JSON-RPC-interface.md
1 # JSON-RPC Interface 2 3 The headless daemon `bitcoind` has the JSON-RPC API enabled by default, the GUI 4 `bitcoin-qt` has it disabled by default. This can be changed with the `-server` 5 option. In the GUI it is possible to execute RPC methods in the Debug Console 6 Dialog. 7 8 ## Endpoints 9 10 There are two JSON-RPC endpoints on the server: 11 12 1. `/` 13 2. `/wallet/<walletname>/` 14 15 ### `/` endpoint 16 17 This endpoint is always active. 18 It can always service non-wallet requests and can service wallet requests when 19 exactly one wallet is loaded. 20 21 ### `/wallet/<walletname>/` endpoint 22 23 This endpoint is only activated when the wallet component has been compiled in. 24 It can service both wallet and non-wallet requests. 25 It MUST be used for wallet requests when two or more wallets are loaded. 26 27 This is the endpoint used by bitcoin-cli when a `-rpcwallet=` parameter is passed in. 28 29 Best practice would dictate using the `/wallet/<walletname>/` endpoint for ALL 30 requests when multiple wallets are in use. 31 32 ### Examples 33 34 ```sh 35 # Get block count from the / endpoint when rpcuser=alice and rpcport=38332 36 $ curl --user alice --data-binary '{"jsonrpc": "2.0", "id": "0", "method": "getblockcount", "params": []}' -H 'content-type: application/json' localhost:38332/ 37 38 # Get balance from the /wallet/walletname endpoint when rpcuser=alice, rpcport=38332 and rpcwallet=desc-wallet 39 $ curl --user alice --data-binary '{"jsonrpc": "2.0", "id": "0", "method": "getbalance", "params": []}' -H 'content-type: application/json' localhost:38332/wallet/desc-wallet 40 41 ``` 42 43 ## Parameter passing 44 45 The JSON-RPC server supports both _by-position_ and _by-name_ [parameter 46 structures](https://www.jsonrpc.org/specification#parameter_structures) 47 described in the JSON-RPC specification. For extra convenience, to avoid the 48 need to name every parameter value, all RPC methods accept a named parameter 49 called `args`, which can be set to an array of initial positional values that 50 are combined with named values. 51 52 Examples: 53 54 ```sh 55 # "params": ["mywallet", false, false, "", false, false, true] 56 bitcoin-cli createwallet mywallet false false "" false false true 57 58 # "params": {"wallet_name": "mywallet", "load_on_startup": true} 59 bitcoin-cli -named createwallet wallet_name=mywallet load_on_startup=true 60 61 # "params": {"args": ["mywallet"], "load_on_startup": true} 62 bitcoin-cli -named createwallet mywallet load_on_startup=true 63 ``` 64 65 ## Versioning 66 67 The RPC interface might change from one major version of Bitcoin Core to the 68 next. This makes the RPC interface implicitly versioned on the major version. 69 The version tuple can be retrieved by e.g. the `getnetworkinfo` RPC in 70 `version`. 71 72 Usually deprecated features can be re-enabled during the grace-period of one 73 major version via the `-deprecatedrpc=` command line option. The release notes 74 of a new major release come with detailed instructions on what RPC features 75 were deprecated and how to re-enable them temporarily. 76 77 ## JSON-RPC 1.1 vs 2.0 78 79 The server recognizes [JSON-RPC v2.0](https://www.jsonrpc.org/specification) requests 80 and responds accordingly. A 2.0 request is identified by the presence of 81 `"jsonrpc": "2.0"` in the request body. If that key + value is not present in a request, 82 the legacy JSON-RPC v1.1 protocol is followed instead, which was the only available 83 protocol in v27.0 and prior releases. 84 85 || 1.1 | 2.0 | 86 |-|-|-| 87 | Request marker | `"version": "1.1"` (or none) | `"jsonrpc": "2.0"` | 88 | Response marker | (none) | `"jsonrpc": "2.0"` | 89 | `"error"` and `"result"` fields in response | both present | only one is present | 90 | HTTP codes in response | `200` unless there is any kind of RPC error (invalid parameters, method not found, etc) | Always `200` unless there is an actual HTTP server error (request parsing error, endpoint not found, etc) | 91 | Notifications: requests that get no reply | (not supported) | Supported for requests that exclude the "id" field. Returns HTTP status `204` "No Content" | 92 93 ## Security 94 95 The RPC interface allows other programs to control Bitcoin Core, 96 including the ability to spend funds from your wallets, affect consensus 97 verification, read private data, and otherwise perform operations that 98 can cause loss of money, data, or privacy. This section suggests how 99 you should use and configure Bitcoin Core to reduce the risk that its 100 RPC interface will be abused. 101 102 - **Securing the executable:** Anyone with physical or remote access to 103 the computer, container, or virtual machine running Bitcoin Core can 104 compromise either the whole program or just the RPC interface. This 105 includes being able to record any passphrases you enter for unlocking 106 your encrypted wallets or changing settings so that your Bitcoin Core 107 program tells you that certain transactions have multiple 108 confirmations even when they aren't part of the best block chain. For 109 this reason, you should not use Bitcoin Core for security sensitive 110 operations on systems you do not exclusively control, such as shared 111 computers or virtual private servers. 112 113 - **Securing local network access:** By default, the RPC interface can 114 only be accessed by a client running on the same computer and only 115 after the client provides a valid authentication credential (username 116 and passphrase). Any program on your computer with access to the file 117 system and local network can obtain this level of access. 118 Additionally, other programs on your computer can attempt to provide 119 an RPC interface on the same port as used by Bitcoin Core in order to 120 trick you into revealing your authentication credentials. For this 121 reason, it is important to only use Bitcoin Core for 122 security-sensitive operations on a computer whose other programs you 123 trust. 124 125 - **Securing remote network access:** You may optionally allow other 126 computers to remotely control Bitcoin Core by setting the `rpcallowip` 127 and `rpcbind` configuration parameters. These settings are only meant 128 for enabling connections over secure private networks or connections 129 that have been otherwise secured (e.g. using a VPN or port forwarding 130 with SSH or stunnel). **Do not enable RPC connections over the public 131 Internet.** Although Bitcoin Core's RPC interface does use 132 authentication, it does not use encryption, so your login credentials 133 are sent as clear text that can be read by anyone on your network 134 path. Additionally, the RPC interface has not been hardened to 135 withstand arbitrary Internet traffic, so changing the above settings 136 to expose it to the Internet (even using something like a Tor onion 137 service) could expose you to unconsidered vulnerabilities. See 138 `bitcoind -help` for more information about these settings and other 139 settings described in this document. 140 141 Related, if you use Bitcoin Core inside a Docker container, you may 142 need to expose the RPC port to the host system. The default way to 143 do this in Docker also exposes the port to the public Internet. 144 Instead, expose it only on the host system's localhost, for example: 145 `-p 127.0.0.1:8332:8332` 146 147 - **Secure authentication:** By default, when no `rpcpassword` is specified, Bitcoin Core generates unique 148 login credentials each time it restarts and puts them into a file 149 readable only by the user that started Bitcoin Core, allowing any of 150 that user's RPC clients with read access to the file to login 151 automatically. The file is `.cookie` in the Bitcoin Core 152 configuration directory, and using these credentials is the preferred 153 RPC authentication method. If you need to generate static login 154 credentials for your programs, you can use the script in the 155 `share/rpcauth` directory in the Bitcoin Core source tree. As a final 156 fallback, you can directly use manually-chosen `rpcuser` and 157 `rpcpassword` configuration parameters---but you must ensure that you 158 choose a strong and unique passphrase (and still don't use insecure 159 networks, as mentioned above). 160 161 - **Secure string handling:** The RPC interface does not guarantee any 162 escaping of data beyond what's necessary to encode it as JSON, 163 although it does usually provide serialized data using a hex 164 representation of the bytes. If you use RPC data in your programs or 165 provide its data to other programs, you must ensure any problem strings 166 are properly escaped. For example, the `createwallet` RPC accepts 167 arguments such as `wallet_name` which is a string and could be used 168 for a path traversal attack without application level checks. Multiple 169 websites have been manipulated because they displayed decoded hex strings 170 that included HTML `<script>` tags. For this reason, and others, it is 171 recommended to display all serialized data in hex form only. 172 173 ## RPC consistency guarantees 174 175 State that can be queried via RPCs is guaranteed to be at least up-to-date with 176 the chain state immediately prior to the call's execution. However, the state 177 returned by RPCs that reflect the mempool may not be up-to-date with the 178 current mempool state. 179 180 ### Transaction Pool 181 182 The mempool state returned via an RPC is consistent with itself and with the 183 chain state at the time of the call. Thus, the mempool state only encompasses 184 transactions that are considered mine-able by the node at the time of the RPC. 185 186 The mempool state returned via an RPC reflects all effects of mempool and chain 187 state related RPCs that returned prior to this call. 188 189 ### Wallet 190 191 The wallet state returned via an RPC is consistent with itself and with the 192 chain state at the time of the call. 193 194 Wallet RPCs will return the latest chain state consistent with prior non-wallet 195 RPCs. The effects of all blocks (and transactions in blocks) at the time of the 196 call is reflected in the state of all wallet transactions. For example, if a 197 block contains transactions that conflicted with mempool transactions, the 198 wallet would reflect the removal of these mempool transactions in the state. 199 200 However, the wallet may not be up-to-date with the current state of the mempool 201 or the state of the mempool by an RPC that returned before this RPC. For 202 example, a wallet transaction that was BIP-125-replaced in the mempool prior to 203 this RPC may not yet be reflected as such in this RPC response. 204 205 ## Limitations 206 207 There is a known issue in the JSON-RPC interface that can cause a node to crash if 208 too many http connections are being opened at the same time because the system runs 209 out of available file descriptors. To prevent this from happening you might 210 want to increase the number of maximum allowed file descriptors in your system 211 and try to prevent opening too many connections to your JSON-RPC interface at the 212 same time if this is under your control. It is hard to give general advice 213 since this depends on your system but if you make several hundred requests at 214 once you are definitely at risk of encountering this issue.