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1 /*
2  * Copyright 2014 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #pragma once
18 
19 #include <stddef.h>
20 #include <stdint.h>
21 #include <stdlib.h>
22 #include <string.h>
23 
24 #include <keymaster/UniquePtr.h>
25 #include <keymaster/mem.h>
26 
27 namespace keymaster {
28 
29 class Serializable {
30   public:
Serializable()31     Serializable() {}
~Serializable()32     virtual ~Serializable() {}
33 
34     /**
35      * Return the size of the serialized representation of this object.
36      */
37     virtual size_t SerializedSize() const = 0;
38 
39     /**
40      * Serialize this object into the provided buffer.  Returns a pointer to the byte after the last
41      * written.  Will not write past \p end, which should point to \p buf + size of the buffer
42      * (i.e. one past the end of the buffer).
43      */
44     virtual uint8_t* Serialize(uint8_t* buf, const uint8_t* end) const = 0;
45 
46     /**
47      * Deserialize from the provided buffer, copying the data into newly-allocated storage.  Returns
48      * true if successful, and advances *buf past the bytes read.
49      */
50     virtual bool Deserialize(const uint8_t** buf_ptr, const uint8_t* end) = 0;
51 
52     // Disallow copying and assignment.
53     Serializable(const Serializable&) = delete;
54     Serializable& operator=(const Serializable&) = delete;
55 
56     // Move only.
57     Serializable(Serializable&&) = default;
58     Serializable& operator=(Serializable&&) = default;
59 };
60 
61 /*
62  * Utility functions for writing Serialize() methods
63  */
64 
65 /**
66  * Convert a pointer into a value.  This is used to make sure compiler won't optimize away pointer
67  * overflow checks. (See http://www.kb.cert.org/vuls/id/162289)
68  */
__pval(const T * p)69 template <typename T> inline uintptr_t __pval(const T* p) {
70     return reinterpret_cast<uintptr_t>(p);
71 }
72 
73 /**
74  * Append a byte array to a buffer.  Note that by itself this function isn't very useful, because it
75  * provides no indication in the serialized buffer of what the array size is.  For writing arrays,
76  * see \p append_size_and_data_to_buf().
77  *
78  * Returns a pointer to the first byte after the data written.
79  */
80 uint8_t* append_to_buf(uint8_t* buf, const uint8_t* end, const void* data, size_t data_len);
81 
82 /**
83  * Append some type of value convertible to a uint32_t to a buffer.  This is primarily used for
84  * writing enumerated values, and uint32_ts.
85  *
86  * Returns a pointer to the first byte after the data written.
87  */
88 template <typename T>
append_uint32_to_buf(uint8_t * buf,const uint8_t * end,T value)89 inline uint8_t* append_uint32_to_buf(uint8_t* buf, const uint8_t* end, T value) {
90     uint32_t val = static_cast<uint32_t>(value);
91     return append_to_buf(buf, end, &val, sizeof(val));
92 }
93 
94 /**
95  * Append a uint64_t to a buffer.  Returns a pointer to the first byte after the data written.
96  */
append_uint64_to_buf(uint8_t * buf,const uint8_t * end,uint64_t value)97 inline uint8_t* append_uint64_to_buf(uint8_t* buf, const uint8_t* end, uint64_t value) {
98     return append_to_buf(buf, end, &value, sizeof(value));
99 }
100 
101 /**
102  * Appends a byte array to a buffer, prefixing it with a 32-bit size field.  Returns a pointer to
103  * the first byte after the data written.
104  *
105  * See copy_size_and_data_from_buf().
106  */
append_size_and_data_to_buf(uint8_t * buf,const uint8_t * end,const void * data,size_t data_len)107 inline uint8_t* append_size_and_data_to_buf(uint8_t* buf, const uint8_t* end, const void* data,
108                                             size_t data_len) {
109     buf = append_uint32_to_buf(buf, end, data_len);
110     return append_to_buf(buf, end, data, data_len);
111 }
112 
113 /**
114  * Appends an array of values that are convertible to uint32_t as uint32ts to a buffer, prefixing a
115  * count so deserialization knows how many values to read.
116  *
117  * See copy_uint32_array_from_buf().
118  */
119 template <typename T>
append_uint32_array_to_buf(uint8_t * buf,const uint8_t * end,const T * data,size_t count)120 inline uint8_t* append_uint32_array_to_buf(uint8_t* buf, const uint8_t* end, const T* data,
121                                            size_t count) {
122     // Check for overflow
123     if (count >= (UINT32_MAX / sizeof(uint32_t)) ||
124         __pval(buf) + count * sizeof(uint32_t) < __pval(buf))
125         return buf;
126     buf = append_uint32_to_buf(buf, end, count);
127     for (size_t i = 0; i < count; ++i)
128         buf = append_uint32_to_buf(buf, end, static_cast<uint32_t>(data[i]));
129     return buf;
130 }
131 
132 /*
133  * Utility functions for writing Deserialize() methods.
134  */
135 
136 /**
137  * Copy \p size bytes from \p *buf_ptr into \p dest.  If there are fewer than \p size bytes to read,
138  * returns false.  Advances *buf_ptr to the next byte to be read.
139  */
140 bool copy_from_buf(const uint8_t** buf_ptr, const uint8_t* end, void* dest, size_t size);
141 
142 /**
143  * Extracts a uint32_t size from *buf_ptr, placing it in \p *size, and then reads *size bytes from
144  * *buf_ptr, placing them in newly-allocated storage in *dest.  If there aren't enough bytes in
145  * *buf_ptr, returns false.  Advances \p *buf_ptr to the next byte to be read.
146  *
147  * See \p append_size_and_data_to_buf().
148  */
149 bool copy_size_and_data_from_buf(const uint8_t** buf_ptr, const uint8_t* end, size_t* size,
150                                  UniquePtr<uint8_t[]>* dest);
151 
152 /**
153  * Copies a value convertible from uint32_t from \p *buf_ptr.  Returns false if there are less than
154  * four bytes remaining in \p *buf_ptr.  Advances \p *buf_ptr to the next byte to be read.
155  */
156 template <typename T>
copy_uint32_from_buf(const uint8_t ** buf_ptr,const uint8_t * end,T * value)157 inline bool copy_uint32_from_buf(const uint8_t** buf_ptr, const uint8_t* end, T* value) {
158     uint32_t val;
159     if (!copy_from_buf(buf_ptr, end, &val, sizeof(val))) return false;
160     *value = static_cast<T>(val);
161     return true;
162 }
163 
164 /**
165  * Copies a uint64_t from \p *buf_ptr.  Returns false if there are less than eight bytes remaining
166  * in \p *buf_ptr.  Advances \p *buf_ptr to the next byte to be read.
167  */
copy_uint64_from_buf(const uint8_t ** buf_ptr,const uint8_t * end,uint64_t * value)168 inline bool copy_uint64_from_buf(const uint8_t** buf_ptr, const uint8_t* end, uint64_t* value) {
169     return copy_from_buf(buf_ptr, end, value, sizeof(*value));
170 }
171 
172 /**
173  * Copies an array of values convertible to uint32_t from \p *buf_ptr, first reading a count of
174  * values to read. The count is returned in \p *count and the values returned in newly-allocated
175  * storage at *data.  Returns false if there are insufficient bytes at \p *buf_ptr.  Advances \p
176  * *buf_ptr to the next byte to be read.
177  */
178 template <typename T>
copy_uint32_array_from_buf(const uint8_t ** buf_ptr,const uint8_t * end,UniquePtr<T[]> * data,size_t * count)179 inline bool copy_uint32_array_from_buf(const uint8_t** buf_ptr, const uint8_t* end,
180                                        UniquePtr<T[]>* data, size_t* count) {
181     if (!copy_uint32_from_buf(buf_ptr, end, count)) return false;
182 
183     uintptr_t array_end = __pval(*buf_ptr) + *count * sizeof(uint32_t);
184     if (*count >= UINT32_MAX / sizeof(uint32_t) || array_end < __pval(*buf_ptr) ||
185         array_end > __pval(end))
186         return false;
187 
188     data->reset(new (std::nothrow) T[*count]);
189     if (!data->get()) return false;
190     for (size_t i = 0; i < *count; ++i)
191         if (!copy_uint32_from_buf(buf_ptr, end, &(*data)[i])) return false;
192     return true;
193 }
194 
195 /**
196  * A simple buffer that supports reading and writing.  Manages its own memory.
197  */
198 class Buffer : public Serializable {
199   public:
Buffer()200     Buffer() : buffer_(nullptr), buffer_size_(0), read_position_(0), write_position_(0) {}
Buffer(size_t size)201     explicit Buffer(size_t size) : buffer_(nullptr) { Reinitialize(size); }
Buffer(const void * buf,size_t size)202     Buffer(const void* buf, size_t size) : buffer_(nullptr) { Reinitialize(buf, size); }
Buffer(Buffer && b)203     Buffer(Buffer&& b) { *this = move(b); }
204     Buffer(const Buffer&) = delete;
205 
~Buffer()206     ~Buffer() { Clear(); }
207 
208     Buffer& operator=(Buffer&& other) {
209         if (this == &other) return *this;
210         buffer_ = move(other.buffer_);
211         buffer_size_ = other.buffer_size_;
212         other.buffer_size_ = 0;
213         read_position_ = other.read_position_;
214         other.read_position_ = 0;
215         write_position_ = other.write_position_;
216         other.write_position_ = 0;
217         return *this;
218     }
219 
220     void operator=(const Buffer& other) = delete;
221 
222     // Grow the buffer so that at least \p size bytes can be written.
223     bool reserve(size_t size);
224 
225     bool Reinitialize(size_t size);
226     bool Reinitialize(const void* buf, size_t size);
227 
228     // Reinitialize with a copy of the provided buffer's readable data.
Reinitialize(const Buffer & buffer)229     bool Reinitialize(const Buffer& buffer) {
230         return Reinitialize(buffer.peek_read(), buffer.available_read());
231     }
232 
begin()233     const uint8_t* begin() const { return peek_read(); }
end()234     const uint8_t* end() const { return peek_read() + available_read(); }
235 
236     void Clear();
237 
238     size_t available_write() const;
239     size_t available_read() const;
buffer_size()240     size_t buffer_size() const { return buffer_size_; }
241 
242     bool write(const uint8_t* src, size_t write_length);
243     bool read(uint8_t* dest, size_t read_length);
peek_read()244     const uint8_t* peek_read() const { return buffer_.get() + read_position_; }
advance_read(int distance)245     bool advance_read(int distance) {
246         if (static_cast<size_t>(read_position_ + distance) <= write_position_) {
247             read_position_ += distance;
248             return true;
249         }
250         return false;
251     }
peek_write()252     uint8_t* peek_write() { return buffer_.get() + write_position_; }
advance_write(int distance)253     bool advance_write(int distance) {
254         if (static_cast<size_t>(write_position_ + distance) <= buffer_size_) {
255             write_position_ += distance;
256             return true;
257         }
258         return false;
259     }
260 
261     size_t SerializedSize() const;
262     uint8_t* Serialize(uint8_t* buf, const uint8_t* end) const;
263     bool Deserialize(const uint8_t** buf_ptr, const uint8_t* end);
264 
265   private:
266     UniquePtr<uint8_t[]> buffer_;
267     size_t buffer_size_;
268     size_t read_position_;
269     size_t write_position_;
270 };
271 
272 }  // namespace keymaster
273