vcs-svn: guard against overflow when computing preimage length
Signed integer overflow produces undefined behavior in C and off_t is a signed type. For predictable behavior, add some checks to protect in advance against overflow. On 32-bit systems ftell as called by buffer_tmpfile_prepare_to_read is likely to fail with EOVERFLOW when reading the corresponding postimage, and this patch does not fix that. So it's more of a futureproofing measure than a complete fix. Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Jonathan Nieder committed
May 27, 2011 at 05:18 UTC
abe27c0cbd97bf6a693004ddb411392ed596a853
1 file changed
+14
-1
vcs-svn/fast_export.c
+14
-1
@@ -166,6 +166,7 @@ static int ends_with(const char *s, size_t len, const char *suffix)
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static int parse_cat_response_line(const char *header, off_t *len)
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{
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size_t headerlen = strlen(header);
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+ uintmax_t n;
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const char *type;
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const char *end;
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@@ -174,14 +175,25 @@ static int parse_cat_response_line(const char *header, off_t *len)
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type = memmem(header, headerlen, " blob ", strlen(" blob "));
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if (!type)
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return error("cat-blob header has wrong object type: %s", header);
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- *len = strtoumax(type + strlen(" blob "), (char **) &end, 10);
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+ n = strtoumax(type + strlen(" blob "), (char **) &end, 10);
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if (end == type + strlen(" blob "))
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return error("cat-blob header does not contain length: %s", header);
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+ if (memchr(type + strlen(" blob "), '-', end - type - strlen(" blob ")))
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+ return error("cat-blob header contains negative length: %s", header);
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+ if (n == UINTMAX_MAX || n > maximum_signed_value_of_type(off_t))
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+ return error("blob too large for current definition of off_t");
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+ *len = n;
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if (*end)
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return error("cat-blob header contains garbage after length: %s", header);
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return 0;
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}
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+static void check_preimage_overflow(off_t a, off_t b)
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+{
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+ if (signed_add_overflows(a, b))
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+ die("blob too large for current definition of off_t");
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+}
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+
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static long apply_delta(off_t len, struct line_buffer *input,
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const char *old_data, uint32_t old_mode)
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{
@@ -204,6 +216,7 @@ static long apply_delta(off_t len, struct line_buffer *input,
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}
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if (old_mode == REPO_MODE_LNK) {
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strbuf_addstr(&preimage.buf, "link ");
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+ check_preimage_overflow(preimage_len, strlen("link "));
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preimage_len += strlen("link ");
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}
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if (svndiff0_apply(input, len, &preimage, out))