package/ghostscript: add upstream security patch for CVE-2021-3781

The file access protection built into Ghostscript proved insufficient for
the "%pipe%" PostScript device, when combined with Ghostscript's requirement
to be able to create and control temporary files in the conventional
temporary file directories (for example, "/tmp" or "/temp).  This exploit is
restricted to Unix-like systems (i.e., it doesn't affect Windows).  The most
severe claimed results are only feasible if the exploit is run as a "high
privilege" user (root/superuser level) \u2013 a practice we would discourage
under any circumstances.

For more details, see the advisory:
https://ghostscript.com/CVE-2021-3781.html

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
(cherry picked from commit 4e415b4164551e712643e9608d8813cc749fd279)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/ghostscript/0002-Bug-704342-Include-device-specifier-strings-in-acces.patch

@@ -0,0 +1,234 @@
+From a9bd3dec9fde03327a4a2c69dad1036bf9632e20 Mon Sep 17 00:00:00 2001
+From: Chris Liddell <chris.liddell@artifex.com>
+Date: Tue, 7 Sep 2021 20:36:12 +0100
+Subject: [PATCH] Bug 704342: Include device specifier strings in access
+ validation
+
+for the "%pipe%", %handle%" and %printer% io devices.
+
+We previously validated only the part after the "%pipe%" Postscript device
+specifier, but this proved insufficient.
+
+This rebuilds the original file name string, and validates it complete. The
+slight complication for "%pipe%" is it can be reached implicitly using
+"|" so we have to check both prefixes.
+
+Addresses CVE-2021-3781
+
+Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
+---
+ base/gdevpipe.c | 22 +++++++++++++++-
+ base/gp_mshdl.c | 11 +++++++-
+ base/gp_msprn.c | 10 ++++++-
+ base/gp_os2pr.c | 13 +++++++++-
+ base/gslibctx.c | 69 ++++++++++---------------------------------------
+ 5 files changed, 65 insertions(+), 60 deletions(-)
+
+diff --git a/base/gdevpipe.c b/base/gdevpipe.c
+index 96d71f5d8..5bdc485be 100644
+--- a/base/gdevpipe.c
++++ b/base/gdevpipe.c
+@@ -72,8 +72,28 @@ pipe_fopen(gx_io_device * iodev, const char *fname, const char *access,
+ #else
+     gs_lib_ctx_t *ctx = mem->gs_lib_ctx;
+     gs_fs_list_t *fs = ctx->core->fs;
++    /* The pipe device can be reached in two ways, explicltly with %pipe%
++       or implicitly with "|", so we have to check for both
++     */
++    char f[gp_file_name_sizeof];
++    const char *pipestr = "|";
++    const size_t pipestrlen = strlen(pipestr);
++    const size_t preflen = strlen(iodev->dname);
++    const size_t nlen = strlen(fname);
++    int code1;
++
++    if (preflen + nlen >= gp_file_name_sizeof)
++        return_error(gs_error_invalidaccess);
++
++    memcpy(f, iodev->dname, preflen);
++    memcpy(f + preflen, fname, nlen + 1);
++
++    code1 = gp_validate_path(mem, f, access);
++
++    memcpy(f, pipestr, pipestrlen);
++    memcpy(f + pipestrlen, fname, nlen + 1);
+ 
+-    if (gp_validate_path(mem, fname, access) != 0)
++    if (code1 != 0 && gp_validate_path(mem, f, access) != 0 )
+         return gs_error_invalidfileaccess;
+ 
+     /*
+diff --git a/base/gp_mshdl.c b/base/gp_mshdl.c
+index 2b964ed74..8d87ceadc 100644
+--- a/base/gp_mshdl.c
++++ b/base/gp_mshdl.c
+@@ -95,8 +95,17 @@ mswin_handle_fopen(gx_io_device * iodev, const char *fname, const char *access,
+     long hfile;	/* Correct for Win32, may be wrong for Win64 */
+     gs_lib_ctx_t *ctx = mem->gs_lib_ctx;
+     gs_fs_list_t *fs = ctx->core->fs;
++    char f[gp_file_name_sizeof];
++    const size_t preflen = strlen(iodev->dname);
++    const size_t nlen = strlen(fname);
+ 
+-    if (gp_validate_path(mem, fname, access) != 0)
++    if (preflen + nlen >= gp_file_name_sizeof)
++        return_error(gs_error_invalidaccess);
++
++    memcpy(f, iodev->dname, preflen);
++    memcpy(f + preflen, fname, nlen + 1);
++
++    if (gp_validate_path(mem, f, access) != 0)
+         return gs_error_invalidfileaccess;
+ 
+     /* First we try the open_handle method. */
+diff --git a/base/gp_msprn.c b/base/gp_msprn.c
+index ed4827968..746a974f7 100644
+--- a/base/gp_msprn.c
++++ b/base/gp_msprn.c
+@@ -168,8 +168,16 @@ mswin_printer_fopen(gx_io_device * iodev, const char *fname, const char *access,
+     uintptr_t *ptid = &((tid_t *)(iodev->state))->tid;
+     gs_lib_ctx_t *ctx = mem->gs_lib_ctx;
+     gs_fs_list_t *fs = ctx->core->fs;
++    const size_t preflen = strlen(iodev->dname);
++    const size_t nlen = strlen(fname);
+ 
+-    if (gp_validate_path(mem, fname, access) != 0)
++    if (preflen + nlen >= gp_file_name_sizeof)
++        return_error(gs_error_invalidaccess);
++
++    memcpy(pname, iodev->dname, preflen);
++    memcpy(pname + preflen, fname, nlen + 1);
++
++    if (gp_validate_path(mem, pname, access) != 0)
+         return gs_error_invalidfileaccess;
+ 
+     /* First we try the open_printer method. */
+diff --git a/base/gp_os2pr.c b/base/gp_os2pr.c
+index f852c71fc..ba54cde66 100644
+--- a/base/gp_os2pr.c
++++ b/base/gp_os2pr.c
+@@ -107,9 +107,20 @@ os2_printer_fopen(gx_io_device * iodev, const char *fname, const char *access,
+            FILE ** pfile, char *rfname, uint rnamelen)
+ {
+     os2_printer_t *pr = (os2_printer_t *)iodev->state;
+-    char driver_name[256];
++    char driver_name[gp_file_name_sizeof];
+     gs_lib_ctx_t *ctx = mem->gs_lib_ctx;
+     gs_fs_list_t *fs = ctx->core->fs;
++    const size_t preflen = strlen(iodev->dname);
++    const int size_t = strlen(fname);
++
++    if (preflen + nlen >= gp_file_name_sizeof)
++        return_error(gs_error_invalidaccess);
++
++    memcpy(driver_name, iodev->dname, preflen);
++    memcpy(driver_name + preflen, fname, nlen + 1);
++
++    if (gp_validate_path(mem, driver_name, access) != 0)
++        return gs_error_invalidfileaccess;
+ 
+     /* First we try the open_printer method. */
+     /* Note that the loop condition here ensures we don't
+diff --git a/base/gslibctx.c b/base/gslibctx.c
+index 6dfed6cd5..318039fad 100644
+--- a/base/gslibctx.c
++++ b/base/gslibctx.c
+@@ -655,82 +655,39 @@ rewrite_percent_specifiers(char *s)
+ int
+ gs_add_outputfile_control_path(gs_memory_t *mem, const char *fname)
+ {
+-    char *fp, f[gp_file_name_sizeof];
+-    const int pipe = 124; /* ASCII code for '|' */
+-    const int len = strlen(fname);
+-    int i, code;
++    char f[gp_file_name_sizeof];
++    int code;
+ 
+     /* Be sure the string copy will fit */
+-    if (len >= gp_file_name_sizeof)
++    if (strlen(fname) >= gp_file_name_sizeof)
+         return gs_error_rangecheck;
+     strcpy(f, fname);
+-    fp = f;
+     /* Try to rewrite any %d (or similar) in the string */
+     rewrite_percent_specifiers(f);
+-    for (i = 0; i < len; i++) {
+-        if (f[i] == pipe) {
+-           fp = &f[i + 1];
+-           /* Because we potentially have to check file permissions at two levels
+-              for the output file (gx_device_open_output_file and the low level
+-              fopen API, if we're using a pipe, we have to add both the full string,
+-              (including the '|', and just the command to which we pipe - since at
+-              the pipe_fopen(), the leading '|' has been stripped.
+-            */
+-           code = gs_add_control_path(mem, gs_permit_file_writing, f);
+-           if (code < 0)
+-               return code;
+-           code = gs_add_control_path(mem, gs_permit_file_control, f);
+-           if (code < 0)
+-               return code;
+-           break;
+-        }
+-        if (!IS_WHITESPACE(f[i]))
+-            break;
+-    }
+-    code = gs_add_control_path(mem, gs_permit_file_control, fp);
++
++    code = gs_add_control_path(mem, gs_permit_file_control, f);
+     if (code < 0)
+         return code;
+-    return gs_add_control_path(mem, gs_permit_file_writing, fp);
++    return gs_add_control_path(mem, gs_permit_file_writing, f);
+ }
+ 
+ int
+ gs_remove_outputfile_control_path(gs_memory_t *mem, const char *fname)
+ {
+-    char *fp, f[gp_file_name_sizeof];
+-    const int pipe = 124; /* ASCII code for '|' */
+-    const int len = strlen(fname);
+-    int i, code;
++    char f[gp_file_name_sizeof];
++    int code;
+ 
+     /* Be sure the string copy will fit */
+-    if (len >= gp_file_name_sizeof)
++    if (strlen(fname) >= gp_file_name_sizeof)
+         return gs_error_rangecheck;
+     strcpy(f, fname);
+-    fp = f;
+     /* Try to rewrite any %d (or similar) in the string */
+-    for (i = 0; i < len; i++) {
+-        if (f[i] == pipe) {
+-           fp = &f[i + 1];
+-           /* Because we potentially have to check file permissions at two levels
+-              for the output file (gx_device_open_output_file and the low level
+-              fopen API, if we're using a pipe, we have to add both the full string,
+-              (including the '|', and just the command to which we pipe - since at
+-              the pipe_fopen(), the leading '|' has been stripped.
+-            */
+-           code = gs_remove_control_path(mem, gs_permit_file_writing, f);
+-           if (code < 0)
+-               return code;
+-           code = gs_remove_control_path(mem, gs_permit_file_control, f);
+-           if (code < 0)
+-               return code;
+-           break;
+-        }
+-        if (!IS_WHITESPACE(f[i]))
+-            break;
+-    }
+-    code = gs_remove_control_path(mem, gs_permit_file_control, fp);
++    rewrite_percent_specifiers(f);
++
++    code = gs_remove_control_path(mem, gs_permit_file_control, f);
+     if (code < 0)
+         return code;
+-    return gs_remove_control_path(mem, gs_permit_file_writing, fp);
++    return gs_remove_control_path(mem, gs_permit_file_writing, f);
+ }
+ 
+ int
+-- 
+2.20.1
+

package/ghostscript/ghostscript.mk

@@ -21,6 +21,9 @@ GHOSTSCRIPT_DEPENDENCIES = \
 	libpng \
 	tiff
 
+# 0002-Bug-704342-Include-device-specifier-strings-in-acces.patch
+GHOSTSCRIPT_IGNORE_CVES += CVE-2021-3781
+
 # Ghostscript includes (old) copies of several libraries, delete them.
 # Inspired by linuxfromscratch:
 # http://www.linuxfromscratch.org/blfs/view/svn/pst/gs.html