Implement setting app specific environment vars

debian/usr.bin.snap-run

@@ -70,6 +70,9 @@
     # reading seccomp filters
     /var/lib/snapd/seccomp/profiles/* r,
 
+    # reading the environment
+    /var/lib/snapd/environment/* r,
+
     # set up snap-specific private /tmp dir
     capability chown,
     /tmp/ w,

src/environment.c

@@ -0,0 +1,85 @@
+/*
+ * Copyright (C) 2016 Canonical Ltd
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "utils.h"
+
+char *env_profile_dir = "/var/lib/snapd/environment/";
+
+void setenv_from_line(char *line)
+{
+	const char *name = NULL;
+	const char *value = NULL;
+	debug("reading line: '%s'", line);
+
+	if (strlen(line) == 0)
+		return;
+
+	// kill final \n
+	char *nl = strchr(line, '\n');
+	if (nl != NULL)
+		*nl = 0;
+
+	// find first "="
+	char *t = strchr(line, '=');
+	if (t == NULL)
+		return;
+
+	// before the "=" is the env key
+	*t = 0;
+	name = line;
+
+	// after the "=" is the env value
+	// note that there is always a t+1 because fgets() gives us a final \0
+	if (*(t + 1) == 0)
+		return;
+	value = t + 1;
+
+	debug("setenv: '%s'='%s'", name, value);
+	if (setenv(name, value, 0) != 0)
+		die("setenv failed");
+}
+
+void apply_environment_file(const char *env_tag)
+{
+	debug("apply_environment_file %s", env_tag);
+
+	if (secure_getenv("SNAPPY_LAUNCHER_ENVIRONMENT_DIR") != NULL)
+		env_profile_dir =
+		    secure_getenv("SNAPPY_LAUNCHER_ENVIRONMENT_DIR");
+
+	char env_path[512];	// ought to be enough for everybody
+	must_snprintf(env_path, sizeof(env_path), "%s/%s", env_profile_dir,
+		      env_tag);
+
+	char buf[1024];		// LD_LIBRARY_PATH can get long
+	debug("reading '%s'", env_path);
+	FILE *f = fopen(env_path, "r");
+	if (f == NULL) {
+		return;
+	}
+	while (fgets(buf, sizeof(buf), f) != NULL) {
+		setenv_from_line(buf);
+	}
+	fclose(f);
+}

src/environment.h

@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2016 Canonical Ltd
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef CORE_LAUNCHER_ENVIRONMENT_H
+#define CORE_LAUNCHER_ENVIRONMENT_H
+
+void apply_environment_file(const char *env_profile);
+
+#endif

src/main.c

@@ -43,6 +43,7 @@
 
 #include "utils.h"
 #include "seccomp.h"
+#include "environment.h"
 
 #define MAX_BUF 1000
 
@@ -569,6 +570,9 @@ int main(int argc, char **argv)
 		if (real_uid != 0 && (getgid() == 0 || getegid() == 0))
 			die("permanently dropping privs did not work");
 	}
+	// apply environment file as *non* root
+	apply_environment_file(aa_profile);
+
 	// and exec the new binary
 	execv(binary, (char *const *)&argv[NR_ARGS]);
 	perror("execv failed");

tests/common.sh

@@ -7,9 +7,13 @@ TMP="$(mktemp -d)"
 trap 'rm -rf $TMP' EXIT
 
 export SNAPPY_LAUNCHER_SECCOMP_PROFILE_DIR="$TMP"
+export SNAPPY_LAUNCHER_ENVIRONMENT_DIR="$TMP/environment"
+mkdir "$SNAPPY_LAUNCHER_ENVIRONMENT_DIR"
+
 export SNAPPY_LAUNCHER_INSIDE_TESTS="1"
 export UBUNTU_CORE_LAUNCHER_NO_ROOT=1
 
+
 FAIL() {
     printf ": FAIL\n"
     exit 1

tests/test_environment

@@ -0,0 +1,28 @@
+#!/bin/sh
+
+set -e
+
+. $(pwd)/common.sh
+
+test() {
+    needle="$1"
+    cat >$TMP/environment/myprofile <<EOF
+$needle
+EOF
+    if ! $L snap.name.app myprofile /usr/bin/env |grep -q "$needle"; then
+        FAIL
+    fi
+    
+    PASS
+}
+
+cat >$TMP//myprofile <<EOF
+@unrestricted
+EOF
+
+
+printf "Set environment from launcher"
+test "LD_LIBRARY_PATH=/some/path"
+
+printf "With '=' in environment"
+test "FOO=bar=baz"