From c7c4043108707c194ab242080db7b51478618c98 Mon Sep 17 00:00:00 2001
From: GreekStapler <dvmap@protonmail.com>
Date: Tue, 31 Jan 2023 21:00:08 +0000
Subject: [PATCH] fix: Using snprintf while ignoring its return value could
 lead to valid inputs getting truncated.

---
 include/vieter_package.h     | 10 ++-----
 src/package/vieter_package.c | 51 ++++++++++++++++++++++--------------
 2 files changed, 33 insertions(+), 28 deletions(-)

diff --git a/include/vieter_package.h b/include/vieter_package.h
index 179ff57..32fb0eb 100644
--- a/include/vieter_package.h
+++ b/include/vieter_package.h
@@ -1,16 +1,10 @@
 #ifndef VIETER_PACKAGE
 #define VIETER_PACKAGE
 
-#include <stdint.h>
-#include <stdbool.h>
-#include <string.h>
-#include <stdlib.h>
-
-#include <archive.h>
-#include <archive_entry.h>
-
 typedef struct vieter_package vieter_package;
 
+
+
 /*
  * Parse package file into something usable by libvieter.
  * The pointer returned by this function will need to freed at a later point.
diff --git a/src/package/vieter_package.c b/src/package/vieter_package.c
index 3bb19ba..031fe15 100644
--- a/src/package/vieter_package.c
+++ b/src/package/vieter_package.c
@@ -1,30 +1,29 @@
+#include <stdlib.h>
+#include <stdbool.h>
+#include <archive.h>
+#include <archive_entry.h>
+
 #include "vieter_package_internal.h"
 #include "sha256.h"
 
-#define SMALL_BUFF_SIZE 128
-
 #define ADD_STRING(section, field) if (pkg_info->field != 0) { \
-	snprintf(aux, SMALL_BUFF_SIZE, section, pkg_info->field); \
-	if (buff_size < strlen(description) + SMALL_BUFF_SIZE + 1) { \
+	size_to_be_written = snprintf(aux, small_buff_size, section, pkg_info->field); \
+	if (size_to_be_written > small_buff_size) { \
+		aux = realloc(aux, size_to_be_written + 1); \
+		small_buff_size = size_to_be_written + 1; \
+		snprintf(aux, small_buff_size, section, pkg_info->field); \
+	} \
+	if (buff_size < strlen(description) + small_buff_size + 1) { \
 		description = realloc(description, buff_size * 2); \
 		buff_size *= 2; \
 	} \
 	strcat(description, aux); \
 }
+
 #define ADD_ARRAY(section, field) i = 0; if (pkg_info->field != NULL) { \
-	snprintf(aux, SMALL_BUFF_SIZE, section, pkg_info->field->array[i]); i++; \
-	if (buff_size < strlen(description) + SMALL_BUFF_SIZE + 1) { \
-		description = realloc(description, buff_size * 2); \
-		buff_size *= 2; \
-	} \
-	strcat(description, aux); \
+	ADD_STRING(section, field->array[i]); i++; \
 	while (pkg_info->field->array[i] != NULL) { \
-	snprintf(aux, SMALL_BUFF_SIZE, "\n%s", pkg_info->field->array[i]); i++; \
-		if (buff_size < strlen(description) + SMALL_BUFF_SIZE + 1) { \
-			description = realloc(description, buff_size * 2); \
-			buff_size *= 2; \
-		} \
-		strcat(description, aux); \
+		ADD_STRING("\n%s", field->array[i]); i++; \
 	} \
 }
 
@@ -170,19 +169,32 @@ void vieter_package_sha256sum(vieter_package *pkg, char *res) {
 	res[j] = '\0';
 }
 
+
+
 char *vieter_package_to_description(vieter_package *pkg) {
 	vieter_package_info *pkg_info = pkg->info;
 
 	size_t buff_size = 1024;
-	char aux[SMALL_BUFF_SIZE];
+	int small_buff_size = 128;
+	int size_to_be_written;
+	char *aux = malloc(sizeof(char) * small_buff_size);
 	char *description = malloc(sizeof(char) * buff_size);
 	// Helper variable for ADD_ARRAY macro
 	int i;
 
 	// special case for FILENAME
 	// assuming .pkg.tar.zst; other formats are valid, this should account for that
-	snprintf(aux, SMALL_BUFF_SIZE, "%%FILENAME%%\n%s-%s-%s.pkg.tar.zst", pkg_info->name,
+	size_to_be_written = snprintf(aux, small_buff_size, "%%FILENAME%%\n%s-%s-%s.pkg.tar.zst", pkg_info->name,
 			pkg_info->version, pkg_info->arch);
+
+	// We neither want to let an arbritrarily long input to overflow the buffer
+	// nor to truncate perfectly valid inputs
+	if (size_to_be_written > small_buff_size) {
+		aux = realloc(aux, size_to_be_written + 1);
+		small_buff_size = size_to_be_written + 1;
+		snprintf(aux, small_buff_size, "%%FILENAME%%\n%s-%s-%s.pkg.tar.zst", pkg_info->name,
+				pkg_info->version, pkg_info->arch);
+	}
 	strcpy(description, aux);
 
 	ADD_STRING("\n\n%%NAME%%\n%s", name);
@@ -216,8 +228,7 @@ char *vieter_package_to_description(vieter_package *pkg) {
 	ADD_ARRAY("\n\n%%MAKEDEPENDS%%\n%s", makedepends);
 	ADD_ARRAY("\n\n%%CHECKDEPENDS%%\n%s", checkdepends);
 
-	snprintf(aux, SMALL_BUFF_SIZE, "\n\n");
-	strcat(description, aux);
+	strcat(description, "\n\n");
 
 	return description;
 }