From mboxrd@z Thu Jan 1 00:00:00 1970 From: Miloslav =?UTF-8?Q?Trma=C4=8D?= Subject: [PATCH 1/2] audit: fix NUL handling in untrusted strings Date: Thu, 11 Sep 2008 00:23:38 +0200 Message-ID: <1221085418.2705.19.camel@amilo> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-audit-bounces@redhat.com Errors-To: linux-audit-bounces@redhat.com To: viro@zeniv.linux.org.uk, Eric Paris Cc: linux-audit , linux-kernel List-Id: linux-audit@redhat.com From: Miloslav Trmac audit_string_contains_control() stops checking at the first NUL byte. If audit_string_contains_control() returns FALSE, audit_log_n_untrustedstring() submits the complete string - including the NUL byte and all following bytes, up to the specified maximum length - to audit_log_n_string(), which copies the data unchanged into the audit record. The audit record can thus contain a NUL byte (and some unchecked data after that). Because the user-space audit daemon treats audit records as NUL-terminated strings, an untrusted string that is shorter than the specified maximum length effectively terminates the audit record. This patch modifies audit_log_n_untrustedstring() to only log the data before the first NUL byte, if any. Signed-off-by: Miloslav Trmac --- kernel/audit.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) diff --git a/kernel/audit.c b/kernel/audit.c index 4414e93..03b6397 100644 --- a/kernel/audit.c +++ b/kernel/audit.c @@ -1362,6 +1362,12 @@ void audit_log_n_string(struct audit_buffer *ab, const char *string, skb_put(skb, slen + 2); /* don't include null terminator */ } +static inline int +audit_is_control_character(unsigned char c) +{ + return c == '"' || c < 0x21 || c > 0x7E; +} + /** * audit_string_contains_control - does a string need to be logged in hex * @string: string to be checked @@ -1371,7 +1377,7 @@ int audit_string_contains_control(const char *string, size_t len) { const unsigned char *p; for (p = string; p < (const unsigned char *)string + len && *p; p++) { - if (*p == '"' || *p < 0x21 || *p > 0x7e) + if (audit_is_control_character(*p)) return 1; } return 0; @@ -1394,10 +1400,15 @@ int audit_string_contains_control(const char *string, size_t len) void audit_log_n_untrustedstring(struct audit_buffer *ab, const char *string, size_t len) { - if (audit_string_contains_control(string, len)) - audit_log_n_hex(ab, string, len); - else - audit_log_n_string(ab, string, len); + const unsigned char *p; + + for (p = string; p < (const unsigned char *)string + len && *p; p++) { + if (audit_is_control_character(*p)) { + audit_log_n_hex(ab, string, len); + return; + } + } + audit_log_n_string(ab, string, p - (const unsigned char *)string); } /**