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validate %FILEPATH% when parsing repo dbs

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Currently we make no effort to validate the %FILENAME% field in the
repo db. This allows for relative paths to be considered valid.

A carefully crafted db entry with a malicious relative path,
(e.g. `../../../../etc/passwd`) will cause pacman to to
overwrite _any_ file on the target's machine.

Add the following validation:

- doesn't start with '.'
- doesn't contain a '/'
- won't overflow PATH_MAX

Signed-off-by: Simon Gomizelj <simongmzlj@gmail.com>
Signed-off-by: Allan McRae <allan@archlinux.org>
This commit is contained in:
Simon Gomizelj 2013-05-22 00:43:11 -04:00 committed by Allan McRae
parent fe794ccb25
commit dd62fde53e
1 changed files with 30 additions and 0 deletions
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30
lib/libalpm/be_sync.c
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@ -479,6 +479,33 @@ cleanup:
return count;
}
/* This function validates %FILENAME%. filename must be between 3 and
* PATH_MAX characters and cannot be contain a path */
static int _alpm_validate_filename(alpm_db_t *db, const char *pkgname,
const char *filename)
{
size_t len = strlen(filename);
if(filename[0] == '.') {
errno = EINVAL;
_alpm_log(db->handle, ALPM_LOG_ERROR, _("%s database is inconsistent: filename "
"of package %s is illegal\n"), db->treename, pkgname);
return -1;
} else if(memchr(filename, '/', len) != NULL) {
errno = EINVAL;
_alpm_log(db->handle, ALPM_LOG_ERROR, _("%s database is inconsistent: filename "
"of package %s is illegal\n"), db->treename, pkgname);
return -1;
} else if(len > PATH_MAX) {
errno = EINVAL;
_alpm_log(db->handle, ALPM_LOG_ERROR, _("%s database is inconsistent: filename "
"of package %s is too long\n"), db->treename, pkgname);
return -1;
}
return 0;
}
#define READ_NEXT() do { \
if(_alpm_archive_fgets(archive, &buf) != ARCHIVE_OK) goto error; \
line = buf.line; \
@ -558,6 +585,9 @@ static int sync_db_read(alpm_db_t *db, struct archive *archive,
}
} else if(strcmp(line, "%FILENAME%") == 0) {
READ_AND_STORE(pkg->filename);
if(_alpm_validate_filename(db, pkg->name, pkg->filename) < 0) {
return -1;
}
} else if(strcmp(line, "%DESC%") == 0) {
READ_AND_STORE(pkg->desc);
} else if(strcmp(line, "%GROUPS%") == 0) {