[Forensics-changes] [yara] 289/407: Add arithmetic mean and abs/fabs.
Hilko Bengen
bengen at moszumanska.debian.org
Sat Jul 1 10:28:38 UTC 2017
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bengen pushed a commit to annotated tag v3.3.0
in repository yara.
commit befaa7c7bd0f6e85c85cb414ea13eadee675f70a
Author: Wesley Shields <wxs at atarininja.org>
Date: Wed Dec 31 16:32:24 2014 -0500
Add arithmetic mean and abs/fabs.
---
libyara/modules/math.c | 101 +++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 101 insertions(+)
diff --git a/libyara/modules/math.c b/libyara/modules/math.c
index 2c6dfd7..c67eab9 100644
--- a/libyara/modules/math.c
+++ b/libyara/modules/math.c
@@ -140,10 +140,111 @@ define_function(data_entropy)
}
+define_function(string_arithmetic_mean)
+{
+ int i;
+ double sum = 0.0;
+ SIZED_STRING* s = sized_string_argument(1);
+
+ if (IS_UNDEFINED(s))
+ return_double(UNDEFINED);
+
+ for (i = 0; i < s->length; i++)
+ sum += (double) s->c_string[i];
+
+ return_double(sum / (double) s->length);
+}
+
+
+define_function(data_arithmetic_mean)
+{
+ int i;
+ double sum = 0.0;
+ bool past_first_block = false;
+ uint64_t total_len = 0;
+
+ int64_t offset = integer_argument(1);
+ int64_t length = integer_argument(2);
+
+ if (IS_UNDEFINED(offset) || IS_UNDEFINED(length))
+ return_double(UNDEFINED);
+
+ YR_SCAN_CONTEXT* context = scan_context();
+ YR_MEMORY_BLOCK* block = NULL;
+
+ if (offset < 0 || length < 0 || offset < context->mem_block->base)
+ {
+ return ERROR_WRONG_ARGUMENTS;
+ }
+
+ foreach_memory_block(context, block)
+ {
+ if (offset >= block->base &&
+ offset < block->base + block->size)
+ {
+ uint64_t data_offset = offset - block->base;
+ uint64_t data_len = min(length, block->size - data_offset);
+ total_len += data_len;
+
+ offset += data_len;
+ length -= data_len;
+
+ for (i = 0; i < data_len; i++)
+ sum += (double) *(block->data + data_offset + i);
+
+ past_first_block = true;
+ }
+ else if (past_first_block)
+ {
+ // If offset is not within current block and we already
+ // past the first block then the we are trying to compute
+ // the checksum over a range of non contiguos blocks. As
+ // range contains gaps of undefined data the checksum is
+ // undefined.
+ return_double(UNDEFINED);
+ }
+
+ if (block->base + block->size > offset + length)
+ break;
+ }
+
+ if (!past_first_block)
+ return_double(UNDEFINED);
+
+ return_double(sum / (double) total_len);
+}
+
+
+define_function(absolute_integer)
+{
+ int64_t x = integer_argument(1);
+
+ if (IS_UNDEFINED(x))
+ return_integer(UNDEFINED);
+
+ return_integer(abs(x));
+}
+
+
+define_function(absolute_double)
+{
+ double x = double_argument(1);
+
+ if (IS_UNDEFINED(x))
+ return_double(UNDEFINED);
+
+ return_double(fabs(x));
+}
+
+
begin_declarations;
+ declare_function("arithmetic_mean", "ii", "d", data_arithmetic_mean);
+ declare_function("arithmetic_mean", "s", "d", string_arithmetic_mean);
declare_function("entropy", "ii", "d", data_entropy);
declare_function("entropy", "s", "d", string_entropy);
+ declare_function("abs", "i", "i", absolute_integer);
+ declare_function("fabs", "d", "d", absolute_double);
end_declarations;
--
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