From 71f41209946e99386f2adeb93d1e0d6c5e48b23e Mon Sep 17 00:00:00 2001
From: Geoffrey Thomas <geofft@twosigma.com>
Date: Thu, 7 Oct 2021 17:14:21 -0400
Subject: [PATCH] Add failing test for nix-rust/nix#1541

---
 ci/libnss_whatami.c | 28 ++++++++++++++++++++++++++++
 ci/test.sh          |  3 ++-
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/ci/libnss_whatami.c b/ci/libnss_whatami.c
index 47b312c..57ced1b 100644
--- a/ci/libnss_whatami.c
+++ b/ci/libnss_whatami.c
@@ -20,6 +20,7 @@
 #include <nss.h>
 #include <pwd.h>
 #include <string.h>
+#include <stdlib.h>
 
 enum nss_status
 _nss_whatami_getpwnam_r(const char *name, struct passwd *result, char *buffer, size_t buflen, int *errnop)
@@ -42,3 +43,30 @@ _nss_whatami_getpwnam_r(const char *name, struct passwd *result, char *buffer, s
 		return NSS_STATUS_NOTFOUND;
 	}
 }
+
+enum nss_status
+_nss_whatami_initgroups_dyn(const char *user, gid_t group, long int *start, long int *size, gid_t **groups, long int limit, int *errnop)
+{
+	if (strcmp(user, "whatami") == 0) {
+		if (*size - *start < 20) {
+			if (limit > 0 && *size + 20 > limit) {
+				*errnop = ERANGE;
+				return NSS_STATUS_TRYAGAIN;
+			}
+			gid_t *newgroups = realloc(*groups, (*size + 20) * sizeof(**groups));
+			if (newgroups == NULL) {
+				*errnop = ENOMEM;
+				return NSS_STATUS_TRYAGAIN;
+			}
+			*groups = newgroups;
+			*size += 20;
+		}
+
+		for (int i = 0; i < 20; i++) {
+			(*groups)[*start + i] = 100001 + i;
+		}
+		*start += 20;
+	}
+
+	return NSS_STATUS_SUCCESS;
+}
diff --git a/ci/test.sh b/ci/test.sh
index fc17079..1caa6c0 100755
--- a/ci/test.sh
+++ b/ci/test.sh
@@ -20,6 +20,7 @@ debian/rules vendor
 dpkg-buildpackage --no-sign
 gcc -fPIC -shared -o ci/libnss_whatami.so.2 ci/libnss_whatami.c
 sudo cp ci/libnss_whatami.so.2 /lib
-sudo sed -i 's/passwd:/& whatami/' /etc/nsswitch.conf
+sudo sed -i 's/\(passwd\|group\):/& whatami/' /etc/nsswitch.conf
 sudo dpkg -i ../nsncd*.deb
 getent passwd whatami | grep nsncd
+getent initgroups whatami | grep '100001.*100020'