CompilerFlags

Differences between revisions 1 and 2
Revision 1 as of 2008-05-02 21:18:34
Size: 1755
Editor: c-76-105-157-155
Comment: initial pass
Revision 2 as of 2008-05-02 21:25:44
Size: 2479
Editor: c-76-105-157-155
Comment: tweaks
Deletions are marked like this. Additions are marked like this.
Line 5: Line 5:
First enabled in Ubuntu 6.10.
See GccSsp for further details.
First enabled in Ubuntu 6.10.  See GccSsp for further details.  Most problems are related to packages that do not use stdlib directly (kernel modules, certain libraries, etc).
Line 8: Line 7:
Failure example: {{{ Failure example:
{{{
Line 12: Line 12:
Disabled with {{{-fno-stack-protector}}} or {{{-nostdlib}}}. Disabled with {{{-fno-stack-protector}}} or {{{-nostdlib}}} in {{{CPPFLAGS}}}.
Line 16: Line 16:
First enabled in Ubuntu 8.10. See [:Security/FortifySource:] for more details. First enabled in Ubuntu 8.10. See [:Security/FortifySource:] for further details.  Most problems are related to common unsafe uses of certain libc functions.
Line 22: Line 22:
  The return value from {{{system()}}} functions should be evaluated and handled appropriately.
Line 26: Line 27:
  When using {{{open()}}} with {{{O_CREAT}}}, best-practice is to define a valid {{{mode}}} argument.
Line 30: Line 32:
 The call to {{{read()}}} was done into a buffer with the wrong size. Double-check the size argument and the buffer size.
Line 31: Line 34:
Reduced checking via {{{-D_FORTIFY_SOURCE=1}}}. Disabled with {{{-U_FORTIFY_SOURCE}}} or {{{-D_FORTIFY_SOURCE=0}}}. Reduced checking via {{{-D_FORTIFY_SOURCE=1}}} in {{{CPPFLAGS}}}. Disabled with {{{-U_FORTIFY_SOURCE}}} or {{{-D_FORTIFY_SOURCE=0}}} in {{{CPPFLAGS}}}.
Line 35: Line 38:
First enabled in Ubuntu 8.10. These options should only cause FTBFS if the package is compiling with {{{-Werror}}}. First enabled in Ubuntu 8.10. These options should only cause build failures if the package is compiling with {{{-Werror}}}.
Line 42: Line 45:
This is caused by code that fails to use {{{"%s"}}} for a {{{*printf}}} function. For example: {{{
printf(buf);
This is caused by code that forgot to use {{{"%s"}}} for a {{{*printf}}} function. For example:
{{{
fprintf(stderr,buf);
Line 45: Line 49:
should be: {{{
printf("%s",buf);
should be:
{{{
fprintf(stderr,"%s",buf);
Line 49: Line 54:
Disabled with {{{-Wno-format-security}}} or {{{-Wformat=0}}}. Disabled with {{{-Wno-format-security}}} or {{{-Wformat=0}}} in {{{CPPFLAGS}}}.
Line 53: Line 58:
First enabled in Ubuntu 8.10. First enabled in Ubuntu 8.10. This option paves the way for using {{{-z now}}} to further harden long-running programs like daemons.

This page documents the Ubuntu-specific default compiler flags in the toolchain. Based on the work from GccSsp, [:Security/HardeningWrapper:], and DistCompiler. Please attempt to fix a source package's problems before disabling a given compiler feature.

-fstack-protector

First enabled in Ubuntu 6.10. See GccSsp for further details. Most problems are related to packages that do not use stdlib directly (kernel modules, certain libraries, etc).

Failure example:

  • '__stack_chk_fail' symbol not found

Disabled with -fno-stack-protector or -nostdlib in CPPFLAGS.

-D_FORTIFY_SOURCE=2

First enabled in Ubuntu 8.10. See [:Security/FortifySource:] for further details. Most problems are related to common unsafe uses of certain libc functions.

Failure examples:

  • error: ignoring return value of 'int system(const char*)', declared with attribute warn_unused_result
    • The return value from system() functions should be evaluated and handled appropriately.

    error: call to '__open_missing_mode' declared with attribute error: open with O_CREAT in second argument needs 3 arguments
    • When using open() with O_CREAT, best-practice is to define a valid mode argument.

    warning: call to ‘__read_chk_warn’ declared with attribute warning: read called with bigger length than size of the destination buffer

    The call to read() was done into a buffer with the wrong size. Double-check the size argument and the buffer size.

Reduced checking via -D_FORTIFY_SOURCE=1 in CPPFLAGS. Disabled with -U_FORTIFY_SOURCE or -D_FORTIFY_SOURCE=0 in CPPFLAGS.

-Wformat -Wformat-security

First enabled in Ubuntu 8.10. These options should only cause build failures if the package is compiling with -Werror.

Failure examples:

  • warning: format not a string literal and no format arguments

This is caused by code that forgot to use "%s" for a *printf function. For example:

  • fprintf(stderr,buf);

should be:

  • fprintf(stderr,"%s",buf);

Disabled with -Wno-format-security or -Wformat=0 in CPPFLAGS.

-Wl,-z,relro

First enabled in Ubuntu 8.10. This option paves the way for using -z now to further harden long-running programs like daemons.

No known failure examples.

Disabled with -Wl,-z,norelro in LDFLAGS.

ToolChain/CompilerFlags (last edited 2021-09-02 05:51:07 by paelzer)