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-Date: Sun, 1 Oct 2023 11:33:26 +0200
-From: Florian Zumbiehl <florz@florz.de>
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-Subject: [exim-dev] Hotfix for some of the ZDI vulnerabilities
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-Message: 1
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-
-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;
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