aws-sigv4: make signature work when post data is binary

User sets the post fields size for binary data.  Hence, we should not be
using strlen on it.

Added test 1937 and 1938 to verify.

Closes #7844

tests/data/Makefile.inc

@@ -215,7 +215,7 @@ test1800 test1801 \
 test1908 test1909 test1910 test1911 test1912 test1913 test1914 test1915 \
 test1916 test1917 test1918 \
 \
-test1933 test1934 test1935 test1936 \
+test1933 test1934 test1935 test1936 test1937 test1938 \
 \
 test2000 test2001 test2002 test2003 test2004 \
 \

tests/data/test1937

@@ -0,0 +1,72 @@
+<testcase>
+<info>
+<keywords>
+HTTP
+HTTP POST
+CURLOPT_AWS_SIGV4
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data nocheck="yes">
+HTTP/1.1 302 OK
+Date: Thu, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Type: text/html
+Content-Length: 0
+Location: /%TESTNUMBER0002
+
+</data>
+<data2>
+HTTP/1.1 200 OK
+Date: Thu, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Content-Type: text/html
+Content-Length: 0
+
+</data2>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+# this relies on the debug feature which allow to set the time
+<features>
+SSL
+debug
+crypto
+</features>
+
+<name>
+HTTP POST with AWS_SIGV4
+</name>
+<tool>
+lib%TESTNUMBER
+</tool>
+
+<command>
+http://%HOSTIP:%HTTPPORT/%TESTNUMBER/testapi/test
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<strip>
+^User-Agent:.*
+^Content-Type:.*
+^Accept:.*
+</strip>
+<protocol nonewline="yes">
+POST /%TESTNUMBER/testapi/test HTTP/1.1
+Host: %HOSTIP:%HTTPPORT
+Authorization: PROVIDER14-HMAC-SHA256 Credential=keyId/19700101/region/service/provider14_request, SignedHeaders=content-type;host;x-provider2-date, Signature=391e410177d0e9ee80728082446ef69d6b29157fe71f8b4805fce7c186fd956d
+X-Provider2-Date: 19700101T000000Z
+Content-Length: 8
+
+postData
+</protocol>
+</verify>
+</testcase>