From a3faa73f03a4d539de4c808d1a4f3b8ebc5ce537 Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@tavianator.com>
Date: Sat, 10 Jun 2017 03:02:39 -0400
Subject: printf: Fix embedded nul bytes

Fixes #26.
---
 dstring.c                 |   4 ++++
 dstring.h                 |  11 +++++++++++
 printf.c                  |  27 ++++++++++++++++-----------
 tests.sh                  |   6 ++++++
 tests/test_printf_nul.out | Bin 0 -> 198 bytes
 5 files changed, 37 insertions(+), 11 deletions(-)
 create mode 100644 tests/test_printf_nul.out

diff --git a/dstring.c b/dstring.c
index 5a6d4b3..54815d6 100644
--- a/dstring.c
+++ b/dstring.c
@@ -95,6 +95,10 @@ int dstrncat(char **dest, const char *src, size_t n) {
 	return dstrcat_impl(dest, src, strnlen(src, n));
 }
 
+int dstrapp(char **str, char c) {
+	return dstrcat_impl(str, &c, 1);
+}
+
 void dstrfree(char *dstr) {
 	if (dstr) {
 		free(dstrheader(dstr));
diff --git a/dstring.h b/dstring.h
index cd867ad..318bb0b 100644
--- a/dstring.h
+++ b/dstring.h
@@ -77,6 +77,17 @@ int dstrcat(char **dest, const char *src);
  */
 int dstrncat(char **dest, const char *src, size_t n);
 
+/**
+ * Append a single character to a dynamic string.
+ *
+ * @param str
+ *         The string to append to.
+ * @param c
+ *         The character to append.
+ * @return 0 on success, -1 on failure.
+ */
+int dstrapp(char **str, char c);
+
 /**
  * Free a dynamic string.
  *
diff --git a/printf.c b/printf.c
index 33753e3..888fecb 100644
--- a/printf.c
+++ b/printf.c
@@ -48,7 +48,12 @@ struct bfs_printf_directive {
 
 /** Print some text as-is. */
 static int bfs_printf_literal(FILE *file, const struct bfs_printf_directive *directive, const struct BFTW *ftwbuf) {
-	return fprintf(file, "%s", directive->str);
+	size_t len = dstrlen(directive->str);
+	if (fwrite(directive->str, 1, len, file) == len) {
+		return 0;
+	} else {
+		return -1;
+	}
 }
 
 /** \c: flush */
@@ -517,8 +522,8 @@ struct bfs_printf *parse_bfs_printf(const char *format, struct cmdline *cmdline)
 			if (!directive) {
 				goto directive_error;
 			}
-			if (dstrncat(&directive->str, &c, 1) != 0) {
-				perror("dstralloc()");
+			if (dstrapp(&directive->str, c) != 0) {
+				perror("dstrapp()");
 				goto directive_error;
 			}
 
@@ -540,8 +545,8 @@ struct bfs_printf *parse_bfs_printf(const char *format, struct cmdline *cmdline)
 						cfprintf(cerr, "%{er}error: '%s': Duplicate flag '%c'.%{rs}\n", format, c);
 						goto directive_error;
 					}
-					if (dstrncat(&directive->str, &c, 1) != 0) {
-						perror("dstrncat()");
+					if (dstrapp(&directive->str, c) != 0) {
+						perror("dstrapp()");
 						goto directive_error;
 					}
 					continue;
@@ -552,8 +557,8 @@ struct bfs_printf *parse_bfs_printf(const char *format, struct cmdline *cmdline)
 
 			// Parse the field width
 			while (c >= '0' && c <= '9') {
-				if (dstrncat(&directive->str, &c, 1) != 0) {
-					perror("dstrncat()");
+				if (dstrapp(&directive->str, c) != 0) {
+					perror("dstrapp()");
 					goto directive_error;
 				}
 				c = *++i;
@@ -562,8 +567,8 @@ struct bfs_printf *parse_bfs_printf(const char *format, struct cmdline *cmdline)
 			// Parse the precision
 			if (c == '.') {
 				do {
-					if (dstrncat(&directive->str, &c, 1) != 0) {
-						perror("dstrncat()");
+					if (dstrapp(&directive->str, c) != 0) {
+						perror("dstrapp()");
 						goto directive_error;
 					}
 					c = *++i;
@@ -774,8 +779,8 @@ struct bfs_printf *parse_bfs_printf(const char *format, struct cmdline *cmdline)
 		}
 
 	one_char:
-		if (dstrncat(&literal->str, &c, 1) != 0) {
-			perror("dstrncat()");
+		if (dstrapp(&literal->str, c) != 0) {
+			perror("dstrapp()");
 			goto error;
 		}
 	}
diff --git a/tests.sh b/tests.sh
index a07ae8a..ef4bbfc 100755
--- a/tests.sh
+++ b/tests.sh
@@ -302,6 +302,7 @@ gnu_tests=(
     test_printf_escapes
     test_printf_times
     test_printf_leak
+    test_printf_nul
     test_quit_after_print
     test_quit_before_print
     test_fstype
@@ -1036,6 +1037,11 @@ function test_printf_leak() {
     bfs_diff basic -maxdepth 0 -printf '%p'
 }
 
+function test_printf_nul() {
+    # NUL byte regression test
+    bfs_diff basic -printf '%h\0%f\n'
+}
+
 function test_fstype() {
     fstype="$($BFS -printf '%F\n' | head -n1)"
     bfs_diff basic -fstype "$fstype"
diff --git a/tests/test_printf_nul.out b/tests/test_printf_nul.out
new file mode 100644
index 0000000..3e30a4f
Binary files /dev/null and b/tests/test_printf_nul.out differ
-- 
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