diff options
Diffstat (limited to 'lib/ssh/doc')
| -rw-r--r-- | lib/ssh/doc/src/ssh_sftp.xml | 106 |
1 files changed, 100 insertions, 6 deletions
diff --git a/lib/ssh/doc/src/ssh_sftp.xml b/lib/ssh/doc/src/ssh_sftp.xml index 251f5a4be3..ab111562f9 100644 --- a/lib/ssh/doc/src/ssh_sftp.xml +++ b/lib/ssh/doc/src/ssh_sftp.xml @@ -196,19 +196,113 @@ </func> <func> - <name>open_tar(ChannelPid, Path) -></name> - <name>open_tar(ChannelPid, Path, Timeout) -> {ok, Handle} | {error, Reason}</name> - <fsummary>Open a tar file on the server to which <v>ChannelPid</v> is connected and return a handle</fsummary> + <name>open_tar(ChannelPid, Path, Mode) -></name> + <name>open_tar(ChannelPid, Path, Mode, Timeout) -> {ok, Handle} | {error, Reason}</name> + <fsummary>Opens a tar file on the server to which <v>ChannelPid</v> is connected and returns a handle</fsummary> <type> <v>ChannelPid = pid()</v> <v>Path = string()</v> + <v>Mode = [read] | [write] | [read,EncryptOpt] | [write,DecryptOpt] </v> + <v>EncryptOpt = {crypto,{InitFun,EncryptFun,CloseFun}}</v> + <v>DecryptOpt = {crypto,{InitFun,DecryptFun}}</v> + <v>InitFun = (fun() -> {ok,CryptoState}) | (fun() -> {ok,CryptoState,ChunkSize}) </v> + <v>CryptoState = any()</v> + <v>ChunkSize = undefined | pos_integer()</v> + <v>EncryptFun = (fun(PlainBin,CryptoState) -> EncryptResult)</v> + <v>EncryptResult = {ok,EncryptedBin,CryptoState} | {ok,EncryptedBin,CryptoState,ChunkSize}</v> + <v>PlainBin = binary()</v> + <v>EncryptedBin = binary()</v> + <v>DecryptFun = (fun(EncryptedBin,CryptoState) -> DecryptResult)</v> + <v>DecryptResult = {ok,PlainBin,CryptoState} | {ok,PlainBin,CryptoState,ChunkSize}</v> + <v>CloseFun = (fun(PlainBin,CryptoState) -> {ok,EncryptedBin})</v> <v>Timeout = timeout()</v> <v>Reason = term()</v> </type> <desc> - <p>Opens a handle to a tar file on the server, the handle - can be used for remote tar manipulation as defined by the - <seealso marker="stdlib:erl_tar#init/3">erl_tar:init/3</seealso> function.</p> + <p>Opens a handle to a tar file on the server associated with <c>ChannelPid</c>. The handle + can be used for remote tar creation and extraction as defined by the + <seealso marker="stdlib:erl_tar#init/3">erl_tar:init/3</seealso> function. + </p> + <p>An example of writing and then reading a tar file:</p> + <code type="none"> + {ok,HandleWrite} = ssh_sftp:open_tar(ChannelPid, ?tar_file_name, [write]), + ok = erl_tar:add(HandleWrite, .... ), + ok = erl_tar:add(HandleWrite, .... ), + ... + ok = erl_tar:add(HandleWrite, .... ), + ok = erl_tar:close(HandleWrite), + + %% And for reading + {ok,HandleRead} = ssh_sftp:open_tar(ChannelPid, ?tar_file_name, [read]), + {ok,NameValueList} = erl_tar:extract(HandleRead,[memory]), + ok = erl_tar:close(HandleRead), + </code> + + <p>The <c>crypto</c> mode option is applied to the generated stream of bytes just prior to sending + them to the sftp server. This is intended for encryption but could of course be used for other + purposes. + </p> + <p>The <c>InitFun</c> is applied once + prior to any other crypto operation. The returned <c>CryptoState</c> is then folded into + repeated applications of the <c>EncryptFun</c> or <c>DecryptFun</c>. The binary returned + from those Funs are sent further to the remote sftp server. Finally - if doing encryption + - the <c>CloseFun</c> is applied to the last piece of data. The <c>CloseFun</c> is + responsible for padding (if needed) and encryption of that last piece. + </p> + <p>The <c>ChunkSize</c> defines the size of the <c>PlainBin</c>s that <c>EncodeFun</c> is applied + to. If the <c>ChunkSize</c> is <c>undefined</c> the size of the <c>PlainBin</c>s varies because + this is inteded for stream crypto while a fixed <c>ChunkSize</c> is intended for block crypto. It + is possible to change the <c>ChunkSize</c>s in the return from the <c>EncryptFun</c> or + <c>DecryptFun</c>. It is in fact possible to change the value between <c>pos_integer()</c> and + <c>undefined</c>. + </p> + <p>The write and read example above can be extended with encryption and decryption:</p> + <code type="none"> + %% First three parameters depending on which crypto type we select: + Key = <<"This is a 256 bit key. abcdefghi">>, + Ivec0 = crypto:rand_bytes(16), + DataSize = 1024, % DataSize rem 16 = 0 for aes_cbc + + %% Initialization of the CryptoState, in this case it is the Ivector. + InitFun = fun() -> {ok, Ivec0, DataSize} end, + + %% How to encrypt: + EncryptFun = + fun(PlainBin,Ivec) -> + EncryptedBin = crypto:block_encrypt(aes_cbc256, Key, Ivec, PlainBin), + {ok, EncryptedBin, crypto:next_iv(aes_cbc,EncryptedBin)} + end, + + %% What to do with the very last block: + CloseFun = + fun(PlainBin, Ivec) -> + EncryptedBin = crypto:block_encrypt(aes_cbc256, Key, Ivec, + pad(16,PlainBin) %% Last chunk + ), + {ok, EncryptedBin} + end, + + Cw = {InitFun,EncryptFun,CloseFun}, + {ok,HandleWrite} = ssh_sftp:open_tar(ChannelPid, ?tar_file_name, [write,{crypto,Cw}]), + ok = erl_tar:add(HandleWrite, .... ), + ok = erl_tar:add(HandleWrite, .... ), + ... + ok = erl_tar:add(HandleWrite, .... ), + ok = erl_tar:close(HandleWrite), + + %% And for decryption (in this crypto example we could use the same InitFun + %% as for encryption): + DecryptFun = + fun(EncryptedBin,Ivec) -> + PlainBin = crypto:block_decrypt(aes_cbc256, Key, Ivec, EncryptedBin), + {ok, PlainBin, crypto:next_iv(aes_cbc,EncryptedBin)} + end, + + Cr = {InitFun,DecryptFun}, + {ok,HandleRead} = ssh_sftp:open_tar(ChannelPid, ?tar_file_name, [read,{crypto,Cw}]), + {ok,NameValueList} = erl_tar:extract(HandleRead,[memory]), + ok = erl_tar:close(HandleRead), + </code> </desc> </func> |