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Add a one-word sentinel value of 0x0 at the end of each buf_t chunk
This helps protect against bugs where any part of a buf_t's memory is passed to a function that expects a NUL-terminated input.
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@ -75,12 +75,33 @@ typedef struct chunk_t {
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#define CHUNK_HEADER_LEN STRUCT_OFFSET(chunk_t, mem[0])
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/* We leave this many NUL bytes at the end of the buffer. */
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#define SENTINEL_LEN 4
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/* Header size plus NUL bytes at the end */
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#define CHUNK_OVERHEAD (CHUNK_HEADER_LEN + SENTINEL_LEN)
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/** Return the number of bytes needed to allocate a chunk to hold
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* <b>memlen</b> bytes. */
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#define CHUNK_ALLOC_SIZE(memlen) (CHUNK_HEADER_LEN + (memlen))
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#define CHUNK_ALLOC_SIZE(memlen) (CHUNK_OVERHEAD + (memlen))
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/** Return the number of usable bytes in a chunk allocated with
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* malloc(<b>memlen</b>). */
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#define CHUNK_SIZE_WITH_ALLOC(memlen) ((memlen) - CHUNK_HEADER_LEN)
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#define CHUNK_SIZE_WITH_ALLOC(memlen) ((memlen) - CHUNK_OVERHEAD)
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#define DEBUG_SENTINEL
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#ifdef DEBUG_SENTINEL
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#define DBG_S(s) s
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#else
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#define DBG_S(s) (void)0
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#endif
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#define CHUNK_SET_SENTINEL(chunk, alloclen) do { \
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uint8_t *a = (uint8_t*) &(chunk)->mem[(chunk)->memlen]; \
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DBG_S(uint8_t *b = &((uint8_t*)(chunk))[(alloclen)-SENTINEL_LEN]); \
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DBG_S(tor_assert(a == b)); \
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memset(a,0,SENTINEL_LEN); \
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} while (0)
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/** Return the next character in <b>chunk</b> onto which data can be appended.
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* If the chunk is full, this might be off the end of chunk->mem. */
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@ -204,6 +225,7 @@ chunk_new_with_alloc_size(size_t alloc)
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ch->datalen = 0;
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ch->memlen = CHUNK_SIZE_WITH_ALLOC(alloc);
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ch->data = &ch->mem[0];
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CHUNK_SET_SENTINEL(ch, alloc);
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return ch;
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}
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#else
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@ -221,6 +243,7 @@ chunk_new_with_alloc_size(size_t alloc)
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ch->datalen = 0;
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ch->memlen = CHUNK_SIZE_WITH_ALLOC(alloc);
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ch->data = &ch->mem[0];
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CHUNK_SET_SENTINEL(ch, alloc);
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return ch;
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}
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#endif
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@ -231,11 +254,13 @@ static INLINE chunk_t *
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chunk_grow(chunk_t *chunk, size_t sz)
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{
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off_t offset;
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const size_t new_alloc = CHUNK_ALLOC_SIZE(sz);
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tor_assert(sz > chunk->memlen);
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offset = chunk->data - chunk->mem;
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chunk = tor_realloc(chunk, CHUNK_ALLOC_SIZE(sz));
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chunk = tor_realloc(chunk, new_alloc);
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chunk->memlen = sz;
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chunk->data = chunk->mem + offset;
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CHUNK_SET_SENTINEL(chunk, new_alloc);
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return chunk;
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}
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