ftpd: new option -a ANON_USER to allow anonymous logins

Anonymous ftpd login is useful even when ftpd authentication feature
is enabled. Anonymous logins provide simple password-less connection
for FTP clients.

To allow password-less connection user command line option '-a USER' is
added. This option specifies the system user to use when
'anonymous' username is given in USER command. No password is required
in this case.

function                                             old     new   delta
ftpd_main                                           2164    2232     +68
packed_usage                                       31015   31046     +31
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 99/0)               Total: 99 bytes

Signed-off-by: Andrey Mozzhuhin <amozzhuhin@yandex.ru>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 29 insertions, 11 deletions

diff --git a/networking/ftpd.c b/networking/ftpd.c
index a4626c0b5..104d414de 100644
--- a/networking/ftpd.c
+++ b/networking/ftpd.c
@@ -47,20 +47,26 @@
 //kbuild:lib-$(CONFIG_FTPD) += ftpd.o
 
 //usage:#define ftpd_trivial_usage
-//usage:       "[-wvS] [-t N] [-T N] [DIR]"
+//usage:       "[-wvS]"IF_FEATURE_FTPD_AUTHENTICATION(" [-a USER]")" [-t N] [-T N] [DIR]"
 //usage:#define ftpd_full_usage "\n\n"
-//usage:       "Anonymous FTP server\n"
-//usage:       "\n"
-//usage:       "ftpd should be used as an inetd service.\n"
-//usage:       "ftpd's line for inetd.conf:\n"
+//usage:        IF_NOT_FEATURE_FTPD_AUTHENTICATION(
+//usage:       "Anonymous FTP server. Accesses by clients occur under ftpd's UID.\n"
+//usage:        )
+//usage:        IF_FEATURE_FTPD_AUTHENTICATION(
+//usage:       "FTP server. "
+//usage:        )
+//usage:       "Chroots to DIR, if this fails (run by non-root), cds to it.\n"
+//usage:       "Should be used as inetd service, inetd.conf line:\n"
 //usage:       "        21 stream tcp nowait root ftpd ftpd /files/to/serve\n"
-//usage:       "It also can be ran from tcpsvd:\n"
+//usage:       "Can be run from tcpsvd:\n"
 //usage:       "        tcpsvd -vE 0.0.0.0 21 ftpd /files/to/serve\n"
 //usage:     "\n        -w      Allow upload"
 //usage:     "\n        -v      Log errors to stderr. -vv: verbose log"
 //usage:     "\n        -S      Log errors to syslog. -SS: verbose log"
+//usage:        IF_FEATURE_FTPD_AUTHENTICATION(
+//usage:     "\n        -a USER Enable 'anonymous' login and map it to USER"
+//usage:        )
 //usage:     "\n        -t,-T   Idle and absolute timeouts"
-//usage:     "\n        DIR     Change root to this directory"
 
 #include "libbb.h"
 #include "common_bufsiz.h"
@@ -1154,6 +1160,7 @@ int ftpd_main(int argc UNUSED_PARAM, char **argv)
 {
 #if ENABLE_FEATURE_FTPD_AUTHENTICATION
         struct passwd *pw = NULL;
+        char *anon_opt = NULL;
 #endif
         unsigned abs_timeout;
         unsigned verbose_S;
@@ -1166,12 +1173,18 @@ int ftpd_main(int argc UNUSED_PARAM, char **argv)
         G.timeout = 2 * 60;
         opt_complementary = "vv:SS";
 #if BB_MMU
-        opts = getopt32(argv,    "vS" IF_FEATURE_FTPD_WRITE("w") "t:+T:+", &G.timeout, &abs_timeout, &G.verbose, &verbose_S);
+        opts = getopt32(argv,    "vS"
+                IF_FEATURE_FTPD_WRITE("w") "t:+T:+" IF_FEATURE_FTPD_AUTHENTICATION("a:"),
+                &G.timeout, &abs_timeout, IF_FEATURE_FTPD_AUTHENTICATION(&anon_opt,)
+                &G.verbose, &verbose_S);
 #else
-        opts = getopt32(argv, "l1AvS" IF_FEATURE_FTPD_WRITE("w") "t:+T:+", &G.timeout, &abs_timeout, &G.verbose, &verbose_S);
+        opts = getopt32(argv, "l1AvS"
+                IF_FEATURE_FTPD_WRITE("w") "t:+T:+" IF_FEATURE_FTPD_AUTHENTICATION("a:"),
+                &G.timeout, &abs_timeout, IF_FEATURE_FTPD_AUTHENTICATION(&anon_opt,)
+                &G.verbose, &verbose_S);
         if (opts & (OPT_l|OPT_1)) {
                 /* Our secret backdoor to ls */
-/* TODO: pass --group-directories-first? would be nice, but ls doesn't do that yet */
+/* TODO: pass --group-directories-first? */
                 if (fchdir(3) != 0)
                         _exit(127);
                 /* memset(&G, 0, sizeof(G)); - ls_main does it */
@@ -1234,7 +1247,12 @@ int ftpd_main(int argc UNUSED_PARAM, char **argv)
 #if ENABLE_FEATURE_FTPD_AUTHENTICATION
         while (1) {
                 uint32_t cmdval = cmdio_get_cmd_and_arg();
-                        if (cmdval == const_USER) {
+                if (cmdval == const_USER) {
+                        if (anon_opt && strcmp(G.ftp_arg, "anonymous") == 0) {
+                                pw = getpwnam(anon_opt);
+                                if (pw)
+                                        break; /* does not even ask for password */
+                        }
                         pw = getpwnam(G.ftp_arg);
                         cmdio_write_raw(STR(FTP_GIVEPWORD)" Please specify password\r\n");
                 } else if (cmdval == const_PASS) {