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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 14:23:12 +0300

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).

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