icu_to_uchar() and icu_from_uchar(), and perhaps other places, are
touchingly naive about integer overflow hazards in buffer size
calculations.  I call particular attention to this bit in
icu_from_uchar():

        len_result = UCNV_GET_MAX_BYTES_FOR_STRING(len_uchar, 
ucnv_getMaxCharSize(icu_converter));

The ICU man pages say that that macro is defined as

#define UCNV_GET_MAX_BYTES_FOR_STRING(length, maxCharSize)      
(((int32_t)(length)+10)*(int32_t)(maxCharSize))

which means that getting this to overflow (resulting in
probably-exploitable memory overruns) would be about as hard as taking
candy from a baby.

I also notice that the general approach to handling ICU-reported
error conditions is like

    if (U_FAILURE(status))
        ereport(ERROR,
                (errmsg("ucnv_fromUChars failed: %s", u_errorName(status))));

This lacks an errcode() setting, which is contrary to project policy,
and the error message violates our message style guidelines.

I don't particularly feel like fixing these things myself, but
somebody needs to; the overflow issues in particular are stop-ship
security hazards.

                        regards, tom lane


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