cryptpw: support "rounds=NNNNNNN$" thing in salts

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/loginutils/cryptpw.c b/loginutils/cryptpw.c
index 9f5f406..d630231 100644
--- a/loginutils/cryptpw.c
+++ b/loginutils/cryptpw.c
@@ -35,7 +35,7 @@
 //usage:       "[OPTIONS] [PASSWORD] [SALT]"
 /* We do support -s, we just don't mention it */
 //usage:#define cryptpw_full_usage "\n\n"
-//usage:       "Crypt PASSWORD using crypt(3)\n"
+//usage:       "Print crypt(3) hashed PASSWORD\n"
 //usage:	IF_LONG_OPTS(
 //usage:     "\n	-P,--password-fd=N	Read password from fd N"
 /* //usage:  "\n	-s,--stdin		Use stdin; like -P0" */
@@ -92,7 +92,8 @@
 int cryptpw_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int cryptpw_main(int argc UNUSED_PARAM, char **argv)
 {
-	char salt[MAX_PW_SALT_LEN];
+	/* Supports: cryptpw -m sha256 PASS 'rounds=999999999$SALT' */
+	char salt[MAX_PW_SALT_LEN + sizeof("rounds=999999999$")];
 	char *salt_ptr;
 	char *password;
 	const char *opt_m, *opt_S;
@@ -122,6 +123,7 @@
 
 	salt_ptr = crypt_make_pw_salt(salt, opt_m);
 	if (opt_S)
+		/* put user's data after the "$N$" prefix */
 		safe_strncpy(salt_ptr, opt_S, sizeof(salt) - (sizeof("$N$")-1));
 
 	xmove_fd(fd, STDIN_FILENO);
diff --git a/testsuite/cryptpw.tests b/testsuite/cryptpw.tests
new file mode 100755
index 0000000..8ec476c
--- /dev/null
+++ b/testsuite/cryptpw.tests
@@ -0,0 +1,28 @@
+#!/bin/sh
+
+# Copyright 2017 by Denys Vlasenko <vda.linux@googlemail.com>
+# Licensed under GPLv2, see file LICENSE in this source tree.
+
+. ./testing.sh
+
+# testing "description" "command" "result" "infile" "stdin"
+
+optional USE_BB_CRYPT_SHA
+testing "cryptpw sha256" \
+	"cryptpw -m sha256 QWErty '123456789012345678901234567890'" \
+	'$5$1234567890123456$5DxfOCmU4vRhtzfsbdK.6wSGMwwVbac7ZkWwusb8Si7\n' "" ""
+
+testing "cryptpw sha256 rounds=99999" \
+	"cryptpw -m sha256 QWErty 'rounds=99999\$123456789012345678901234567890'" \
+	'$5$rounds=99999$1234567890123456$aYellycJGZM6AKyVzaQsSrDBdTixubtMnM6J.MN0xM8\n' "" ""
+
+testing "cryptpw sha512" \
+	"cryptpw -m sha512 QWErty '123456789012345678901234567890'" \
+	'$6$1234567890123456$KB7QqxFyqmJSWyQYcCuGeFukgz1bPQoipWZf7.9L7z3k8UNTXa6UikbKcUGDc2ANn7DOGmDaroxDgpK16w/RE0\n' "" ""
+
+testing "cryptpw sha512 rounds=99999" \
+	"cryptpw -m sha512 QWErty 'rounds=99999\$123456789012345678901234567890'" \
+	'$6$rounds=99999$1234567890123456$BfF6gD6ZjUmwawH5QaAglYAxtU./yvsz0fcQ464l49aMI2DZW3j5ri28CrxK7riPWNpLuUpfaIdY751SBYKUH.\n' "" ""
+SKIP=
+
+exit $FAILCOUNT