How AESCBC128/258 works in TLS1.0 - ssl

Question

I am learning TLS protocol 1.0/1.1/1.2 recently. I notice AESCBC128/256 can be used for TLS 1.0 although it is not mentioned in the initial TLS1.0 RFC. I am wonderring how the AESCBC IV/salt is exchanged between client and server? Is it the same as TLS 1.2 that always exchange IV within the application data (the first 16 bytes of the data)? If any official materials describe this would be grateful.

Answer 1

TLS_RSA_WITH_AES_128_CBC_SHA is mandatory to implement in TLS 1.2 (see RFC 5246).
Section §6.2.3.2 explains how CBC works:
For block ciphers (such as 3DES or AES), the encryption and MAC
functions convert TLSCompressed.fragment structures to and from block
TLSCiphertext.fragment structures.
struct {
opaque IV[SecurityParameters.record_iv_length];
block-ciphered struct {
opaque content[TLSCompressed.length];
opaque MAC[SecurityParameters.mac_length];
uint8 padding[GenericBlockCipher.padding_length];
uint8 padding_length;
};
} GenericBlockCipher;
The MAC is generated as described in Section 6.2.3.1.
AES ciphersuites were introduced by RFC 3268 in June 2002, hence for TLS prior to 1.2. Note in particular this:
Cipher Usage
The new ciphersuites proposed here are very similar to the following,
defined in [TLS]:
TLS_RSA_WITH_3DES_EDE_CBC_SHA
TLS_DH_DSS_WITH_3DES_EDE_CBC_SHA
TLS_DH_RSA_WITH_3DES_EDE_CBC_SHA
TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA
TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA
TLS_DH_anon_WITH_3DES_EDE_CBC_SHA
All the ciphersuites described here use the AES in cipher block
chaining (CBC) mode. Furthermore, they use SHA-1 [SHA-1] in an HMAC
construction as described in section 5 of [TLS]. (Although the TLS
ciphersuite names include the text "SHA", this actually refers to the
modified SHA-1 version of the algorithm.)
If you now look at section §6.2.3.2 of RFC 2246 (TLS 1.0 and hence also 1.1) you can read this:
Note: With block ciphers in CBC mode (Cipher Block Chaining) the
initialization vector (IV) for the first record is generated with
the other keys and secrets when the security parameters are set.
The IV for subsequent records is the last ciphertext block from
the previous record.
The glossary also says:
cipher block chaining (CBC)
CBC is a mode in which every plaintext block encrypted with a
block cipher is first exclusive-ORed with the previous ciphertext
block (or, in the case of the first block, with the
initialization vector). For decryption, every block is first
decrypted, then exclusive-ORed with the previous ciphertext block
(or IV).