.\" $OpenBSD: EVP_EncodeInit.3,v 1.7 2019/06/06 01:06:58 schwarze Exp $ .\" full merge up to: OpenSSL f430ba31 Jun 19 19:39:01 2016 +0200 .\" selective merge up to: OpenSSL e9b77246 Jan 20 19:58:49 2017 +0100 .\" .\" This file was written by Matt Caswell . .\" Copyright (c) 2016 The OpenSSL Project. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in .\" the documentation and/or other materials provided with the .\" distribution. .\" .\" 3. All advertising materials mentioning features or use of this .\" software must display the following acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" .\" .\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to .\" endorse or promote products derived from this software without .\" prior written permission. For written permission, please contact .\" openssl-core@openssl.org. .\" .\" 5. Products derived from this software may not be called "OpenSSL" .\" nor may "OpenSSL" appear in their names without prior written .\" permission of the OpenSSL Project. .\" .\" 6. 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IN NO EVENT SHALL THE OpenSSL PROJECT OR .\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; .\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED .\" OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: June 6 2019 $ .Dt EVP_ENCODEINIT 3 .Os .Sh NAME .Nm EVP_ENCODE_CTX_new , .Nm EVP_ENCODE_CTX_free , .Nm EVP_EncodeInit , .Nm EVP_EncodeUpdate , .Nm EVP_EncodeFinal , .Nm EVP_EncodeBlock , .Nm EVP_DecodeInit , .Nm EVP_DecodeUpdate , .Nm EVP_DecodeFinal , .Nm EVP_DecodeBlock .Nd EVP base64 encode/decode routines .Sh SYNOPSIS .In openssl/evp.h .Ft EVP_ENCODE_CTX * .Fn EVP_ENCODE_CTX_new void .Ft void .Fo EVP_ENCODE_CTX_free .Fa "EVP_ENCODE_CTX *ctx" .Fc .Ft void .Fo EVP_EncodeInit .Fa "EVP_ENCODE_CTX *ctx" .Fc .Ft int .Fo EVP_EncodeUpdate .Fa "EVP_ENCODE_CTX *ctx" .Fa "unsigned char *out" .Fa "int *outl" .Fa "const unsigned char *in" .Fa "int inl" .Fc .Ft void .Fo EVP_EncodeFinal .Fa "EVP_ENCODE_CTX *ctx" .Fa "unsigned char *out" .Fa "int *outl" .Fc .Ft int .Fo EVP_EncodeBlock .Fa "unsigned char *t" .Fa "const unsigned char *f" .Fa "int n" .Fc .Ft void .Fo EVP_DecodeInit .Fa "EVP_ENCODE_CTX *ctx" .Fc .Ft int .Fo EVP_DecodeUpdate .Fa "EVP_ENCODE_CTX *ctx" .Fa "unsigned char *out" .Fa "int *outl" .Fa "const unsigned char *in" .Fa "int inl" .Fc .Ft int .Fo EVP_DecodeFinal .Fa "EVP_ENCODE_CTX *ctx" .Fa "unsigned char *out" .Fa "int *outl" .Fc .Ft int .Fo EVP_DecodeBlock .Fa "unsigned char *t" .Fa "const unsigned char *f" .Fa "int n" .Fc .Sh DESCRIPTION The EVP encode routines provide a high level interface to base64 encoding and decoding. Base64 encoding converts binary data into a printable form that uses the characters A-Z, a-z, 0-9, "+" and "/" to represent the data. For every 3 bytes of binary data provided, 4 bytes of base64-encoded data will be produced, plus some occasional newlines. If the input data length is not a multiple of 3, then the output data will be padded at the end using the "=" character. .Pp .Fn EVP_ENCODE_CTX_new allocates, initializes and returns a context to be used for the encode and decode functions. .Pp .Fn EVP_ENCODE_CTX_free frees .Fa ctx . .Pp Encoding of binary data is performed in blocks of 48 input bytes (or less for the final block). For each 48-byte input block encoded, 64 bytes of base64 data is output, plus an additional newline character, i.e. 65 bytes in total. The final block, which may be less than 48 bytes, will output 4 bytes for every 3 bytes of input. If the data length is not divisible by 3, then a full 4 bytes is still output for the final 1 or 2 bytes of input. Similarly a newline character will also be output. .Pp .Fn EVP_EncodeInit initialises .Fa ctx for the start of a new encoding operation. .Pp .Fn EVP_EncodeUpdate encodes .Fa inl bytes of data found in the buffer pointed to by .Fa in . The output is stored in the buffer .Fa out and the number of bytes output is stored in .Pf * Fa outl . It is the caller's responsibility to ensure that the buffer at .Fa out is sufficiently large to accommodate the output data. Only full blocks of data (48 bytes) will be immediately processed and output by this function. Any remainder is held in the .Fa ctx object and will be processed by a subsequent call to .Fn EVP_EncodeUpdate or .Fn EVP_EncodeFinal . To calculate the required size of the output buffer, add together the value of .Fa inl with the amount of unprocessed data held in .Fa ctx and divide the result by 48 (ignore any remainder). This gives the number of blocks of data that will be processed. Ensure the output buffer contains 65 bytes of storage for each block, plus an additional byte for a NUL terminator. .Fn EVP_EncodeUpdate may be called repeatedly to process large amounts of input data. In the event of an error , .Fn EVP_EncodeUpdate will set .Pf * Fa outl to 0 and return 0. On success 1 will be returned. .Pp .Fn EVP_EncodeFinal must be called at the end of an encoding operation. It will process any partial block of data remaining in the .Fa ctx object. The output data will be stored in .Fa out and the length of the data written will be stored in .Pf * Fa outl . It is the caller's responsibility to ensure that .Fa out is sufficiently large to accommodate the output data, which will never be more than 65 bytes plus an additional NUL terminator, i.e. 66 bytes in total. .Pp .Fn EVP_EncodeBlock encodes a full block of input data in .Fa f and of length .Fa n and stores it in .Fa t . For every 3 bytes of input provided, 4 bytes of output data will be produced. If .Sy n is not divisible by 3, then the block is encoded as a final block of data and the output is padded such that it is always divisible by 4. Additionally a NUL terminator character will be added. For example, if 16 bytes of input data are provided, then 24 bytes of encoded data is created plus 1 byte for a NUL terminator, i.e. 25 bytes in total. The length of the data generated .Em without the NUL terminator is returned from the function. .Pp .Fn EVP_DecodeInit initialises .Fa ctx for the start of a new decoding operation. .Pp .Fn EVP_DecodeUpdate decodes .Fa inl characters of data found in the buffer pointed to by .Fa in . The output is stored in the buffer .Fa out and the number of bytes output is stored in .Pf * Fa outl . It is the caller's responsibility to ensure that the buffer at .Fa out is sufficiently large to accommodate the output data. This function will attempt to decode as much data as possible in 4-byte chunks. Any whitespace, newline or carriage return characters are ignored. Any partial chunk of unprocessed data (1, 2 or 3 bytes) that remains at the end will be held in the .Fa ctx object and processed by a subsequent call to .Fn EVP_DecodeUpdate . If any illegal base64 characters are encountered or if the base64 padding character "=" is encountered in the middle of the data, then the function returns -1 to indicate an error. A return value of 0 or 1 indicates successful processing of the data. A return value of 0 additionally indicates that the last input data characters processed included the base64 padding character "=" and therefore no more non-padding character data is expected to be processed. For every 4 valid base64 bytes processed \(em ignoring whitespace, carriage returns and line feeds \(em 3 bytes of binary output data will be produced, or less at the end of the data where the padding character "=" has been used. .Pp .Fn EVP_DecodeFinal must be called at the end of a decoding operation. If there is any unprocessed data still in .Fa ctx , then the input data must not have been a multiple of 4 and therefore an error has occurred. The function will return -1 in this case. Otherwise the function returns 1 on success. .Pp .Fn EVP_DecodeBlock will decode the block of .Fa n characters of base64 data contained in .Fa f and store the result in .Fa t . Any leading whitespace will be trimmed as will any trailing whitespace, newlines, carriage returns or EOF characters. After such trimming the length of the data in .Fa f must be divisible by 4. For every 4 input bytes, exactly 3 output bytes will be produced. The output will be padded with 0 bits if necessary to ensure that the output is always 3 bytes for every 4 input bytes. This function will return the length of the data decoded or -1 on error. .Sh RETURN VALUES .Fn EVP_ENCODE_CTX_new returns a pointer to the newly allocated .Vt EVP_ENCODE_CTX object or .Dv NULL on error. .Pp .Fn EVP_EncodeUpdate returns 0 on error or 1 on success. .Pp .Fn EVP_EncodeBlock returns the number of bytes encoded excluding the NUL terminator. .Pp .Fn EVP_DecodeUpdate returns -1 on error and 0 or 1 on success. If 0 is returned, then no more non-padding base64 characters are expected. .Pp .Fn EVP_DecodeFinal returns -1 on error or 1 on success. .Pp .Fn EVP_DecodeBlock returns the length of the data decoded or -1 on error. .Sh SEE ALSO .Xr BIO_f_base64 3 , .Xr evp 3 .Sh HISTORY The .Fn EVP_Encode* and .Fn EVP_Decode* functions first appeared in SSLeay 0.5.1 and have been available since .Ox 2.4 . .Pp .Fn EVP_ENCODE_CTX_new and .Fn EVP_ENCODE_CTX_free first appeared in OpenSSL 1.1.0 and have been available since .Ox 6.5 .