www.libssh2.org | Daily snapshots | Mailing list archive | Docs | Examples | github

Archive Index This month's Index

Subject: Re: [PATCH][WIP][v2] Fix out-of-buffer-boundary reads (Was: [SECURITY ADVISORY] Truncated Difffie-Hellman secret length)

Re: [PATCH][WIP][v2] Fix out-of-buffer-boundary reads (Was: [SECURITY ADVISORY] Truncated Difffie-Hellman secret length)

From: Yuriy M. Kaminskiy <yumkam_at_gmail.com>
Date: Sun, 27 Mar 2016 22:28:20 +0300

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 http://cool.haxx.se/cgi-bin/mailman/listinfo/libssh2-devel
Received on 2016-03-27

the libssh2 team