From: Pablo Correa Gómez <ablocorrea@hotmail.com>
Date: Sat, 16 Oct 2021 22:09:16 +0000 (+0200)
Subject: Use thread-safe getpwnam_r and getpwuid_r in multi-threaded code
X-Git-Tag: v2.4b1~13^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=038ceabd05ead6c77d5e20e0972eb2872a82c5c5;p=thirdparty%2Fcups.git

Use thread-safe getpwnam_r and getpwuid_r in multi-threaded code

getpwnam and getpwuid are thread-unsafe and potentially dangerous
in multi-threaded code. Substitue all their occurrences in
multi-threaded code with getpwnam_r and getpwuid_r, which are
thread-safe.
---

diff --git a/cups/auth.c b/cups/auth.c
index 177eec8ce3..dd6bd63f0a 100644
--- a/cups/auth.c
+++ b/cups/auth.c
@@ -1087,12 +1087,14 @@ cups_local_auth(http_t *http)		/* I - HTTP connection to server */
     * Verify that the current cupsUser() matches the current UID...
     */
 
-    struct passwd	*pwd;		/* Password information */
+    struct passwd	pwd;		/* Password information */
+    struct passwd	*result;	/* Auxiliary pointer */
     const char		*username;	/* Current username */
 
     username = cupsUser();
 
-    if ((pwd = getpwnam(username)) != NULL && pwd->pw_uid == getuid())
+    getpwnam_r(username, &pwd, cg->pw_buf, PW_BUF_SIZE, &result);
+    if (result && pwd.pw_uid == getuid())
     {
       httpSetAuthString(http, "PeerCred", username);
 
diff --git a/cups/cups-private.h b/cups/cups-private.h
index cf2559d958..06ad2c3bca 100644
--- a/cups/cups-private.h
+++ b/cups/cups-private.h
@@ -85,6 +85,11 @@ typedef struct _cups_globals_s		/**** CUPS global state data ****/
 			*cups_statedir,	/* CUPS_STATEDIR environment var */
 			*home,		/* HOME environment var */
 			*localedir;	/* LOCALDIR environment var */
+#ifndef _WIN32
+#define PW_BUF_SIZE 16384		/* As per glibc manual page */
+  char			pw_buf[PW_BUF_SIZE];
+					/* Big buffer for struct passwd buffers */
+#endif
 
   /* adminutil.c */
   time_t		cupsd_update;	/* Last time we got or set cupsd.conf */
diff --git a/cups/globals.c b/cups/globals.c
index a25902562a..3105f13baf 100644
--- a/cups/globals.c
+++ b/cups/globals.c
@@ -325,10 +325,12 @@ cups_globals_alloc(void)
 
   if (!cg->home)
   {
-    struct passwd	*pw;		/* User info */
+    struct passwd	pw;		/* User info */
+    struct passwd	*result;	/* Auxiliary pointer */
 
-    if ((pw = getpwuid(getuid())) != NULL)
-      cg->home = _cupsStrAlloc(pw->pw_dir);
+    getpwuid_r(getuid(), &pw, cg->pw_buf, PW_BUF_SIZE, &result);
+    if (result)
+      cg->home = _cupsStrAlloc(pw.pw_dir);
   }
 #endif /* _WIN32 */
 
diff --git a/cups/usersys.c b/cups/usersys.c
index a9386e7f10..5e19c0ca6a 100644
--- a/cups/usersys.c
+++ b/cups/usersys.c
@@ -1256,9 +1256,10 @@ cups_finalize_client_conf(
     * Try the USER environment variable as the default username...
     */
 
-    const char *envuser = getenv("USER");
-					/* Default username */
-    struct passwd *pw = NULL;		/* Account information */
+    const char *envuser = getenv("USER");	/* Default username */
+    struct passwd pw;				/* Account information */
+    struct passwd *result = NULL;		/* Auxiliary pointer */
+    _cups_globals_t *cg = _cupsGlobals();	/* Pointer to library globals */
 
     if (envuser)
     {
@@ -1267,16 +1268,16 @@ cups_finalize_client_conf(
       * override things...  This makes sure that printing after doing su
       * or sudo records the correct username.
       */
-
-      if ((pw = getpwnam(envuser)) != NULL && pw->pw_uid != getuid())
-	pw = NULL;
+      getpwnam_r(envuser, &pw, cg->pw_buf, PW_BUF_SIZE, &result);
+      if (result && pw.pw_uid != getuid())
+        result = NULL;
     }
 
-    if (!pw)
-      pw = getpwuid(getuid());
+    if (!result)
+      getpwuid_r(getuid(), &pw, cg->pw_buf, PW_BUF_SIZE, &result);
 
-    if (pw)
-      strlcpy(cc->user, pw->pw_name, sizeof(cc->user));
+    if (result)
+      strlcpy(cc->user, pw.pw_name, sizeof(cc->user));
     else
 #endif /* _WIN32 */
     {