was sent remote side and don't verify if it
>>> fits buffer) is *everywhere* in libssh2. I've sent some patches for
>>> kex.c via gh pull request, but quickly discovered it is much worse. Very
>>> WIP (and incomplete) patch for *other* files is attached; unfortunately,
>>> in most cases, I have no idea how such errors should be handled within libssh2,
>>> don't know libssh2 code base well enough, so I give up at this.
>>>
>>> Note that in early connection setup "malicious server" is not required,
>>> "malicious MITM" can insert broken packets as well.
>>>
>>> In general, please re-review all `grep ntoh -r src/`, in many cases
>>> surrounding code looks problematic in one way or other.
>>>
>>>
>>> ---
>>> Changelog:
>>> v2: fixed obvious errors
>>> Note: This is still NOT COMPLETE work, all XXX comment must be reviewed and acted upon.
>>>
>>> src/agent.c | 32 ++++++++--------
>>> src/channel.c | 10 ++++-
>>> src/hostkey.c | 19 +++++++--
>>> src/kex.c | 43 +++++++++++----------
>>> src/packet.c | 45 +++++++++++++++++-----
>>> src/publickey.c | 117 +++++++++++++++++++++++++++++++++++++++++++-------------
>>> src/session.c | 2 +
>>> src/sftp.c | 42 ++++++++++++++++----
>>> src/sftp.h | 1 +
>>> src/userauth.c | 32 ++++++++++++++++
>>> 10 files changed, 260 insertions(+), 83 deletions(-)
>>>
>>> diff --git a/src/agent.c b/src/agent.c
>>> index c2ba422..255b63d 100644
>>> --- a/src/agent.c
>>> +++ b/src/agent.c
>>> @@ -449,12 +449,12 @@ agent_sign(LIBSSH2_SESSION *session, unsigned char **sig, size_t *sig_len,
>>> goto error;
>>> }
>>> method_len = _libssh2_ntohu32(s);
>>> - s += 4;
>>> - len -= method_len;
>>> - if (len < 0) {
>>> + if (method_len < 0 || len < method_len) {
>>> rc = LIBSSH2_ERROR_AGENT_PROTOCOL;
>>> goto error;
>>> }
>>> + s += 4;
>>> + len -= method_len;
>>> s += method_len;
>>>
>>> /* Read the signature */
>>> @@ -464,12 +464,12 @@ agent_sign(LIBSSH2_SESSION *session, unsigned char **sig, size_t *sig_len,
>>> goto error;
>>> }
>>> *sig_len = _libssh2_ntohu32(s);
>>> - s += 4;
>>> - len -= *sig_len;
>>> - if (len < 0) {
>>> + if ((size_t)len < *sig_len) {
>>> rc = LIBSSH2_ERROR_AGENT_PROTOCOL;
>>> goto error;
>>> }
>>> + len -= *sig_len;
>>> + s += 4;
>>>
>>> *sig = LIBSSH2_ALLOC(session, *sig_len);
>>> if (!*sig) {
>>> @@ -558,15 +558,15 @@ agent_list_identities(LIBSSH2_AGENT *agent)
>>> goto error;
>>> }
>>> identity->external.blob_len = _libssh2_ntohu32(s);
>>> - s += 4;
>>> -
>>> - /* Read the blob */
>>> - len -= identity->external.blob_len;
>>> - if (len < 0) {
>>> + if ((size_t)len < identity->external.blob_len) {
>>> rc = LIBSSH2_ERROR_AGENT_PROTOCOL;
>>> LIBSSH2_FREE(agent->session, identity);
>>> goto error;
>>> }
>>> + s += 4;
>>> +
>>> + /* Read the blob */
>>> + len -= identity->external.blob_len;
>>>
>>> identity->external.blob = LIBSSH2_ALLOC(agent->session,
>>> identity->external.blob_len);
>>> @@ -587,16 +587,16 @@ agent_list_identities(LIBSSH2_AGENT *agent)
>>> goto error;
>>> }
>>> comment_len = _libssh2_ntohu32(s);
>>> - s += 4;
>>> -
>>> - /* Read the comment */
>>> - len -= comment_len;
>>> - if (len < 0) {
>>> + if (comment_len < 0 || len < comment_len) {
>>> rc = LIBSSH2_ERROR_AGENT_PROTOCOL;
>>> LIBSSH2_FREE(agent->session, identity->external.blob);
>>> LIBSSH2_FREE(agent->session, identity);
>>> goto error;
>>> }
>>> + s += 4;
>>> +
>>> + /* Read the comment */
>>> + len -= comment_len;
>>>
>>> identity->external.comment = LIBSSH2_ALLOC(agent->session,
>>> comment_len + 1);
>>> diff --git a/src/channel.c b/src/channel.c
>>> index 32d914d..38572be 100644
>>> --- a/src/channel.c
>>> +++ b/src/channel.c
>>> @@ -225,6 +225,7 @@ _libssh2_channel_open(LIBSSH2_SESSION * session, const char *channel_type,
>>> }
>>>
>>> if (session->open_state == libssh2_NB_state_sent) {
>>> + unsigned char *end;
>>> rc = _libssh2_packet_requirev(session, reply_codes,
>>> &session->open_data,
>>> &session->open_data_len, 1,
>>> @@ -238,7 +239,11 @@ _libssh2_channel_open(LIBSSH2_SESSION * session, const char *channel_type,
>>> goto channel_error;
>>> }
>>>
>>> + end = session->open_data + session->open_data_len;
>>> +
>>> if (session->open_data[0] == SSH_MSG_CHANNEL_OPEN_CONFIRMATION) {
>>> + if (13+4 > (end - session->open_data))
>>> + goto channel_error;
>>> session->open_channel->remote.id =
>>> _libssh2_ntohu32(session->open_data + 5);
>>> session->open_channel->local.window_size =
>>> @@ -265,7 +270,8 @@ _libssh2_channel_open(LIBSSH2_SESSION * session, const char *channel_type,
>>> return session->open_channel;
>>> }
>>>
>>> - if (session->open_data[0] == SSH_MSG_CHANNEL_OPEN_FAILURE) {
>>> + if (session->open_data[0] == SSH_MSG_CHANNEL_OPEN_FAILURE &&
>>> + 4 <= (end - (session->open_data + 5))) {
>>> unsigned int reason_code = _libssh2_ntohu32(session->open_data + 5);
>>> switch (reason_code) {
>>> case SSH_OPEN_ADMINISTRATIVELY_PROHIBITED:
>>> @@ -1399,6 +1405,7 @@ _libssh2_channel_flush(LIBSSH2_CHANNEL *channel, int streamid)
>>>
>>> if (((packet_type == SSH_MSG_CHANNEL_DATA)
>>> || (packet_type == SSH_MSG_CHANNEL_EXTENDED_DATA))
>>> + && packet->data_len >= 5 + (packet_type == SSH_MSG_CHANNEL_EXTENDED_DATA ? 4 : 0)
>>> && (_libssh2_ntohu32(packet->data + 1) == channel->local.id)) {
>>> /* It's our channel at least */
>>> long packet_stream_id =
>>> @@ -1418,6 +1425,7 @@ _libssh2_channel_flush(LIBSSH2_CHANNEL *channel, int streamid)
>>> bytes_to_flush, packet_stream_id,
>>> channel->local.id, channel->remote.id);
>>>
>>> + /* XXX assert(packet->data_len >= 13); XXX */
>>> /* It's one of the streams we wanted to flush */
>>> channel->flush_refund_bytes += packet->data_len - 13;
>>> channel->flush_flush_bytes += bytes_to_flush;
>>> diff --git a/src/hostkey.c b/src/hostkey.c
>>> index 2a0a8f9..7b780e2 100644
>>> --- a/src/hostkey.c
>>> +++ b/src/hostkey.c
>>> @@ -66,31 +66,42 @@ hostkey_method_ssh_rsa_init(LIBSSH2_SESSION * session,
>>> libssh2_rsa_ctx *rsactx;
>>> const unsigned char *s, *e, *n;
>>> unsigned long len, e_len, n_len;
>>> + const unsigned char *end = hostkey_data + hostkey_data_len;
>>> int ret;
>>>
>>> - (void) hostkey_data_len;
>>> -
>>> if (*abstract) {
>>> hostkey_method_ssh_rsa_dtor(session, abstract);
>>> *abstract = NULL;
>>> }
>>>
>>> s = hostkey_data;
>>> + if (4 > end - s)
>>> + return -1;
>>> len = _libssh2_ntohu32(s);
>>> s += 4;
>>> + if (len > (size_t)(end - s))
>>> + return -1;
>>>
>>> if (len != 7 || strncmp((char *) s, "ssh-rsa", 7) != 0) {
>>> return -1;
>>> }
>>> - s += 7;
>>> + s += len;
>>>
>>> + if (4 > end - s)
>>> + return -1;
>>> e_len = _libssh2_ntohu32(s);
>>> s += 4;
>>> + if (e_len > (size_t)(end - s))
>>> + return -1;
>>>
>>> e = s;
>>> s += e_len;
>>> + if (4 > end - s)
>>> + return -1;
>>> n_len = _libssh2_ntohu32(s);
>>> s += 4;
>>> + if (n_len > (size_t)(end - s))
>>> + return -1;
>>> n = s;
>>>
>>> ret = _libssh2_rsa_new(&rsactx, e, e_len, n, n_len, NULL, 0,
>>> @@ -181,6 +192,8 @@ hostkey_method_ssh_rsa_sig_verify(LIBSSH2_SESSION * session,
>>> (void) session;
>>>
>>> /* Skip past keyname_len(4) + keyname(7){"ssh-rsa"} + signature_len(4) */
>>> + if (15 > sig_len)
>>> + return -1;
>>> sig += 15;
>>> sig_len -= 15;
>>> return _libssh2_rsa_sha1_verify(rsactx, sig, sig_len, m, m_len);
>>> diff --git a/src/kex.c b/src/kex.c
>>> index 40dbeab..2381d52 100644
>>> --- a/src/kex.c
>>> +++ b/src/kex.c
>>> @@ -2463,21 +2463,20 @@ static int kex_agree_comp(LIBSSH2_SESSION *session,
>>> * within the given packet.
>>> */
>>> static int kex_string_pair(unsigned char **sp, /* parsing position */
>>> - unsigned char *data, /* start pointer to packet */
>>> - size_t data_len, /* size of total packet */
>>> + unsigned char *end, /* end of packet */
>>> size_t *lenp, /* length of the string */
>>> unsigned char **strp) /* pointer to string start */
>>> {
>>> unsigned char *s = *sp;
>>> - *lenp = _libssh2_ntohu32(s);
>>>
>>> - /* the length of the string must fit within the current pointer and the
>>> - end of the packet */
>>> - if (*lenp > (data_len - (s - data) -4))
>>> + if (4 > end - s)
>>> return 1;
>>> - *strp = s + 4;
>>> - s += 4 + *lenp;
>>> -
>>> + *lenp = _libssh2_ntohu32(s);
>>> + s += 4;
>>> + if (*lenp > (size_t)(end - s))
>>> + return 1;
>>> + *strp = s;
>>> + s += *lenp;
>>> *sp = s;
>>> return 0;
>>> }
>>> @@ -2493,6 +2492,10 @@ static int kex_agree_methods(LIBSSH2_SESSION * session, unsigned char *data,
>>> size_t kex_len, hostkey_len, crypt_cs_len, crypt_sc_len, comp_cs_len;
>>> size_t comp_sc_len, mac_cs_len, mac_sc_len;
>>> unsigned char *s = data;
>>> + unsigned char *end = data + data_len;
>>> +
>>> + if (1 + 16 > end - s)
>>> + return -1;
>>>
>>> /* Skip packet_type, we know it already */
>>> s++;
>>> @@ -2501,21 +2504,24 @@ static int kex_agree_methods(LIBSSH2_SESSION * session, unsigned char *data,
>>> s += 16;
>>>
>>> /* Locate each string */
>>> - if(kex_string_pair(&s, data, data_len, &kex_len, &kex))
>>> + if(kex_string_pair(&s, end, &kex_len, &kex))
>>> + return -1;
>>> + if(kex_string_pair(&s, end, &hostkey_len, &hostkey))
>>> return -1;
>>> - if(kex_string_pair(&s, data, data_len, &hostkey_len, &hostkey))
>>> + if(kex_string_pair(&s, end, &crypt_cs_len, &crypt_cs))
>>> return -1;
>>> - if(kex_string_pair(&s, data, data_len, &crypt_cs_len, &crypt_cs))
>>> + if(kex_string_pair(&s, end, &crypt_sc_len, &crypt_sc))
>>> return -1;
>>> - if(kex_string_pair(&s, data, data_len, &crypt_sc_len, &crypt_sc))
>>> + if(kex_string_pair(&s, end, &mac_cs_len, &mac_cs))
>>> return -1;
>>> - if(kex_string_pair(&s, data, data_len, &mac_cs_len, &mac_cs))
>>> + if(kex_string_pair(&s, end, &mac_sc_len, &mac_sc))
>>> return -1;
>>> - if(kex_string_pair(&s, data, data_len, &mac_sc_len, &mac_sc))
>>> + if(kex_string_pair(&s, end, &comp_cs_len, &comp_cs))
>>> return -1;
>>> - if(kex_string_pair(&s, data, data_len, &comp_cs_len, &comp_cs))
>>> + if(kex_string_pair(&s, end, &comp_sc_len, &comp_sc))
>>> return -1;
>>> - if(kex_string_pair(&s, data, data_len, &comp_sc_len, &comp_sc))
>>> +
>>> + if (1 > end - s)
>>> return -1;
>>>
>>> /* If the server sent an optimistic packet, assume that it guessed wrong.
>>> @@ -2524,9 +2530,6 @@ static int kex_agree_methods(LIBSSH2_SESSION * session, unsigned char *data,
>>> session->burn_optimistic_kexinit = *(s++);
>>> /* Next uint32 in packet is all zeros (reserved) */
>>>
>>> - if (data_len < (unsigned) (s - data))
>>> - return -1; /* short packet */
>>> -
>>> if (kex_agree_kex_hostkey(session, kex, kex_len, hostkey, hostkey_len)) {
>>> return -1;
>>> }
>>> diff --git a/src/packet.c b/src/packet.c
>>> index 5f1feb8..3659daa 100644
>>> --- a/src/packet.c
>>> +++ b/src/packet.c
>>> @@ -85,10 +85,12 @@ packet_queue_listener(LIBSSH2_SESSION * session, unsigned char *data,
>>> char failure_code = SSH_OPEN_ADMINISTRATIVELY_PROHIBITED;
>>> int rc;
>>>
>>> - (void) datalen;
>>> -
>>> if (listen_state->state == libssh2_NB_state_idle) {
>>> unsigned char *s = data + (sizeof("forwarded-tcpip") - 1) + 5;
>>> + unsigned char *end = data + datalen;
>>> + if (4*4 > (end - s)) {
>>> + return 0; /* XXX ??? XXX */
>>> + }
>>> listen_state->sender_channel = _libssh2_ntohu32(s);
>>> s += 4;
>>>
>>> @@ -99,15 +101,27 @@ packet_queue_listener(LIBSSH2_SESSION * session, unsigned char *data,
>>>
>>> listen_state->host_len = _libssh2_ntohu32(s);
>>> s += 4;
>>> + if (listen_state->host_len > (size_t)(end - s)) {
>>> + return 0; /* XXX ??? XXX */
>>> + }
>>> listen_state->host = s;
>>> s += listen_state->host_len;
>>> + if (4*2 > (end - s)) {
>>> + return 0; /* XXX ??? XXX */
>>> + }
>>> listen_state->port = _libssh2_ntohu32(s);
>>> s += 4;
>>>
>>> listen_state->shost_len = _libssh2_ntohu32(s);
>>> s += 4;
>>> + if (listen_state->shost_len > (size_t)(end - s)) {
>>> + return 0; /* XXX ??? XXX */
>>> + }
>>> listen_state->shost = s;
>>> s += listen_state->shost_len;
>>> + if (4 > (end - s)) {
>>> + return 0; /* XXX ??? XXX */
>>> + }
>>> listen_state->sport = _libssh2_ntohu32(s);
>>>
>>> _libssh2_debug(session, LIBSSH2_TRACE_CONN,
>>> @@ -271,10 +285,12 @@ packet_x11_open(LIBSSH2_SESSION * session, unsigned char *data,
>>> LIBSSH2_CHANNEL *channel = x11open_state->channel;
>>> int rc;
>>>
>>> - (void) datalen;
>>> -
>>> if (x11open_state->state == libssh2_NB_state_idle) {
>>> unsigned char *s = data + (sizeof("x11") - 1) + 5;
>>> + unsigned char *end = data + datalen;
>>> + if (4*4 > (end - s)) {
>>> + return 0; /* XXX ??? XXX */
>>> + }
>>> x11open_state->sender_channel = _libssh2_ntohu32(s);
>>> s += 4;
>>> x11open_state->initial_window_size = _libssh2_ntohu32(s);
>>> @@ -283,8 +299,14 @@ packet_x11_open(LIBSSH2_SESSION * session, unsigned char *data,
>>> s += 4;
>>> x11open_state->shost_len = _libssh2_ntohu32(s);
>>> s += 4;
>>> + if (x11open_state->shost_len > (size_t)(end - s)) {
>>> + return 0; /* XXX ??? XXX */
>>> + }
>>> x11open_state->shost = s;
>>> s += x11open_state->shost_len;
>>> + if (4 > (end - s)) {
>>> + return 0; /* XXX ??? XXX */
>>> + }
>>> x11open_state->sport = _libssh2_ntohu32(s);
>>>
>>> _libssh2_debug(session, LIBSSH2_TRACE_CONN,
>>> @@ -807,22 +829,26 @@ _libssh2_packet_add(LIBSSH2_SESSION * session, unsigned char *data,
>>> else if (len == sizeof("exit-signal") - 1
>>> && !memcmp("exit-signal", data + 9,
>>> sizeof("exit-signal") - 1)) {
>>> + unsigned char *end = data + datalen;
>>> + unsigned char *s = data + 9 + sizeof("exit-signal");
>>> /* command terminated due to signal */
>>> if(datalen >= 20)
>>> channelp = _libssh2_channel_locate(session, channel);
>>>
>>> - if (channelp) {
>>> + if (channelp && end - s >= 4) {
>>> /* set signal name (without SIG prefix) */
>>> - uint32_t namelen =
>>> - _libssh2_ntohu32(data + 9 + sizeof("exit-signal"));
>>> + uint32_t namelen = _libssh2_ntohu32(s);
>>> + s += 4;
>>> + if (namelen > (size_t)(end - s))
>>> + /* XXX ??? XXX */;
>>> + else {
>>> channelp->exit_signal =
>>> LIBSSH2_ALLOC(session, namelen + 1);
>>> if (!channelp->exit_signal)
>>> rc = _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
>>> "memory for signal name");
>>> else {
>>> - memcpy(channelp->exit_signal,
>>> - data + 13 + sizeof("exit_signal"), namelen);
>>> + memcpy(channelp->exit_signal, s, namelen);
>>> channelp->exit_signal[namelen] = '\0';
>>> /* TODO: save error message and language tag */
>>> _libssh2_debug(session, LIBSSH2_TRACE_CONN,
>>> @@ -832,6 +858,7 @@ _libssh2_packet_add(LIBSSH2_SESSION * session, unsigned char *data,
>>> channelp->local.id,
>>> channelp->remote.id);
>>> }
>>> + }
>>> }
>>> }
>>>
>>> diff --git a/src/publickey.c b/src/publickey.c
>>> index bfee0a8..d19efb7 100644
>>> --- a/src/publickey.c
>>> +++ b/src/publickey.c
>>> @@ -247,6 +247,7 @@ publickey_response_success(LIBSSH2_PUBLICKEY * pkey)
>>> switch (response) {
>>> case LIBSSH2_PUBLICKEY_RESPONSE_STATUS:
>>> /* Error, or processing complete */
>>> + if (data_len >= 4)
>>> {
>>> unsigned long status = _libssh2_ntohu32(s);
>>>
>>> @@ -258,6 +259,7 @@ publickey_response_success(LIBSSH2_PUBLICKEY * pkey)
>>> publickey_status_error(pkey, session, status);
>>> return -1;
>>> }
>>> + /* fallthru */
>>> default:
>>> LIBSSH2_FREE(session, data);
>>> if (response < 0) {
>>> @@ -403,6 +405,7 @@ static LIBSSH2_PUBLICKEY *publickey_init(LIBSSH2_SESSION *session)
>>> if (session->pkeyInit_state == libssh2_NB_state_sent3) {
>>> while (1) {
>>> unsigned char *s;
>>> + unsigned char *end;
>>> rc = publickey_packet_receive(session->pkeyInit_pkey,
>>> &session->pkeyInit_data,
>>> &session->pkeyInit_data_len);
>>> @@ -419,6 +422,7 @@ static LIBSSH2_PUBLICKEY *publickey_init(LIBSSH2_SESSION *session)
>>> }
>>>
>>> s = session->pkeyInit_data;
>>> + end = session->pkeyInit_data + session->pkeyInit_data_len;
>>> if ((response =
>>> publickey_response_id(&s, session->pkeyInit_data_len)) < 0) {
>>> _libssh2_error(session, LIBSSH2_ERROR_PUBLICKEY_PROTOCOL,
>>> @@ -432,19 +436,33 @@ static LIBSSH2_PUBLICKEY *publickey_init(LIBSSH2_SESSION *session)
>>> {
>>> unsigned long status, descr_len, lang_len;
>>>
>>> - status = _libssh2_ntohu32(s);
>>> - s += 4;
>>> - descr_len = _libssh2_ntohu32(s);
>>> - s += 4;
>>> - /* description starts here */
>>> - s += descr_len;
>>> - lang_len = _libssh2_ntohu32(s);
>>> - s += 4;
>>> - /* lang starts here */
>>> - s += lang_len;
>>> -
>>> - if (s >
>>> - session->pkeyInit_data + session->pkeyInit_data_len) {
>>> + if (4*2 > end - s)
>>> + s = NULL;
>>> + else {
>>> + status = _libssh2_ntohu32(s);
>>> + s += 4;
>>> + descr_len = _libssh2_ntohu32(s);
>>> + s += 4;
>>> + /* description starts here */
>>> + if (descr_len > (size_t)(end - s))
>>> + s = NULL;
>>> + else {
>>> + s += descr_len;
>>> + if (4 > end - s)
>>> + s = NULL;
>>> + else {
>>> + lang_len = _libssh2_ntohu32(s);
>>> + s += 4;
>>> + /* lang starts here */
>>> + if (lang_len > (size_t)(end - s))
>>> + s = NULL;
>>> + else
>>> + s += lang_len;
>>> + }
>>> + }
>>> + }
>>> +
>>> + if (s == NULL) {
>>> _libssh2_error(session,
>>> LIBSSH2_ERROR_PUBLICKEY_PROTOCOL,
>>> "Malformed publickey subsystem packet");
>>> @@ -810,6 +828,7 @@ libssh2_publickey_list_fetch(LIBSSH2_PUBLICKEY * pkey, unsigned long *num_keys,
>>> }
>>>
>>> while (1) {
>>> + unsigned char *end;
>>> rc = publickey_packet_receive(pkey, &pkey->listFetch_data,
>>> &pkey->listFetch_data_len);
>>> if (rc == LIBSSH2_ERROR_EAGAIN) {
>>> @@ -822,6 +841,7 @@ libssh2_publickey_list_fetch(LIBSSH2_PUBLICKEY * pkey, unsigned long *num_keys,
>>> }
>>>
>>> pkey->listFetch_s = pkey->listFetch_data;
>>> + end = pkey->listFetch_data + pkey->listFetch_data_len;
>>> if ((response =
>>> publickey_response_id(&pkey->listFetch_s,
>>> pkey->listFetch_data_len)) < 0) {
>>> @@ -836,19 +856,34 @@ libssh2_publickey_list_fetch(LIBSSH2_PUBLICKEY * pkey, unsigned long *num_keys,
>>> {
>>> unsigned long status, descr_len, lang_len;
>>>
>>> - status = _libssh2_ntohu32(pkey->listFetch_s);
>>> - pkey->listFetch_s += 4;
>>> - descr_len = _libssh2_ntohu32(pkey->listFetch_s);
>>> - pkey->listFetch_s += 4;
>>> - /* description starts at pkey->listFetch_s */
>>> - pkey->listFetch_s += descr_len;
>>> - lang_len = _libssh2_ntohu32(pkey->listFetch_s);
>>> - pkey->listFetch_s += 4;
>>> - /* lang starts at pkey->listFetch_s */
>>> - pkey->listFetch_s += lang_len;
>>> -
>>> - if (pkey->listFetch_s >
>>> - pkey->listFetch_data + pkey->listFetch_data_len) {
>>> + if (4*2 > end - pkey->listFetch_s)
>>> + pkey->listFetch_s = NULL;
>>> + else {
>>> + status = _libssh2_ntohu32(pkey->listFetch_s);
>>> + pkey->listFetch_s += 4;
>>> + descr_len = _libssh2_ntohu32(pkey->listFetch_s);
>>> + pkey->listFetch_s += 4;
>>> + if (descr_len > (size_t)(end - pkey->listFetch_s))
>>> + pkey->listFetch_s = NULL;
>>> + else {
>>> + /* description starts at pkey->listFetch_s */
>>> + pkey->listFetch_s += descr_len;
>>> + if (4 > end - pkey->listFetch_s)
>>> + pkey->listFetch_s = NULL;
>>> + else {
>>> + lang_len = _libssh2_ntohu32(pkey->listFetch_s);
>>> + pkey->listFetch_s += 4;
>>> + if (lang_len > (size_t)(end - pkey->listFetch_s))
>>> + pkey->listFetch_s = NULL;
>>> + else {
>>> + /* lang starts at pkey->listFetch_s */
>>> + pkey->listFetch_s += lang_len;
>>> + }
>>> + }
>>> + }
>>> + }
>>> +
>>> + if (pkey->listFetch_s == NULL) {
>>> _libssh2_error(session, LIBSSH2_ERROR_PUBLICKEY_PROTOCOL,
>>> "Malformed publickey subsystem packet");
>>> goto err_exit;
>>> @@ -887,8 +922,12 @@ libssh2_publickey_list_fetch(LIBSSH2_PUBLICKEY * pkey, unsigned long *num_keys,
>>> if (pkey->version == 1) {
>>> unsigned long comment_len;
>>>
>>> + if (4 > end - pkey->listFetch_s)
>>> + goto err_exit;
>>> comment_len = _libssh2_ntohu32(pkey->listFetch_s);
>>> pkey->listFetch_s += 4;
>>> + if (comment_len > (size_t)(end - pkey->listFetch_s))
>>> + goto err_exit;
>>> if (comment_len) {
>>> list[keys].num_attrs = 1;
>>> list[keys].attrs =
>>> @@ -911,24 +950,42 @@ libssh2_publickey_list_fetch(LIBSSH2_PUBLICKEY * pkey, unsigned long *num_keys,
>>> list[keys].num_attrs = 0;
>>> list[keys].attrs = NULL;
>>> }
>>> + if (4 > end - pkey->listFetch_s)
>>> + goto err_exit;
>>> list[keys].name_len = _libssh2_ntohu32(pkey->listFetch_s);
>>> pkey->listFetch_s += 4;
>>> + if (list[keys].name_len > (size_t)(end - pkey->listFetch_s))
>>> + goto err_exit;
>>> list[keys].name = pkey->listFetch_s;
>>> pkey->listFetch_s += list[keys].name_len;
>>> + if (4 > end - pkey->listFetch_s)
>>> + goto err_exit;
>>> list[keys].blob_len = _libssh2_ntohu32(pkey->listFetch_s);
>>> pkey->listFetch_s += 4;
>>> + if (list[keys].blob_len > (size_t)(end - pkey->listFetch_s))
>>> + goto err_exit;
>>> list[keys].blob = pkey->listFetch_s;
>>> pkey->listFetch_s += list[keys].blob_len;
>>> } else {
>>> /* Version == 2 */
>>> + if (4 > end - pkey->listFetch_s)
>>> + goto err_exit;
>>> list[keys].name_len = _libssh2_ntohu32(pkey->listFetch_s);
>>> pkey->listFetch_s += 4;
>>> + if (list[keys].name_len > (size_t)(end - pkey->listFetch_s))
>>> + goto err_exit;
>>> list[keys].name = pkey->listFetch_s;
>>> pkey->listFetch_s += list[keys].name_len;
>>> + if (4 > end - pkey->listFetch_s)
>>> + goto err_exit;
>>> list[keys].blob_len = _libssh2_ntohu32(pkey->listFetch_s);
>>> pkey->listFetch_s += 4;
>>> + if (list[keys].blob_len > (size_t)(end - pkey->listFetch_s))
>>> + goto err_exit;
>>> list[keys].blob = pkey->listFetch_s;
>>> pkey->listFetch_s += list[keys].blob_len;
>>> + if (4 > end - pkey->listFetch_s)
>>> + goto err_exit;
>>> list[keys].num_attrs = _libssh2_ntohu32(pkey->listFetch_s);
>>> pkey->listFetch_s += 4;
>>> if (list[keys].num_attrs) {
>>> @@ -943,14 +1000,22 @@ libssh2_publickey_list_fetch(LIBSSH2_PUBLICKEY * pkey, unsigned long *num_keys,
>>> goto err_exit;
>>> }
>>> for(i = 0; i < list[keys].num_attrs; i++) {
>>> + if (4 > end - pkey->listFetch_s)
>>> + goto err_exit;
>>> list[keys].attrs[i].name_len =
>>> _libssh2_ntohu32(pkey->listFetch_s);
>>> pkey->listFetch_s += 4;
>>> + if (list[keys].attrs[i].name_len > (size_t)(end - pkey->listFetch_s))
>>> + goto err_exit;
>>> list[keys].attrs[i].name = (char *) pkey->listFetch_s;
>>> pkey->listFetch_s += list[keys].attrs[i].name_len;
>>> + if (4 > end - pkey->listFetch_s)
>>> + goto err_exit;
>>> list[keys].attrs[i].value_len =
>>> _libssh2_ntohu32(pkey->listFetch_s);
>>> pkey->listFetch_s += 4;
>>> + if (list[keys].attrs[i].value_len > (size_t)(end - pkey->listFetch_s))
>>> + goto err_exit;
>>> list[keys].attrs[i].value = (char *) pkey->listFetch_s;
>>> pkey->listFetch_s += list[keys].attrs[i].value_len;
>>>
>>> diff --git a/src/session.c b/src/session.c
>>> index 06e61dd..ba1bad5 100644
>>> --- a/src/session.c
>>> +++ b/src/session.c
>>> @@ -763,6 +763,7 @@ session_startup(LIBSSH2_SESSION *session, libssh2_socket_t sock)
>>> return rc;
>>>
>>> session->startup_service_length =
>>> + (5 > session->startup_data_len) ? 0 :
>>> _libssh2_ntohu32(session->startup_data + 1);
>>>
>>> if ((session->startup_service_length != (sizeof("ssh-userauth") - 1))
>>> @@ -1410,6 +1411,7 @@ libssh2_poll_channel_read(LIBSSH2_CHANNEL *channel, int extended)
>>> packet = _libssh2_list_first(&session->packets);
>>>
>>> while (packet) {
>>> + /* XXX assert(packet->data_len >= 5) XXX */
>>> if ( channel->local.id == _libssh2_ntohu32(packet->data + 1)) {
>>> if ( extended == 1 &&
>>> (packet->data[0] == SSH_MSG_CHANNEL_EXTENDED_DATA
>>> diff --git a/src/sftp.c b/src/sftp.c
>>> index c142713..ad38638 100644
>>> --- a/src/sftp.c
>>> +++ b/src/sftp.c
>>> @@ -249,6 +249,7 @@ sftp_packet_add(LIBSSH2_SFTP *sftp, unsigned char *data,
>>> "Out of sync with the world");
>>> }
>>>
>>> + /* XXX ??? assert(data_len >= 5); XXX */
>>> request_id = _libssh2_ntohu32(&data[1]);
>>>
>>> _libssh2_debug(session, LIBSSH2_TRACE_SFTP, "Received packet id %d",
>>> @@ -635,21 +636,25 @@ sftp_attr2bin(unsigned char *p, const LIBSSH2_SFTP_ATTRIBUTES * attrs)
>>>
>>> /* sftp_bin2attr
>>> */
>>> -static int
>>> -sftp_bin2attr(LIBSSH2_SFTP_ATTRIBUTES * attrs, const unsigned char *p)
>>> +static const unsigned char *
>>> +sftp_bin2attr(LIBSSH2_SFTP_ATTRIBUTES * attrs, const unsigned char *s, const unsigned char *end)
>>> {
>>> - const unsigned char *s = p;
>>> -
>>> memset(attrs, 0, sizeof(LIBSSH2_SFTP_ATTRIBUTES));
>>> + if (4 < end - p)
>>> + return NULL;
>>> attrs->flags = _libssh2_ntohu32(s);
>>> s += 4;
>>>
>>> if (attrs->flags & LIBSSH2_SFTP_ATTR_SIZE) {
>>> + if (8 < end - p)
>>> + return NULL;
>>> attrs->filesize = _libssh2_ntohu64(s);
>>> s += 8;
>>> }
>>>
>>> if (attrs->flags & LIBSSH2_SFTP_ATTR_UIDGID) {
>>> + if (4*2 < end - p)
>>> + return NULL;
>>> attrs->uid = _libssh2_ntohu32(s);
>>> s += 4;
>>> attrs->gid = _libssh2_ntohu32(s);
>>> @@ -657,18 +662,22 @@ sftp_bin2attr(LIBSSH2_SFTP_ATTRIBUTES * attrs, const unsigned char *p)
>>> }
>>>
>>> if (attrs->flags & LIBSSH2_SFTP_ATTR_PERMISSIONS) {
>>> + if (4 < end - p)
>>> + return NULL;
>>> attrs->permissions = _libssh2_ntohu32(s);
>>> s += 4;
>>> }
>>>
>>> if (attrs->flags & LIBSSH2_SFTP_ATTR_ACMODTIME) {
>>> + if (4*2 < end - p)
>>> + return NULL;
>>> attrs->atime = _libssh2_ntohu32(s);
>>> s += 4;
>>> attrs->mtime = _libssh2_ntohu32(s);
>>> s += 4;
>>> }
>>>
>>> - return (s - p);
>>> + return s;
>>> }
>>>
>>> /* ************
>>> @@ -1698,7 +1707,7 @@ static ssize_t sftp_readdir(LIBSSH2_SFTP_HANDLE *handle, char *buffer,
>>> if (attrs)
>>> memset(attrs, 0, sizeof(LIBSSH2_SFTP_ATTRIBUTES));
>>>
>>> - s += sftp_bin2attr(attrs ? attrs : &attrs_dummy, s);
>>> + s = sftp_bin2attr(attrs ? attrs : &attrs_dummy, s, handle->u.dir.names_end);
>>>
>>> handle->u.dir.next_name = (char *) s;
>>> end:
>>> @@ -1789,6 +1798,7 @@ static ssize_t sftp_readdir(LIBSSH2_SFTP_HANDLE *handle, char *buffer,
>>>
>>> handle->u.dir.names_left = num_names;
>>> handle->u.dir.names_packet = data;
>>> + handle->u.dir.names_end = data + data_len;
>>> handle->u.dir.next_name = (char *) data + 9;
>>>
>>> /* use the name popping mechanism from the start of the function */
>>> @@ -2252,7 +2262,7 @@ static int sftp_fstat(LIBSSH2_SFTP_HANDLE *handle,
>>> }
>>> }
>>>
>>> - sftp_bin2attr(attrs, data + 5);
>>> + sftp_bin2attr(attrs, data + 5, data + data_len);
>>> LIBSSH2_FREE(session, data);
>>>
>>> return 0;
>>> @@ -2559,6 +2569,7 @@ static int sftp_unlink(LIBSSH2_SFTP *sftp, const char *filename,
>>>
>>> sftp->unlink_state = libssh2_NB_state_idle;
>>>
>>> + /* XXX ??? assert(data_len >= 5+4); XXX */
>>> retcode = _libssh2_ntohu32(data + 5);
>>> LIBSSH2_FREE(session, data);
>>>
>>> @@ -2669,6 +2680,7 @@ static int sftp_rename(LIBSSH2_SFTP *sftp, const char *source_filename,
>>>
>>> sftp->rename_state = libssh2_NB_state_idle;
>>>
>>> + /* XXX ??? assert(data_len >= 5+4); XXX */
>>> retcode = _libssh2_ntohu32(data + 5);
>>> LIBSSH2_FREE(session, data);
>>>
>>> @@ -2793,6 +2805,7 @@ static int sftp_fstatvfs(LIBSSH2_SFTP_HANDLE *handle, LIBSSH2_SFTP_STATVFS *st)
>>> "Error waiting for FXP EXTENDED REPLY");
>>> }
>>>
>>> + /* XXX ??? assert(data_len >= 5+4); XXX */
>>> if (data[0] == SSH_FXP_STATUS) {
>>> int retcode = _libssh2_ntohu32(data + 5);
>>> sftp->fstatvfs_state = libssh2_NB_state_idle;
>>> @@ -2919,6 +2932,7 @@ static int sftp_statvfs(LIBSSH2_SFTP *sftp, const char *path,
>>> "Error waiting for FXP EXTENDED REPLY");
>>> }
>>>
>>> + /* XXX ??? assert(data_len >= 5+4); XXX */
>>> if (data[0] == SSH_FXP_STATUS) {
>>> int retcode = _libssh2_ntohu32(data + 5);
>>> sftp->statvfs_state = libssh2_NB_state_idle;
>>> @@ -3051,6 +3065,7 @@ static int sftp_mkdir(LIBSSH2_SFTP *sftp, const char *path,
>>>
>>> sftp->mkdir_state = libssh2_NB_state_idle;
>>>
>>> + /* XXX ??? assert(data_len >= 5+4); XXX */
>>> retcode = _libssh2_ntohu32(data + 5);
>>> LIBSSH2_FREE(session, data);
>>>
>>> @@ -3145,6 +3160,7 @@ static int sftp_rmdir(LIBSSH2_SFTP *sftp, const char *path,
>>>
>>> sftp->rmdir_state = libssh2_NB_state_idle;
>>>
>>> + /* XXX ??? assert(data_len >= 5+4); XXX */
>>> retcode = _libssh2_ntohu32(data + 5);
>>> LIBSSH2_FREE(session, data);
>>>
>>> @@ -3188,6 +3204,7 @@ static int sftp_stat(LIBSSH2_SFTP *sftp, const char *path,
>>> ((stat_type ==
>>> LIBSSH2_SFTP_SETSTAT) ? sftp_attrsize(attrs->flags) : 0);
>>> unsigned char *s, *data;
>>> + unsigned char *data_end;
>>> static const unsigned char stat_responses[2] =
>>> { SSH_FXP_ATTRS, SSH_FXP_STATUS };
>>> int rc;
>>> @@ -3258,6 +3275,8 @@ static int sftp_stat(LIBSSH2_SFTP *sftp, const char *path,
>>>
>>> sftp->stat_state = libssh2_NB_state_idle;
>>>
>>> + /* XXX ??? assert(data_len >= 5+4); XXX */
>>> +
>>> if (data[0] == SSH_FXP_STATUS) {
>>> int retcode;
>>>
>>> @@ -3273,7 +3292,7 @@ static int sftp_stat(LIBSSH2_SFTP *sftp, const char *path,
>>> }
>>>
>>> memset(attrs, 0, sizeof(LIBSSH2_SFTP_ATTRIBUTES));
>>> - sftp_bin2attr(attrs, data + 5);
>>> + sftp_bin2attr(attrs, data + 5, data + data_len);
>>> LIBSSH2_FREE(session, data);
>>>
>>> return 0;
>>> @@ -3389,6 +3408,8 @@ static int sftp_symlink(LIBSSH2_SFTP *sftp, const char *path,
>>>
>>> sftp->symlink_state = libssh2_NB_state_idle;
>>>
>>> + /* XXX ??? assert(data_len >= 5+4); XXX */
>>> +
>>> if (data[0] == SSH_FXP_STATUS) {
>>> int retcode;
>>>
>>> @@ -3410,8 +3431,13 @@ static int sftp_symlink(LIBSSH2_SFTP *sftp, const char *path,
>>> "no name entries");
>>> }
>>>
>>> + /* XXX ??? assert(data_len >= 5+4*2); XXX */
>>> +
>>> /* this reads a u32 and stores it into a signed 32bit value */
>>> link_len = _libssh2_ntohu32(data + 9);
>>> +
>>> + /* XXX ??? assert(data_len-(5+4*2) >= link_len); XXX */
>>> +
>>> if (link_len < target_len) {
>>> memcpy(target, data + 13, link_len);
>>> target[link_len] = 0;
>>> diff --git a/src/sftp.h b/src/sftp.h
>>> index 2ed32ce..91fc0a7 100644
>>> --- a/src/sftp.h
>>> +++ b/src/sftp.h
>>> @@ -122,6 +122,7 @@ struct _LIBSSH2_SFTP_HANDLE
>>> uint32_t names_left;
>>> void *names_packet;
>>> char *next_name;
>>> + char *names_end;
>>> } dir;
>>> } u;
>>>
>>> diff --git a/src/userauth.c b/src/userauth.c
>>> index cdfa25e..c799a40 100644
>>> --- a/src/userauth.c
>>> +++ b/src/userauth.c
>>> @@ -69,6 +69,7 @@ static char *userauth_list(LIBSSH2_SESSION *session, const char *username,
>>> service(14)"ssh-connection" + method_len(4) = 27 */
>>> unsigned long methods_len;
>>> unsigned char *s;
>>> + unsigned char *end;
>>> int rc;
>>>
>>> if (session->userauth_list_state == libssh2_NB_state_idle) {
>>> @@ -143,7 +144,18 @@ static char *userauth_list(LIBSSH2_SESSION *session, const char *username,
>>> return NULL;
>>> }
>>>
>>> + if (5 > session->userauth_list_data_len) {
>>> + /* XXX ??? XXX */
>>> +userauth_packet_overrun:
>>> + LIBSSH2_FREE(session, session->userauth_list_data);
>>> + session->userauth_list_data = NULL;
>>> + session->userauth_list_state = libssh2_NB_state_idle;
>>> + return NULL;
>>> + }
>>> methods_len = _libssh2_ntohu32(session->userauth_list_data + 1);
>>> + if (methods_len > session->userauth_list_data_len - 5) {
>>> + goto userauth_packet_overrun;
>>> + }
>>>
>>> /* Do note that the memory areas overlap! */
>>> memmove(session->userauth_list_data, session->userauth_list_data + 5,
>>> @@ -1561,6 +1573,7 @@ userauth_keyboard_interactive(LIBSSH2_SESSION * session,
>>> LIBSSH2_USERAUTH_KBDINT_RESPONSE_FUNC((*response_callback)))
>>> {
>>> unsigned char *s;
>>> + unsigned char *end;
>>> int rc;
>>>
>>> static const unsigned char reply_codes[4] = {
>>> @@ -1685,10 +1698,15 @@ userauth_keyboard_interactive(LIBSSH2_SESSION * session,
>>>
>>> /* server requested PAM-like conversation */
>>> s = session->userauth_kybd_data + 1;
>>> + end = session->userauth_kybd_data + session->userauth_kybd_data_len;
>>>
>>> /* string name (ISO-10646 UTF-8) */
>>> + if (4 > end - s)
>>> + goto cleanup; /* XXX ??? XXX */
>>> session->userauth_kybd_auth_name_len = _libssh2_ntohu32(s);
>>> s += 4;
>>> + if (session->userauth_kybd_auth_name_len > (size_t)(end - s))
>>> + goto cleanup; /* XXX ??? XXX */
>>> if(session->userauth_kybd_auth_name_len) {
>>> session->userauth_kybd_auth_name =
>>> LIBSSH2_ALLOC(session,
>>> @@ -1706,8 +1724,12 @@ userauth_keyboard_interactive(LIBSSH2_SESSION * session,
>>> }
>>>
>>> /* string instruction (ISO-10646 UTF-8) */
>>> + if (4 > end - s)
>>> + goto cleanup; /* XXX ??? XXX */
>>> session->userauth_kybd_auth_instruction_len = _libssh2_ntohu32(s);
>>> s += 4;
>>> + if (session->userauth_kybd_auth_instruction_len > (size_t)(end - s))
>>> + goto cleanup; /* XXX ??? XXX */
>>> if(session->userauth_kybd_auth_instruction_len) {
>>> session->userauth_kybd_auth_instruction =
>>> LIBSSH2_ALLOC(session,
>>> @@ -1725,13 +1747,19 @@ userauth_keyboard_interactive(LIBSSH2_SESSION * session,
>>> }
>>>
>>> /* string language tag (as defined in [RFC-3066]) */
>>> + if (4 > end - s)
>>> + goto cleanup; /* XXX ??? XXX */
>>> language_tag_len = _libssh2_ntohu32(s);
>>> s += 4;
>>> + if (language_tag_len > (size_t)(end - s))
>>> + goto cleanup; /* XXX ??? XXX */
>>>
>>> /* ignoring this field as deprecated */
>>> s += language_tag_len;
>>>
>>> /* int num-prompts */
>>> + if (4 > end - s)
>>> + goto cleanup; /* XXX ??? XXX */
>>> session->userauth_kybd_num_prompts = _libssh2_ntohu32(s);
>>> s += 4;
>>>
>>> @@ -1760,9 +1788,13 @@ userauth_keyboard_interactive(LIBSSH2_SESSION * session,
>>>
>>> for(i = 0; i < session->userauth_kybd_num_prompts; i++) {
>>> /* string prompt[1] (ISO-10646 UTF-8) */
>>> + if (4 > end - s)
>>> + goto cleanup; /* XXX ??? XXX */
>>> session->userauth_kybd_prompts[i].length =
>>> _libssh2_ntohu32(s);
>>> s += 4;
>>> + if (session->userauth_kybd_prompts[i].length > (size_t)(end - s))
>>> + goto cleanup; /* XXX ??? XXX */
>>> session->userauth_kybd_prompts[i].text =
>>> LIBSSH2_CALLOC(session,
>>> session->userauth_kybd_prompts[i].length);
_______________________________________________
libssh2-devel https://cool.haxx.se/cgi-bin/mailman/listinfo/libssh2-devel
Received on 2019-03-31

the libssh2 team