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SUSE:SLE-12-SP1:Update
krb5-appl
CVE-2019-25017.patch
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File CVE-2019-25017.patch of Package krb5-appl
From 63f3e734c633a87c745a81a49fdb3fc8881f28ff Mon Sep 17 00:00:00 2001 From: Samuel Cabrero <scabrero@suse.de> Date: Mon, 11 Jan 2021 12:25:29 +0100 Subject: [PATCH 2/2] CVE-2019-25017 An issue was discovered in rcp in MIT krb5-appl through 1.0.3. Due to the rcp implementation being derived from 1983 rcp, the server chooses which files/directories are sent to the client. However, the rcp client only performs cursory validation of the object name returned (only directory traversal attacks are prevented). A malicious rcp server (or Man-in-The-Middle attacker) can overwrite arbitrary files in the rcp client target directory. If recursive operation (-r) is performed, the server can manipulate subdirectories as well (for example, to overwrite the .ssh/authorized_keys file). Check the filenames sent by the server match those requested by the client. This checking provides some protection against a malicious server sending unexpected filenames, but it comes at a risk of rejecting wanted files due to differences between client and server wildcard expansion rules. For this reason, this also adds a new -T flag to disable the check. Related to CVE-2019-6111 (openssh) and CVE-2019-7283 (netkit-rsh). Signed-off-by: Samuel Cabrero <scabrero@suse.de> --- bsd/krcp.c | 43 +++++++++++++++++++++++++++++++++++-------- bsd/rcp.M | 10 +++++++++- 2 files changed, 44 insertions(+), 9 deletions(-) diff --git a/bsd/krcp.c b/bsd/krcp.c index d56b40c..54095f1 100644 --- a/bsd/krcp.c +++ b/bsd/krcp.c @@ -46,6 +46,7 @@ char copyright[] = #endif #include <sys/file.h> #include <fcntl.h> +#include <fnmatch.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/ioctl.h> @@ -87,7 +88,7 @@ char **save_argv(int, char **); char *strsave(); #endif int rcmd_stream_write(), rcmd_stream_read(); -void usage(void), sink(int, char **), +void usage(void), sink(int, char **, const char *), source(int, char **), rsource(char *, struct stat *), verifydir(char *); int response(void), hosteq(char *, char *), okname(char *), susystem(char *); @@ -106,6 +107,7 @@ krb5_sigtype lostconn(int); int iamremote, targetshouldbedirectory; int iamrecursive; int pflag; +int Tflag; int forcenet; struct passwd *pwd; int userid; @@ -163,6 +165,7 @@ int main(argc, argv) exit(1); } + Tflag = 0; for (argc--, argv++; argc > 0 && **argv == '-'; argc--, argv++) { (*argv)++; while (**argv) switch (*(*argv)++) { @@ -175,6 +178,9 @@ int main(argc, argv) pflag++; break; + case 'T': /* Related to CVE-2019-6111. Disable filename checks */ + Tflag++; + break; case 'D': argc--, argv++; if (argc == 0) @@ -236,7 +242,7 @@ int main(argc, argv) iamremote = 1; rcmd_stream_init_normal(); - sink(--argc, ++argv); + sink(--argc, ++argv, NULL); exit(errs); default: @@ -548,7 +554,7 @@ int main(argc, argv) perror("rcp seteuid user"); errs++; exit(errs); } } - sink(1, argv+argc-1); + sink(1, argv+argc-1, src); if (euid == 0) { if(krb5_seteuid(0)) { perror("rcp seteuid 0"); errs++; exit(errs); @@ -564,7 +570,7 @@ int main(argc, argv) if (setreuid(0, userid)) { perror("rcp setreuid 0,user"); errs++; exit(errs); } - sink(1, argv+argc-1); + sink(1, argv+argc-1, src); if (setreuid(userid, 0)) { perror("rcp setreuid user,0"); errs++; exit(errs); } @@ -575,7 +581,7 @@ int main(argc, argv) if(seteuid(userid)) { perror("rcp seteuid user"); errs++; exit(errs); } - sink(1, argv+argc-1); + sink(1, argv+argc-1, src); if(seteuid(0)) { perror("rcp seteuid 0"); errs++; exit(errs); } @@ -909,9 +915,10 @@ struct timeval *tvp; #endif -void sink(argc, argv) +void sink(argc, argv, src) int argc; char **argv; + const char *src; { mode_t mode; mode_t mask = umask(0); @@ -927,6 +934,7 @@ void sink(argc, argv) char *myargv[1]; char cmdbuf[RCP_BUFSIZ], nambuf[RCP_BUFSIZ]; int setimes = 0; + char *src_copy = NULL, *restrict_pattern = NULL; struct timeval tv[2]; #define atime tv[0] #define mtime tv[1] @@ -944,6 +952,21 @@ void sink(argc, argv) ga(); if (stat(targ, &stb) == 0 && (stb.st_mode & S_IFMT) == S_IFDIR) targisdir = 1; + if (src != NULL && !iamrecursive && !Tflag) { + /* + * Prepare to try to restrict incoming filenames to match + * the requested destination file glob. + */ + if ((src_copy = strdup(src)) == NULL) { + error("rcp: strdup failed\n"); + exit(1); + } + if ((restrict_pattern = strrchr(src_copy, '/')) != NULL) { + *restrict_pattern++ = '\0'; + } else { + restrict_pattern = src_copy; + } + } for (first = 1; ; first = 0) { cp = cmdbuf; if (rcmd_stream_read(rem, cp, 1, 0) <= 0) @@ -1022,6 +1045,10 @@ void sink(argc, argv) error("Unexpected filename: %s\n", cp); exit(1); } + if (restrict_pattern != NULL && + fnmatch(restrict_pattern, cp, 0) != 0) { + SCREWUP("filename does not match request"); + } if (targisdir) { if(strlen(targ) + strlen(cp) + 2 >= sizeof(nambuf)) SCREWUP("target name too long"); @@ -1045,7 +1072,7 @@ void sink(argc, argv) } else if (mkdir(nambuf, mode) < 0) goto bad; myargv[0] = nambuf; - sink(1, myargv); + sink(1, myargv, src); if (setimes) { setimes = 0; if (utimes(nambuf, tv) < 0) @@ -1186,7 +1213,7 @@ void usage() { #ifdef KERBEROS fprintf(stderr, - "Usage: \trcp [-PN | -PO] [-p] [-x] [-k realm] f1 f2; or:\n\trcp [-PN | -PO] [-r] [-p] [-x] [-k realm] f1 ... fn d2\n"); + "Usage: \trcp [-PN | -PO] [-p] [-T] [-x] [-k realm] f1 f2; or:\n\trcp [-PN | -PO] [-r] [-p] [-T] [-x] [-k realm] f1 ... fn d2\n"); #else fputs("usage: rcp [-p] f1 f2; or: rcp [-rp] f1 ... fn d2\n", stderr); #endif diff --git a/bsd/rcp.M b/bsd/rcp.M index dcd206c..2e9b14f 100644 --- a/bsd/rcp.M +++ b/bsd/rcp.M @@ -22,7 +22,7 @@ rcp \- remote file copy .SH SYNOPSIS .B rcp -[\fB\-p\fP] [\fB\-x\fP] [\fB\-k\fP \fIrealm\fP ] [\fB-c\fP \fIccachefile\fP] [\fB-C\fP \fIconfigfile\fP] [\fB\-D\fP \fIport\fP] +[\fB\-p\fP] [\fB\-x\fP] [\fB\-T\fP] [\fB\-k\fP \fIrealm\fP ] [\fB-c\fP \fIccachefile\fP] [\fB-C\fP \fIconfigfile\fP] [\fB\-D\fP \fIport\fP] [\fB\-N\fP] [\fB\-PN | \-PO\fP] .I file1 file2 @@ -128,6 +128,14 @@ remotely-running rcp process (started via the Kerberos remote shell daemon) which direction files are being sent. These options should not be used by the user. In particular, \fB-f\fP does \fBnot\fP mean that the user's Kerberos ticket should be forwarded! +.TP +.B \-T +Checks that the received filenames match those requested on the command-line +to prevent the remote end from sending unexpected or unwanted files. +Because of differences in how various operating systems and shells interpret +filename wildcards, these checks may cause wanted files to be rejected. +This option disables these checks at the expense of fully trusting that +the server will not send unexpected filenames. .PP .B Rcp handles third party copies, where neither source nor target files are on -- 2.30.0
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