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From 3e0812fe9d3f4712638a1c4c49bf2b2a7dc4311b Mon Sep 17 00:00:00 2001
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From: Ben Gamari <ben@smart-cactus.org>
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Date: Mon, 1 Jul 2019 11:03:33 -0400
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Subject: [PATCH] Call initgroups before setuid
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Previously we would fail to call initgroups before setuid'ing. This
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meant that our groups we not be reset to reflect those our new user
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belongs to. Fix this.
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---
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cbits/runProcess.c | 32 +++++++++++++++++++++++++++++---
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include/runProcess.h | 4 ++++
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2 files changed, 33 insertions(+), 3 deletions(-)
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diff --git a/cbits/runProcess.c b/cbits/runProcess.c
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index 10794bc..84d5fd4 100644
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--- a/cbits/runProcess.c
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+++ b/cbits/runProcess.c
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@@ -33,6 +33,10 @@ static long max_fd = 0;
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extern void blockUserSignals(void);
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extern void unblockUserSignals(void);
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+// These are arbitrarily chosen -- JP
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+#define forkSetgidFailed 124
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+#define forkSetuidFailed 125
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+
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// See #1593. The convention for the exit code when
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// exec() fails seems to be 127 (gleened from C's
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// system()), but there's no equivalent convention for
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@@ -40,9 +44,8 @@ extern void unblockUserSignals(void);
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#define forkChdirFailed 126
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#define forkExecFailed 127
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-// These are arbitrarily chosen -- JP
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-#define forkSetgidFailed 124
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-#define forkSetuidFailed 125
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+#define forkGetpwuidFailed 128
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+#define forkInitgroupsFailed 129
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__attribute__((__noreturn__))
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static void childFailed(int pipe, int failCode) {
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@@ -182,6 +185,23 @@ runInteractiveProcess (char *const args[],
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}
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if ( childUser) {
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+ // Using setuid properly first requires that we initgroups.
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+ // However, to do this we must know the username of the user we are
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+ // switching to.
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+ struct passwd pw;
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+ struct passwd *res = NULL;
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+ int buf_len = sysconf(_SC_GETPW_R_SIZE_MAX);
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+ char *buf = malloc(buf_len);
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+ gid_t suppl_gid = childGroup ? *childGroup : getgid();
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+ if ( getpwuid_r(*childUser, &pw, buf, buf_len, &res) != 0) {
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+ childFailed(forkCommunicationFds[1], forkGetpwuidFailed);
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+ }
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+ if ( res == NULL ) {
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+ childFailed(forkCommunicationFds[1], forkGetpwuidFailed);
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+ }
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+ if ( initgroups(res->pw_name, suppl_gid) != 0) {
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+ childFailed(forkCommunicationFds[1], forkInitgroupsFailed);
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+ }
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if ( setuid( *childUser) != 0) {
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// ERROR
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childFailed(forkCommunicationFds[1], forkSetuidFailed);
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@@ -330,6 +350,12 @@ runInteractiveProcess (char *const args[],
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case forkSetuidFailed:
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*failed_doing = "runInteractiveProcess: setuid";
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break;
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+ case forkGetpwuidFailed:
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+ *failed_doing = "runInteractiveProcess: getpwuid";
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+ break;
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+ case forkInitgroupsFailed:
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+ *failed_doing = "runInteractiveProcess: initgroups";
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+ break;
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default:
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*failed_doing = "runInteractiveProcess: unknown";
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break;
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diff --git a/include/runProcess.h b/include/runProcess.h
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index 3807389..dff3905 100644
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--- a/include/runProcess.h
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+++ b/include/runProcess.h
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@@ -21,6 +21,10 @@
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#include <unistd.h>
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#include <sys/types.h>
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+#if !(defined(_MSC_VER) || defined(__MINGW32__) || defined(_WIN32))
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+#include <pwd.h>
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+#include <grp.h>
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+#endif
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#ifdef HAVE_FCNTL_H
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#include <fcntl.h>
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