pwd: Fully implement fgetpwent_r/getpwent_r

These functions require a deep copy of the structure into the
caller-provided buffer. Also make sure to store NULL in result on error.

Use the stream to differentiate the two functions and avoid duplication.

Signed-off-by: Samuel Holland <samuel@sholland.org>

1 files changed, 74 insertions, 45 deletions

diff --git a/libgcompat/pwd.c b/libgcompat/pwd.c
index 50d8da0..34c5d7b 100644
--- a/libgcompat/pwd.c
+++ b/libgcompat/pwd.c
@@ -1,63 +1,92 @@
 /* some musl versions incorrectly mark fgetpwent() as a GNU extension */
 #define _GNU_SOURCE
+#include <assert.h>  /* assert */
+#include <errno.h>   /* ENOENT, ERANGE */
+#include <pthread.h> /* pthread_mutex_* */
+#include <pwd.h>     /* fgetpwent, getpwent, struct passwd */
+#include <stddef.h>  /* NULL, size_t */
+#include <stdio.h>   /* FILE */
+#include <string.h>  /* memcpy, stpcpy, strlcpy, strlen */
 
-#include <errno.h>
-#include <pwd.h>
-#include <stdio.h>
-#include <string.h>
+static pthread_mutex_t pwent_mutex = PTHREAD_MUTEX_INITIALIZER;
 
-int getpwent_r(struct passwd *pwbuf, char *buf, size_t buflen,
-               struct passwd **pwbufp)
+static int __fgetpwent_r(FILE *stream, struct passwd *pwd, char *buf,
+                         size_t len, struct passwd **result)
 {
-	struct passwd *pwd;
+	struct passwd *pwtmp;
+	char *cursor = buf, *end = buf + len;
 
-	if (pwbufp == NULL || pwbuf == NULL) {
-		return ERANGE;
+	*result = NULL;
+	pthread_mutex_lock(&pwent_mutex);
+	pwtmp = stream != NULL ? fgetpwent(stream) : getpwent();
+	if (pwtmp == NULL) {
+		pthread_mutex_unlock(&pwent_mutex);
+		return ENOENT;
 	}
-
-	if (buflen < 1) {
-		return ERANGE;
+	memcpy(pwd, pwtmp, sizeof(*pwd));
+	if (pwtmp->pw_name != NULL) {
+		pwd->pw_name = cursor;
+		cursor += strlcpy(cursor, pwtmp->pw_name, end - cursor) + 1;
+		if (cursor > end) {
+			goto err_unlock;
+		}
 	}
-
-	if (buf != NULL) {
-		*buf = '\0';
+	if (pwtmp->pw_passwd != NULL) {
+		pwd->pw_passwd = cursor;
+		cursor += strlcpy(cursor, pwtmp->pw_passwd, end - cursor) + 1;
+		if (cursor > end) {
+			goto err_unlock;
+		}
 	}
-
-	if ((pwd = getpwent()) == NULL) {
-		*pwbufp = NULL;
-		return ENOENT;
+	if (pwtmp->pw_gecos != NULL) {
+		pwd->pw_gecos = cursor;
+		cursor += strlcpy(cursor, pwtmp->pw_gecos, end - cursor) + 1;
+		if (cursor > end) {
+			goto err_unlock;
+		}
 	}
-
-	memcpy(pwbuf, pwd, sizeof(*pwd));
-	*pwbufp = pwbuf;
+	if (pwtmp->pw_dir != NULL) {
+		pwd->pw_dir = cursor;
+		cursor += strlcpy(cursor, pwtmp->pw_dir, end - cursor) + 1;
+		if (cursor > end) {
+			goto err_unlock;
+		}
+	}
+	if (pwtmp->pw_shell != NULL) {
+		pwd->pw_shell = cursor;
+		cursor += strlcpy(cursor, pwtmp->pw_shell, end - cursor) + 1;
+		if (cursor > end) {
+			goto err_unlock;
+		}
+	}
+	pthread_mutex_unlock(&pwent_mutex);
+	*result = pwd;
 
 	return 0;
+
+err_unlock:
+	pthread_mutex_unlock(&pwent_mutex);
+	return ERANGE;
 }
 
-int fgetpwent_r(FILE *filp, struct passwd *pwbuf, char *buf, size_t buflen,
-                struct passwd **pwbufp)
+/**
+ * Get passwd file entry.
+ */
+int fgetpwent_r(FILE *stream, struct passwd *pwd, char *buf, size_t len,
+                struct passwd **result)
 {
-	struct passwd *pwd;
-
-	if (pwbufp == NULL || pwbuf == NULL) {
-		return ERANGE;
-	}
+	assert(stream != NULL);
 
-	if (buflen < 1) {
-		return ERANGE;
-	}
-
-	if (buf != NULL) {
-		*buf = '\0';
-	}
-
-	if ((pwd = fgetpwent(filp)) == NULL) {
-		*pwbufp = NULL;
-		return ENOENT;
-	}
-
-	memcpy(pwbuf, pwd, sizeof(*pwd));
-	*pwbufp = pwbuf;
+	return fgetpwent_r(stream, pwd, buf, len, result);
+}
 
-	return 0;
+/**
+ * Get user database entry.
+ *
+ * LSB 5.0: LSB-Core-generic/baselib-getpwent-r-1.html
+ */
+int getpwent_r(struct passwd *pwd, char *buf, size_t len,
+               struct passwd **result)
+{
+	return __fgetpwent_r(NULL, pwd, buf, len, result);
 }