| Message ID | 20171230153049.3014-1-aurelien@aurel32.net |
|---|---|
| State | New |
| Headers | show |
| Series | [v4] elf: Check for empty tokens before dynamic string token expansion [BZ #22625] | expand |
On Sat, Dec 30, 2017 at 04:30:49PM +0100, Aurelien Jarno wrote: > The fillin_rpath function in elf/dl-load.c loops over each RPATH or > RUNPATH tokens and interprets empty tokens as the current directory > ("./"). In practice the check for empty token is done *after* the > dynamic string token expansion. The expansion process can return an > empty string for the $ORIGIN token if __libc_enable_secure is set > or if the path of the binary can not be determined (/proc not mounted). > > Fix that by moving the check for empty tokens before the dynamic string > token expansion. In addition, check for NULL pointer or empty strings > return by expand_dynamic_string_token. > > The above changes highlighted a bug in decompose_rpath, an empty array > is represented by the first element being NULL at the fillin_rpath > level, but by using a -1 pointer in decompose_rpath and other functions. > > Changelog: > [BZ #22625] > * elf/dl-load.c (fillin_rpath): Check for empty tokens before dynamic > string token expansion. Check for NULL pointer or empty string possibly > returned by expand_dynamic_string_token. > (decompose_rpath): Check for empty path after dynamic string > token expansion. > --- > ChangeLog | 10 ++++++++++ > NEWS | 4 ++++ > elf/dl-load.c | 49 +++++++++++++++++++++++++++++++++---------------- > 3 files changed, 47 insertions(+), 16 deletions(-) > > diff --git a/ChangeLog b/ChangeLog > index 26e5f96f5d..cd6fc15767 100644 > --- a/ChangeLog > +++ b/ChangeLog > @@ -1,3 +1,13 @@ > +2017-12-30 Aurelien Jarno <aurelien@aurel32.net> > + Dmitry V. Levin <ldv@altlinux.org> > + > + [BZ #22625] > + * elf/dl-load.c (fillin_rpath): Check for empty tokens before dynamic > + string token expansion. Check for NULL pointer or empty string possibly > + returned by expand_dynamic_string_token. > + (decompose_rpath): Check for empty path after dynamic string > + token expansion. > + > 2017-12-29 Dmitry V. Levin <ldv@altlinux.org> > > [BZ #22433] > diff --git a/NEWS b/NEWS > index 95f368340b..1b59e519ab 100644 > --- a/NEWS > +++ b/NEWS > @@ -164,6 +164,10 @@ Security related changes: > CVE-2017-1000366 has been applied, but it is mentioned here only because > of the CVE assignment.) Reported by Qualys. > > + CVE-2017-16997: Incorrect handling of RPATH or RUNPATH containing $ORIGIN > + for AT_SECURE or SUID binaries could be used to load libraries from the > + current directory. > + > The following bugs are resolved with this release: > > [The release manager will add the list generated by > diff --git a/elf/dl-load.c b/elf/dl-load.c > index ae86f0b85e..a0620c2829 100644 > --- a/elf/dl-load.c > +++ b/elf/dl-load.c > @@ -389,31 +389,40 @@ fillin_rpath (char *rpath, struct r_search_path_elem **result, const char *sep, > { > char *cp; > size_t nelems = 0; > - char *to_free; > > while ((cp = __strsep (&rpath, sep)) != NULL) > { > struct r_search_path_elem *dirp; > + char *to_free = NULL; > + size_t len = 0; > > - to_free = cp = expand_dynamic_string_token (l, cp); > + /* `strsep' can pass an empty string. */ > + if (*cp != '\0') > + { > + to_free = cp = expand_dynamic_string_token (l, cp); > > - size_t len = strlen (cp); > + /* expand_dynamic_string_token can return NULL in case of empty > + path or memory allocation failure. */ > + if (cp == NULL) > + continue; > > - /* `strsep' can pass an empty string. This has to be > - interpreted as `use the current directory'. */ > - if (len == 0) > - { > - static const char curwd[] = "./"; > - cp = (char *) curwd; > - } > + /* Compute the length after dynamic string token expansion and > + ignore empty paths. */ > + len = strlen (cp); > + if (len == 0) > + { > + free (to_free); > + continue; > + } > > - /* Remove trailing slashes (except for "/"). */ > - while (len > 1 && cp[len - 1] == '/') > - --len; > + /* Remove trailing slashes (except for "/"). */ > + while (len > 1 && cp[len - 1] == '/') > + --len; > > - /* Now add one if there is none so far. */ > - if (len > 0 && cp[len - 1] != '/') > - cp[len++] = '/'; > + /* Now add one if there is none so far. */ > + if (len > 0 && cp[len - 1] != '/') > + cp[len++] = '/'; > + } > > /* See if this directory is already known. */ > for (dirp = GL(dl_all_dirs); dirp != NULL; dirp = dirp->next) > @@ -569,6 +578,14 @@ decompose_rpath (struct r_search_path_struct *sps, > necessary. */ > free (copy); > > + /* There is no path after expansion. */ > + if (result[0] == NULL) > + { > + free (result); > + sps->dirs = (struct r_search_path_elem **) -1; > + return false; > + } > + > sps->dirs = result; > /* The caller will change this value if we haven't used a real malloc. */ > sps->malloced = 1; This is fine, thanks.
diff --git a/ChangeLog b/ChangeLog index 26e5f96f5d..cd6fc15767 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,13 @@ +2017-12-30 Aurelien Jarno <aurelien@aurel32.net> + Dmitry V. Levin <ldv@altlinux.org> + + [BZ #22625] + * elf/dl-load.c (fillin_rpath): Check for empty tokens before dynamic + string token expansion. Check for NULL pointer or empty string possibly + returned by expand_dynamic_string_token. + (decompose_rpath): Check for empty path after dynamic string + token expansion. + 2017-12-29 Dmitry V. Levin <ldv@altlinux.org> [BZ #22433] diff --git a/NEWS b/NEWS index 95f368340b..1b59e519ab 100644 --- a/NEWS +++ b/NEWS @@ -164,6 +164,10 @@ Security related changes: CVE-2017-1000366 has been applied, but it is mentioned here only because of the CVE assignment.) Reported by Qualys. + CVE-2017-16997: Incorrect handling of RPATH or RUNPATH containing $ORIGIN + for AT_SECURE or SUID binaries could be used to load libraries from the + current directory. + The following bugs are resolved with this release: [The release manager will add the list generated by diff --git a/elf/dl-load.c b/elf/dl-load.c index ae86f0b85e..a0620c2829 100644 --- a/elf/dl-load.c +++ b/elf/dl-load.c @@ -389,31 +389,40 @@ fillin_rpath (char *rpath, struct r_search_path_elem **result, const char *sep, { char *cp; size_t nelems = 0; - char *to_free; while ((cp = __strsep (&rpath, sep)) != NULL) { struct r_search_path_elem *dirp; + char *to_free = NULL; + size_t len = 0; - to_free = cp = expand_dynamic_string_token (l, cp); + /* `strsep' can pass an empty string. */ + if (*cp != '\0') + { + to_free = cp = expand_dynamic_string_token (l, cp); - size_t len = strlen (cp); + /* expand_dynamic_string_token can return NULL in case of empty + path or memory allocation failure. */ + if (cp == NULL) + continue; - /* `strsep' can pass an empty string. This has to be - interpreted as `use the current directory'. */ - if (len == 0) - { - static const char curwd[] = "./"; - cp = (char *) curwd; - } + /* Compute the length after dynamic string token expansion and + ignore empty paths. */ + len = strlen (cp); + if (len == 0) + { + free (to_free); + continue; + } - /* Remove trailing slashes (except for "/"). */ - while (len > 1 && cp[len - 1] == '/') - --len; + /* Remove trailing slashes (except for "/"). */ + while (len > 1 && cp[len - 1] == '/') + --len; - /* Now add one if there is none so far. */ - if (len > 0 && cp[len - 1] != '/') - cp[len++] = '/'; + /* Now add one if there is none so far. */ + if (len > 0 && cp[len - 1] != '/') + cp[len++] = '/'; + } /* See if this directory is already known. */ for (dirp = GL(dl_all_dirs); dirp != NULL; dirp = dirp->next) @@ -569,6 +578,14 @@ decompose_rpath (struct r_search_path_struct *sps, necessary. */ free (copy); + /* There is no path after expansion. */ + if (result[0] == NULL) + { + free (result); + sps->dirs = (struct r_search_path_elem **) -1; + return false; + } + sps->dirs = result; /* The caller will change this value if we haven't used a real malloc. */ sps->malloced = 1;
The fillin_rpath function in elf/dl-load.c loops over each RPATH or RUNPATH tokens and interprets empty tokens as the current directory ("./"). In practice the check for empty token is done *after* the dynamic string token expansion. The expansion process can return an empty string for the $ORIGIN token if __libc_enable_secure is set or if the path of the binary can not be determined (/proc not mounted). Fix that by moving the check for empty tokens before the dynamic string token expansion. In addition, check for NULL pointer or empty strings return by expand_dynamic_string_token. The above changes highlighted a bug in decompose_rpath, an empty array is represented by the first element being NULL at the fillin_rpath level, but by using a -1 pointer in decompose_rpath and other functions. Changelog: [BZ #22625] * elf/dl-load.c (fillin_rpath): Check for empty tokens before dynamic string token expansion. Check for NULL pointer or empty string possibly returned by expand_dynamic_string_token. (decompose_rpath): Check for empty path after dynamic string token expansion. --- ChangeLog | 10 ++++++++++ NEWS | 4 ++++ elf/dl-load.c | 49 +++++++++++++++++++++++++++++++++---------------- 3 files changed, 47 insertions(+), 16 deletions(-)