Messages in this thread Patch in this message | | | Subject | [PATCH 1/2] audit: fix NUL handling in untrusted strings | From | Miloslav Trmač <> | Date | Thu, 11 Sep 2008 00:23:38 +0200 |
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From: Miloslav Trmac <mitr@redhat.com>
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 <mitr@redhat.com> --- 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); } /**
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