Use malloc()ed buffers instead of stack buffers in gr_copy() and pw_copy().

This allows pw(8) to operate on passwd and group files with longer lines
than could be accomodated by a stack buffer.  It doesn't take more than a
few hundred users to exceed 8192 bytes in /etc/group.

MFC after:	3 weeks
Sponsored by:	The University of Oslo

2 files changed, 48 insertions, 26 deletions

diff --git a/libutil/gr_util.c b/libutil/gr_util.c
index 6153209..99f268c 100644
--- a/libutil/gr_util.c
+++ b/libutil/gr_util.c
@@ -164,11 +164,12 @@ gr_tmp(int mfd)
 int
 gr_copy(int ffd, int tfd, const struct group *gr, struct group *old_gr)
 {
-	char buf[8192], *end, *line, *p, *q, *r, t;
+	char *buf, *end, *line, *p, *q, *r, *tmp;
 	struct group *fgr;
 	const struct group *sgr;
-	size_t len;
+	size_t len, size;
 	int eof, readlen;
+	char t;
 
 	if (old_gr == NULL && gr == NULL)
 		return(-1);
@@ -186,6 +187,10 @@ gr_copy(int ffd, int tfd, const struct group *gr, struct group *old_gr)
 	if (sgr == NULL)
 		sgr = gr;
 
+	/* initialize the buffer */
+	if ((buf = malloc(size = 1024)) == NULL)
+		goto err;
+
 	eof = 0;
 	len = 0;
 	p = q = end = buf;
@@ -199,10 +204,16 @@ gr_copy(int ffd, int tfd, const struct group *gr, struct group *old_gr)
 		if (q >= end) {
 			if (eof)
 				break;
-			if ((size_t)(q - p) >= sizeof(buf)) {
-				warnx("group line too long");
-				errno = EINVAL; /* hack */
-				goto err;
+			while ((size_t)(q - p) >= size) {
+				if ((tmp = realloc(buf, size * 2)) == NULL) {
+					warnx("group line too long");
+					goto err;
+				}
+				p = tmp + (p - buf);
+				q = tmp + (q - buf);
+				end = tmp + (end - buf);
+				buf = tmp;
+				size = size * 2;
 			}
 			if (p < end) {
 				q = memmove(buf, p, end -p);
@@ -210,7 +221,7 @@ gr_copy(int ffd, int tfd, const struct group *gr, struct group *old_gr)
 			} else {
 				p = q = end = buf;
 			}
-			readlen = read(ffd, end, sizeof(buf) - (end -buf));
+			readlen = read(ffd, end, size - (end - buf));
 			if (readlen == -1)
 				goto err;
 			else
@@ -219,7 +230,7 @@ gr_copy(int ffd, int tfd, const struct group *gr, struct group *old_gr)
 				break;
 			end += len;
 			len = end - buf;
-			if (len < (ssize_t)sizeof(buf)) {
+			if (len < size) {
 				eof = 1;
 				if (len > 0 && buf[len -1] != '\n')
 					++len, *end++ = '\n';
@@ -281,7 +292,7 @@ gr_copy(int ffd, int tfd, const struct group *gr, struct group *old_gr)
 			if (write(tfd, q, end - q) != end - q)
 				goto err;
 			q = buf;
-			readlen = read(ffd, buf, sizeof(buf));
+			readlen = read(ffd, buf, size);
 			if (readlen == 0)
 				break;
 			else
@@ -303,12 +314,12 @@ gr_copy(int ffd, int tfd, const struct group *gr, struct group *old_gr)
 	   write(tfd, "\n", 1) != 1)
 		goto err;
  done:
-	if (line != NULL)
-		free(line);
+	free(line);
+	free(buf);
 	return (0);
  err:
-	if (line != NULL)
-		free(line);
+	free(line);
+	free(buf);
 	return (-1);
 }
 
diff --git a/libutil/pw_util.c b/libutil/pw_util.c
index d790328..0c34e67 100644
--- a/libutil/pw_util.c
+++ b/libutil/pw_util.c
@@ -427,11 +427,12 @@ pw_make_v7(const struct passwd *pw)
 int
 pw_copy(int ffd, int tfd, const struct passwd *pw, struct passwd *old_pw)
 {
-	char buf[8192], *end, *line, *p, *q, *r, t;
+	char *buf, *end, *line, *p, *q, *r, *tmp;
 	struct passwd *fpw;
 	const struct passwd *spw;
-	size_t len;
+	size_t len, size;
 	int eof, readlen;
+	char t;
 
 	if (old_pw == NULL && pw == NULL)
 			return (-1);
@@ -449,6 +450,10 @@ pw_copy(int ffd, int tfd, const struct passwd *pw, struct passwd *old_pw)
 	if (spw == NULL)
 		spw = pw;
 
+	/* initialize the buffer */
+	if ((buf = malloc(size = 1024)) == NULL)
+		goto err;
+
 	eof = 0;
 	len = 0;
 	p = q = end = buf;
@@ -462,10 +467,16 @@ pw_copy(int ffd, int tfd, const struct passwd *pw, struct passwd *old_pw)
 		if (q >= end) {
 			if (eof)
 				break;
-			if ((size_t)(q - p) >= sizeof(buf)) {
-				warnx("passwd line too long");
-				errno = EINVAL; /* hack */
-				goto err;
+			while ((size_t)(q - p) >= size) {
+				if ((tmp = realloc(buf, size * 2)) == NULL) {
+					warnx("passwd line too long");
+					goto err;
+				}
+				p = tmp + (p - buf);
+				q = tmp + (q - buf);
+				end = tmp + (end - buf);
+				buf = tmp;
+				size = size * 2;
 			}
 			if (p < end) {
 				q = memmove(buf, p, end - p);
@@ -473,7 +484,7 @@ pw_copy(int ffd, int tfd, const struct passwd *pw, struct passwd *old_pw)
 			} else {
 				p = q = end = buf;
 			}
-			readlen = read(ffd, end, sizeof(buf) - (end - buf));
+			readlen = read(ffd, end, size - (end - buf));
 			if (readlen == -1)
 				goto err;
 			else
@@ -482,7 +493,7 @@ pw_copy(int ffd, int tfd, const struct passwd *pw, struct passwd *old_pw)
 				break;
 			end += len;
 			len = end - buf;
-			if (len < (ssize_t)sizeof(buf)) {
+			if (len < size) {
 				eof = 1;
 				if (len > 0 && buf[len - 1] != '\n')
 					++len, *end++ = '\n';
@@ -545,7 +556,7 @@ pw_copy(int ffd, int tfd, const struct passwd *pw, struct passwd *old_pw)
 			if (write(tfd, q, end - q) != end - q)
 				goto err;
 			q = buf;
-			readlen = read(ffd, buf, sizeof(buf));
+			readlen = read(ffd, buf, size);
 			if (readlen == 0)
 				break;
 			else
@@ -567,12 +578,12 @@ pw_copy(int ffd, int tfd, const struct passwd *pw, struct passwd *old_pw)
 	    write(tfd, "\n", 1) != 1)
 		goto err;
  done:
-	if (line != NULL)
-		free(line);
+	free(line);
+	free(buf);
 	return (0);
  err:
-	if (line != NULL)
-		free(line);
+	free(line);
+	free(buf);
 	return (-1);
 }