bsdinstall/distfetch.c: check environment variables before downloading and handle memory allocation errors

1. Currently, distfetch checks environment variables existence
when it will use them or in a case (in chdir()) it doesn't check
at all. As they are necessary to set before doing anything with
it, check them, if they set or not, before proceeding any further.
This also avoids extra cleaning when that environment variable
isn't set.

2. Handle memory allocation error in malloc(PATH_MAX) and replace
(sizeof const char *) with (sizeof char *). Both are similar and
const doesn't have a size.

3. Indent the error message a bit in chdir().

Signed-off-by: rilysh <nightquick@proton.me>
Reviewed by: imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/1071

1 files changed, 23 insertions, 10 deletions

diff --git a/usr.sbin/bsdinstall/distfetch/distfetch.c b/usr.sbin/bsdinstall/distfetch/distfetch.c
index c431e187799d..094929d89ea1 100644
--- a/usr.sbin/bsdinstall/distfetch/distfetch.c
+++ b/usr.sbin/bsdinstall/distfetch/distfetch.c
@@ -46,7 +46,7 @@ static int fetch_files(int nfiles, char **urls);
 int
 main(void)
 {
-	char *diststring;
+	char *diststring, *dists, *distdir, *distsite;
 	char **urls;
 	int i;
 	int ndists = 0;
@@ -54,17 +54,24 @@ main(void)
 	char error[PATH_MAX + 512];
 	struct bsddialog_conf conf;
 
-	if (getenv("DISTRIBUTIONS") == NULL)
+	if ((dists = getenv("DISTRIBUTIONS")) == NULL)
 		errx(EXIT_FAILURE, "DISTRIBUTIONS variable is not set");
 
-	diststring = strdup(getenv("DISTRIBUTIONS"));
+	if ((distdir = getenv("BSDINSTALL_DISTDIR")) == NULL)
+		errx(EXIT_FAILURE, "BSDINSTALL_DISTDIR variable is not set");
+
+	if ((distsite = getenv("BSDINSTALL_DISTSITE")) == NULL)
+		errx(EXIT_FAILURE, "BSDINSTALL_DISTSITE variable is not set");
+
+	if ((diststring = strdup(dists)) == NULL)
+		errx(EXIT_FAILURE, "Error: diststring variable out of memory!");
+
 	for (i = 0; diststring[i] != 0; i++)
 		if (isspace(diststring[i]) && !isspace(diststring[i+1]))
 			ndists++;
 	ndists++; /* Last one */
 
-	urls = calloc(ndists, sizeof(const char *));
-	if (urls == NULL) {
+	if ((urls = calloc(ndists, sizeof(char *))) == NULL) {
 		free(diststring);
 		errx(EXIT_FAILURE, "Error: distfetch URLs out of memory!");
 	}
@@ -78,15 +85,21 @@ main(void)
 	bsddialog_backtitle(&conf, OSNAME " Installer");
 
 	for (i = 0; i < ndists; i++) {
-		urls[i] = malloc(PATH_MAX);
+		if ((urls[i] = malloc(PATH_MAX)) == NULL) {
+			free(urls);
+			free(diststring);
+			bsddialog_end();
+			errx(EXIT_FAILURE, "Error: distfetch URLs out of memory!");
+		}
+
 		snprintf(urls[i], PATH_MAX, "%s/%s",
-		    getenv("BSDINSTALL_DISTSITE"), strsep(&diststring, " \t"));
+			 distsite, strsep(&diststring, " \t"));
 	}
 
-	if (chdir(getenv("BSDINSTALL_DISTDIR")) != 0) {
+	if (chdir(distdir) != 0) {
 		snprintf(error, sizeof(error),
-		    "Could not change to directory %s: %s\n",
-		    getenv("BSDINSTALL_DISTDIR"), strerror(errno));
+			 "Could not change to directory %s: %s\n",
+			 distdir, strerror(errno));
 		conf.title = "Error";
 		bsddialog_msgbox(&conf, error, 0, 0);
 		bsddialog_end();