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Fix #19107 Add bounds check to strformat #19286

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Dec 25, 2021
Merged

Fix #19107 Add bounds check to strformat #19286

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12 changes: 10 additions & 2 deletions lib/pure/strformat.nim
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Original file line number Diff line number Diff line change
Expand Up @@ -574,6 +574,9 @@ template formatValue(result: var string; value: cstring; specifier: string) =
result.add value

proc strformatImpl(f: string; openChar, closeChar: char): NimNode =
template missingCloseChar =
error("invalid format string: missing closing character '" & closeChar & "'")

if openChar == ':' or closeChar == ':':
error "openChar and closeChar must not be ':'"
var i = 0
Expand Down Expand Up @@ -618,6 +621,8 @@ proc strformatImpl(f: string; openChar, closeChar: char): NimNode =
let start = i
inc i
i += f.skipWhitespace(i)
if i == f.len:
missingCloseChar
if f[i] == closeChar or f[i] == ':':
result.add newCall(bindSym"add", res, newLit(subexpr & f[start ..< i]))
else:
Expand All @@ -627,6 +632,9 @@ proc strformatImpl(f: string; openChar, closeChar: char): NimNode =
subexpr.add f[i]
inc i

if i == f.len:
missingCloseChar

var x: NimNode
try:
x = parseExpr(subexpr)
Expand All @@ -639,10 +647,10 @@ proc strformatImpl(f: string; openChar, closeChar: char): NimNode =
while i < f.len and f[i] != closeChar:
options.add f[i]
inc i
if i == f.len:
missingCloseChar
if f[i] == closeChar:
inc i
else:
doAssert false, "invalid format string: missing '}'"
result.add newCall(formatSym, res, x, newLit(options))
elif f[i] == closeChar:
if i<f.len-1 and f[i+1] == closeChar:
Expand Down