2 * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
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25 #ifndef BR_BEARSSL_PEM_H__
26 #define BR_BEARSSL_PEM_H__
35 /** \file bearssl_pem.h
39 * PEM is a traditional encoding layer use to store binary objects (in
40 * particular X.509 certificates, and private keys) in text files. While
41 * the acronym comes from an old, defunct standard ("Privacy Enhanced
42 * Mail"), the format has been reused, with some variations, by many
43 * systems, and is a _de facto_ standard, even though it is not, actually,
44 * specified in all clarity anywhere.
48 * BearSSL contains a generic, streamed PEM decoder, which handles the
51 * - The input source (a sequence of bytes) is assumed to be the
52 * encoding of a text file in an ASCII-compatible charset. This
53 * includes ISO-8859-1, Windows-1252, and UTF-8 encodings. Each
54 * line ends on a newline character (U+000A LINE FEED). The
55 * U+000D CARRIAGE RETURN characters are ignored, so the code
56 * accepts both Windows-style and Unix-style line endings.
58 * - Each object begins with a banner that occurs at the start of
59 * a line; the first banner characters are "`-----BEGIN `" (five
60 * dashes, the word "BEGIN", and a space). The banner matching is
63 * - The _object name_ consists in the characters that follow the
64 * banner start sequence, up to the end of the line, but without
65 * trailing dashes (in "normal" PEM, there are five trailing
66 * dashes, but this implementation is not picky about these dashes).
67 * The BearSSL decoder normalises the name characters to uppercase
68 * (for ASCII letters only) and accepts names up to 127 characters.
70 * - The object ends with a banner that again occurs at the start of
71 * a line, and starts with "`-----END `" (again case-insensitive).
73 * - Between that start and end banner, only Base64 data shall occur.
74 * Base64 converts each sequence of three bytes into four
75 * characters; the four characters are ASCII letters, digits, "`+`"
76 * or "`-`" signs, and one or two "`=`" signs may occur in the last
77 * quartet. Whitespace is ignored (whitespace is any ASCII character
78 * of code 32 or less, so control characters are whitespace) and
79 * lines may have arbitrary length; the only restriction is that the
80 * four characters of a quartet must appear on the same line (no
81 * line break inside a quartet).
83 * - A single file may contain more than one PEM object. Bytes that
84 * occur between objects are ignored.
89 * The PEM decoder offers a state-machine API. The caller allocates a
90 * decoder context, then injects source bytes. Source bytes are pushed
91 * with `br_pem_decoder_push()`. The decoder stops accepting bytes when
92 * it reaches an "event", which is either the start of an object, the
93 * end of an object, or a decoding error within an object.
95 * The `br_pem_decoder_event()` function is used to obtain the current
96 * event; it also clears it, thus allowing the decoder to accept more
97 * bytes. When a object start event is raised, the decoder context
98 * offers the found object name (normalised to ASCII uppercase).
100 * When an object is reached, the caller must set an appropriate callback
101 * function, which will receive (by chunks) the decoded object data.
103 * Since the decoder context makes no dynamic allocation, it requires
104 * no explicit deallocation.
108 * \brief PEM decoder context.
110 * Contents are opaque (they should not be accessed directly).
113 #ifndef BR_DOXYGEN_IGNORE
114 /* CPU for the T0 virtual machine. */
118 const unsigned char *ip
;
120 uint32_t dp_stack
[32];
121 uint32_t rp_stack
[32];
124 const unsigned char *hbuf
;
127 void (*dest
)(void *dest_ctx
, const void *src
, size_t len
);
132 unsigned char buf
[255];
135 } br_pem_decoder_context
;
138 * \brief Initialise a PEM decoder structure.
140 * \param ctx decoder context to initialise.
142 void br_pem_decoder_init(br_pem_decoder_context
*ctx
);
145 * \brief Push some bytes into the decoder.
147 * Returned value is the number of bytes actually consumed; this may be
148 * less than the number of provided bytes if an event is raised. When an
149 * event is raised, it must be read (with `br_pem_decoder_event()`);
150 * until the event is read, this function will return 0.
152 * \param ctx decoder context.
153 * \param data new data bytes.
154 * \param len number of new data bytes.
155 * \return the number of bytes actually received (may be less than `len`).
157 size_t br_pem_decoder_push(br_pem_decoder_context
*ctx
,
158 const void *data
, size_t len
);
161 * \brief Set the receiver for decoded data.
163 * When an object is entered, the provided function (with opaque context
164 * pointer) will be called repeatedly with successive chunks of decoded
165 * data for that object. If `dest` is set to 0, then decoded data is
166 * simply ignored. The receiver can be set at any time, but, in practice,
167 * it should be called immediately after receiving a "start of object"
170 * \param ctx decoder context.
171 * \param dest callback for receiving decoded data.
172 * \param dest_ctx opaque context pointer for the `dest` callback.
175 br_pem_decoder_setdest(br_pem_decoder_context
*ctx
,
176 void (*dest
)(void *dest_ctx
, const void *src
, size_t len
),
180 ctx
->dest_ctx
= dest_ctx
;
184 * \brief Get the last event.
186 * If an event was raised, then this function returns the event value, and
187 * also clears it, thereby allowing the decoder to proceed. If no event
188 * was raised since the last call to `br_pem_decoder_event()`, then this
189 * function returns 0.
191 * \param ctx decoder context.
192 * \return the raised event, or 0.
194 int br_pem_decoder_event(br_pem_decoder_context
*ctx
);
197 * \brief Event: start of object.
199 * This event is raised when the start of a new object has been detected.
200 * The object name (normalised to uppercase) can be accessed with
201 * `br_pem_decoder_name()`.
203 #define BR_PEM_BEGIN_OBJ 1
206 * \brief Event: end of object.
208 * This event is raised when the end of the current object is reached
209 * (normally, i.e. with no decoding error).
211 #define BR_PEM_END_OBJ 2
214 * \brief Event: decoding error.
216 * This event is raised when decoding fails within an object.
217 * This formally closes the current object and brings the decoder back
218 * to the "out of any object" state. The offending line in the source
221 #define BR_PEM_ERROR 3
224 * \brief Get the name of the encountered object.
226 * The encountered object name is defined only when the "start of object"
227 * event is raised. That name is normalised to uppercase (for ASCII letters
228 * only) and does not include trailing dashes.
230 * \param ctx decoder context.
231 * \return the current object name.
233 static inline const char *
234 br_pem_decoder_name(br_pem_decoder_context
*ctx
)