294 lines
10 KiB
C
294 lines
10 KiB
C
/*
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* Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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#ifndef BR_BEARSSL_PEM_H__
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#define BR_BEARSSL_PEM_H__
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#include <stddef.h>
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#include <stdint.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/** \file bearssl_pem.h
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*
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* # PEM Support
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*
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* PEM is a traditional encoding layer use to store binary objects (in
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* particular X.509 certificates, and private keys) in text files. While
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* the acronym comes from an old, defunct standard ("Privacy Enhanced
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* Mail"), the format has been reused, with some variations, by many
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* systems, and is a _de facto_ standard, even though it is not, actually,
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* specified in all clarity anywhere.
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*
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* ## Format Details
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*
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* BearSSL contains a generic, streamed PEM decoder, which handles the
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* following format:
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*
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* - The input source (a sequence of bytes) is assumed to be the
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* encoding of a text file in an ASCII-compatible charset. This
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* includes ISO-8859-1, Windows-1252, and UTF-8 encodings. Each
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* line ends on a newline character (U+000A LINE FEED). The
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* U+000D CARRIAGE RETURN characters are ignored, so the code
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* accepts both Windows-style and Unix-style line endings.
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*
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* - Each object begins with a banner that occurs at the start of
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* a line; the first banner characters are "`-----BEGIN `" (five
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* dashes, the word "BEGIN", and a space). The banner matching is
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* not case-sensitive.
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*
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* - The _object name_ consists in the characters that follow the
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* banner start sequence, up to the end of the line, but without
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* trailing dashes (in "normal" PEM, there are five trailing
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* dashes, but this implementation is not picky about these dashes).
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* The BearSSL decoder normalises the name characters to uppercase
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* (for ASCII letters only) and accepts names up to 127 characters.
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*
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* - The object ends with a banner that again occurs at the start of
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* a line, and starts with "`-----END `" (again case-insensitive).
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*
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* - Between that start and end banner, only Base64 data shall occur.
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* Base64 converts each sequence of three bytes into four
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* characters; the four characters are ASCII letters, digits, "`+`"
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* or "`-`" signs, and one or two "`=`" signs may occur in the last
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* quartet. Whitespace is ignored (whitespace is any ASCII character
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* of code 32 or less, so control characters are whitespace) and
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* lines may have arbitrary length; the only restriction is that the
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* four characters of a quartet must appear on the same line (no
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* line break inside a quartet).
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*
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* - A single file may contain more than one PEM object. Bytes that
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* occur between objects are ignored.
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*
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*
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* ## PEM Decoder API
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*
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* The PEM decoder offers a state-machine API. The caller allocates a
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* decoder context, then injects source bytes. Source bytes are pushed
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* with `br_pem_decoder_push()`. The decoder stops accepting bytes when
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* it reaches an "event", which is either the start of an object, the
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* end of an object, or a decoding error within an object.
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*
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* The `br_pem_decoder_event()` function is used to obtain the current
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* event; it also clears it, thus allowing the decoder to accept more
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* bytes. When a object start event is raised, the decoder context
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* offers the found object name (normalised to ASCII uppercase).
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*
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* When an object is reached, the caller must set an appropriate callback
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* function, which will receive (by chunks) the decoded object data.
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*
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* Since the decoder context makes no dynamic allocation, it requires
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* no explicit deallocation.
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*/
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/**
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* \brief PEM decoder context.
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*
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* Contents are opaque (they should not be accessed directly).
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*/
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typedef struct {
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#ifndef BR_DOXYGEN_IGNORE
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/* CPU for the T0 virtual machine. */
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struct {
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uint32_t *dp;
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uint32_t *rp;
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const unsigned char *ip;
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} cpu;
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uint32_t dp_stack[32];
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uint32_t rp_stack[32];
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int err;
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const unsigned char *hbuf;
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size_t hlen;
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void (*dest)(void *dest_ctx, const void *src, size_t len);
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void *dest_ctx;
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unsigned char event;
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char name[128];
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unsigned char buf[255];
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size_t ptr;
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#endif
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} br_pem_decoder_context;
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/**
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* \brief Initialise a PEM decoder structure.
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*
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* \param ctx decoder context to initialise.
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*/
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void br_pem_decoder_init(br_pem_decoder_context *ctx);
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/**
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* \brief Push some bytes into the decoder.
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*
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* Returned value is the number of bytes actually consumed; this may be
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* less than the number of provided bytes if an event is raised. When an
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* event is raised, it must be read (with `br_pem_decoder_event()`);
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* until the event is read, this function will return 0.
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*
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* \param ctx decoder context.
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* \param data new data bytes.
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* \param len number of new data bytes.
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* \return the number of bytes actually received (may be less than `len`).
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*/
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size_t br_pem_decoder_push(br_pem_decoder_context *ctx,
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const void *data, size_t len);
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/**
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* \brief Set the receiver for decoded data.
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*
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* When an object is entered, the provided function (with opaque context
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* pointer) will be called repeatedly with successive chunks of decoded
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* data for that object. If `dest` is set to 0, then decoded data is
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* simply ignored. The receiver can be set at any time, but, in practice,
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* it should be called immediately after receiving a "start of object"
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* event.
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*
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* \param ctx decoder context.
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* \param dest callback for receiving decoded data.
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* \param dest_ctx opaque context pointer for the `dest` callback.
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*/
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static inline void
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br_pem_decoder_setdest(br_pem_decoder_context *ctx,
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void (*dest)(void *dest_ctx, const void *src, size_t len),
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void *dest_ctx)
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{
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ctx->dest = dest;
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ctx->dest_ctx = dest_ctx;
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}
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/**
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* \brief Get the last event.
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*
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* If an event was raised, then this function returns the event value, and
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* also clears it, thereby allowing the decoder to proceed. If no event
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* was raised since the last call to `br_pem_decoder_event()`, then this
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* function returns 0.
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*
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* \param ctx decoder context.
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* \return the raised event, or 0.
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*/
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int br_pem_decoder_event(br_pem_decoder_context *ctx);
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/**
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* \brief Event: start of object.
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*
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* This event is raised when the start of a new object has been detected.
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* The object name (normalised to uppercase) can be accessed with
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* `br_pem_decoder_name()`.
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*/
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#define BR_PEM_BEGIN_OBJ 1
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/**
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* \brief Event: end of object.
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*
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* This event is raised when the end of the current object is reached
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* (normally, i.e. with no decoding error).
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*/
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#define BR_PEM_END_OBJ 2
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/**
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* \brief Event: decoding error.
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*
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* This event is raised when decoding fails within an object.
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* This formally closes the current object and brings the decoder back
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* to the "out of any object" state. The offending line in the source
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* is consumed.
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*/
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#define BR_PEM_ERROR 3
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/**
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* \brief Get the name of the encountered object.
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*
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* The encountered object name is defined only when the "start of object"
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* event is raised. That name is normalised to uppercase (for ASCII letters
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* only) and does not include trailing dashes.
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*
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* \param ctx decoder context.
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* \return the current object name.
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*/
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static inline const char *
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br_pem_decoder_name(br_pem_decoder_context *ctx)
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{
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return ctx->name;
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}
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/**
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* \brief Encode an object in PEM.
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*
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* This function encodes the provided binary object (`data`, of length `len`
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* bytes) into PEM. The `banner` text will be included in the header and
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* footer (e.g. use `"CERTIFICATE"` to get a `"BEGIN CERTIFICATE"` header).
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*
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* The length (in characters) of the PEM output is returned; that length
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* does NOT include the terminating zero, that this function nevertheless
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* adds. If using the returned value for allocation purposes, the allocated
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* buffer size MUST be at least one byte larger than the returned size.
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*
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* If `dest` is `NULL`, then the encoding does not happen; however, the
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* length of the encoded object is still computed and returned.
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*
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* The `data` pointer may be `NULL` only if `len` is zero (when encoding
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* an object of length zero, which is not very useful), or when `dest`
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* is `NULL` (in that case, source data bytes are ignored).
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*
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* Some `flags` can be specified to alter the encoding behaviour:
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*
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* - If `BR_PEM_LINE64` is set, then line-breaking will occur after
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* every 64 characters of output, instead of the default of 76.
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*
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* - If `BR_PEM_CRLF` is set, then end-of-line sequence will use
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* CR+LF instead of a single LF.
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*
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* The `data` and `dest` buffers may overlap, in which case the source
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* binary data is destroyed in the process. Note that the PEM-encoded output
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* is always larger than the source binary.
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*
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* \param dest the destination buffer (or `NULL`).
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* \param data the source buffer (can be `NULL` in some cases).
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* \param len the source length (in bytes).
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* \param banner the PEM banner expression.
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* \param flags the behavioural flags.
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* \return the PEM object length (in characters), EXCLUDING the final zero.
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*/
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size_t br_pem_encode(void *dest, const void *data, size_t len,
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const char *banner, unsigned flags);
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/**
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* \brief PEM encoding flag: split lines at 64 characters.
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*/
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#define BR_PEM_LINE64 0x0001
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/**
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* \brief PEM encoding flag: use CR+LF line endings.
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*/
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#define BR_PEM_CRLF 0x0002
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#ifdef __cplusplus
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}
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#endif
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#endif
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