[Buildroot] [PATCH 1/2] package/pure-ftpd: fix CVE-2019-20176

[Yann E. MORIN]

Fabrice, All,

On 2020-02-29 21:34 +0100, Fabrice Fontaine spake thusly:
> In Pure-FTPd 1.0.49, a stack exhaustion issue was discovered in the
> listdir function in ls.c.
> 
> Signed-off-by: Fabrice Fontaine <fontaine.fabrice at gmail.com>

Series applied to master, thanks.

Regards,
Yann E. MORIN.

> ---
>  ...-to-store-every-file-name-to-display.patch | 70 +++++++++++++++++++
>  package/pure-ftpd/pure-ftpd.mk                |  3 +
>  2 files changed, 73 insertions(+)
>  create mode 100644 package/pure-ftpd/0001-listdir-reuse-a-single-buffer-to-store-every-file-name-to-display.patch
> 
> diff --git a/package/pure-ftpd/0001-listdir-reuse-a-single-buffer-to-store-every-file-name-to-display.patch b/package/pure-ftpd/0001-listdir-reuse-a-single-buffer-to-store-every-file-name-to-display.patch
> new file mode 100644
> index 0000000000..2f791d1d6e
> --- /dev/null
> +++ b/package/pure-ftpd/0001-listdir-reuse-a-single-buffer-to-store-every-file-name-to-display.patch
> @@ -0,0 +1,70 @@
> +From aea56f4bcb9948d456f3fae4d044fd3fa2e19706 Mon Sep 17 00:00:00 2001
> +From: Frank Denis <github at pureftpd.org>
> +Date: Mon, 30 Dec 2019 17:40:04 +0100
> +Subject: [PATCH] listdir(): reuse a single buffer to store every file name to
> + display
> +
> +Allocating a new buffer for each entry is useless.
> +
> +And as these buffers are allocated on the stack, on systems with a
> +small stack size, with many entries, the limit can easily be reached,
> +causing a stack exhaustion and aborting the user session.
> +
> +Reported by Antonio Morales from the GitHub Security Lab team, thanks!
> +[Retrieved from:
> +https://github.com/jedisct1/pure-ftpd/commit/aea56f4bcb9948d456f3fae4d044fd3fa2e19706]
> +Signed-off-by: Fabrice Fontaine <fontaine.fabrice at gmail.com>
> +---
> + src/ls.c | 15 ++++++++-------
> + 1 file changed, 8 insertions(+), 7 deletions(-)
> +
> +diff --git a/src/ls.c b/src/ls.c
> +index cf804c7..f8a588f 100644
> +--- a/src/ls.c
> ++++ b/src/ls.c
> +@@ -661,6 +661,8 @@ static void listdir(unsigned int depth, int f, void * const tls_fd,
> +     char *names;
> +     PureFileInfo *s;
> +     PureFileInfo *r;
> ++    char *alloca_subdir;
> ++    size_t sizeof_subdir;
> +     int d;
> + 
> +     if (depth >= max_ls_depth || matches >= max_ls_files) {
> +@@ -690,14 +692,12 @@ static void listdir(unsigned int depth, int f, void * const tls_fd,
> +     }
> +     outputfiles(f, tls_fd);
> +     r = dir;
> ++    sizeof_subdir = PATH_MAX + 1U;
> ++    if ((alloca_subdir = ALLOCA(sizeof_subdir)) == NULL) {
> ++        goto toomany;
> ++    }
> +     while (opt_R && r != s) {
> +         if (r->name_offset != (size_t) -1 && !chdir(FI_NAME(r))) {
> +-            char *alloca_subdir;
> +-            const size_t sizeof_subdir = PATH_MAX + 1U;
> +-
> +-            if ((alloca_subdir = ALLOCA(sizeof_subdir)) == NULL) {
> +-                goto toomany;
> +-            }
> +             if (SNCHECK(snprintf(alloca_subdir, sizeof_subdir, "%s/%s",
> +                                  name, FI_NAME(r)), sizeof_subdir)) {
> +                 goto nolist;
> +@@ -706,8 +706,8 @@ static void listdir(unsigned int depth, int f, void * const tls_fd,
> +             wrstr(f, tls_fd, alloca_subdir);
> +             wrstr(f, tls_fd, ":\r\n\r\n");
> +             listdir(depth + 1U, f, tls_fd, alloca_subdir);
> ++
> +             nolist:
> +-            ALLOCA_FREE(alloca_subdir);
> +             if (matches >= max_ls_files) {
> +                 goto toomany;
> +             }
> +@@ -720,6 +720,7 @@ static void listdir(unsigned int depth, int f, void * const tls_fd,
> +         r++;
> +     }
> +     toomany:
> ++    ALLOCA_FREE(alloca_subdir);
> +     free(names);
> +     free(dir);
> +     names = NULL;
> diff --git a/package/pure-ftpd/pure-ftpd.mk b/package/pure-ftpd/pure-ftpd.mk
> index 2d69efe3f9..3af66a066c 100644
> --- a/package/pure-ftpd/pure-ftpd.mk
> +++ b/package/pure-ftpd/pure-ftpd.mk
> @@ -11,6 +11,9 @@ PURE_FTPD_LICENSE = ISC
>  PURE_FTPD_LICENSE_FILES = COPYING
>  PURE_FTPD_DEPENDENCIES = $(if $(BR2_PACKAGE_LIBICONV),libiconv)
>  
> +# 0001-listdir-reuse-a-single-buffer-to-store-every-file-name-to-display.patch
> +PURE_FTPD_IGNORE_CVES += CVE-2019-20176
> +
>  PURE_FTPD_CONF_OPTS = \
>  	--with-altlog \
>  	--with-puredb
> -- 
> 2.25.0
> 
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