Alignment with arbitrary number of mismatches or gaps
This is not something mappers will be good at, because you're going to hit most of the genome. Depending on how many reads you have it may be better to work in reverse, iterating over all the kmers in the genome and working out whether or not they are fewer than 7 mismatches (plus indels) away from any reads:

for gp in genomePositions
    genomeKmer = genome[gp:(gp+23-1)]
    for read in reads
        errors = 0
        for rp in 1..23
            if (genomeKmer[rp] != read[rp])
                errors += 1
        if (errors &lt; 7)
            print gp