[PATCH 2/2] libselinux: selabel_digest -v: handle unexpected output

selabel_digest -v runs openssl to obtain a digest for validation but
doesn't correctly handle the case where no output is
produced. Initialize the buffer and reject unexpected output.

Signed-off-by: Stephen Smalley <[email protected]>
---
 libselinux/utils/selabel_digest.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/libselinux/utils/selabel_digest.c b/libselinux/utils/selabel_digest.c
index 2c395db6..689ca7f4 100644
--- a/libselinux/utils/selabel_digest.c
+++ b/libselinux/utils/selabel_digest.c
@@ -39,10 +39,17 @@ static int run_check_digest(const char *cmd, const char *selabel_digest,
 	}
 
 	/* Only expect one line "(stdin)= x.." so read and find first space */
+	files_digest[0] = '\0';
 	while (fgets(files_digest, sizeof(files_digest) - 1, fp) != NULL)
 		;
 
 	files_ptr = strstr(files_digest, " ");
+	if (!files_ptr) {
+		fprintf(stderr, "Unexpected output from '%s': %s\n", cmd,
+			files_digest);
+		pclose(fp);
+		return -1;
+	}
 
 	rc = strncmp(selabel_digest, files_ptr + 1, digest_len * 2);
 	if (rc) {
-- 
2.55.0