/src/botan/build/include/public/botan/xof.h

Source
/*
* Extendable Output Function Base Class
* (C) 2023 Jack Lloyd
*     2023 Fabian Albert, René Meusel - Rohde & Schwarz Cybersecurity
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#ifndef BOTAN_XOF_BASE_CLASS_H_
#define BOTAN_XOF_BASE_CLASS_H_

#include <botan/concepts.h>
#include <botan/secmem.h>
#include <botan/sym_algo.h>

#include <memory>
#include <string>
#include <string_view>

namespace Botan {

/**
 * This class represents an eXtendable Output Function (XOF) objects
 *
 * A XOF transforms an arbitrary length input message into an indefinite
 * stream of output bits. Typically, it is illegal to call `update()` after
 * the first call to `output()`.
 */
class BOTAN_PUBLIC_API(3, 2) XOF /* NOLINT(*special-member-functions) */ {
   public:
      virtual ~XOF() = default;

      /**
       * Create an instance based on a name, or return null if the
       * algo/provider combination cannot be found. If provider is
       * empty then best available is chosen.
       */
      static std::unique_ptr<XOF> create(std::string_view algo_spec, std::string_view provider = "");

      /**
       * Create an instance based on a name
       * If provider is empty then best available is chosen.
       * @param algo_spec algorithm name
       * @param provider provider implementation to use
       * Throws Lookup_Error if not found.
       */
      static std::unique_ptr<XOF> create_or_throw(std::string_view algo_spec, std::string_view provider = "");

      /**
       * @return list of available providers for this algorithm, empty if not available
       * @param algo_spec algorithm name
       */
      static std::vector<std::string> providers(std::string_view algo_spec);

      /**
       * @return provider information about this implementation. Default is "base",
       * might also return "sse2", "avx2", "openssl", or some other arbitrary string.
       */
      virtual std::string provider() const;

      /**
       * Reset the state.
       */
      void clear() {
         m_xof_started = false;
         reset();
      }

      /**
       * @return the hash function name
       */
      virtual std::string name() const = 0;

      /**
       * Some XOFs can be parameterized with a @p salt and/or @p key. If required,
       * this must be called before calling XOF::update().
       *
       * @sa XOF::valid_salt_length()
       * @sa XOF::key_spec()
       *
       * @param salt  a salt value to parameterize the XOF
       * @param key   a key to parameterize the XOF
       */
      void start(std::span<const uint8_t> salt = {}, std::span<const uint8_t> key = {});

      /**
       * @returns true if salt length is acceptable, false otherwise
       */
      virtual bool valid_salt_length(size_t salt_len) const {
         // Salts are not supported by default
         return salt_len == 0;
      }

      /**
       * @returns an object describing limits on the key size
       */
      virtual Key_Length_Specification key_spec() const {
         // Keys are not supported by default
         return Key_Length_Specification(0);
      }

      /**
       * @return the intrinsic processing block size of this XOF
       */
      virtual size_t block_size() const = 0;

      /**
       * Return a new XOF object with the same state as *this.
       *
       * If the XOF is not yet in the output phase, it efficiently allows
       * using several messages with a common prefix.
       * Otherwise, the copied state will produce the same output
       * bit stream as the original object at the time of this invocation.
       *
       * This function should be called `clone` but for consistency with
       * other classes it is called `copy_state`.
       *
       * @return new XOF object
       */
      virtual std::unique_ptr<XOF> copy_state() const = 0;

      /**
       * @return new object representing the same algorithm as *this
       */
      virtual std::unique_ptr<XOF> new_object() const = 0;

      /**
       * Typically, this is `true` for new objects and becomes `false`
       * once `output()` was called for the first time.
       *
       * @returns true iff calling `update()` is legal in the current object state
       */
      virtual bool accepts_input() const = 0;

      /**
       * Add @p input data to the XOF's internal state
       *
       * @param input  the data that shall be
       */
      void update(std::span<const uint8_t> input) {
         if(!m_xof_started) {
            // If the user didn't start() before the first input, we enforce
            // it with a default value, here.
            start();
         }
         add_data(input);
      }

      /**
       * @return the next @p bytes output bytes as the specified container type @p T.
       */
      template <concepts::resizable_byte_buffer T = secure_vector<uint8_t>>
      T output(size_t bytes) {
         T out(bytes);
         generate_bytes(out);
         return out;
      }

      /**
       * @return the next @p count output bytes as a std::array<>.
       */
      template <size_t count>
      std::array<uint8_t, count> output() {
         std::array<uint8_t, count> out;  // NOLINT(*-member-init)
         generate_bytes(out);
         return out;
      }

      /**
       * Convenience overload to generate a std::vector<uint8_t>. Same as calling
       * `XOF::output<std::vector<uint8_t>>()`.
       *
       * @return the next @p bytes output bytes as a byte vector.
       */
      std::vector<uint8_t> output_stdvec(size_t bytes) { return output<std::vector<uint8_t>>(bytes); }

      /**
       * Fill @p output with the next output bytes. The number of bytes
       * depends on the size of @p output.
       */
      void output(std::span<uint8_t> output) { generate_bytes(output); }

      /**
       * @return the next single output byte
       */
      uint8_t output_next_byte() {
         uint8_t out = 0;
         generate_bytes({&out, 1});
         return out;
      }

   private:
      /**
       * Take @p salt and/or @p key to pre-parameterize the XOF. This must be called
       * before calling XOF::update().
       *
       * @param salt  a salt value to parameterize the XOF
       * @param key   a key to parameterize the XOF
       */
      virtual void start_msg(std::span<const uint8_t> salt, std::span<const uint8_t> key);

      /**
       * Consume @p input data bytes into the XOF's internal state
       *
       * Typically, XOFs may consume an arbitrary length of input data but
       * should refuse accepting more input once the first output bit was
       * generated. Implementations should throw `Invalid_State` in this
       * case.
       *
       * @param input  the span to be consumed entirely into the internal state
       * @throws        Invalid_State if input is added after generating output
       */
      virtual void add_data(std::span<const uint8_t> input) = 0;

      /**
       * Fill the entire @p output span with the next bytes in their output
       * stream.
       *
       * The first invocation to `generate_bytes()` should typically transition
       * the XOF's state to "output mode" and prevent any further calls to
       * `XOF::add_data()`.
       *
       * @param output  the span to be filled entirely with output bytes
       */
      virtual void generate_bytes(std::span<uint8_t> output) = 0;

      /**
       * Clear the XOF's internal state and allow for new input.
       */
      virtual void reset() = 0;

   private:
      bool m_xof_started = false;
};

}  // namespace Botan

#endif

Coverage Report

Created: 2026-02-07 06:16

Line	Count	Source
1		/*
2		* Extendable Output Function Base Class
3		* (C) 2023 Jack Lloyd
4		* 2023 Fabian Albert, René Meusel - Rohde & Schwarz Cybersecurity
5		*
6		* Botan is released under the Simplified BSD License (see license.txt)
7		*/
8
9		#ifndef BOTAN_XOF_BASE_CLASS_H_
10		#define BOTAN_XOF_BASE_CLASS_H_
11
12		#include <botan/concepts.h>
13		#include <botan/secmem.h>
14		#include <botan/sym_algo.h>
15
16		#include <memory>
17		#include <string>
18		#include <string_view>
19
20		namespace Botan {
21
22		/**
23		* This class represents an eXtendable Output Function (XOF) objects
24		*
25		* A XOF transforms an arbitrary length input message into an indefinite
26		* stream of output bits. Typically, it is illegal to call `update()` after
27		* the first call to `output()`.
28		*/
29		class BOTAN_PUBLIC_API(3, 2) XOF /* NOLINT(special-member-functions) / {
30		public:
31	0	virtual ~XOF() = default;
32
33		/**
34		* Create an instance based on a name, or return null if the
35		* algo/provider combination cannot be found. If provider is
36		* empty then best available is chosen.
37		*/
38		static std::unique_ptr<XOF> create(std::string_view algo_spec, std::string_view provider = "");
39
40		/**
41		* Create an instance based on a name
42		* If provider is empty then best available is chosen.
43		* @param algo_spec algorithm name
44		* @param provider provider implementation to use
45		* Throws Lookup_Error if not found.
46		*/
47		static std::unique_ptr<XOF> create_or_throw(std::string_view algo_spec, std::string_view provider = "");
48
49		/**
50		* @return list of available providers for this algorithm, empty if not available
51		* @param algo_spec algorithm name
52		*/
53		static std::vector<std::string> providers(std::string_view algo_spec);
54
55		/**
56		* @return provider information about this implementation. Default is "base",
57		* might also return "sse2", "avx2", "openssl", or some other arbitrary string.
58		*/
59		virtual std::string provider() const;
60
61		/**
62		* Reset the state.
63		*/
64	0	void clear() {
65	0	m_xof_started = false;
66	0	reset();
67	0	}
68
69		/**
70		* @return the hash function name
71		*/
72		virtual std::string name() const = 0;
73
74		/**
75		* Some XOFs can be parameterized with a @p salt and/or @p key. If required,
76		* this must be called before calling XOF::update().
77		*
78		* @sa XOF::valid_salt_length()
79		* @sa XOF::key_spec()
80		*
81		* @param salt a salt value to parameterize the XOF
82		* @param key a key to parameterize the XOF
83		*/
84		void start(std::span<const uint8_t> salt = {}, std::span<const uint8_t> key = {});
85
86		/**
87		* @returns true if salt length is acceptable, false otherwise
88		*/
89	0	virtual bool valid_salt_length(size_t salt_len) const {
90		// Salts are not supported by default
91	0	return salt_len == 0;
92	0	}
93
94		/**
95		* @returns an object describing limits on the key size
96		*/
97	0	virtual Key_Length_Specification key_spec() const {
98		// Keys are not supported by default
99	0	return Key_Length_Specification(0);
100	0	}
101
102		/**
103		* @return the intrinsic processing block size of this XOF
104		*/
105		virtual size_t block_size() const = 0;
106
107		/**
108		* Return a new XOF object with the same state as *this.
109		*
110		* If the XOF is not yet in the output phase, it efficiently allows
111		* using several messages with a common prefix.
112		* Otherwise, the copied state will produce the same output
113		* bit stream as the original object at the time of this invocation.
114		*
115		* This function should be called `clone` but for consistency with
116		* other classes it is called `copy_state`.
117		*
118		* @return new XOF object
119		*/
120		virtual std::unique_ptr<XOF> copy_state() const = 0;
121
122		/**
123		* @return new object representing the same algorithm as *this
124		*/
125		virtual std::unique_ptr<XOF> new_object() const = 0;
126
127		/**
128		* Typically, this is `true` for new objects and becomes `false`
129		* once `output()` was called for the first time.
130		*
131		* @returns true iff calling `update()` is legal in the current object state
132		*/
133		virtual bool accepts_input() const = 0;
134
135		/**
136		* Add @p input data to the XOF's internal state
137		*
138		* @param input the data that shall be
139		*/
140	0	void update(std::span<const uint8_t> input) {
141	0	if(!m_xof_started) {
142		// If the user didn't start() before the first input, we enforce
143		// it with a default value, here.
144	0	start();
145	0	}
146	0	add_data(input);
147	0	}
148
149		/**
150		* @return the next @p bytes output bytes as the specified container type @p T.
151		*/
152		template <concepts::resizable_byte_buffer T = secure_vector<uint8_t>>
153	0	T output(size_t bytes) {
154	0	T out(bytes);
155	0	generate_bytes(out);
156	0	return out;
157	0	}
158
159		/**
160		* @return the next @p count output bytes as a std::array<>.
161		*/
162		template <size_t count>
163		std::array<uint8_t, count> output() {
164		std::array<uint8_t, count> out; // NOLINT(*-member-init)
165		generate_bytes(out);
166		return out;
167		}
168
169		/**
170		* Convenience overload to generate a std::vector<uint8_t>. Same as calling
171		* `XOF::output<std::vector<uint8_t>>()`.
172		*
173		* @return the next @p bytes output bytes as a byte vector.
174		*/
175	0	std::vector<uint8_t> output_stdvec(size_t bytes) { return output<std::vector<uint8_t>>(bytes); }
176
177		/**
178		* Fill @p output with the next output bytes. The number of bytes
179		* depends on the size of @p output.
180		*/
181	0	void output(std::span<uint8_t> output) { generate_bytes(output); }
182
183		/**
184		* @return the next single output byte
185		*/
186	0	uint8_t output_next_byte() {
187	0	uint8_t out = 0;
188	0	generate_bytes({&out, 1});
189	0	return out;
190	0	}
191
192		private:
193		/**
194		* Take @p salt and/or @p key to pre-parameterize the XOF. This must be called
195		* before calling XOF::update().
196		*
197		* @param salt a salt value to parameterize the XOF
198		* @param key a key to parameterize the XOF
199		*/
200		virtual void start_msg(std::span<const uint8_t> salt, std::span<const uint8_t> key);
201
202		/**
203		* Consume @p input data bytes into the XOF's internal state
204		*
205		* Typically, XOFs may consume an arbitrary length of input data but
206		* should refuse accepting more input once the first output bit was
207		* generated. Implementations should throw `Invalid_State` in this
208		* case.
209		*
210		* @param input the span to be consumed entirely into the internal state
211		* @throws Invalid_State if input is added after generating output
212		*/
213		virtual void add_data(std::span<const uint8_t> input) = 0;
214
215		/**
216		* Fill the entire @p output span with the next bytes in their output
217		* stream.
218		*
219		* The first invocation to `generate_bytes()` should typically transition
220		* the XOF's state to "output mode" and prevent any further calls to
221		* `XOF::add_data()`.
222		*
223		* @param output the span to be filled entirely with output bytes
224		*/
225		virtual void generate_bytes(std::span<uint8_t> output) = 0;
226
227		/**
228		* Clear the XOF's internal state and allow for new input.
229		*/
230		virtual void reset() = 0;
231
232		private:
233		bool m_xof_started = false;
234		};
235
236		} // namespace Botan
237
238		#endif