Add a function for parsing RFC 5280's "TBSCertificate".

net/data/parse_certificate_unittest/tbs_negative_serial_number.pem

Index: net/data/parse_certificate_unittest/tbs_negative_serial_number.pem
diff --git a/net/data/parse_certificate_unittest/tbs_negative_serial_number.pem b/net/data/parse_certificate_unittest/tbs_negative_serial_number.pem
new file mode 100644
index 0000000000000000000000000000000000000000..143394065a5e00c19f30b920b3dfdc6009624e27
--- /dev/null
+++ b/net/data/parse_certificate_unittest/tbs_negative_serial_number.pem
@@ -0,0 +1,81 @@
+This is a valid TBSCertificate. However the Serial Number is negative (which
+strictly speaking is not correct).
+
+
+
+-----BEGIN TBS CERTIFICATE-----
+MCigAwIBAgIIiR6QqQAANUAwAwQBATADBAEFMAMEAQgwAwQBCjADBAHz
+-----END TBS CERTIFICATE-----
+
+$ openssl asn1parse -i < [TBS CERTIFICATE]
+    0:d=0  hl=2 l=  40 cons: SEQUENCE          
+    2:d=1  hl=2 l=   3 cons:  cont [ 0 ]        
+    4:d=2  hl=2 l=   1 prim:   INTEGER           :02
+    7:d=1  hl=2 l=   8 prim:  INTEGER           :-76E16F56FFFFCAC0
+   17:d=1  hl=2 l=   3 cons:  SEQUENCE          
+   19:d=2  hl=2 l=   1 prim:   OCTET STRING      [HEX DUMP]:01
+   22:d=1  hl=2 l=   3 cons:  SEQUENCE          
+   24:d=2  hl=2 l=   1 prim:   OCTET STRING      [HEX DUMP]:05
+   27:d=1  hl=2 l=   3 cons:  SEQUENCE          
+   29:d=2  hl=2 l=   1 prim:   OCTET STRING      [HEX DUMP]:08
+   32:d=1  hl=2 l=   3 cons:  SEQUENCE          
+   34:d=2  hl=2 l=   1 prim:   OCTET STRING      :
+
+   37:d=1  hl=2 l=   3 cons:  SEQUENCE          
+   39:d=2  hl=2 l=   1 prim:   OCTET STRING      [HEX DUMP]:F3
+
+
+
+-----BEGIN SERIAL NUMBER-----
+iR6QqQAANUA=
+-----END SERIAL NUMBER-----
+
+
+
+-----BEGIN SIGNATURE ALGORITHM-----
+MAMEAQE=
+-----END SIGNATURE ALGORITHM-----
+
+$ openssl asn1parse -i < [SIGNATURE ALGORITHM]
+    0:d=0  hl=2 l=   3 cons: SEQUENCE          
+    2:d=1  hl=2 l=   1 prim:  OCTET STRING      [HEX DUMP]:01
+
+
+
+-----BEGIN ISSUER-----
+MAMEAQU=
+-----END ISSUER-----
+
+$ openssl asn1parse -i < [ISSUER]
+    0:d=0  hl=2 l=   3 cons: SEQUENCE          
+    2:d=1  hl=2 l=   1 prim:  OCTET STRING      [HEX DUMP]:05
+
+
+
+-----BEGIN VALIDITY-----
+MAMEAQg=
+-----END VALIDITY-----
+
+$ openssl asn1parse -i < [VALIDITY]
+    0:d=0  hl=2 l=   3 cons: SEQUENCE          
+    2:d=1  hl=2 l=   1 prim:  OCTET STRING      [HEX DUMP]:08
+
+
+
+-----BEGIN SUBJECT-----
+MAMEAQo=
+-----END SUBJECT-----
+
+$ openssl asn1parse -i < [SUBJECT]
+    0:d=0  hl=2 l=   3 cons: SEQUENCE          
+    2:d=1  hl=2 l=   1 prim:  OCTET STRING      :
+
+
+
+-----BEGIN SPKI-----
+MAMEAfM=
+-----END SPKI-----
+
+$ openssl asn1parse -i < [SPKI]
+    0:d=0  hl=2 l=   3 cons: SEQUENCE          
+    2:d=1  hl=2 l=   1 prim:  OCTET STRING      [HEX DUMP]:F3