commit 043fe327878eba75efa13794c9845f85c3c629f2 Author: Guido Vranken Date: Fri May 19 14:04:25 2017 +0200 Prevent two kinds of stack buffer OOB reads and a crash for invalid input data Pre-authentication remote crash/information disclosure for clients If clients use a HTTP proxy with NTLM authentication (i.e. "--http-proxy [|'auto'|'auto-nct'] ntlm2"), a man-in-the-middle attacker between the client and the proxy can cause the client to crash or disclose at most 96 bytes of stack memory. The disclosed stack memory is likely to contain the proxy password. If the proxy password is not reused, this is unlikely to compromise the security of the OpenVPN tunnel itself. Clients who do not use the --http-proxy option with ntlm2 authentication are not affected. CVE: 2017-7520 Signed-off-by: Guido Vranken Acked-by: Gert Doering Message-Id: URL: https://www.mail-archive.com/search?l=mid&q=CAO5O-EJvHKid-zTj+hmFG_3Gv78ixqCayE9=C62DZaxN32WNtQ@mail.gmail.com Signed-off-by: Gert Doering (cherry picked from commit 7718c8984f04b507c1885f363970e2124e3c6c77) Index: openvpn-2.4.0/src/openvpn/ntlm.c =================================================================== --- openvpn-2.4.0.orig/src/openvpn/ntlm.c +++ openvpn-2.4.0/src/openvpn/ntlm.c @@ -193,7 +193,7 @@ ntlm_phase_3(const struct http_proxy_inf */ char pwbuf[sizeof(p->up.password) * 2]; /* for unicode password */ - char buf2[128]; /* decoded reply from proxy */ + unsigned char buf2[128]; /* decoded reply from proxy */ unsigned char phase3[464]; char md4_hash[MD4_DIGEST_LENGTH+5]; @@ -299,7 +299,13 @@ ntlm_phase_3(const struct http_proxy_inf tib_len = 96; } { - char *tib_ptr = buf2 + buf2[0x2c]; /* Get Target Information block pointer */ + char *tib_ptr; + int tib_pos = buf2[0x2c]; + if (tib_pos + tib_len > sizeof(buf2)) + { + return NULL; + } + tib_ptr = buf2 + tib_pos; /* Get Target Information block pointer */ memcpy(&ntlmv2_blob[0x1c], tib_ptr, tib_len); /* Copy Target Information block into the blob */ } }