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Request #61255 Unserialize should handle incorrect or missing string-length
Submitted: 2012-03-02 22:26 UTC Modified: 2012-03-03 10:39 UTC
Avg. Score:4.0 ± 0.0
Reproduced:1 of 1 (100.0%)
Same Version:1 (100.0%)
Same OS:1 (100.0%)
From: mi+php at aldan dot algebra dot com Assigned:
Status: Wont fix Package: *Data Exchange functions
PHP Version: 5.3.10 OS: All
Private report: No CVE-ID: None
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 [2012-03-02 22:26 UTC] mi+php at aldan dot algebra dot com
A serializing string "foo" produces an intuitive result 's:3:"foo"' and unserialize() properly decodes that back.

It would be useful, however, if the unserialize function could handle (even if less efficiently) cases, where the string-length is missing or even specified incorrectly. Currently any such mismatches result in empty output from the function, even though `s:"foo"' or `s::"foo"' or even `s:4:"foo"' is no harder to understand.

The feature would be of help to those of us, who need to a massive search/replace in the dump of serialized objects.

Test script:
$s1 = "s:7:\"1234567\"";
$s2 = "s:6:\"1234567\"";
$s3 = "s:8:\"1234567\"";
$s4 = "s::\"1234567\"";

print "S1: >" . unserialize($s1) . "<\n";
print "S2: >" . unserialize($s2) . "<\n";
print "S3: >" . unserialize($s3) . "<\n";
print "S4: >" . unserialize($s4) . "<\n";

Expected result:
S1: >1234567<
S2: >1234567<
S3: >1234567<
S4: >1234567<

Actual result:
S1: >1234567<
S2: ><
S3: ><
S4: ><


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 [2012-03-03 00:45 UTC] anon at anon dot anon
It depends on the lengths because the strings aren't escaped. serialize('"') = s:1:""";
 [2012-03-03 04:18 UTC] mi+php at aldan dot algebra dot com
If the length is what's driving the parsing, then why are the strings S2 and S3 empty in my test? Shouldn't S2 be '123456' and S3 be '1234567"'?
 [2012-03-03 10:39 UTC]
-Status: Open +Status: Wont fix
 [2012-03-03 10:39 UTC]
As mentioned, " is not escaped, making the length required. This is not even considering whether it would be a good idea to otherwise make unserialize lax.

You are of course free to write your own serialization/unserialization library, like igbinary.
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