[KeyVault] Add disclaimers regarding CBC and CBCPAD operations (Azure#22627)

Author: timovv

sdk/keyvault/keyvault-keys/src/cryptographyClient.ts

@@ -258,6 +258,8 @@ export class CryptographyClient {
    * Decrypts the given ciphertext with the specified decryption parameters.
    * Depending on the algorithm used in the decryption parameters, the set of possible decryption parameters will change.
    *
+   * Microsoft recommends you not use CBC without first ensuring the integrity of the ciphertext using, for example, an HMAC. See https://docs.microsoft.com/dotnet/standard/security/vulnerabilities-cbc-mode for more information.
+   *
    * Example usage:
    * ```ts
    * let client = new CryptographyClient(keyVaultKey, credentials);
@@ -279,6 +281,9 @@ export class CryptographyClient {
    * let client = new CryptographyClient(keyVaultKey, credentials);
    * let result = await client.decrypt("RSA1_5", encryptedBuffer);
    * ```
+   *
+   * Microsoft recommends you not use CBC without first ensuring the integrity of the ciphertext using, for example, an HMAC. See https://docs.microsoft.com/dotnet/standard/security/vulnerabilities-cbc-mode for more information.
+   *
    * @param algorithm - The algorithm to use.
    * @param ciphertext - The text to decrypt.
    * @param options - Additional options.

sdk/keyvault/keyvault-keys/src/cryptographyClientModels.ts

@@ -283,6 +283,8 @@ export interface AesCbcEncryptParameters {
   /**
    * The initialization vector used for encryption. If omitted we will attempt to generate an IV using crypto's `randomBytes` functionality.
    * An error will be thrown if creating an IV fails, and you may recover by passing in your own cryptographically secure IV.
+   *
+   * When passing your own IV, make sure you use a cryptographically random, non-repeating IV.
    */
   iv?: Uint8Array;
 }
@@ -347,7 +349,8 @@ export interface AesCbcDecryptParameters {
    * The initialization vector used during encryption.
    */
   /**
-   * The ciphertext to decrypt.
+   * The ciphertext to decrypt. Microsoft recommends you not use CBC without first ensuring the integrity of the ciphertext using an HMAC, for example.
+   * See https://docs.microsoft.com/dotnet/standard/security/vulnerabilities-cbc-mode for more information.
    */
   ciphertext: Uint8Array;
   /**