IAM AWS S3 to restrict to a specific sub-folder

Here's a policy that will work for you:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "s3:ListAllMyBuckets"
            ],
            "Resource": [
                "*"
            ]
        },
        {
            "Effect": "Allow",
            "Action": [
                "s3:PutObject",
                "s3:GetObject"
            ],
            "Resource": [
                "arn:aws:s3:::mybucket/toto3/*"
            ]
        },
        {
            "Sid": "Stmt1457617230000",
            "Effect": "Allow",
            "Action": [
                "s3:ListBucket"
            ],
            "Condition": {
                "StringLike": {
                    "s3:prefix": [
                        "",
                        "toto3/"
                    ]
                }
            },
            "Resource": [
                "arn:aws:s3:::mybucket*"
            ]
        }
    ]
}

Details:

• ListAllMyBuckets is required by the Console. It shows a list of all buckets.
• Any action permitted within the toto3/ path.
• ListBucket (retrieve objects list) permitted in the root of the bucket and in the toto3/ path.

I successfully tested this solution.

AWS Documentation Reference: Allow Users to Access a Personal "Home Directory" in Amazon S3

I edit your code to have the following and it works ! THanks !!

 {
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": "s3:*",
            "Resource": [
                "arn:aws:s3:::mybucket/toto3/*"
            ]
        },
        {
            "Effect": "Allow",
            "Action": [
                "s3:ListAllMyBuckets",
                "s3:GetBucketLocation"
            ],
            "Resource": "arn:aws:s3:::*"
        },
        {
            "Effect": "Allow",
            "Action": "s3:ListBucket",
            "Resource": "arn:aws:s3:::mybucket",
            "Condition": {
                "StringLike": {
                    "s3:prefix": [
                        "",
                        "toto3/",
                        "toto3*"
                    ]
                }
            }
        }
    ]
}