CVE-2019-11841

A message-forgery issue was discovered in crypto/openpgp/clearsign/clearsign.go in supplementary Go cryptography libraries 2019-03-25. According to the OpenPGP Message Format specification in RFC 4880 chapter 7, a cleartext signed message can contain one or more optional "Hash" Armor Headers. The "Hash" Armor Header specifies the message digest algorithm(s) used for the signature. However, the Go clearsign package ignores the value of this header, which allows an attacker to spoof it. Consequently, an attacker can lead a victim to believe the signature was generated using a different message digest algorithm than what was actually used. Moreover, since the library skips Armor Header parsing in general, an attacker can not only embed arbitrary Armor Headers, but also prepend arbitrary text to cleartext messages without invalidating the signatures.

A message-forgery issue was discovered in crypto/openpgp/clearsign/clearsign.go in supplementary Go cryptography libraries 2019-03-25. According to the OpenPGP Message Format specification in RFC 4880 chapter 7, a cleartext signed message can contain one or more optional "Hash" Armor Headers. The "Hash" Armor Header specifies the message digest algorithm(s) used for the signature. However, the Go clearsign package ignores the value of this header, which allows an attacker to spoof it. Consequently, an attacker can lead a victim to believe the signature was generated using a different message digest algorithm than what was actually used. Moreover, since the library skips Armor Header parsing in general, an attacker can not only embed arbitrary Armor Headers, but also prepend arbitrary text to cleartext messages without invalidating the signatures.

The clearsign package accepts some malformed messages, making it possible for an attacker to trick a human user (but not a Go program) into thinking unverified text is part of the message. With fix, messages with malformed headers in the SIGNED MESSAGE section are rejected.

A message-forgery issue was discovered in `crypto/openpgp/clearsign/clearsign.go` in supplementary Go cryptography libraries 2019-03-25. According to the OpenPGP Message Format specification in RFC 4880 chapter 7, a cleartext signed message can contain one or more optional "Hash" Armor Headers. The "Hash" Armor Header specifies the message digest algorithm(s) used for the signature. However, the Go clearsign package ignores the value of this header, which allows an attacker to spoof it. Consequently, an attacker can lead a victim to believe the signature was generated using a different message digest algorithm than what was actually used. Moreover, since the library skips Armor Header parsing in general, an attacker can not only embed arbitrary Armor Headers, but also prepend arbitrary text to cleartext messages without invalidating the signatures.

Se descubrió un problema de falsificación de mensaje en Crypto/OpenPGP/ClearSign/ClearSign. en las librerías de criptografía complementario 25-03-2019. De acuerdo con la especificación de formato de mensaje OpenPGP en RFC 4880 capítulo 7, un mensaje con signo de texto no cifrado puede contener uno o más opcional "hash " encabezados de la estructura. Los encabezados de la estructura "hash " especifica los algoritmos de Resumen de mensaje utilizados para la firma. No obstante, el paquete go ClearSign ignora el valor de este encabezado, lo que permite a un atacante sumarlo. Por lo tanto, un atacante puede llevar a una víctima a creer que la firma se generó utilizando un algoritmo de Resumen de mensaje diferente de lo que se usó realmente. Además, dado que la librería omite el análisis del encabezado de la estructura en general, un atacante no solo puede incrustar encabezados de estructura arbitrarios, sino también anteponer texto arbitrario a mensajes sin invalidar las firmas.