printf: protect against bogus format specifiers. Hopefully closes bug 4184

diff --git a/coreutils/printf.c b/coreutils/printf.c
index a14306f..d877e05 100644 (file)
--- a/coreutils/printf.c
+++ b/coreutils/printf.c
@@ -33,7 +33,8 @@
    The 'format' argument is re-used as many times as necessary
    to convert all of the given arguments.
 
-   David MacKenzie <djm@gnu.ai.mit.edu> */
+   David MacKenzie <djm@gnu.ai.mit.edu>
+*/
 
 
 //   19990508 Busy Boxed! Dave Cinege
@@ -251,10 +252,12 @@ static char **print_formatted(char *f, char **argv)
                                ++f;
                                ++direc_length;
                        }
-                       /*
-                       if (!strchr ("diouxXfeEgGcs", *f))
-                       fprintf(stderr, "%%%c: invalid directive", *f);
-                       */
+                       /* needed - try "printf %" without it */
+                       if (!strchr("diouxXfeEgGcs", *f)) {
+                               bb_error_msg("invalid directive '%s'", direc_start);
+                               /* causes main() to exit with error */
+                               return saved_argv - 1;
+                       }
                        ++direc_length;
                        if (*argv) {
                                print_direc(direc_start, direc_length, field_width,
@@ -285,7 +288,8 @@ int printf_main(int argc UNUSED_PARAM, char **argv)
        char **argv2;
 
        /* We must check that stdout is not closed.
-        * The reason for this is highly non-obvious. printf_main is used from shell.
+        * The reason for this is highly non-obvious.
+        * printf_main is used from shell.
         * Shell must correctly handle 'printf "%s" foo'
         * if stdout is closed. With stdio, output gets shoveled into
         * stdout buffer, and even fflush cannot clear it out. It seems that
@@ -298,7 +302,7 @@ int printf_main(int argc UNUSED_PARAM, char **argv)
        /* bash builtin errors out on "printf '-%s-\n' foo",
         * coreutils-6.9 works. Both work with "printf -- '-%s-\n' foo".
         * We will mimic coreutils. */
-       if (argv[1] && argv[1][0] == '-' && argv[1][1] == '-' && argv[1][2] == '\0')
+       if (argv[1] && argv[1][0] == '-' && argv[1][1] == '-' && !argv[1][2])
                argv++;
        if (!argv[1])
                bb_show_usage();
@@ -309,12 +313,12 @@ int printf_main(int argc UNUSED_PARAM, char **argv)
        do {
                argv = argv2;
                argv2 = print_formatted(format, argv);
-       } while (argv2 != argv && *argv2);
+       } while (argv2 > argv && *argv2);
 
        /* coreutils compat (bash doesn't do this):
        if (*argv)
                fprintf(stderr, "excess args ignored");
        */
 
-       return EXIT_SUCCESS;
+       return (argv2 < argv); /* if true, print_formatted errored out */
 }

diff --git a/testsuite/printf.tests b/testsuite/printf.tests
index 18f25e3..d6b60fb 100755 (executable)
--- a/testsuite/printf.tests
+++ b/testsuite/printf.tests
@@ -24,4 +24,10 @@ testing "printf repeatedly use pattern for each argv" \
        "foo\n$HOME\n" \
        "" ""
 
+# Why ()s are necessary I have no idea...
+testing "printf aborts on bare %" \
+       "(${bb}printf '%' a b c) 2>&1; echo \$?" \
+       "printf: invalid directive '%'\n""1\n" \
+       "" ""
+
 exit $FAILCOUNT