Add some policy controls for VerifySignedData().

net/data/verify_signed_data_unittest/rsa2048-pkcs1-sha512.pem

+This test data was produced by creating a self-signed RSA cert using OpenSSL,
+and then extracting the relevant fields.
+
+It uses RSA PKCS#1 v1.5 with SHA-512 and a 2048-bit key.
+
+(1) Generate self-signed certificate
+
+  openssl genrsa -out rsa_key.pem 2048
+  openssl req -new -key rsa_key.pem -x509 -nodes -days 365 -sha512 -out cert.pem
+
+(2) Extract public key
+
+  openssl x509 -in cert.pem -pubkey -noout > pubkey.pem
+  cat pubkey.pem
+
+(3) Extract signed data (tbsCertificate)
+
+  openssl asn1parse -in cert.pem -out tbs -noout -strparse 4
+  base64 tbs
+
+(4) Extract signature algorithm
+
+  # Find the offset of the signature algorithm near the end (589 in this case)
+  openssl asn1parse -in cert.pem
+
+  openssl asn1parse -in cert.pem -out alg -noout -strparse 589
+  base64 alg
+
+(5) Extract the signature
+
+  # Find the final offset of BIT STRING (506 in this case)
+  openssl asn1parse -in cert.pem
+
+  openssl asn1parse -in cert.pem -out sig -noout -strparse 506
+  base64 sig
+
+
+
+-----BEGIN PUBLIC KEY-----
+MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAzcu2shJRrXFAwMkf30y2AY1zIg9VF/h
+egYcejzdR2AzUb8vU2TXld2i8pp44l+DrvtqmzS7G+yxx3uOx+zsoqBaUT0c9HfkbE+IRmcLkQF
+vYpSpm6Eu8OS14CSmEtiR91Et8LR0+bd0Gn3pgmb+epFJBaBPeDSiI/smqKCs7yP04+tS4Q4r47
+G04LhSp4/hmqH32b4Gcm9nsihHV9FfPfVdxDQUEJp3AgyBPwhPZEAyhoQS73TjjxXHqJRSz37Sl
+ueMVPuNncqbT4nAMKz25J1CtRlQh21uZzfY2QRP3m6rAZquQUos1febC6A7qmhQljWKKmXtfVY+
+fAamstdHrWwIDAQAB
+-----END PUBLIC KEY-----
+
+$ openssl asn1parse -i < [PUBLIC KEY]
+    0:d=0  hl=4 l= 290 cons: SEQUENCE          
+    4:d=1  hl=2 l=  13 cons:  SEQUENCE          
+    6:d=2  hl=2 l=   9 prim:   OBJECT            :rsaEncryption
+   17:d=2  hl=2 l=   0 prim:   NULL              
+   19:d=1  hl=4 l= 271 prim:  BIT STRING        
+
+
+
+-----BEGIN ALGORITHM-----
+MA0GCSqGSIb3DQEBDQUA
+-----END ALGORITHM-----
+
+$ openssl asn1parse -i < [ALGORITHM]
+    0:d=0  hl=2 l=  13 cons: SEQUENCE          
+    2:d=1  hl=2 l=   9 prim:  OBJECT            :sha512WithRSAEncryption
+   13:d=1  hl=2 l=   0 prim:  NULL              
+
+
+
+-----BEGIN DATA-----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+-----END DATA-----
+
+
+
+-----BEGIN SIGNATURE-----
+A4IBAQAhKSNq+X/CfzhtNsMo6MJpTBjJBV5fhHerIZr6e3ozCTBCR29vYsVnJ4/6i5lL1pNeOhM
+ldthnuSlMzTS1Zme1OqRWB3U8QmwCFwhDxW/i4fdT8kxDAmELNp4z0GcXbe27V895PE0R/m8P47
+B6xbra+SQlEMW12K1EndUqrO6vgLbobV14mveWdgc0KIOnDKgsTHV8NTV1w3qtp1ujfvizYfBZu
+yyMOA1yZPDpREZtClro7lufwDQ7+LgSdtNLMDAMzapfIjAEPVNVLmJzMgzaHqMsZM8gP8vWAdfc
+R4mCmWXVotrM6d1rjJGdRADAONYCC4/+d1IMkVGoVfpaej6I
+-----END SIGNATURE-----
+
+$ openssl asn1parse -i < [SIGNATURE]
+    0:d=0  hl=4 l= 257 prim: BIT STRING