<p>Harald Welte <strong>merged</strong> this change.</p><p><a href="https://gerrit.osmocom.org/13306">View Change</a></p><div style="white-space:pre-wrap">Approvals:
Harald Welte: Looks good to me, approved
Jenkins Builder: Verified
</div><pre style="font-family: monospace,monospace; white-space: pre-wrap;">osmo_bsc_bssap: check bssmap length field<br><br>At the moment the length field of the bssmap header is not parsed.<br>Instead the length is computed out of the known header length and the<br>number of bytes received. This is prone to error, lets make sure that<br>extranous data at the end of a message is ignored by parsing the bssmap<br>length correctly.<br><br>Change-Id: Idef2e783d2377a2ad1f697ea4d26491a32b3e549<br>Related: OS#3806<br>---<br>M src/osmo-bsc/osmo_bsc_bssap.c<br>1 file changed, 31 insertions(+), 1 deletion(-)<br><br></pre><pre style="font-family: monospace,monospace; white-space: pre-wrap;"><span>diff --git a/src/osmo-bsc/osmo_bsc_bssap.c b/src/osmo-bsc/osmo_bsc_bssap.c</span><br><span>index 85aab22..65618fd 100644</span><br><span>--- a/src/osmo-bsc/osmo_bsc_bssap.c</span><br><span>+++ b/src/osmo-bsc/osmo_bsc_bssap.c</span><br><span>@@ -1081,6 +1081,36 @@</span><br><span> return 0;</span><br><span> }</span><br><span> </span><br><span style="color: hsl(120, 100%, 40%);">+/* Extract and verify the length information from the BSSMAP header. */</span><br><span style="color: hsl(120, 100%, 40%);">+static unsigned int bssmap_msg_len(struct msgb *msg, unsigned int length,</span><br><span style="color: hsl(120, 100%, 40%);">+ const struct gsm_subscriber_connection *conn)</span><br><span style="color: hsl(120, 100%, 40%);">+{</span><br><span style="color: hsl(120, 100%, 40%);">+ unsigned int expected_len;</span><br><span style="color: hsl(120, 100%, 40%);">+ unsigned int calculated_len;</span><br><span style="color: hsl(120, 100%, 40%);">+ struct bssmap_header *bssmap_header;</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+ bssmap_header = (struct bssmap_header *)msg->l3h;</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+ calculated_len = length - sizeof(struct bssmap_header);</span><br><span style="color: hsl(120, 100%, 40%);">+ expected_len = bssmap_header->length;</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+ /* In case of contradictory length information, decide for the</span><br><span style="color: hsl(120, 100%, 40%);">+ * shorter length */</span><br><span style="color: hsl(120, 100%, 40%);">+ if (calculated_len > expected_len) {</span><br><span style="color: hsl(120, 100%, 40%);">+ LOGPFSML(conn->fi, LOGL_NOTICE,</span><br><span style="color: hsl(120, 100%, 40%);">+ "BSSMAP message contains extra data, expected %u bytes, got %u bytes, truncated\n",</span><br><span style="color: hsl(120, 100%, 40%);">+ expected_len, calculated_len);</span><br><span style="color: hsl(120, 100%, 40%);">+ return expected_len;</span><br><span style="color: hsl(120, 100%, 40%);">+ } else if (calculated_len < expected_len) {</span><br><span style="color: hsl(120, 100%, 40%);">+ LOGPFSML(conn->fi, LOGL_NOTICE,</span><br><span style="color: hsl(120, 100%, 40%);">+ "Short BSSMAP message, expected %u bytes, got %u bytes\n",</span><br><span style="color: hsl(120, 100%, 40%);">+ expected_len, calculated_len);</span><br><span style="color: hsl(120, 100%, 40%);">+ return calculated_len;</span><br><span style="color: hsl(120, 100%, 40%);">+ }</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+ return expected_len;</span><br><span style="color: hsl(120, 100%, 40%);">+}</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span> int bsc_handle_dt(struct gsm_subscriber_connection *conn,</span><br><span> struct msgb *msg, unsigned int len)</span><br><span> {</span><br><span>@@ -1093,7 +1123,7 @@</span><br><span> switch (msg->l3h[0]) {</span><br><span> case BSSAP_MSG_BSS_MANAGEMENT:</span><br><span> msg->l4h = &msg->l3h[sizeof(struct bssmap_header)];</span><br><span style="color: hsl(0, 100%, 40%);">- bssmap_rcvmsg_dt1(conn, msg, len - sizeof(struct bssmap_header));</span><br><span style="color: hsl(120, 100%, 40%);">+ bssmap_rcvmsg_dt1(conn, msg, bssmap_msg_len(msg, len, conn));</span><br><span> break;</span><br><span> case BSSAP_MSG_DTAP:</span><br><span> dtap_rcvmsg(conn, msg, len);</span><br><span></span><br></pre><p>To view, visit <a href="https://gerrit.osmocom.org/13306">change 13306</a>. To unsubscribe, or for help writing mail filters, visit <a href="https://gerrit.osmocom.org/settings">settings</a>.</p><div itemscope itemtype="http://schema.org/EmailMessage"><div itemscope itemprop="action" itemtype="http://schema.org/ViewAction"><link itemprop="url" href="https://gerrit.osmocom.org/13306"/><meta itemprop="name" content="View Change"/></div></div>
<div style="display:none"> Gerrit-Project: osmo-bsc </div>
<div style="display:none"> Gerrit-Branch: master </div>
<div style="display:none"> Gerrit-MessageType: merged </div>
<div style="display:none"> Gerrit-Change-Id: Idef2e783d2377a2ad1f697ea4d26491a32b3e549 </div>
<div style="display:none"> Gerrit-Change-Number: 13306 </div>
<div style="display:none"> Gerrit-PatchSet: 4 </div>
<div style="display:none"> Gerrit-Owner: dexter <pmaier@sysmocom.de> </div>
<div style="display:none"> Gerrit-Reviewer: Harald Welte <laforge@gnumonks.org> </div>
<div style="display:none"> Gerrit-Reviewer: Jenkins Builder (1000002) </div>
<div style="display:none"> Gerrit-Reviewer: Pau Espin Pedrol <pespin@sysmocom.de> </div>
<div style="display:none"> Gerrit-Reviewer: dexter <pmaier@sysmocom.de> </div>