From florz@florz.de Sun Oct 1 10:33:31 2023 Received: from [10.0.0.9] (helo=cumin.exim.org) by mailman with esmtp (Exim 4.94.2) (envelope-from ) id 1qmspP-003gpc-28 for exim-dev@lists.exim.org; Sun, 01 Oct 2023 09:33:31 +0000 Authentication-Results: exim.org; iprev=pass (rain.florz.de) smtp.remote-ip=2a07:12c0:1c00:40::1; dmarc=none header.from=florz.de; arc=none Received: from rain.florz.de ([2a07:12c0:1c00:40::1]:36467) by cumin.exim.org with esmtps (TLS1.3) tls TLS_AES_256_GCM_SHA384 (Exim 4.94.2-31-503e55a2c) (envelope-from ) id 1qmspN-00EIpR-5w for exim-dev@lists.exim.org; Sun, 01 Oct 2023 09:33:30 +0000 Received: from [2a07:12c0:1c00:43::121] (port=60772 helo=florz.florz.de) by rain.florz.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.92) (envelope-from ) id 1qmspL-0007Zj-F8 for exim-dev@lists.exim.org; Sun, 01 Oct 2023 11:33:27 +0200 Received: from florz by florz.florz.de with local (Exim 4.92) (envelope-from ) id 1qmspK-0001ZU-Sl for exim-dev@lists.exim.org; Sun, 01 Oct 2023 11:33:26 +0200 Date: Sun, 1 Oct 2023 11:33:26 +0200 From: Florian Zumbiehl To: exim-dev@lists.exim.org Message-ID: <20231001093326.GS3837@florz.florz.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.10.1 (2018-07-13) X-Spam-Score: 0.0 (/) Message-ID-Hash: D3TCMSGJTLM76H6APEQXZEYOLYJKKCNZ X-Message-ID-Hash: D3TCMSGJTLM76H6APEQXZEYOLYJKKCNZ X-MailFrom: florz@florz.de X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; header-match-config-1; header-match-exim-dev.lists.exim.org-0; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.3 Precedence: list Subject: [exim-dev] Hotfix for some of the ZDI vulnerabilities List-Id: Exim MTA development list List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: Message: 1 Status: RO Content-Length: 5347 Hi, below you find a patch that fixes some (probably three?) of what I guess are the vulnerabilities reported by ZDI. Please note that the patch is only mildly tested, it is developed based on the git master branch, but can be applied to older versions with minor massaging. If you go back far enough, proxy.c was part of smtp_in.c, but if you adjust for that, the patch can be made to apply there, too. Obviously, I have no idea whether this actually addresses what ZDI has reported, but if not, these probably should be fixed, too, and if so, given the fact that I managed to rather easily find these vulnerabilities based on the information that's publicly available, I don't think there is much point to trying to keep this secret any longer--if anything, it's counterproductive. Also mind you that this is a hot fix, it's neither elegant, nor does it do any useful error reporting, the goal was simply to prevent out of bounds accesses. Florian --- --- a/src/auths/external.c +++ b/src/auths/external.c @@ -100,6 +100,9 @@ if (expand_nmax == 0) /* skip if rxd da if ((rc = auth_prompt(CUS"")) != OK) return rc; +if (expand_nmax != 1) + return FAIL; + if (ob->server_param2) { uschar * s = expand_string(ob->server_param2); --- a/src/auths/spa.c +++ b/src/auths/spa.c @@ -165,12 +165,18 @@ if (auth_get_no64_data(&data, msgbuf) != return FAIL; /* dump client response */ -if (spa_base64_to_bits(CS &response, sizeof(response), CCS data) < 0) +int l = spa_base64_to_bits(CS &response, sizeof(response), CCS data); +if (l < 0) { DEBUG(D_auth) debug_printf("auth_spa_server(): bad base64 data in " "response: %s\n", data); return FAIL; } +if(l < (char *)&response.buffer - (char *)&response)return FAIL; +unsigned long o = IVAL(&response.uUser.offset, 0); +if((l < o) || (l - o < SVAL(&response.uUser.len, 0)))return FAIL; +o = IVAL(&response.ntResponse.offset, 0); +if((l < o) || (l - o < 24))return FAIL; /*************************************************************** PH 07-Aug-2003: The original code here was this: @@ -345,7 +351,10 @@ if (!smtp_read_response(sx, US buffer, b /* convert the challenge into the challenge struct */ DSPA("\n\n%s authenticator: challenge (%s)\n\n", ablock->name, buffer + 4); -spa_base64_to_bits(CS (&challenge), sizeof(challenge), CCS (buffer + 4)); +int l = spa_base64_to_bits(CS (&challenge), sizeof(challenge), CCS (buffer + 4)); +if((l < 0) || (l < (char *)&challenge.buffer - (char *)&challenge))return FAIL; +unsigned long o = IVAL(&challenge.uDomain.offset, 0); +if((l < o) || (l - o < SVAL(&challenge.uDomain.len, 0)))return FAIL; spa_build_auth_response(&challenge, &response, CS username, CS password); spa_bits_to_base64(US msgbuf, US &response, spa_request_length(&response)); --- a/src/smtp_in.c +++ b/src/smtp_in.c @@ -1172,6 +1172,8 @@ while (capacity > 0) do { ret = read(fd, to, 1); } while (ret == -1 && errno == EINTR && !had_command_timeout); if (ret == -1) return -1; + if (!ret) + break; have++; if (last) return have; @@ -1320,6 +1322,8 @@ if ((ret == PROXY_INITIAL_READ) && (memc goto proxyfail; } + if (ret < 16) + goto proxyfail; /* The v2 header will always be 16 bytes per the spec. */ size = 16 + ntohs(hdr.v2.len); DEBUG(D_receive) debug_printf("Detected PROXYv2 header, size %d (limit %d)\n", @@ -1340,7 +1344,7 @@ if ((ret == PROXY_INITIAL_READ) && (memc { retmore = read(fd, (uschar*)&hdr + ret, size-ret); } while (retmore == -1 && errno == EINTR && !had_command_timeout); - if (retmore == -1) + if (retmore < 1) goto proxyfail; ret += retmore; DEBUG(D_receive) debug_printf("PROXYv2: have %d/%d required octets\n", ret, size); @@ -1362,6 +1366,8 @@ if (ret >= 16 && memcmp(&hdr.v2, v2sig, switch (hdr.v2.fam) { case 0x11: /* TCPv4 address type */ + if (ret < 28) + goto proxyfail; iptype = US"IPv4"; tmpaddr.sin_addr.s_addr = hdr.v2.addr.ip4.src_addr; inet_ntop(AF_INET, &tmpaddr.sin_addr, CS &tmpip, sizeof(tmpip)); @@ -1388,6 +1394,8 @@ if (ret >= 16 && memcmp(&hdr.v2, v2sig, proxy_external_port = tmpport; goto done; case 0x21: /* TCPv6 address type */ + if (ret < 52) + goto proxyfail; iptype = US"IPv6"; memmove(tmpaddr6.sin6_addr.s6_addr, hdr.v2.addr.ip6.src_addr, 16); inet_ntop(AF_INET6, &tmpaddr6.sin6_addr, CS &tmpip6, sizeof(tmpip6)); @@ -1446,10 +1454,13 @@ else if (ret >= 8 && memcmp(hdr.v1.line, goto proxyfail; ret += r2; + if(ret > 107) + goto proxyfail; + hdr.v1.line[ret] = 0; p = string_copy(hdr.v1.line); end = memchr(p, '\r', ret - 1); - if (!end || (end == (uschar*)&hdr + ret) || end[1] != '\n') + if (!end || end[1] != '\n') { DEBUG(D_receive) debug_printf("Partial or invalid PROXY header\n"); goto proxyfail;