From 54e60b1162ab626049c2bd96c70c777b8bd06e82 Mon Sep 17 00:00:00 2001 From: Roland Mainz Date: Fri, 20 Mar 2015 13:23:20 +0100 Subject: [PATCH] * Thu Mar 19 2015 Roland Mainz - 1.13.1-2 - fix for CVE-2014-5355 (#1193939) "krb5: unauthenticated denial of service in recvauth_common() and others" --- ..._5355_fix_krb5_read_message_handling.patch | 110 ++++++++++++++++++ krb5.spec | 8 +- 2 files changed, 117 insertions(+), 1 deletion(-) create mode 100644 krb5-1.12.1-CVE_2014_5355_fix_krb5_read_message_handling.patch diff --git a/krb5-1.12.1-CVE_2014_5355_fix_krb5_read_message_handling.patch b/krb5-1.12.1-CVE_2014_5355_fix_krb5_read_message_handling.patch new file mode 100644 index 0000000..c90a4dd --- /dev/null +++ b/krb5-1.12.1-CVE_2014_5355_fix_krb5_read_message_handling.patch @@ -0,0 +1,110 @@ +From 21e4e653d8258d525f4b6ca87797d42a8bccc282 Mon Sep 17 00:00:00 2001 +From: Greg Hudson +Date: Tue, 9 Dec 2014 12:37:44 -0500 +Subject: [PATCH] Fix krb5_read_message handling [CVE-2014-5355] + +In recvauth_common, do not use strcmp against the data fields of +krb5_data objects populated by krb5_read_message(), as there is no +guarantee that they are C strings. Instead, create an expected +krb5_data value and use data_eq(). + +In the sample user-to-user server application, check that the received +client principal name is null-terminated before using it with printf +and krb5_parse_name. + +CVE-2014-5355: + +In MIT krb5, when a server process uses the krb5_recvauth function, an +unauthenticated remote attacker can cause a NULL dereference by +sending a zero-byte version string, or a read beyond the end of +allocated storage by sending a non-null-terminated version string. +The example user-to-user server application (uuserver) is similarly +vulnerable to a zero-length or non-null-terminated principal name +string. + +The krb5_recvauth function reads two version strings from the client +using krb5_read_message(), which produces a krb5_data structure +containing a length and a pointer to an octet sequence. krb5_recvauth +assumes that the data pointer is a valid C string and passes it to +strcmp() to verify the versions. If the client sends an empty octet +sequence, the data pointer will be NULL and strcmp() will dereference +a NULL pointer, causing the process to crash. If the client sends a +non-null-terminated octet sequence, strcmp() will read beyond the end +of the allocated storage, possibly causing the process to crash. + +uuserver similarly uses krb5_read_message() to read a client principal +name, and then passes it to printf() and krb5_parse_name() without +verifying that it is a valid C string. + +The krb5_recvauth function is used by kpropd and the Kerberized +versions of the BSD rlogin and rsh daemons. These daemons are usually +run out of inetd or in a mode which forks before processing incoming +connections, so a process crash will generally not result in a +complete denial of service. + +Thanks to Tim Uglow for discovering this issue. + +CVSSv2: AV:N/AC:L/Au:N/C:N/I:N/A:P/E:POC/RL:OF/RC:C + +[tlyu@mit.edu: CVSS score] + +(cherry picked from commit 102bb6ebf20f9174130c85c3b052ae104e5073ec) + +ticket: 8050 +version_fixed: 1.13.2 +status: resolved +--- + src/appl/user_user/server.c | 4 +++- + src/lib/krb5/krb/recvauth.c | 9 ++++++--- + 2 files changed, 9 insertions(+), 4 deletions(-) + +diff --git a/src/appl/user_user/server.c b/src/appl/user_user/server.c +index 09ea4e0..f2b5b61 100644 +--- a/src/appl/user_user/server.c ++++ b/src/appl/user_user/server.c +@@ -111,8 +111,10 @@ int main(argc, argv) + } + #endif + ++ /* principal name must be sent null-terminated. */ + retval = krb5_read_message(context, (krb5_pointer) &sock, &pname_data); +- if (retval) { ++ if (retval || pname_data.length == 0 || ++ pname_data.data[pname_data.length - 1] != '\0') { + com_err ("uu-server", retval, "reading pname"); + return 2; + } +diff --git a/src/lib/krb5/krb/recvauth.c b/src/lib/krb5/krb/recvauth.c +index da836283..5adc6dd 100644 +--- a/src/lib/krb5/krb/recvauth.c ++++ b/src/lib/krb5/krb/recvauth.c +@@ -59,6 +59,7 @@ recvauth_common(krb5_context context, + krb5_rcache rcache = 0; + krb5_octet response; + krb5_data null_server; ++ krb5_data d; + int need_error_free = 0; + int local_rcache = 0, local_authcon = 0; + +@@ -77,7 +78,8 @@ recvauth_common(krb5_context context, + */ + if ((retval = krb5_read_message(context, fd, &inbuf))) + return(retval); +- if (strcmp(inbuf.data, sendauth_version)) { ++ d = make_data((char *)sendauth_version, strlen(sendauth_version) + 1); ++ if (!data_eq(inbuf, d)) { + problem = KRB5_SENDAUTH_BADAUTHVERS; + response = 1; + } +@@ -93,8 +95,9 @@ recvauth_common(krb5_context context, + */ + if ((retval = krb5_read_message(context, fd, &inbuf))) + return(retval); +- if (appl_version && strcmp(inbuf.data, appl_version)) { +- if (!problem) { ++ if (appl_version != NULL && !problem) { ++ d = make_data(appl_version, strlen(appl_version) + 1); ++ if (!data_eq(inbuf, d)) { + problem = KRB5_SENDAUTH_BADAPPLVERS; + response = 2; + } diff --git a/krb5.spec b/krb5.spec index e1c9bac..a2c4f5b 100644 --- a/krb5.spec +++ b/krb5.spec @@ -43,7 +43,7 @@ Summary: The Kerberos network authentication system Name: krb5 Version: 1.13.1 -Release: 1%{?dist} +Release: 2%{?dist} # - Maybe we should explode from the now-available-to-everybody tarball instead? # http://web.mit.edu/kerberos/dist/krb5/1.13/krb5-1.13.1-signed.tar # - The sources below are stored in a lookaside cache. Upload with @@ -95,6 +95,7 @@ Patch129: krb5-1.11-run_user_0.patch Patch134: krb5-1.11-kpasswdtest.patch Patch136: krb5-socket_wrapper_eventfd_prototype_mismatch.patch Patch140: krb5-1.14-Support-KDC_ERR_MORE_PREAUTH_DATA_REQUIRED.patch +Patch141: krb5-1.12.1-CVE_2014_5355_fix_krb5_read_message_handling.patch License: MIT URL: http://web.mit.edu/kerberos/www/ @@ -317,6 +318,7 @@ ln NOTICE LICENSE %endif %patch140 -p1 -b .krb5-1.14-support-kdc_err_more_preauth_data_required +%patch141 -p1 -b .krb5-1.12.1-cve_2014_5355_fix_krb5_read_message_handling # Take the execute bit off of documentation. chmod -x doc/krb5-protocol/*.txt doc/ccapi/*.html @@ -989,6 +991,10 @@ exit 0 %changelog +* Thu Mar 20 2015 Roland Mainz - 1.13.1-2 +- fix for CVE-2014-5355 (#1193939) "krb5: unauthenticated + denial of service in recvauth_common() and others" + * Fri Feb 13 2015 Roland Mainz - 1.13.1-1 - Update to krb5-1.13.1 - drop patch for CVE_2014_5353_fix_LDAP_misused_policy_name_crash, fixed in krb5-1.13.1