1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193

use {
    log::*,
    solana_sdk::{
        account::{AccountSharedData, ReadableAccount},
        pubkey::Pubkey,
        rent::Rent,
        transaction::{Result, TransactionError},
        transaction_context::TransactionContext,
    },
};

#[derive(Debug, PartialEq)]
pub(crate) enum RentState {
    /// account.lamports == 0
    Uninitialized,
    /// 0 < account.lamports < rent-exempt-minimum
    /// Parameter is the size of the account data
    RentPaying(usize),
    /// account.lamports >= rent-exempt-minimum
    RentExempt,
}

impl RentState {
    pub(crate) fn from_account(account: &AccountSharedData, rent: &Rent) -> Self {
        if account.lamports() == 0 {
            Self::Uninitialized
        } else if !rent.is_exempt(account.lamports(), account.data().len()) {
            Self::RentPaying(account.data().len())
        } else {
            Self::RentExempt
        }
    }

    pub(crate) fn transition_allowed_from(
        &self,
        pre_rent_state: &RentState,
        do_support_realloc: bool,
    ) -> bool {
        if let Self::RentPaying(post_data_size) = self {
            if let Self::RentPaying(pre_data_size) = pre_rent_state {
                if do_support_realloc {
                    post_data_size == pre_data_size // Cannot be RentPaying if resized
                } else {
                    true // RentPaying can continue to be RentPaying
                }
            } else {
                false // Only RentPaying can continue to be RentPaying
            }
        } else {
            true // Post not-RentPaying always ok
        }
    }
}

pub(crate) fn submit_rent_state_metrics(pre_rent_state: &RentState, post_rent_state: &RentState) {
    match (pre_rent_state, post_rent_state) {
        (&RentState::Uninitialized, &RentState::RentPaying(_)) => {
            inc_new_counter_info!("rent_paying_err-new_account", 1);
        }
        (&RentState::RentPaying(_), &RentState::RentPaying(_)) => {
            inc_new_counter_info!("rent_paying_ok-legacy", 1);
        }
        (_, &RentState::RentPaying(_)) => {
            inc_new_counter_info!("rent_paying_err-other", 1);
        }
        _ => {}
    }
}

pub(crate) fn check_rent_state(
    pre_rent_state: Option<&RentState>,
    post_rent_state: Option<&RentState>,
    transaction_context: &TransactionContext,
    index: usize,
    do_support_realloc: bool,
    include_account_index_in_err: bool,
) -> Result<()> {
    if let Some((pre_rent_state, post_rent_state)) = pre_rent_state.zip(post_rent_state) {
        let expect_msg = "account must exist at TransactionContext index if rent-states are Some";
        check_rent_state_with_account(
            pre_rent_state,
            post_rent_state,
            transaction_context
                .get_key_of_account_at_index(index)
                .expect(expect_msg),
            &transaction_context
                .get_account_at_index(index)
                .expect(expect_msg)
                .borrow(),
            do_support_realloc,
            include_account_index_in_err.then(|| index),
        )?;
    }
    Ok(())
}

pub(crate) fn check_rent_state_with_account(
    pre_rent_state: &RentState,
    post_rent_state: &RentState,
    address: &Pubkey,
    account_state: &AccountSharedData,
    do_support_realloc: bool,
    account_index: Option<usize>,
) -> Result<()> {
    submit_rent_state_metrics(pre_rent_state, post_rent_state);
    if !solana_sdk::incinerator::check_id(address)
        && !post_rent_state.transition_allowed_from(pre_rent_state, do_support_realloc)
    {
        debug!(
            "Account {} not rent exempt, state {:?}",
            address, account_state,
        );
        if let Some(account_index) = account_index {
            let account_index = account_index as u8;
            Err(TransactionError::InsufficientFundsForRent { account_index })
        } else {
            Err(TransactionError::InvalidRentPayingAccount)
        }
    } else {
        Ok(())
    }
}

#[cfg(test)]
mod tests {
    use {super::*, solana_sdk::pubkey::Pubkey};

    #[test]
    fn test_from_account() {
        let program_id = Pubkey::new_unique();
        let uninitialized_account = AccountSharedData::new(0, 0, &Pubkey::default());

        let account_data_size = 100;

        let rent = Rent::free();
        let rent_exempt_account = AccountSharedData::new(1, account_data_size, &program_id); // if rent is free, all accounts with non-zero lamports and non-empty data are rent-exempt

        assert_eq!(
            RentState::from_account(&uninitialized_account, &rent),
            RentState::Uninitialized
        );
        assert_eq!(
            RentState::from_account(&rent_exempt_account, &rent),
            RentState::RentExempt
        );

        let rent = Rent::default();
        let rent_minimum_balance = rent.minimum_balance(account_data_size);
        let rent_paying_account = AccountSharedData::new(
            rent_minimum_balance.saturating_sub(1),
            account_data_size,
            &program_id,
        );
        let rent_exempt_account = AccountSharedData::new(
            rent.minimum_balance(account_data_size),
            account_data_size,
            &program_id,
        );

        assert_eq!(
            RentState::from_account(&uninitialized_account, &rent),
            RentState::Uninitialized
        );
        assert_eq!(
            RentState::from_account(&rent_paying_account, &rent),
            RentState::RentPaying(account_data_size)
        );
        assert_eq!(
            RentState::from_account(&rent_exempt_account, &rent),
            RentState::RentExempt
        );
    }

    #[test]
    fn test_transition_allowed_from() {
        let post_rent_state = RentState::Uninitialized;
        assert!(post_rent_state.transition_allowed_from(&RentState::Uninitialized, true));
        assert!(post_rent_state.transition_allowed_from(&RentState::RentExempt, true));
        assert!(post_rent_state.transition_allowed_from(&RentState::RentPaying(0), true));

        let post_rent_state = RentState::RentExempt;
        assert!(post_rent_state.transition_allowed_from(&RentState::Uninitialized, true));
        assert!(post_rent_state.transition_allowed_from(&RentState::RentExempt, true));
        assert!(post_rent_state.transition_allowed_from(&RentState::RentPaying(0), true));

        let post_rent_state = RentState::RentPaying(2);
        assert!(!post_rent_state.transition_allowed_from(&RentState::Uninitialized, true));
        assert!(!post_rent_state.transition_allowed_from(&RentState::RentExempt, true));
        assert!(!post_rent_state.transition_allowed_from(&RentState::RentPaying(3), true));
        assert!(!post_rent_state.transition_allowed_from(&RentState::RentPaying(1), true));
        assert!(post_rent_state.transition_allowed_from(&RentState::RentPaying(2), true));
    }
}